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Africanized Bees: Better Understanding, Better Prepared
What you need to know to protect yourself and your bees.
Authors: Philip Moore, Michael Wilson, John Skinner
Department of Entomology and Plant Pathology, the University of Tennessee, Knoxville TN
Date: January 8, 2015
The African honey bee (Apis mellifera scutellata) was introduced from the savannahs of eastern and southern Africa to the eucalyptus forests of São Paulo Brazil by Professor Warwick E. Kerr in 1956. Kerr described the colonies as “the most prolific, productive, and industrious bees.” His intention was to breed a race of honey bee that would be more adapted to the tropical climate of South America than the temperate climate adapted European races of honey bee. Although African bees were originally considered to be “accidentally released”, several studies including those published by Kerr (1967), do not uphold that view. Kerr performed hybridization experiments, reared and artificially inseminated African queens with Italian honey bee (A. m. lingustic) drones, and distributed these bees to beekeepers in southern Brazil (Kerr 1967). Although the spread of the African honey bee was quickly recognized in Brazil and Argentina, the first English language published accounts of problems with defensiveness of the African bees came in 1964 by Nogueira-Neto. By 1972, the US had taken notice and published a report of the impending problem.
In 1990 the much anticipated arrival of the original African bees’ descendants, now called Africanized honey bees or “killer bees” reached the southern US and in 2 years, had spread to Arizona, New Mexico, and southwestern Texas. Africanized honey bees (AHB) are now found throughout much of South, Central and southern North America, but may have reached an upper and lower limit to their spread at about the 34°N and 34°S latitude (Visscher et al 1997; Kerr et al 1982), based in part to their inability to survive extended cold periods (Taylor 2003; Villa et al 1991, 1993). As Africanized honey bees spread, more than 1000 people and tens-of-thousands of domestic animals have been killed in stinging incidents (Breed et al 2004). This created a fear-driven public health crisis and forced many beekeepers in South America out of business, but we now have a better understanding of Africanized honey bees’ defensive behavior and beekeeper’s coping mechanisms. Beekeeping in South and Central America has since rebounded and commercial US beekeepers have had few issues.
The key to understanding the differences in Africanized honey bees and European honey bees is to recognize that they are the same species and therefore very similar, except for having evolved to persist in significantly different habitats. No honey bees (Apis mellifera) are native to the New World. Nearly all of the honey bees used for beekeeping in North America and up until recently
South America were imported from Europe and were adapted to survive in temperate climates. These include many subspecies like Italians (A. m. linguistic), Carniolans from Slovenia and the Balkans (A. m. carnica), and the European black bee, also known as the German black bee (A. m. mellifera). These European bees are good honey producers in the temperate climates of North America and well adapted to the climate. They evolved to construct large, honey laden nests in order to survive the winter. African honey bees (A. m. scutellata), in contrast, evolved to survive in tropical climates, and thus do not have winter to contend with, but instead are limited by rainfall and floral availability. Therefore they build smaller nests, do not store large amounts of honey, are sensitive to cold, and migrate to find a new home when floral resources diminish. However, Africanized bees are hybrids of European and A. m. scutellata genetics and the expression of these behaviors may vary in Africanized bees. Distinguishing between these subspecies is possible through laboratory diagnostics by morphometrics or genetic analysis. To the average person, the greatest difference between the European and African honey bees is their defensive behavior.
Better understanding: Africanized bee (left) and European bee (right) are indistinguishable to the un-aided eye. The color difference seen here can also be found in European honey bees. Credit: Scott Bauer. Courtesy: USDA-ARS
Defensive response of Africanized honey bees is more rapid, intense, and involves a greater proportion of the colony population. A study of honey bees in Africa suggests that African bees (A. m. scutellata) have a lower threshold for defensive response and react more intensely, faster, and in larger numbers (Schneider and McNally 1992). When given the same stimuli, Africanized bees in the New World sting 4 to 10 times more frequently (Guzman-Novoa et al 2002a, 2002b, 1999; Guzman-Novoa and Page 1993, 1994) and pursue with 10 to 30 times more bees than European colonies (Guzman-Novoa et al 2003, Prieto-Merlos 2002; Stort and Goncalves 1991). One reason for the Africanized bees more intense response may be greater alarm pheromone release; one study found 9 of 12 alarm chemical components were stronger in Africanized bees than European bees (Collins et al 1989). Defensive bees may also be more sensitive to alarm pheromones (Harris and Woodring 1999).
Another aspect of nest defense, the number and duration of workers guarding the entrance, may be reinforced by the alarm pheromone of Africanized bees (Hunt et al 2003). Guarding is a distinct worker defensive task, whereas soldiers are any bees involved in pursuing and stinging intruders. Guards compose about 10 percent of the colony population. They are usually middle aged (between 13 and 16 days old) and will remain a guard for one to three and up to six days (Hunt et al 2003). In one study, European guards persisted in that role for 3 days, where Africanized bees guarded for 4.7 days on average (Hunt et al 2003). The longer a bee remains a guard, the more responsive it becomes to alarm pheromones (Breed and Rogers 1991, Breed et al 1989).
The primary purpose of guard bees is to defend against robbing, identifying and removing conspecific intruders (Breed 1991, Breed et al 1992), but guards may also influence recruitment of other soldier bees to defend against larger intruders. Few guard bees of European colonies fly out and orient towards an intruder, instead they produce alarm pheromone to recruit soldiers to attack. Africanized guards are seven times more likely to fly out and sting (Guzman et al 2003). In a maximal defensive act, an estimated 10 percent of European workers in a colony may be involved, whereas 50 percent of Africanized workers may pursue and sting under certain circumstances (Breed 1991); even foragers with pollen loads have been observed stinging (Prieto-Merlos 2002). The defensive perimeter for Africanized bees is also greater and soldiers will attack intruders 100 or more meters from the nest, pursing intruders for several kilometers, while European honey bees will only defend about a 50 meter perimeter (Spivak et al 1991).
Defensive behavior is influenced by genetic heritability, exemplified by different races of honey bees with different defensive characteristics (Ruttner 1988). However, since a worker population may contain genes from up to 17 different drone fathers, the defensive behavior of a honey bee colony is highly variable. However, in colonies with a low proportion of aggressive bees, the defensive bees in the minority may recruit other less aggressive bees into stinging (Guzman-Novoa et al 2003). Highly defensive behavior, measured by number of stings, may be a dominant trait at the colony level (DeGrandi-Hoffman et al 1998; Guzman-Novoa and Page 1993, 1994). Other environmental factors and stimuli also influence defensive behavior.
Better prepared; Eric Erickson trains first responder John Estes of Tucson Arizona to use soapy water to neutralize an Africanized bee attack. Credit: Jack Dykinga. Courtesy of: USDA-ARS
The colonization of much of the western hemisphere by the African honey bee (Apis mellifera scutellata) in the last 60 years is one of the most rapid and impressive biological invasions in recent history (Schneider et al 2004). Originally, African honey bees were thought to displace European honey bee subspecies through hybridization and to give rise to “Africanized honey bees” in Latin America. However the incredible success of African bees that have invaded European populations, has led to much of the European characteristics to be lost and existing honey bee populations to remain essentially African in their nesting behavior (McNally and Schneider 1992), swarming and absconding behavior (Otis et al 2002; Rubink et al 1996; Schneider 1995; Schneider and McNally 1992 and 1994; Sousa et al 2002), foraging and diet selection (Fewell and Bertran 2002; Schneider and Hall 1997; Schneider and McNally 1993), and maternal DNA characteristics (Clarke et al 2001 and 2002; Hall 1999; Segura 1989).
The effect of African populations on feral colonies in the Neotropics (including all of South and Central America along with the Caribbean, Southern Florida and Mexico) is especially acute in terms of genetic introgression. When African bees first expand into a new location, both European and African genetic markers are found, but after 5-10 years, African genes predominate and European genes typically decrease to less than 10 percent (Schneider et al 2003). At least six different mechanisms are responsible for the loss of European genetic lineage. The relative effect of these mechanisms differs depending on managed or feral settings. For example, because of the effect of re-queening in commercial apiaries, European maternal lineage is more likely to be retained, while open mating contributes to paternal African introgression. The paternal effect of Africanized introgression is likely to bring increased defensive behavior into stocks quickly as defensive behavior seems to be significantly influenced by paternity (Guzman-Nova et al 2005).
Growth Rate and Swarming
African colonies have a greater emphasis on pollen collection than European colonies (Fewell and Bertram 2002; Franck et al 2000) and convert the pollen into greater populations of brood (Schneider and McNally 1994; Spivak et al 1991), devoting as much as two to four times more comb area to brood rearing (McNally and Schneider 1992 and 1996). The higher growth rate allows African bees in the Neotropics to swarm up to 16 times per year, compared to 3 to 6 times for feral European colonies (Otis 1991; Winston 1992). The increased swarming allows African colonies to increase in density quickly and lead to overrepresentation of African genetics in the available mating pool.
One factor that may be contributing to the loss the European genes is the reduced fitness of hybrid bees resulting from incompatibilities between European maternal and African paternal alleles. European bees have adapted to temperate climates, where African bees are adapted to tropical environments, which may reflect some of these incompatibilities. Hybrid workers exhibit greater frequency in small differences in wing symmetry resulting from developmental disturbances (Schneider et al 2003). Hybrids also have lower metabolic rates when reared from European maternity (Harrison and Hall 1993). These disruptions may affect flight performance and colony dispersal ability. Hybrids may also be less efficient foragers (Quezada-Euán and Hinsull 1996), store less honey, and produce less brood (Taylor 1999 and 2003). Although the negative effect of hybridization remains a controversial aspect of the African bee invasion (Rinderer et al. 1991 and 1993; Sheppard et al 1991; Lobo 1995; Quezada-Euán and Hinsull 1995), it does exemplify potential consequences in the long-term survival of European lineage in overlapping habitat.
Drone Advantage in Mating
Several advantages allow African drones to disproportionately mate with European queens. One primary component is the sheer numerical advantage. African colonies produce a greater proportion of drones than European colonies in the same setting (Rinderer et al 1987; Otis et al 2002). This is due in part to a greater swarming tendency; however a couple of other interesting attributes also contribute. African drones will invade and habitat in European colonies, which may suppress the production of European drones (Rinderer et al 1985) and higher rates of queen loss in African colonies leads to queen-less colonies that rear large numbers of worker-produced drones (DeGrandi-Hoffman and Schneider 2002; Zillikens et al 1998). Other than greater abundance, other factors that may contribute to African drone mating success are not well understood, such as higher rates of sperm usage by queens mated with African and European drones (DeGrandi-Hoffman et al 2003).
Paternal African Virgin Queens
When virgin queens produced by European colonies mate with African and European drones, the resulting colony will be composed of paternal African and European workers. In the next queen replacement cycle, these colonies will rear virgin queens from both African and European paternal lineage, but those from African paternity have a competitive advantage. Paternal African virgin queens develop faster and therefore emerge earlier than their European paternity counterparts, which may give them the opportunity to eliminate rivals confined in their queen cells (DeGrandi-Hoffman et al 1993 and 1998; Schneider and DeGrandi-Hoffman 2002 and 2003). Paternal African queens also kill more rivals than their European-paternity sister queens, produce more “piping” sounds that may prevent emergence of virgin queens or enhance dueling success, and attract workers to perform more “vibration signals” that may promote queen survival (Schneider and DeGrandi-Hoffman 2003; Schneider et al 2001). These factors in combination may result in paternal African queens becoming more likely to become the new laying queen of these colonies. With each new queen replacement cycle, virgin queens disproportionately mate with African drones, and African genetic introgression into European colonies continues.
African Allelic Dominance
In Neotropical areas where a high proportion of European genetics persist, honey bee colonies often exhibit African behavioral traits; therefore African alleles may be dominant for some characteristics, further contributing to the spread of the African pheonotype. African alleles may be dominate for worker foraging (Fewell and Bertram 2002; Schneider and Hall 1997), queen behavior (Schneider and DeGrandi-Hoffman 2003), and resistance to the Varroa mite (Guzmán-Novoa et al 1996). However the most notable behavior is the aggressive defensive behavior shown by African bees. This aggressive behavior appears to be linked to paternal rather than maternal factors. Colonies of hybrid workers composed of a European queen mated with New World Africanized drones show defensiveness not different from African bees (DeGrandi-Hoffman et al 1998; Guzmán-Novoa and Page 1994; Guzmán-Novoa et al 2002; Hunt and Guzmán-Novoa 2002), while colonies headed by an African queen mated with European drones show decreased defensiveness (DeGrandi-Hoffman et al 1998), although still greater than European colonies. Since queens mate with up to 17 drones, the aggressiveness of the colony may be dependent on the relative abundance of paternal African workers in the population.
Nest usurpation is a form of parasitism where African swarms invade European colonies, replacing the queen and therefore eliminate the European maternal lineage. The frequency of usurpation is regionally variable; between 0 and 40 percent of colonies annually has been reported in different regions of Mexico (Vergara et al 1993), 5 percent in Venezuela (Danka et al 1992), and 25 percent in southern Arizona (Schneider et al 2004). Unfortunately, nest usurpation is among the least understood aspects of the African bee invasion and it is unknown how African swarms find and invade a host colony. It is likely that unknown pheromones are involved in associating the condition of the colony; particularly susceptible colonies are queenless or have a caged queen, however queenright colonies can also be invaded (Dietz et al 1989).
Better understanding: Judith Hooper and David Gilley analyze volatiles from Africanized bee pheromones involved in nest usurpation. Credit: Scott Bauer. Courtesy of: USDA-ARS
The Africanized Honey Bee in the United States
The African bee first appeared in Texas in 1990 (Hunter et al 1993) and has since spread throughout Texas, and Arizona, through most of New Mexico and Oklahoma, and parts of Arkansas, Louisiana, Florida, California, Nevada, and Utah. Africanized bees are displacing European genotypes as has been seen in Latin America (Loper 2002, Looper at al 1999; Schneider et al. 2004), however the spread is slower and more erratic. The slower spread may be due to limited winter survivability (Taylor 2003; Villa et al 1991 and 1993); and preference for arid conditions (Villa et al 2002; Ruttner 1998), which may confine the spread to the southern regions of the US. In addition, the adaptations that allow African bees to adapt to tropical climates may inhibit their expansion to temperate climates, which have vastly different pollen and nectar resource availability and day length (Schneider and McNally 1992; Rinderer 1993; Villa et al 1993). The affect of migratory beekeeping practices, tracheal and Varroa mites, and density of European colonies on the spread of African bees in the US is not well understood.
Better understanding: Distribution and spread of Africanized bees in the US 1990-2011. Courtesy of USDA-ARS
The economic affect of Africanized bees on US agriculture has been less severe than anticipated, perhaps due to the slower than expected spread and lessons learned from experiences in Latin America. The use of African bees in US agricultural practices is considered unworkable. However, African bees have been successfully integrated into many Latin American agricultural practices (Ratniek and Visscher 1996; Guzman-Novoa and Page 1994). Some beneficial characteristics of African bees like reduced susceptibility to mites, some bacterial diseases, and pesticides may be valuable (Arechavaleta-Velasco and Guzman-Novoa 2002; Danka et al 1986; Danka and Villa 1996; Ratnieks and Visscher 1996). However, utilizing African bees requires substantial alteration in beekeeping techniques and requeening with European queens is still necessary.
Africanized Bees and the Varroa Mite
Varroa mites (Varroa destructor) are considered the most serious threat to European honey bee colonies (De Jong et al 1982). However the interaction of Africanized bees with Varroa mites is strikingly different from that of European bees. Although the relationship varies by region, honey bees in much of South America appear to not be impacted by Varroa parasitism (Calderon et al 2010). One aspect of resistance is grooming behavior. Moretto et al (1991) found grooming behavior of African bees in Brazil to be eight times more efficient at removing Varroa than Italian bees and 31 percent of infested African honey bee workers removed Varroa by their own or another bee’s grooming action (Moretto 1997). These results were confirmed by Arechavaleta-Velasco and Guzman-Novoa (2001) in Mexico, however, Vandame et al (2002) only found eleven percent of mites removed by African bees compared to eight percent by European bees in Mexico. Therefore alternative attributes are possibly conferring resistance. Workers of Africanized bee colonies are more efficient at removing Varroa infested brood than European workers in the same conditions, displaying superior hygienic behavior (Moretto et al 1991; Spivak and Gilliam 1998; Vandame et al. 2000 and 2002). Shorter development time of pupating African bees (10-13 hours less than European bees) is also suggested to limit the reproduction of mites (Camazine 1986; Ritter and De Jong 1984). All of these factors are expected to reduce the reproductive potential of female Varroa mites.
Living with Africanized bees, where they exist, requires caution and diligence, but not alarm. Sensationalist news accounts of “killer bees” have mostly been over-blown, but the risk to unsuspecting or unwitting people and animals is still possible. Africanized bees will only sting to defend their nest. If you come upon a bee nest, leave the area immediately and contact the local extension office or a pest-control company. Protecting oneself during a bee stinging event requires seeking immediate shelter in a building or car. Run as quickly as possible to shelter. Do not enter a body of water; the bees will wait for you at the surface. Do not swat at the bees or attempt any other defense; escaping the scene is paramount.
Once you have reached shelter, treat the stings like a typical honey bee sting. Remove the stinger by scraping with a fingernail or credit card as soon as possible and apply ice to reduce swelling and pain. Any abnormal reaction like shortness of breath, hives, or lightheadedness will require a trip to the emergency room for epinephrine. In minor cases the pain and swelling will subside in a few hours.
Animals should not be tied up, preventing their escape. Confined animals are the most common victims of Africanized bees. Areas around the home should be free of debris that allows a swarm to colonize. Any opening greater than 1/8 inch may provide a cavity and should be sealed. Swarming activity peaks in May-June, use caution and inspect your property around this time. Look for bees coming and going to identify a possible nest location. Do not attempt to investigate or move an object if activity is seen, contact a professional and wear protective clothing before entering the area.
Better understanding, better prepared: Mona Chambers, measuring an Africanized honey bee wing, one of the traits that differentiate these bees from European bees. Credit: Scott Bauer. Courtesy of: USDA-ARS
Information for first-responders can be found here. Beekeepers with aggressive colonies that are suspected of being Africanized should contact their state Apiary Inspector. Requeening may suffice to reduce the aggression; otherwise the colony may need to be destroyed to prevent its spread and potential liability. Identifying honey bees as Africanized is accomplished through morphometrics. To submit a sample for diagnosis see here.
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Thank you to Stan Schneider (Univ. of N. Carolina) for review of this article
USDA-ARS Areawide Project to Improve Honey Bee Health
The goal of the USDA-ARS Areawide program is to increase colony survival and availability for pollination and thus increase the profitability of beekeeping. A comprehensive bee management system is taking shape, centered around the following objectives.
- Increase colony strength for pollination of almonds and subsequent crops.
- Demonstrate that resistant bee stocks reduce operating costs and increase survivor-ship.
- Demonstrate improved parasitic mite control with proper timing of application.
- Improve the content and delivery methods for carbohydrate and protein diets.
- Improve the integrated use of controls for pests and diseases including non-chemical beekeeping methodology.
Participating ARS labs
- Honey Bee Breeding, Genetics and Physiology Research Unit: Baton Rouge, Louisiana bee lab
- Bee Research Laboratory in Beltsville: Beltsville, Maryland bee lab
- Carl Hayden Bee Research Center Tucson, Arizona bee lab
- Honey Bee Research Unit (HBRU) at Kika de la Garza Subtropical Agricultural Research Center: Weslaco, Texas bee lab
USDA-ARS Bee Labs
The USDA-ARS sponsors five bee research labs at
- Baton Rouge, Louisiana
- Beltsville, Maryland
- Logan, Utah
- Tucson, Arizona.
- Weslaco, Texas
Honey Bee Breeding, Genetics and Physiology Research Unit
The mission of the Honey Bee Breeding, Genetics and Physiology Research Unit is directly related to improving honey bee stock and honey bee management. This broad mission includes components related to problems caused by varroa mites, tracheal mites and Africanized honey bees. The devastating problems caused by varroa mites and the serious problems caused by tracheal mites are targeted as the most critical. Scientists are engaged in breeding and testing honey bees for resistance to mites, evaluating mite-bee interactions to better describe breeding criteria, and evaluate stock production processes to explore and solve stock problems caused by mites.
Bee Research Laboratory in Beltsville
The mission of the Bee Research Laboratory in Beltsville is to conduct research on the biology and control of honey bee parasites, diseases, and pests to ensure an adequate supply of bees for pollination and honey production. Using biological, molecular, chemical and non-chemical approaches, scientists are developing new, cost-effective strategies for controlling parasitic mites like Varroa destructor, bacterial diseases like American foulbrood, and emergent pests like the small hive beetle. Additional research focuses on virus transmission, and the impact of pests and pathogens on longevity and colony survival. Bee Research Laboratory staff also provides authoritative diagnosis of bee diseases and pests for Federal and State regulatory agencies and beekeepers on a worldwide basis.
Pollinating Insects - Biology, Management and Systematics Research Unit
The mission of the Pollinating Insect-Biology, Management, Systematics Research is the development of non-Apis bees, for example the alfalfa leafcutting bee and the blue orchard bee, as crop pollinators. Research emphasis areas include the development and improvement of management systems for bee populations, biological studies of bees, plant-pollination systems, and bee biosystematics. Cross-pollinated crops not effectively pollinated by honey bees have been targeted for improved pollination management, and the candidacy of selected pollinator species continues to be evaluated. Current research on established species, like the alfalfa leafcutting bee and the blue orchard bee, is directed toward developing control programs for pests and diseases, improving management that will result in better bee health and demonstrating pollination efficacy and increased producer profitability on "new" crops.
Carl Hayden Bee Research Center
The mission of the Carl Hayden Bee Research Center (CHBRC) is to conduct research to optimize the health of honey bee colonies, through improved nutrition and control of Varroa mites, in order to maximize production of honey bee pollinated crops.
Honey Bee Research Unit (HBRU) at Kika de la Garza Subtropical Agricultural Research Center
Mission: The mission of the Honey Bee Research Unit (HBRU) is to develop technology for managing honey bees in the presence of africanized honey bees, parasitic mites, stress and diseases. This lab was shut down in 2012. Many of the researchers migrated to the Carl Hayden Bee Lab in Tucson Arizona.
Honey Bee Winter Loss Survey
Honey Bee Colony Losses in the USA. The Bee Informed Partnership.The Bee Informed Partnership conducts an annual Winter Loss Survey for beekeepers on, or near, April 1st. To participate in the survey, sign up to be notified by email here.
This data has been collected since the Apiary Inspectors of America winter loss survey of 2006-2007. See documents below for previous year's results.
Losses 2006-2007, published in the American Bee Journal
Losses 2007-2008, published in PlosOne
Losses 2008-2009, published in the Journal of Apicultural Research
Losses 2009-2010, published in the Journal of Apicultural ResearchLosses 2010-2011, published in the Journal of Apicultural Research
U.S. Honey Bee Colony Losses 2011-2012
U.S. Honey Bee Colony Losses 2012-2013
U.S. Honey Bee Colony Losses 2013-2014
U.S. Honey Bee Colony Losses 2014-2015
The Bee Informed Partnership conducts an annual Winter Loss Survey for beekeepers on, or near, April 1st. To participate in the survey, go to this link.
Preliminary Results: Honey Bee Colony Losses in the U.S., Winter 2014-2015.
Note: This is a preliminary analysis. Sample sizes and estimates are likely to change. A more detailed final report is being prepared for publication in a peer-reviewed journal at a later date.
Nathalie Steinhauer1, Karen Rennich1, Kathleen Lee2, Jeffery Pettis3, David R. Tarpy4, Juliana Rangel5, Dewey Caron6, Ramesh Sagili6, John A. Skinner7, Michael E. Wilson7, James T. Wilkes8, Keith S. Delaplane9, Robyn Rose10, Dennis vanEngelsdorp1
1 Department of Entomology, University of Maryland, College Park, MD 20742
2 Department of Entomology, University of Minnesota, St. Paul, MN 55108
3 United States Department of Agriculture, Agricultural Research Service, Beltsville, MD
4 Department of Entomology, North Carolina State University, Raleigh NC 27695
5 Department of Entomology, Texas A&M University, College Station, TX 77843
6 Department of Horticulture, Oregon State University, Corvallis, OR 97331
7 Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996
8 Department of Computer Science, Appalachian State University, Boone, NC 28608
9 Department of Entomology, University of Georgia, Athens, GA 30602
10 United States Department of Agriculture, Animal and Plant Health Inspection Service, Riverdale, MD
Corresponding Author: firstname.lastname@example.org
The Bee Informed Partnership (http://beeinformed.org), in collaboration with the Apiary Inspectors of America (AIA) and the United States Department of Agriculture (USDA), is releasing preliminary results for the ninth annual national survey of honey bee colony losses. For the 2014/2015 winter season, a preliminary 6,128 beekeepers in the United States provided valid responses. Collectively, these beekeepers managed 398,247 colonies in October 2014, representing about 14.5% of the country’s estimated 2.74 million managed honey bee colonies1.
About two-thirds of the respondents (67.2%) experienced winter colony loss rates greater than the average self-reported acceptable winter mortality rate of 18.7%. Preliminary results estimate that a total of 23.1% of the colonies managed in the Unites States were lost over the 2014/2015 winter. This would represent a decrease in losses of 0.6% compared to the previous 2013/2014 winter, which had reported a total loss estimated at 23.7%. This is the second year in a row the reported colony loss rate was notably lower than the 9-year average total loss of 28.7% (see Figure 1).
Figure 1: Summary of the total colony losses overwinter (October 1 – April 1) and over the year (April 1 – April 1) of managed honey bee colonies in the United States. The acceptable range is the average percentage of acceptable colony losses declared by the survey participants in each of the nine years of the survey. Winter and Annual losses are calculated based on different respondent pools.
Beekeepers do not only lose colonies in the winter but also throughout the summer, sometimes at significant levels. To quantify this claim of non-winter colony mortality of surveyed beekeepers, we have included summer and annual colony losses since 2010/2011. In the summer of 2014 (April – October), colony losses surpassed winter losses at 27.4% (totalsummer loss). This compares to summer losses of 19.8% in 2013. Importantly, commercial beekeepers appear to consistently lose greater numbers of colonies over the summer months than over the winter months, whereas the opposite seems true for smaller-scale beekeepers. Responding beekeepers reported losing 42.1% of the total number of colonies managed over the last year (total annual loss, between April 2014 and April 2015). This represents the second highest annual loss recorded to date.
As in previous years, colony losses were not consistent across the country, with annual losses exceeding 60% in several states, while Hawaii reported the lowest total annual colony loss of ~14% (see Figure 2).
Figure 2: Total annual loss (%) 2014-2015 by state. Respondents who managed colonies in more than one state had all of their colonies counted in each state in which they reported managing colonies. Data for states with fewer than five respondents are withheld.
This survey was conducted by the Bee Informed Partnership, which receives a majority of its funding from the National Institute of Food and Agriculture, USDA (award number: 2011-67007-20017).
1 Based on NASS 2015 figures
2 Previous survey results found a total colony loss in the winters of 24% in the winter of 2013/2014, 30% in 2012/2013, 22% in 2011/2012, 30% in 2010/2011, 32% in 2009/2010, 29% in 2008/2009, 36% in 2007/2008, and 32% in 2006/2007 (see reference list).
- Lee, KV; Steinhauer, N; Rennich, K; Wilson, ME; Tarpy, DR; Caron, DM; Rose, R; Delaplane, KS; Baylis, K; Lengerich, EJ; Pettis, J; Skinner, JA; Wilkes, JT; Sagili, R; vanEngelsdorp, D; for the Bee Informed Partnership (2015) A national survey of managed honey bee 2013–2014 annual colony losses in the USA. Apidologie, 1–14. DOI:10.1007/s13592-015-0356-z
- Steinhauer, NA; Rennich, K; Wilson, ME; Caron, DM; Lengerich, EJ; Pettis, JS; Rose, R; Skinner, JA; Tarpy, DR; Wilkes, JT; vanEngelsdorp, D (2014) A national survey of managed honey bee 2012-2013 annual colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research, 53(1): 1–18. DOI:10.3896/IBRA.1.53.1.01
- Spleen, AM; Lengerich, EJ; Rennich, K; Caron, D; Rose, R; Pettis, JS; Henson, M; Wilkes, JT; Wilson, M; Stitzinger, J; Lee, K; Andree, M; Snyder, R; vanEngelsdorp, D (2013) A national survey of managed honey bee 2011-12 winter colony losses in the United States: results from the Bee Informed Partnership. Journal of Apicultural Research, 52(2): 44–53. DOI:10.3896/IBRA.1.52.2.07
- vanEngelsdorp, D; Caron, D; Hayes, J; Underwood, R; Henson, M; Rennich, K; Spleen, A; Andree, M; Snyder, R; Lee, K; Roccasecca, K; Wilson, M; Wilkes, J; Lengerich, E; Pettis, J (2012) A national survey of managed honey bee 2010-11 winter colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research, 51(1): 115–124. DOI:10.3896/IBRA.220.127.116.11
- vanEngelsdorp, D; Hayes, J; Underwood, RM; Caron, D; Pettis, J (2011) A survey of managed honey bee colony losses in the USA, fall 2009 to winter 2010. Journal of Apicultural Research, 50(1): 1–10. DOI:10.3896/IBRA.1.50.1.01
- vanEngelsdorp, D; Hayes, J; Underwood, RM; Pettis, JS (2010) A survey of honey bee colony losses in the United States, fall 2008 to spring 2009. Journal of Apicultural Research, 49(1): 7–14. DOI:10.3896/IBRA.1.49.1.03
- vanEngelsdorp, D; Hayes, J; Underwood, RM; Pettis, J (2008) A Survey of Honey Bee Colony Losses in the U.S., Fall 2007 to Spring 2008. PLoS ONE, 3(12). DOI:10.1371/journal.pone.0004071
- vanEngelsdorp, D; Underwood, R; Caron, D; Hayes, J (2007) An estimate of managed colony losses in the winter of 2006-2007: A report commissioned by the apiary inspectors of America. American Bee Journal, 147(7): 599–603.
Pollination Security for Fruit and Vegetable Crops in the Northeast
Researchers work to make crop pollination sustainable in the Northeast
Editor:Philip Moore, The University of Tennessee
Last Edited: January 15, 2015
The pollinator security project was initiated in 2011 to address a gap in knowledge with respect to pollinator communities in northeastern cropland.
Reports of declining native pollinators, decreased availability of honey bee rental colonies, and general public misunderstanding led to the creation of this working group to produce a sustainable pollination strategy for stakeholders.
The goal is to contribute to long-term profitability of fruit and vegetable production and the outcome is this webpage along with other farm training and publications to increase knowledge and adoption of practices that protect pollinator communities.
One component of this project is video segments which highlight aspects of fruit or vegetable production in the Northeast.
Part One: Commercial Blueberry Pollination in Maine's Blueberry Barrens
Part 1: Commercial Blueberry Pollination in Maine's Blueberry Barrens
Part 2: Lowbush Blueberry in Maine, Native Plants and Native Bees in a Modern System
Part 3: Pollinator Plantings (The Bee Module) for Maine Lowbush Blueberry
Part 4: Landscape Ecology in Maine's Blueberry Growing Region
Part 5: How to Estimate Native Bee Abundance in the Field
Part 6: Economics of Lowbush Blueberry in Maine
Part 8: Research Topics in Lowbush Blueberry Pollination
Part 9: Pollinator Habitat Enhancement in Cranberries
Specific objectives of this project are to :
1. Determine the contributions of pollinator communities and identify which site characteristics have the greatest influence on pollinator effectiveness in apple, lowbush blueberry, cranberry, and cucurbit.
2. Develop hypotheis-driven model based on factors shown to affect pollination deficits.
3. Quantify pesticide residues in pollen and relate to crop and management strategies, and estimated risk to the bee community.
4. Assess shared parasite load between introduced and native pollinator communities.
5. Analyze the economics of pollination services and determine the value of pollination service.
6. Heighten our understanding of the grower community to understand why farmers accept innovation and to increase adoption of pollinator conservation measures.
7. Facilitate knowledge transfer allowing growers to both assess and improve pollination security.
This content is produced by a group of researchers from across the northeast:
Anne Averil, The University of Massachusetts
Frank Drummond, The University of Maine
Kimberly Stoner, The Connecticut Agricultural Experiment Station
Bryan Danforth, Cornell University
John Burand, The University of Massachusetts
Brian Eitzer, The Connecticut Agricultural Experiment Station
Aaron Hoshide, The University of Maine
Cyndy Loftin, The University of Maine
Tom Stevens, The University of Massachusetts
John Skinner, The University of Tennessee
Dave Yarborough, The University of Maine
Tracy Zarrillo, The Connecticut Agricultural Experiment Station
Kalyn Bickerman, The University of Maine
Eric Asare, The University of Maine
Shannon Chapin, The University of Maine
Eric Venturini, The University of Maine
Sam Hanes, The University of Maine
Kourtney Collum, The University of Maine
Michael Wilson, The University of Tennessee
Philip Moore, The University of Tennessee
Aaron Hoshide- The University of Maine
Dr. Hoshide is in the School of Economics and serves as the lead on agricultural farm economics for the Pollinator Security for Northeastern Corps project. He is developing economic analyses on management decisions and providing end-user information. He is collaborating in the assessment of the economic cost / benefit ratio of native pollinators across blueberry and cranberry and investigating the economic incentives and impediments to growers who may choose to implement production practices to enhance pollination.
Kourtney Collum - The University of Maine
Kourtney Collum is a Ph.D. student in the Anthropology & Environmental Policy program at the University of Maine, working under the supervision of Dr. Samuel Hanes. As a research assistant on the USDA funded “Pollination Security” project, Kourtney examines the social and political factors that influence the adoption of pollinator conservation.
Through a comparative study of lowbush blueberry growers in Maine, USA and Prince Edward Island (PEI), Canada, Kourtney’s research examines the influence of agricultural policy, governmental and non-governmental agricultural organizations, and social capital on blueberry growers’ pollination management practices. Through her research Kourtney aims to identify what pollinator conservation practices are currently being used in Maine and PEI, and what the barriers are to blueberry growers adopting diversified pollination management strategies—such as conservation of native bees—in order to secure adequate pollination and enhance environmental stewardship. The goal of her research is to inform future agricultural policy so that it can maximize existing social and political resources to help blueberry growers secure pollination for their crops.
Prior to entering the PhD program, Kourtney completed a Master of Science degree in Forest Resources at the University of Maine and a Bachelor of Science degree in Anthropology & Environmental Studies at Western Michigan University.
Samuel Hanes - University of Maine
Dr. Hanes is in the Department of Anthropology and has been conducting a sociological analysis of farmers, for the Pollinator Security in Northeastern Crops project, as it relates to their understanding of pollination, pollinator biology, and the management of pollinators. This research characterizes grower philosophies and perceptions, but also sheds light on best strategies for outreach and technology transfer.
Anne Averill - The University of Massachusetts- Amherst
Dr. Anne Averill is Project Director and works to coordinate the research and outreach efforts of the many cooperators in the Pollinator Security for Northeastern Crops USDA-SCRI grant.
She is a professor and co-director of the Environmental Science undergraduate major in the Department of Environmental Conservation at UMass-Amherst. Her specialization is in Insect Behavior and Ecology (Insect/Plant Interactions, Cranberry Entomology). For the SCRI project, she also leads the research on cranberry. She is conducting studies of the bee community in this crop, with a focus on bumble bees, the most abundant of the native pollinators in bog systems. Much of the work involves survey and impacts of pathogens, habitat enhancements, and pesticides on bees in the cranberry system. She works extensively with the cranberry industry and grower cooperators, and is particularly interested in how the transition to new fungicides and insecticides utilized during bloom may impact foraging bees.
Cynthia Loftin - University of Maine, USGS
Dr. Loftin is currently studying the spatial analysis of pollination deficit and bee community assessment associated with blueberry fields in Maine. This role includes editing available land cover maps to reflect current landscapes surrounding Maine's blueberry fields, assessing change in field distribution since the base map was produced, and compiling other spatial data sets to be used in the landscape analysis. Dr. Loftin has been working with the Maine team in the Pollinator Security for Northeastern Crops project to develop the spatial
forms of the variables identified in the multivariate discriminate model of pollination deficit to apply in a spatially explicit model. Model predictions will be assessed with ground-truthing to variables and their modeled relationships adjusted based on the performance assessment.
Dr. Loftin also will develop the spatial scale analysis of landscape variables and pollination deficit and will collaborate with project scientists from the other teams to develop similar spatial analyses where appropriate spatial data are available. Dr. Loftin will integrate aspects of the spatial analysis as demonstrations in a graduate level Geographical Information Systems course (GIS), providing both a learning opportunity for students as well as an outreach opportunity to blueberry growers who will receive the analysis products for their farm.
John Skinner - University of Tennessee
Dr. Skinner is in the Department of Entomology and Plant Pathology where he is Professor and Extension Apiculturist. He is the Director for the eXtension.org Community of Practice in Bee Health.
His work in the Pollinator Security for Northeastern Corps project has been to oversee provision of electronic access to information through extension.org/bee_health, which includes the project plan, objectives, members, and results. Much of his recent effort has been filming and then posting extensive video footage of the participating commodities in the project and the pollinator situation as it currently exists in each crop.
Bryan Danforth - Cornell University
Dr. Danforth is a professor of Entomology and serves the team as an authority on bees and bee biology; his group has been providing information on the apple pollination system, which allows comparison across all of our crop systems. He has been coordinating research in NY apple and has been rounding out the survey work of the Pollinator Security for Northeastern Crops project by submitting bees from apple orchards and pollen samples for analysis of pathogen identification/prevalence and pesticide loads, respectively.
UMass Extension Symposium: Pollinator Health for Agriculture and Landscapes - March 26, 2015
UMass Extension Symposium: Pollinator Health for Agriculture and Landscapes
March 26, 2015
Campus Center Auditorium, University of Massachusetts, Amherst
8:00 AM Registration and Coffee
8:45 AM Welcome, Anne Averill, Dept. of Environmental Conservation, UMass
9:00 – 10:00 AM Biology, Diversity and Conservation of Native Bees in the Northeast, Joan Milam, Department of Environmental Conservation, UMass
Pollinators are key elements of native biodiversity, and bees in particular provide important ecosystem services in terms of pollination for native plants that support plant and wildlife diversity. Not only are bees important pollinators of natural systems, they are responsible for the pollination of the fruits, nuts and vegetables grown in the United States. This talk will cover bee basics: what makes a bee a bee, the great diversity of bee species, and what we can do to help conserve native bees.
10:00 – 10:45 AM The Natural History and Ecology of Honey bees in Our Landscapes, Dr. Frank Drummond, School of Biology and Ecology, University of Maine
Honey bees are amazing animals. They are one of the few insects that have been domesticated by humans, but they still remain somewhat wild. Dr. Drummond will take a look at the history of honey bees in the U.S. up to the 1960s and then how changes occurred through the present that have determined the current honey bee status and health.
10:45 – 11:00 AM Break
11:00 – 11:45 AM How Healthy are the Bees? Dr. Frank Drummond, School of Biology and Ecology, University of Maine
We have all heard about CCD, colony collapse, bee decline, a new silent spring...so, the question is how is the honey bee doing AND also the hundreds of species that are referred to as native bees? Dr. Drummond will discuss bee health...what is meant by "health"...what do scientists know about bee "health" and what is the global picture that is beginning to form about bee health. Dr. Drummond will attempt to provide background knowledge for better understanding several of the other talks in this conference about what we can DO about bee declines.
11:45 – 1:00 Lunch on your own – Many options on main floor of campus center Take time to view exhibits
1:00 – 2:00 Designing Pollinator Support Plantings: Think Like a Bee Dr. Lois Berg Stack, University of Maine, Northern New England Pollinator Habitat Working Group
Dr. Berg Stack will help us to think like a bee when designing pollinator support plantings. Effective pollinator support plantings provide flower resources, nest sites and water. Good site assessment allows for the selection of plants that complement existing resources, and good process can produce an effective long-term resource that requires limited maintenance.
2:00 – 2:10 Break
2:10 – 3:00 PM Neonicotinoids in Agriculture and Landscapes: Do They Harm Honey Bees or Native Bees? Dr. Kim Stoner, The Connecticut Agricultural Experiment Station
For 10 years, controversy has been swirling around the possible effects of neonicotinoids on bees. Dr. Stoner will talk about what we have learned and what we still don’t know about routes by which bees could be exposed to these systemic insecticides and how bee health may be affected.
3:00 – 4:00 PM Creating a Bee-friendly Landscape: Protecting Bees from Pesticide Exposure Dr. Anne Averill, Department of Environmental Conservation, UMass
In addition to the neonicotinoids, what are the different classes of pesticides, what are their risks to pollinators, how do they interact with other stressors, and how can pollinators be protected from exposure? Guidelines on how to best manage pests while reducing the hazard to bees will be covered. Bees require an extensive safe landscape, so Dr. Averill will also address how to grow flowering plants that are safe in our yards. She will conclude with a broad look of how national and international programs address pollinator health and safety.
4 Pesticide Credits have been approved in all categories.
Pollinator Health for Agriculture and Landscapes Registration Deadline – March 21, 2015
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Registration includes coffee, parking pass & handouts
Make check payable to: University of Massachusetts
Return to: Attn: Ellen Weeks, Agriculture & Landscape Program
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Honey Bee Viruses, the Deadly Varroa Mite Associates
If your bees have Varroa, your bees have viruses.
Authors: Philip A. Moore, Michael E. Wilson, and John A. Skinner
Department of Entomology and Plant Pathology, the University of Tennessee, Knoxville TN
Date: August 21, 2014
Varroa mites (Varroa spp.) are a ubiquitous parasite of honey bee (Apis spp.) colonies. They are common nearly everywhere honey bees are found, and every beekeeper should assume they have a Varroa infestation, if they are in a geographic area that has Varroa (Varroa mites are not established in Australia as of spring 2014). Varroa mites were first introduced to the western honey bee (Apis mellifera) about 70 years ago after bringing A. mellifera to the native range of the eastern honey bee (Apis cerana). Varroa mites (Varroa jacobsoni) in eastern honey bee colonies cause little damage. But after switching hosts and being dispersed across the world through natural and commercial transportation of honey bee colonies, Varroa has became a major western honey bee pest since the 1980’s. Varroa mites (Varroa destructor) are now the most serious pest of western honey bee colonies and one of the primary causes of honey bee decline (Dietemann et al. 2012). A western honey bee colony with Varroa, that is not treated to kill the pest, will likely die within one to three years (Korpela et al. 1993; Fries et al. 2006).
Varroa Life History
Varroa mites attack honey bee colonies as an external parasite of adult and developing bees, by feeding on hemolymph (fluid of the circulatory system similar to blood), spreading disease, and reducing their lifespan. Evidence suggests that Varroa and their vectored viruses affect the immune response of honey bees, making them more susceptible to disease agents (Yang and Cox-Foster 2005). For more information on this topic see here. Mature female Varroa mites survive on immature and adult honey bees (worker, drone, and rarely queen), are reddish brown, and about the size of a pin head. Male mites are a smaller size and tan color, do not feed on bees, and are only found inside brood cells (Rosenkranz et al. 2010).
Varroa have two life stages, phoretic and reproductive. The phoretic stage is when a mature Varroa mite is attached to an adult bee and survives on the bee’s hemolymph. During this stage the mite may change hosts often transmitting viruses by picking up the virus on one individual and injecting it to another during feeding. Phoretic mites may fall off the host, sometimes being bitten when bees groom each other, or it may die of old age. Mites found on the bottom board of the hive or that fall though a screen bottom board are called the “natural mite drop”. But these mites that fall off of bees represent a small portion of the total mite population because the reproductive mites are hidden under cell cappings.
Image 1: Reproductive Varroa mite on a developing pupa (reddish oval) and two immature Varroa (opaque ovals). Credit: Abdullah Ibrahim (arrows added for emphasis)
The reproductive life stage of Varroa begins when an adult female mite is ready to lay eggs and moves from an adult bee into the cell of a developing larval bee. After the brood cell is capped and the larva begins pupating, the mite begins to feed. After about three days from capping, the mite lays its eggs, one unfertilized egg (male) and four to six fertilized (female) eggs (Rosenkranz et al. 2010). After the eggs hatch, the female mites feed on the pupa, mate with the male mite and the surviving sexually mature female mites stay attached to the host bee when it emerges as an adult. It takes six to seven days for a female mite to mature from egg to adult and it can live two to three months in the summer and five to eight months in the fall. Only mature female mites can survive outside of a brood cell (the phoretic stage), and on average a mite will produce 1.2 viable mature female offspring per worker cell invaded (Schulz 1984; Fuchs & Langenbach 1989). However, since the development time is longer for drone brood, the average viable offspring for a mite in a drone cell increases to 2.2 per cell invaded (Schulz 1984; Fuchs & Langenbach 1989). For more on Varroa life history see here.
One of the serious problems caused by Varroa is the transmission of viruses to honey bees which cause deadly diseases. Viruses found in honey bees have been known to scientists for 50 years and were generally considered harmless until the 1980’s when Varroa became a widespread problem. Since then, nearly twenty honey bee viruses have been discovered and the majority of them have an association with Varroa mites, which act as a physical and or biological vector (Kevan et al. 2006). Therefore controlling Varroa populations in a hive will often control the associated viruses and finding symptoms of the viral diseases is indicative of a Varroa epidemic in the colony. Viruses are however, the least understood of honey bee diseases. Emerging information of honey bee viruses continue to alter our understanding of the role viruses play in honey bee colonies (Genersch and Aubert 2010).
Viral Life History
Viruses are microscopic organisms that consist of genetic material (RNA or DNA) contained in a protein coat. Viruses do not acquire their own nutrients or live independently, and can only multiply within living cells of a host. An individual virus unit is called a virus particle or virion and the abundance of these particles in a host is called the virus titer. A virus particle injects itself in to a host cell and uses the cells’ organelles to make copies of itself. This process will continue without obvious change to the cell, until the host cell becomes damaged or dies, releasing large amounts of infective virus particles. All forms of life are attacked by viruses and most are host specific.
Honey Bee Viruses
Viruses of the honey bee typically infect the larval or pupa stage, but the symptoms are often most obvious in adult bees. Many of these viruses are consumed in pollen or the jelly produced by nurse bees that are fed to developing bees. Many viruses are also transmitted by Varroa. Varroa, when feeding on the hemolymph transfer the viruses directly into the open circulatory system, which reaches every cell in the insect body.
Honey bee viruses are not limited to honey bees. Honey bee viruses have been found in other non-Apis bee species, other colony inhabitants like small hive beetle, and in pollen and nectar (Andersen 1991; Bailey and Gibbs 1964; Genersch et al. 2006; Singh et al 2010). For more on honey bee pathogens found in native bees see here. Transfer of honey bee viruses from infected colonies to non-infected individuals or colonies can occur during foraging on common flowers or through robbing of weak or collapsed colonies (Singh et al 2010).
Identification of a virus is difficult due to the small size of particles. Expensive and often uncommon laboratory equipment is required for accurate diagnosis. However, symptoms of some viral diseases are more visible, especially with overt infection. A lack of symptoms does not rule out the presence of a virus. Viruses can remain in a latent form within the host, acting as a reservoir of infection, complicating diagnosis and control, and only becoming an outbreak when conditions are right.
Viral Prevalence in the United States
The USDA-APHIS National Honey Bee Pests and Diseases Survey has taken samples from honey bee colonies in over 27 states since the year 2009. Data from these surveys and other data are complied into a database with the Bee Informed Partnership and used to determine baseline disease level, determine the absence of exotic honey bee pests that have not yet been found in America, and to gauge the overall health of U.S. honey bee colonies. Results of virus presence from the 2013 survey are below (Figure 1). Deformed wing virus (DWV) and Black queen cell virus (BQCV) were present in over 80% of sampled colonies. Other viruses were much less common, but still present in 10-20 percent of colonies sampled. Of the viruses tested for presence, only slow bee paralysis virus (SBPV) was not found in the U.S
Figure 1: 2013 USDA-APHIS National Honey Bee Pests and Diseases Survey, Virus Prevalence Results (Virus abbreviations: BQCV=Black queen cell virus; DWV= Deformed wing virus; LSV2= Lake Sinai virus 2; ABPV= Acute bee paralysis virus; KBV= Kashmir bee virus; IAPV= Israel acute paralysis virus; CBPV= Chronic bee paralysis virus; SBPV= Slow bee paralysis virus)
Sacbrood, a disease cause by a virus, was the first honey bee virus to be discovered in the early 20th century and now has a recognized widespread distribution. It is perhaps the most common honey bee virus (Shen et al. 2005). This disease has been found in adult, queen, egg, and larval bees, in all forms of food, and in Varroa mites, suggesting a wide range of transmission routes. Although it is commonly found without serious outbreak, sacbrood is more likely to cause disease when the division of labor is less defined, in the early parts of the year before the nectar flow, or during prolong dearth (Bailey 1981). It often goes unnoticed since it usually infects only a small portion of brood, and adult bees will usually detect and remove infected larvae.
Image 2: Sacbrood infected pupa. Credit: Michael E. Wilson
The disease causes larvae to fail to shed their final skin prior to pupation, after the larva has spun its cocoon. Infected larvae remain on their back with their head towards the cell capping. Fluid accumulates in the body and the color will change from pearly white to pale yellow, with the head changing color first. Then, after the larva dies, it becomes dark brown with the head black (Image 2). Larvae that have ingested sufficient quantities of sacbrood in their food die after being sealed in their comb.
Sacbrood multiplies in several body tissues of young larvae but these larvae appear normal until cell capping. Each larva that dies from sacbrood contains enough virus particles to infect every larva in 1000 colonies (Bailey 1981). But in most instances, diseased larvae are quickly removed in the early stages of the disease by nurse bees. The cell cappings are first punctured to detect the disease, which a good sign of infection for the beekeeper look for (Image 6). Then, young worker bees remove the diseased larvae from the colony. Adult bees, although not susceptible to infection, become a harbor as the virus collects in the bee’s hypopharyngeal glands, which are used to produce larval jelly (Bailey 1981). These infected adult bees, however, cease to eat pollen and soon stop tending larvae. They will become foragers more quickly in life than usual and tend to collect nectar instead of pollen (Bailey 1981). Nectar that contains the virus becomes diluted in the colony when mixed with nectar from other foragers. Whereas pollen, is collected and compacted into the “pollen basket” and deposited intact into a cell. Dilute virus containing nectar is less likely to cause infection than when the virus is concentrated in a pollen pellet. Therefore use caution when transferring frames with pollen among colonies. Little is known of the other transmission routes: through Varroa mites, between workers, from bee feces or through transovarial transmission (from queen to egg). Sacbrood usually subsides in late spring when the honey flow begins, but if symptoms persist, requeening with hygienic stock is recommended (Frazier et al. 2011).
Deformed Wing Virus (DWV)
Deformed wing virus is common, widely distributed, and closely associated with Varroa mites. Both the virus titers and prevalence of the virus in colonies are directly linked to Varroa infestations (Bowens-Walker et al. 1999). In heavily Varroa infested colonies, nearly 100 percent of adult workers may be infected with DWV and have high virus titers even without showing symptoms (de Miranda et al. 2012). DWV is strongly associated with winter colony mortality (Highfield et al 2009; Genersch et al 2010). Control of DWV is usually achieved by treatment against Varroa, After treatment a gradual decrease in virus titers occurs as infected bees are replaced by healthy ones (Martin et al 2010). DWV can be found in all castes and life stages of honey bees and will persist in adults without obvious symptoms. DWV is also transmitted through food, feces, from queen to egg, and from drone to queen (de Miranda et al. 2012).
Image 3: Adult bees with deformed wings resulting from DWV. Credit: Katherine Aronstein
Acute infections of DWV are typically linked to high Varroa infestation levels (Martin et al 2010). Covert infections (a detectable level of virus without damaging symptoms) can occur through transovarial transmission (Chen et al. 2004), and through larval food (Chen et al. 2006). Symptoms noted in acute infections include early death of pupae, deformed wings, shortened abdomen, and cuticle discoloration in adult bees, which die within 3 days causing the colony to eventually collapse. Not all mite infested pupae develop these symptoms, but all adult honey bees with symptoms develop from parasitized pupae. Bees infected as adults can have high virus titers but do not develop symptoms. DWV may also affect aggression (Fujiyuki et al. 2004) and learning behaviors of adult bees (Iqbal and Muller 2007). DWV appears to replicate in Varroa, making it a biological as well as physical vector. Infection of pupae may be dependent on DWV replication in Varroa prior to transmission. Winter colony mortality is strongly associated with DWV presence, irrespective of Varroa infestation. This suggests that Varroa infection should be reduced in a colony far in advance of producing overwintering bees, to ensure reduction in DWV titers. DWV is closely related to Kakugo Virus and Varroa destructor Virus 1, which together form the Deformed Wing Virus Complex (de Miranda et al. 2012).
Black Queen Cell Virus (BQCV)
Black queen cell virus is a widespread and common virus that persists as asymptomatic infections of worker bees and brood. Although generally understood as being asymptomatic in adult bees, Shutler et al. (2014) found BQCV to be associated with the symptom K-wing, where the wing pair is disjointed and more perpendicular to one another. Queen pupae with symptoms display a pale yellow sac-like skin similar to sacbrood. The pupae rapidly darken after death and turn the wall of the queen cell dark brown to black. Symptomatic drone pupae have also been observed. Unlike other viruses that are associated with Varroa, BQCV is strongly associated with Nosema apis and little evidence supports its co-occurrence with Varroa, although, BQCV has been isolated from Varroa (Ribière et al. 2008). Nosema disease affects a bee’s mid gut, increasing susceptibility of the alimentary tract to infection by BQCV. BQCV can be orally transmitted to adults only when Nosema has co-infected (Ribière et al. 2008). It can also be transmitted by injection to pupae. BQCV has a seasonal relationship similar to Nosema, with a strong peak in spring. Because of the seasonal occurrence with Nosema, queen rearing operations who produce queens in the spring are susceptible to BQCV (Ribière et al. 2008).
Image 4: Dysentery on the front of a hive is a symptom but not indicative of Nosema disease. Credit: Michael E. Wilson
Chronic Bee Paralysis Virus (CBPV)
Chronic bee paralysis virus was one of the first honey bee viruses to be isolated. It is unique among honey bee viruses in that it has a distinct particle size and genome composition. It is also the only common honey bee virus to have both visual behavior and physiological modifications resulting from infection. Symptoms of the disease are observed in adult bees displaying one of two sets of symptoms called syndromes (Genersch & Aubert 2010). Type 1 symptoms include trembling motion of the wings and bodies of adult bees, who are unable to fly, and crawl along the ground or up plant stems, often clustering together. The bees may also have a bloated abdomen, causing dysentery and will die within a few days after displaying symptoms.
Type 2 symptoms are greasy, hairless, black adult bees that can fly, but within a few days, become flightless, trembling, and soon die (Image 5). Both of these syndromes can occur within the same colony. Severely affected colonies, often the strongest in an apiary (Ribiere at al. 2010), quickly lose adult workers, causing collapse and often leaving few adult bees with the queen on unattended comb (Bailey & Ball 1991). These symptoms, however, are similar and often confused with other honey bee maladies including Nosema apis, colony collapse disorder (CCD), tracheal mites, chemical toxicity, and other viruses.
Image 5: Bees with CBPV type 2 symptoms: greasy and hairless. Credit: The Food and Environment Research Agency (Fera), Crown Copyright
Transmission of the virus primarily occurs through direct body contact, although oral transmission also occurs but is much less virulent. Direct body transmission happens when bees are either crowded or confined within the hive for a long period of time (due to poor weather or during long-distance transportation) or when too many colonies are foraging within a limited area, such as a monoculture of sunflower with high honey bee colony density (Genersch & Aubert 2010). In both instances, small cuts from broken hairs on an adult bee’s cuticle and direct contact with infected adult bees spreads the virus through their exposed pores; if this occurs rapidly and enough adult bees are infected, an outbreak with colony mortality will occur. Feces from infected bees within a colony can also spread the disease, and other transmission routes are still being investigated, including possible Varroa transmission. The virus is widespread and an outbreak can occur at any time of year. Spring and summer are the most common seasons for mortality from the virus, but it will persist in a colony year-round without displaying any overt symptoms (de Miranda et al. 2012).
Two new viruses related to CBPV with no yet described symptoms are Lake Sinai virus 1 (LSV1) and Lake Sinai virus 2 (LSV2) (Runckel et al. 2011). New molecular tools have allowed researchers to identify the presence of these and other new viruses and their seasonality in test colonies. Little else is know of the Lake Sinai viruses, including its pathogenic or epidemiological significance. Other described honey bee viruses that were discovered before the advent of molecular techniques have no genomic data to reference; therefore newly discovered viruses may in fact be the already discovered viruses of the past such as Bee virus X and Y, Arkansas Bee Virus or Berkeley Bee Virus (Runckel et al. 2011).
Acute Bee Paralysis Virus Complex
Acute bee paralysis virus (ABPV), Kashmir bee virus (KBV), and Israel acute paralysis virus (IAPV) are a complex of associated viruses with similar transmission routes and affect similar life stages. These viruses are widespread at low titers and can quickly develop high titers due to extremely virulent pathology. Frequently associated with colony loss, this virus complex is especially deadly when colonies are heavily infested with Varroa mites. (Ball 1989; Genersch 2010, Genersh et al. 2010). These viruses have not been shown to cause symptoms in larval life stages, but show quick mortality in pupae and adult bees.
Acute Bee Paralysis Virus (ABPV)
Acute bee paralysis virus was accidentally discovered when CBPV was first isolated. ABPV displays similar symptoms as CBPV however the acute adjective describes a bees’ more rapid mortality compared to CBPV. Unlike CBPV, ABPV virulence is directly related to Varroa infestation. APBV is transmitted in larval jelly from asymptomatic infected adult bees to developing larva or when vectored by Varroa mites to larvae and pupae. ABPV is common and typically cause covert infections (no obvious symptoms) when transmitted orally from adult to developing bee. It takes about one billion viral particles to cause death via ingestion, but when vectored by Varroa and directly injected into the developing bee’s hemolymph, only 100 virus particles will cause death (Genersch & Aubert 2010). When the virus is picked up by Varroa, the transmission rate to pupae is between 50 and 90 percent. The longer the feeding period of Varroa, the greater the transmission rate will become. (Genersch & Aubert 2010). Pupae infected with ABPV die before emerging, making the appearance of paralysis symptoms less obvious. The decline in emerging bees causes a colony to dwindle towards collapse. A colony infected with an ABPV epidemic will die within one season (Sumpter and Martin 2004).
Kashmir Bee Virus (KBV)
Kashmir bee virus has widespread distribution and is considered the most virulent of honey bee viruses under laboratory condition (Allen and Ball 1996). When KBV is injected in to adult bee hemolymph, death occurs in just 3 days (de Miranda et al. 2012). KBV does not cause infection when fed to developing bees, but does persist in adult and developing bees without any obvious symptoms. When Varroa mites transmit the virus, it becomes deadly to all forms of the bee lifecycle but displays no clearly defined symptoms. Even with moderate levels of mite infestation, KBV, like ABPV, can kill colonies (Todd et al. 2007). Control of Varroa mites is necessary to prevent colony losses from KBV.
Israeli Acute Paralysis Virus (IAPV)
Symptoms of IAPV are similar to ABPV and CBPV including: shivering wings, darkened hairless abdomens and thoraxes, progressing into paralysis and death. IAPV is found in all life stages and castes of bees. IAPV and other viruses were found to be strongly associated with colony collapse disorder (CCD) in the United States, but no direct relationship between the viruses and CCD has yet been shown (Cox-Foster et al. 2007). IAPV is extremely virulent at high titers, as when vectored by Varroa and is covert at low titers.
Slow Bee Paralysis Virus
In contrast to ABPV, which produces symptoms in a few days after infection, SBPV induces paralysis after 12 days, and only on the two fore (anterior) legs. SBPV persists as a covert infection and is transmitted by Varroa to adults and pupae. The disease will kill adult bees and eventually the entire colony (de Miranda et al. 2012). Prevalence of the virus is limited. It has not been found in the U.S., but has been found in England, Switzerland, Fiji and Western Samoa and only in Britain has SBPV been associated with colony deaths (Carreck et al. 2010).
Most pathogens invade the digestive system through oral ingestion of inoculated food. These pathogens infect the mid gut epithelial cells, which are constantly being replaced and are protected by membranes and filters which confine the pathogen to gut tissues. Parasites that infect gut tissue like Nosema apis and Nosema cerana can create lesions in the epithelium that allow a virus like BQCV to pass into the hemolymph and infect other cells in the body. In contrast the external parasite Varroa destructor feeds directly on bee hemolymph providing an opening in the cuticle for viruses to enter. Most virus infections rarely cause infection when ingested orally, but only a few virus particles are necessary to cause infection when injected directly into the hemolymph. Many viruses can be directly transmitted by Varroa mites, such as: DWV, those in the acute bee paralysis virus complex, and slow bee paralysis virus. Other viruses, like sacbrood, have been detected in Varroa mites but Varroa has not been shown to directly transmit the virus. Some viruses, like DWV, have been shown to directly multiply in Varroa mites, however in most cases we don’t know the exact relationship of Varroa mites to viruses or enough about how transmission occurs from mites to bees. Knowledge about the presence, role, and transmitting routes of these viruses in native bees, and other potential non-Varroa transmission routes is also lacking in detail, complicating recommendations for control. Research does show viruses clearly affect honey bee health and warrant attention from the beekeeper and researcher alike.
Viruses persist in normal, healthy colonies, only to explode during times of stress. Many viruses are only damaging when in combination with another stressor like Varroa or Nosema. Active, integrated management of Varroa and other stressors is essential to minimizing virus titers. To learn more about reducing stressors with best management practices see here.
Routinely inspect your colonies for possible disease. Have a thorough knowledge of symptoms and identify when colonies are slow to build up or have sporadic brood patterns, indicating brood has been pulled out and removed (Image 6). If you suspect you have a disease, take a sample and send it to be identified. For more information on submitting a sample for diagnosis see here.
Image 6: Punctured cell cappings that indicate adult bees have detected a brood disease (note DWV infected adult bee). Credit: The Food and Environment Research Agency (Fera), Crown Copyright (Arrows added for emphasis)
Other future avenues of control include breeding hygienic bee strains that detect brood diseases and remove infected individuals from colonies or breeding of resistance to Varroa infestation. Specific resistance to viruses are not yet considered in most breeding programs. There is evidence of specific viral resistance in honey bees, and there has been at least some attempt to breed resistance to IAPV. For more on this topic see here.
Another promising research area for controlling honey bee viruses in the use of gene silencing called RNAi. The private bee research company Beeologics, as well as public and private university researchers are developing this method and a consumer product may be available in the near future as RNAi technology continues to become more efficient and inexpensive. For more on this topic see here.
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Thank you to Jay Evans (USDA-ARS) for review of this article
Pollinating Highbush Blueberries
Investment in this critical component of blueberry production is essential for profitable yields
Pollinating Highbush Blueberries
Investment in this critical component of blueberry production is essential for profitable yields
Rufus Isaacs, Jason Gibbs, Emily May
Department of Entomology, Michigan State University
Eric Hanson and Jim Hancock
Department of Horticulture, Michigan State University
Northern highbush blueberries (Vaccinium corymbosum) are common throughout the northern U.S. states and Canada, and are native to eastern North America. They require pollination to ensure that flowers present at bloom turn into large, harvestable berries later in the season. Pollination is achieved by the movement of pollen by bees.
By planning ahead for how fields will be pollinated, growers can help ensure they receive the maximum return on their investments in land, bushes, and other management inputs. Given the high per-acre input costs of blueberry production, spending money to ensure high levels of pollination makes sound business sense. Other things being equal, well-pollinated fields have larger berries, higher yields, and more even ripening than fields with sub-optimal pollination.
Across Michigan’s blueberry industry, most pollination is by managed honey bees that are brought to fields in hives. Many of these colonies have been overwintered in warmer states, and they arrive back in Michigan as fruit crops start blooming in southwest Michigan. Bumble bee colonies can also be purchased for placement in fields, and there are many other wild bee species that nest in and around crop fields. By combining these pollinators into an Integrated Crop Pollination strategy, the risk of poor pollination may be minimized.
Pollen is moved by bees
For pollination to occur, sufficient compatible blueberry pollen must be moved from the male part of flowers (anthers) to the female part (stigma) while the flowers are receptive. Bees are responsible for this movement of pollen, so blueberry pollination depends on having enough bees active in the field during bloom to deliver pollen. Each flower must be visited once by a bumble bee or most native bees, or three times by honey bees to get enough pollen so that berries will grow to maximum size. There can be 10 million flowers per acre, so there is a lot of work for bees to do!
The pollen produced by blueberry flowers is relatively heavy and doesn’t waft on the wind. It is held inside the flower by salt shaker-like structures called anthers until bees visit. They may release the pollen by jiggling the flower with their legs, as is the case for honey bees. Bumble bees and some other native bees are better adapted to release the pollen using a vibration behavior known as “buzz pollination”. When the bees shake the anthers the pollen collects on their bodies. As the bees move from flower to flower, pollen grains are transferred to the stigma. Flowers are receptive to pollen immediately on opening, and their chance of turning into a berry declines after 3 days, with flowers unlikely to turn in to fruit after 5-6 days. Once compatible pollen is deposited on the stigma, the pollen germinates and fertilizes the ovules which produce the tiny seeds. Fertilized seeds release hormones that stimulate berry growth, leading to larger berries.
Figure 1. Comparison of blueberries picked on the same day in July from clusters that had either been bagged to exclude pollinators (left) or were uncovered during bloom (right) allowing bees to visit. Both sets had the same number of blooms during flowering in May. Credit: Rufus Isaacs
Things to know before planting
Northern highbush blueberry bushes can produce berries even when there is no or limited pollen deposition by bees. This means that some proportion of the flowers can turn into berries, even if there are poor pollination conditions or low bee activity during bloom. However, these berries will be small, slow to ripen, may drop off early, and most would not be considered marketable (Figure 1, left). To reach maximum potential yield, it is important that the flowers are visited by bees during bloom to transfer sufficient pollen to the stigma while the flower is still viable so that fertilization can occur, leading to seed set, berry expansion, and larger berries (Figure 1, right). If designing a blueberry field of any appreciable size (over a few acres), make sure there will be space for a beekeeper to drop hives on pallets near the field.
Table 1. Variation among highbush blueberry cultivars in the need for a pollinizing cultivar to provide cross-compatible pollen during bloom.
Dependence on a pollinizing cultivar
Low: no pollinizer needed
Duke, Draper, Bluejay, Nelson, and Rubel
Intermediate: pollinizer beneficial
Bluecrop, Legacy, Jersey, Liberty, Elliott, and Aurora
High: pollinizer needed
Brigitta, Spartan, Chippewa, Polaris, and Toro
For some cultivars it is not sufficient just to get high rates of pollen transfer from bees, because the type of pollen can be important. Some cultivars benefit from the transfer of cross-compatible pollen, meaning that the field should be designed to have a combination of cultivars that bloom around the same time and that are compatible. For cultivars dependent on having cross-pollination for full yields, this can provide a 10-20% increase in yield from the improved fruit set and berry size. Table 1 provides a guide to cultivars and their level of dependence on this cross pollination for full yields. However, many popular northern highbush blueberry cultivars are self-fruitful, meaning they can be fertilized by pollen from the same cultivar (High group in the table), and this is one reason why solid blocks of some cultivars can be highly productive. Other cultivars are intermediate, meaning that a benefit can be gained by interplanting with another cultivar, but for many commercial settings growers might consider the increased complications in management outweigh the benefits.
In a third group, cross-pollination is needed, and this is achieved by bees moving pollen between cultivars as they fly from row to row. In this situation, planting fields with alternating blocks of co-blooming and compatible cultivars ensures cross-pollination. While alternate rows of two compatible cultivars would be the best for pollination, it would also cause difficulties with harvesting and spraying. Alternating blocks of up to eight rows allows pollen exchange and is easier to manage. Alternating blocks of larger sizes will result in too few exchanges between cultivars that need cross pollination. Before purchasing blueberry plants, check with your nursery to determine the need for planting fields with alternating cultivars.
Using honey bees for blueberry pollination
Wait until bloom has started to bring in bees. Flowers of blueberries are generally less attractive to honey bees than other flowers due to the relatively low nectar reward. Because of this, it is best to bring in bees once the crop has started to bloom so that bees forage more on blueberries than other flowers (Figure 2). If brought in too early, bees may learn to forage elsewhere reducing their focus on your crop fields. Move bees into blueberry fields after 5% bloom but before 25% percent of full bloom. Placement near to the blueberry field can also help to keep them focused on the crop. Still, some cultivars (notably Jersey) have low attractiveness, and bees may still fly over this cultivar to reach another.
Figure 2. A honey bee drinking nectar from a blueberry flower. This is the workhorse of blueberry pollination, and to achieve high yields the fields must be stocked with sufficient numbers of healthy colonies during bloom to ensure there are enough bees for sufficient transfer of pollen between flowers. Credit: Jason Gibbs
Renting healthy colonies. If you are renting honey bee hives, you should expect to receive healthy and vigorous bees. A healthy colony contains around 30,000 worker honey bees and will have six frames of brood. Having weak hives will affect how much pollination the fields receive, so it is worth taking time to ensure you have strong hives. If you suspect weak colonies, talk to your beekeeper about getting additional hives or replacing them. One strong hive of 30,000 bees will provide better pollination than two 15,000 bee hives because there will be more worker bees that fly to visit flowers. One way for growers to ensure they receive strong colonies is to establish a pollination agreement that lays out the grower’s expectations. This can include the strength of the colonies and how quickly the colonies will be taken out of the field after bloom. Example pollination contracts are available online.
Honey bee stocking densities. There have been many changes in blueberry production and in bees over the past few decades, and yet many people still refer to bee stocking recommendations published in 1992. We consider those to be suitable for fields with lower bloom density, such as in a field affected by frost or when it is still establishing, and these can also be used in small fields surrounded by natural lands that will have higher populations of wild bees. However, if fields have a high flower density as some of the newer cultivars and intensive production systems provide or if field sizes are large without wild habitat nearby, then these recommendations are too low. The last few decades have also seen the loss of feral honey bee colonies due to the parasitic Varrroa mite, so those colonies are no longer contributing to blueberry pollination. All of these factors can make fruit production more dependent than ever on managed bees, so it is important to stock fields with sufficient bees to supply enough visits to flowers while they are most viable (i.e. in the first three days after opening). A final point to make here is that if the weather is hot during bloom and flowers open quickly, this increases the chance that they will not get visited before they lose viability. Higher stocking densities can counteract this potential limiting factor.
Table 2. Recommended stocking density of honey bees for highbush blueberry pollination. Cultivars have varying rates of need for honey bees, and within each group we show a range of hives per acre to stock at, ranging from low rates for use in young, frost-damaged, or small fields to high rates for use in mature, healthy, or large fields. Adapted from Pritts & Hancock, 1992.
Honey bee hives/acre
Weymouth, Bluetta, Blueray
Elliot, Coville, Berkeley, Stanley
Research and experience in blueberries has shown variation across northern highbush cultivars in their needs for bee pollination (Table 2), due to the relative attractiveness of different cultivars and their degree of self-compatibility. The table below shows a range of stocking densities from the lower rates recommended two decades ago to the updated double rate that we consider the required stocking density for fully productive modern fields. This shows 5 hives per acre for Jersey and Earliblue, but some growers are using up to 8 colonies per acre to ensure good pollination if spring weather is cool and there are only a few good days for honey bee activity. These higher stocking densities can also be considered a form of pollination insurance, to make sure that whatever the spring brings there will be the best chance of good pollination.
A rule of thumb is that you'll need 4 to 8 honey bees per bush in the warmest part of the day during bloom to get blueberries pollinated. Also, if you see flowers turning brown and discolored on the bush, pollination was not sufficient – in well-pollinated fields the corollas fall off when they are still bright white. Check your fields this season, and if needed you can try to get additional hives from a beekeeper, or plan on increased stocking next spring.
Hive placement. If possible, place the colonies in sheltered locations with the entrances facing east or south. This will encourage earlier activity as the hive warms in the morning sun. Hives should be spread out around the farm to maximize floral visitation, with a maximum of 300 yards between hives. Placement in an open area slightly away from the edge of the fields also reduces the risk of pesticide drifting onto colonies of the colonies being disturbed by a tractor.
Using bumble bee colonies
Bumble bees are very efficient at pollinating blueberry, with activity at lower temperatures than honey bees, faster visits to flowers, and higher rates of pollen transfer per flower visit. A single visit of a bumble bee to a blueberry flower can deposit sufficient pollen to get full pollination, whereas three visits are needed by honey bees.
Figure 3. Bumble bees are efficient pollinators of blueberry, so they should be encouraged on the farm. They can also be purchased from commercial suppliers and their colony boxes placed near fields to provide crop pollination. Credit: Jason Gibbs
The common Eastern bumble bee, Bombus impatiens (Figure 3), has been reared for use as a crop pollinator. These insects are available commercially and can be shipped directly to the farm in eastern US states and Canada. Koppert is one supplier based in Michigan that provides the bees in Quads, each containing four colonies housed within a weather-proof box. Our evaluations with this species in commercial Jersey fields found they provided comparable yield and fruit set to honey bees, when tested in small fields at the recommended stocking density of 3 colonies per acre. Growers may also purchase bumble bees to integrate with honey bees, thereby diversifying pollination sources. This approach should help ensure movement of pollen between flowers during conditions that are unsuitable for honey bees. Rearing bumble bees takes time so orders should be made 14-16 weeks in advance to guarantee delivery. Place Quads through the farm and well away from honey bee hives. A door on the box of the Quads can be used to collect the bees and move them before spraying.
Wild bee pollinators
While ants, butterflies, and hover flies will visit blueberry flowers to gather nectar, bees are the most effective at moving pollen. Over 150 wild bee species have been found in Michigan blueberry fields, and about ten of these were sufficiently abundant during bloom and carried enough pollen to be considered valuable crop pollinators. These bees do best in farms with flowers for them to visit outside the crop bloom period and in farms where there are some undisturbed areas for nesting (Figure 4), and farms can be managed to enhance their abundance.
Wild bees fall into several major categories, including: bumble bees, miner bees, sweat bees, mason bees, and carpenter bees. Bumble bees and some sweat bees form social colonies later in the summer, but in spring during blueberry bloom these are bees are in a solitary phase. Miner bees, mason bees and carpenter bees are solitary: each nest is built by a single female. Miner bees are abundant during the spring, and some species, such as Andrena carolina, are specialists on blueberries.
Figure 4. Many wild bee species require flowers to visit when the crop is not in bloom and areas of undistubed soil for nesting. Top, a miner bee gathering pollen from an early spring flower; bottom, a sweat bee searching for a place to nest in the soil. Credit: Jason Gibbs
Wild bees nest in different areas in and around blueberry fields. Miner bees and most sweat bees make underground nests. A female bee tunnels into the soil, preparing brood cells for her young on side branches from the main tunnel. Pollen and nectar is collected and shaped into a ball placed in a each cell. A single egg is laid on each pollen ball which provides food for the developing larva. These bees need untilled soil and have been seen nesting underneath blueberry bushes in the weed-free strip. Thick layers of mulch can prevent ground nesting bees from digging tunnels. Some bees also nest in the undisturbed soil in nearby woods. Bumble bees also need undisturbed soil to nest in abandoned rodent burrows or grass tussocks, but they will also use old mattresses, compost piles, and other protected sites with small entrances. Finally some wild bees, such as carpenter bees, and some sweat bees, and mason bees prefer to nest in twigs, dead wood, or pre-existing cavities. Brambles, logs, and tree stumps in adjacent habitat and fence rows can be useful nesting sites for these bees.
In small blueberry fields surrounded by natural habitat, wild bees can provide the majority of pollination. However, as blueberry farm size and intensity increase, the high abundance of flowers and the small amount of natural area results in too few native bees for full pollination, and so growers rent honey bees. Still, by creating bee habitat that includes a mix of plants that bloom before and after blueberries growers can help support native bees as part of an Integrated Crop Pollination strategy. For more on native plants to support pollinators in the Great Lakes region, visit www.nativeplants.msu.edu. Every little bit of habitat will help, so consider this a long-term process of building bee habitat back into the farm landscape. The Natural Resources Conservation Service can provide cost share for growers interested in establishing pollinator habitat in their farms. See your local NRCS office for details of programs that can support this.
Pest management during pollination
Most insecticides have some level of toxicity to bees, and so there are restrictions on their use during bloom. Not spraying while honey bees are in the field is the most effective way to avoid any risk of poisoning, so monitoring for pest problems carefully before and during bloom can help minimize the need for pest control at this time of the season. However, insect outbreaks do occur and this time of the season is an important one for control of mummyberry, so if a pesticide application is necessary during bloom the compounds that are least toxic to bees should be used, with careful observation of the pollinator restrictions on the label. Two insecticides that can be applied during bloom for control of moth larvae in blueberry are products containing Bacillus thuringensis (Bt) (e.g. Dipel, Javelin), and the insect growth regulators Intrepid and Confirm.
The U.S. Environmental Protection Agency (EPA) has developed new pesticide labeling guidelines for certain insecticides, which limit their use where honey bees are present. This information is gradually being added to the labels of some insecticides, including neonicotinoids and the new product Exirel. Since these pesticides have never been labeled for use during bloom in blueberry, this is not a significant change but it provides more information. The EPA’s infographic can be downloaded from: www.epa.gov/pesticides/ecosystem/pollinator/bee-label-info-graphic.pdf.
If spraying during the bloom period, one of the most important things growers can do to minimize effects on bees is to apply when the bees are not foraging. Late evening is the best time to apply sprays during bloom, because the compounds have time to be absorbed and for the residues to dry before bees are active the following morning. Dust formulations must be avoided because particles can be picked up easily by the bees’ hairy bodies.
Recent research has also found that certain fungicides have effects on bees, harming their gut microbes and making them more susceptible to parasite infections. This can in turn result in reduced colony health and increased mortality. Follow the same basic principles of spraying only when necessary and when bees are not foraging to reduce the potential for harming bees during bloom.
More information and a list of pesticides with their toxicity to bees is available from a recently-updated extension bulletin from Oregon State University at http://bit.ly/OSU_ReduceBeePoisoning. This document also contains a list of insecticides and fungicides ranked by their relative risk to bees, and plenty of other good information on how to prevent bee poisoning. Another important aspect of reducing the chance for pesticide incidents during bloom is to have good communication with your beekeeper. This should start in the winter with a discussion about how many hives you plan to rent, where they should be put, and when they should be delivered and removed. A recent MSU article on how to minimize pesticide exposure to bees is posted here: http://msue.anr.msu.edu/news/minimizing_pesticide_exposure_to_bees_in_fruit_crops
Pollination is an essential component of growing blueberries. To attain high levels of fruit set with large evenly-ripening berries requires bees to deposit enough pollen on stigmas during bloom. This can be done by honey bees, other managed bees, and wild bees. As with pest management, reliance on one strategy may not be the most sustainable approach, so diversifying pollination sources can spread risk to ensure consistent pollination and profitable yields every year. Whichever bees are visiting flowers during bloom, ensuring the health and safety of these insects is an important part of maintaining good pollination. Follow label restrictions and practice good pollinator stewardship so they can provide the all-important transfer of pollen that will lead to large berries and high yields.
This article was first published by Michigan State University Extension. Development of the article was supported by MSU’s AgBioResearch, Project GREEEN, and the USDA-SCRI Integrated
Crop Pollination project (www.projecticp.org)
Managing Small Hive Beetles
What you can do to prevent or limit their damage
Author: Jon Zawislak, University of Arkansas, Division of Agriculture
The small hive beetle Aethina tumida (SHB) is an invasive pest of bee hives, originally from sub-Saharan Africa. These beetles inhabit almost all honey bee colonies in their native range, but they do little damage there and are rarely considered a serious hive pest.
It is unknown how this pest found its way into the U.S., but was first discovered to be damaging honey bee colonies in Florida in the late 1990s. It has since spread to more than 30 states, being particularly prevalent in the southeast. The beetles have likely been transported with package bees and by migratory beekeepers, but the adult beetles are strong fliers and are capable of traveling several miles at a time on their own.
In the United States these beetles are usually considered to be a secondary or opportunistic pest, only causing excessive damage after bee colonies have already become stressed or weakened by other factors. Infestations of beetles can put significant stress on bee colonies, which can be compounded by the stress of varroa mites and other conditions. If large populations of beetles are allowed to build up, even strong colonies can be overwhelmed in a short time.
Honey bee colonies appear able to contend with fairly large populations of adult beetles with little effect. However, high beetle populations are able to lay enormous numbers of eggs. These eggs develop quickly and result in rapid destruction of unprotected combs in a short time. There is no established threshold number for small hive beetles, as their ability to devastate a bee colony is related to many factors of colony strength and overall health. By maintaining strong bee colonies, and keeping adult beetle populations low, beekeepers can suppress the beetles’ reproductive potential.
Fig. 1. SHB adults are often observed in the hive with their head and antennae tucked down beneath the thorax. They are oblong in shape, around 6 mm long, and with variable coloration that ranges from tan to reddish-brown, dark brown or black.
Fig. 2. SHB larvae will grow to about 1/2" in length. They possess 3 pairs of well-developed legs, and have rows of short spines projecting from their bodies.
Adult SHB are 5-7 mm (1/4”) in length, oblong or oval in shape, tan to reddish brown, dark brown or black in color, and covered in fine hairs, but their size and appearance can be highly variable within a population. The adults are usually observed in the hive with their heads tucked down beneath the thorax, so that antennae and legs are often not apparent (Fig. 1). The larvae are elongated, cream-colored to slightly golden grubs, growing to 10-12 mm (1/2”). They may be mistaken for young larvae of the greater wax moth (Galleria mellonella). The two types of larvae can be differentiated by their appearance. Beetle larvae (Fig. 2) have three pairs of well-developed legs near the anterior end, while wax moth larvae have three pairs of legs near the anterior and four pairs of less-developed prolegs toward the posterior. SHB larvae also have numerous dorsal spines, which wax moth larvae are lacking. Both pests can be found simultaneously in the same hive, however.
Honey bees are not able to efficiently remove adult beetles from the hive, and their hard shells resist stinging. Rather, the bees are observed to pursue adult beetles across the combs. Beetles will seek cracks and crevices in which to escape from the bees, who in turn will imprison the beetles in these cracks, preventing them from escaping. The beetles have developed the ability to stimulate the mouth parts of worker bees with their antennae, similar to drones begging for food, and are able to trick their guards into feeding them. This behavior allows the beetles to survive in confinement for extended periods. Opening hives for inspections may free the beetles from their confinement.
Sometimes the SHB population becomes too large for the worker bees to protect against, and the beetle population can increase rapidly. This may happen due to weakening colony health or declining bee population, or due to beekeeper action. When swarming occurs, the number of bees available to patrol the interior of the hive is reduced, which may allow the beetle population to surge. When colonies are split, or nucs are created, the number of bees in the new colonies may be insufficient to protect against the beetle population. Mating nucs used in queen rearing may be particularly susceptible to SHB. Over-supering hives provides the beetles with excessive space in which to move and hide and provides additional oviposition sites, while increasing the area that the worker bees must patrol.
The use of grease patties for tracheal mite control, or the addition of protein supplement patties for spring build-up, may increase SHB infestations. Both adult and larval beetles are attracted to these patties as a food source. If patties are found to be infested with larvae, they should be removed immediately, and disposed of by wrapping them in several layers of plastic bags to prevent SHB from escaping.
The adult female beetles will lay egg masses in cracks and crevices around the hive, or directly on pollen and brood combs. Beetles may puncture the capping or wall of a brood cell and deposit eggs inside of it. A single female beetle can produce over 1000 eggs in her lifetime. Beetle eggs are similar in shape to those of honey bees, but approximately 2/3 the size. Eggs generally hatch in 2-4 days, and the larvae immediately begin to feed on pollen, honey, and bee brood. In 7-10 days, beetles complete their larval development and will exit the hive to pupate in the soil. The majority of larvae remain within about 180 cm (6’) of the hive they exit, but can crawl much longer distances if needed. Larvae will burrow up to 10 cm (4”) into the soil, where they remain 3-6 weeks to complete pupation. Within 1-2 days of emerging from the soil, adult beetles will seek out a host bee colony, which they locate by odors (Fig. 3).
The adults are strong fliers, and can disperse to other beehives easily. Beetles are also thought to travel with honey bee swarms. Individual beetles can live up to 6 months or more, and several overlapping generations of beetles can mature within in a colony in a single season. Beetle reproduction ceases during the winter, when adult beetles are able to overwinter within the bee cluster.
Fig. 3. Life Cycle of the Small Hive Beetle.
Economic damage from SHB occurs when the bee population is insufficient to protect the honey combs from the scavenging beetle larvae. When adult beetles first invade a colony, they may go unnoticed until their populations increase through reproduction or immigration. Both adult and larval beetles will prey upon honey bee eggs and brood.
When large numbers of beetle eggs hatch in weak colonies, the combs of honey can become “wormy” and take on a glistening, slimy appearance (Fig. 4). Unlike wax moths, these beetle larvae do not necessarily damage the combs themselves, and do not produce extensive webbing. Ruined honey can be washed from the combs, which may then be frozen for 24 hours to kill any beetles or eggs on them, and placed back onto a strong hive to be cleaned and repaired by the bees.
When large numbers of adult beetles defecate in the honey, they introduce yeasts, causing the honey to ferment and run out of the cells. In this case, the queen bee may cease laying, and the entire colony may abscond. Weak colonies are particularly vulnerable to attack, but even strong colonies can be overwhelmed by large populations of beetles. Nucleus colonies used for queen production or colony splits can be especially vulnerable to beetle attacks.
Beetles can create sudden problems if bee escapes are used prior to harvesting, and supers of honey are left virtually undefended by bees. If honey is removed from the hive, but not immediately extracted, beetles can invade the honey house and quickly ruin a large portion of a honey harvest. Wet cappings from recently extracted honey are also extremely attractive and vulnerable to beetle infestation. Honey contaminated by small hive beetles will be rejected by bees, is entirely unfit for human consumption, and should never be bottled or mixed with other honey for packing.
Fig. 4. Honeycombs infested with SHB larvae take on a glistening or "slimey" appearance. Honey contaminated by beetle larvae is unfit for consumption by either bees or humans.
Beetles are easily detected by visual inspection of colonies. When a hive is opened, adult beetles may be observed running across the underside of the outer cover, on either side of the inner cover, and on the top bars of frames. Also, beetles may be seen running across the surfaces of combs (Fig. 5). To detect beetles in the top hive body, open the hive and place the outer cover on the ground in a sunny spot, and place the top hive body into the cover (Fig. 6). Conduct normal colony inspection activities on the rest of the hive. If present in the top super, adult beetles will retreat from the sunlight, and after about 10 minutes you may lift the hive body and look for beetles in the cover. Beetles in the lower hive body will similarly retreat to the bottom board as the colony is disturbed.
Strips of corrugated cardboard, with the paper removed from one side, or pieces of corrugated plastic (obtained as scraps from a sign shop) can be placed on the bottom board at the rear of the hive. Adult beetles, fleeing from bees, may seek shelter in the small spaces of the corrugations, and can be easily seen. Bees may chew up and remove cardboard strips left in a hive for extended periods.
Varroa sticky boards are usually ineffective in detecting small hive beetles. Adult beetles prefer dark conditions, and will migrate toward the tops of hives that have screen bottoms, and may be more easily detected by placing corrugated strips on the top bars of the upper super or above the inner cover
Small hive beetle larvae are often found clustered together in corners of a hive or on frames. This behavior also differentiates them from wax moth larvae, which are found scattered throughout a hive. Older beetle larvae orient toward light sources, and in the honey house, a single fluorescent light near the floor may attract beetle larvae, which exit the hives when seeking a place to pupate. These larvae can be swept up and drowned in soapy water.
Surfaces of combs that appear slimy, or fermented honey bubbling from the combs, are positive signs of beetle activity. Fermented honey has an odor described as decaying oranges.
If you suspect the presence of hive beetles, you may contact your state apiary inspector to arrange a visit, or you may bring a specimen in alcohol to your local Cooperative Extension office for positive identification.
Fig. 5. Adult beetles may be seen running across the combs, often pursued by honey bees.
Fig. 6. To detect SHB in the top super of a hive, place it on the hive lid in a sunny spot for abotu 10 minutes. The bright light will drive the beetles down to the bottom. If present, adult beetles should be visible on the lid when the super is lifted.
Prevention is the most effective tactic of small hive beetle control. Chemical controls are available, but are of limited use. Good beekeeping management practices in the bee yard and in the honey house are sufficient to contain hive beetle problems in most cases. A combination of cultural and mechanical controls will usually help to maintain beetle infestations within a manageable range.
Keep bee colonies healthy and strong. Reduce stresses from diseases, mite parasitism, and other factors. Maintain and propagate bee stocks with hygienic traits that are better able to detect and remove pests and diseased brood. Eliminate, requeen, or strengthen weak colonies.
Use caution when combining colonies or exchanging combs and hive bodies, because beetles and their eggs can be introduced into other colonies, which can be overwhelmed. Making splits from heavily infested hives can cause a serious outbreak if insufficient numbers of bees remain to protect the hive. Avoid over-supering hives, which increases the area that the bees must patrol.
Maintain a clean apiary and honey house to reduce attraction to beetles. Avoid tossing burr comb onto the ground around hives, which may attract pests. Adult beetles tend to prefer shady locations. If possible, place hives where they receive direct sunlight at least part of the day. Keep hives and frames in good condition. Warped, cracked and rotten hive bodies provide beetles with many places to hide, and make them more difficult to detect by bees or beekeepers. When debris is left to accumulate on a bottom board, beetle larvae can complete pupation inside the hive. Regular cleaning or use of screen bottom boards can prevent this build-up of debris.
Honey that is removed from a colony should be extracted within 1-2 days. Wax cappings are an attractive food for beetles, and should be processed quickly or stored in sealed containers. Honey supers can be removed from weak colonies to lessen the territory of combs that the bees must patrol. If not ready for extraction, these supers can be placed on strong colonies, in a manner similar to protecting them from wax moth infestations. However, if small hive beetles or their eggs are present on the combs, the addition of these beetles can be sufficient to cause the strong colony to collapse. Honey supers can be frozen at -12°C (10°F) for 24 hours to kill all stages of beetles before transferring supers to a strong colony. Store empty supers under conditions of good air circulation and less than 50% humidity.
Pollen traps should not be left on heavily infested hives for extended periods. The unprotected pollen can serve as a substantial protein source for beetles, as well as a protected breeding site.
Utilize mechanical traps in the hive to reduce the number of adult beetles that can produce eggs, while also reducing the need for pesticides.
Mechanical Traps for eliminating Small Hive Beetles
Numerous mechanical trap designs are available for use in the hive to control the adult SHB population. Most traps kill beetles by drowning them in vegetable oil or mineral oil. The traps have small openings that allow beetles to enter, but restrict the larger honey bees. Some traps utilize a fermenting bait to attract the beetles into the trap, but beetles will enter non-baited traps to escape from the bees. By maintaining a manageable adult beetle population in the hive, beekeepers can often prevent a major infestation of beetle larvae, which cause the the most destruction.
The West Trap is placed on the bottom board, and requires a wooden shim to maintain proper space beneath the frames. It contains a shallow pool of oil, and is covered by a slatted screen that excludes bees. Adult beetles enter the trap from above, to escape from bees, and fall into the oil and drown. Hives must be kept extremely level for these traps to be effective. These traps preclude the use of screen bottom boards for ventilation.
The Hood Trap attaches to a standard bee hive frame. It has a compartment filled with apple cider vinegar as an attractant, and compartments filled with mineral oil, which drown the beetles as they enter. A potential drawback of this design is the empty space around the trap, which bees will often fill with drone comb, increasing a problem with varroa if left unattended. This area of drone comb, however, can be regularly removed and disposed of when about 50% of the drone cells are capped, which can effectively trap and remove a portion of reproducing varroa mites before they can emerge.
The Freeman Beetle Trap is similar to the West Trap in function. It replaces the bottom board with a 3 mm (1/8”) screen mesh, as used for varroa control. An oil-filled tray is inserted into a compartment below the screen. Adult beetles enter the trap to escape from bees, and fall into the oil and drown. Wandering beetle larvae may also fall into the trap as they attempt to exit the hive to pupate. These traps can passively eliminate some varroa mites as well. Hives must be kept level for these traps to work.
A variety of beetle traps, such as AJ’s Beetle Eater and Beetle Jail Jr., consist of shallow oil-filled troughs with slotted lids. These traps are suspended between frames of brood or honey. Adult beetles enter the traps to hide from bees, and are drowned in the oil. These types of traps are inexpensive and easy to use, but may need to be emptied and refilled regularly. Over time the bees may tend to propolize over some of the openings. Some manufacturers suggests placing a small sheet of vinyl across the top of the trap to prevent propolizing, but this may provide the beetles with sufficient cover without entering the trap. Similar in design and function, Cutt’s Beetle Blasters are disposable, and can be discarded when full of beetles.
Beetlejail traps are designed to prevent hive beetles from invading a bee hive, by trapping them as they seek to enter, and drowning them in oil.
Sonny-Mel traps are homemade, consisting of a small plastic sandwich box, with 3mm (1/8”) holes. The bottom of the trap contains a shallow layer or layer of mineral oil, and a smaller container (usually a small plastic jar lid or bottle cap) of liquid bait. To make a bait, combine 1 cup water, 1/2 cup apple cider vinegar, 1/4 cup sugar, and the peel of 1 ripe banana (chopped in small pieces); allow to ferment for 1-2 days. These traps are placed on the top bars of the upper super, and require the addition of a wooden frame to provide space for the trap.
This summary is provided as a convenience for the reader. The mention of any brand name or commercial product does not constitute or imply any endorsement, nor discrimination against similar products not mentioned.
The pupal stage is a vulnerable time in the beetle life cycle. Slightly moist, loose, sandy soil is optimal for their development. Locating colonies on hard clay or rocky soil, rather than light sandy soil, can reduce the number of beetle larvae that successfully pupate. If numerous larvae are discovered in the hive, the soil around the colony can be treated with a permethrin drench to prevent the larvae from pupating, killing them in the soil. Use with caution, as permethrin is highly toxic to bees!
Prepare the site by removing fresh water sources and feeding stations. Mow vegetation around the hives to be treated, to allow the solution to directly contact the soil. Mix 5 ml (1 teaspoon) GardStar® 40% EC into 1 gallon of water (enough to treat 6 hives). To avoid contaminating the bee hive surface with pesticide drift, do not use a sprayer. Apply the solution using a sprinkler can. Thoroughly drench the area in front of the hive (and beneath it, if screen bottom boards are used), wetting an area 18-24 inches around the hive, ensuring that wandering beetle larvae will contact treated soil.
Application should be made late in the evening when few bees are flying. Do not contact any surface of the bee hive or landing board with insecticide. USDA testing indicates that permethrin binds to the soil and remains active for 30-90 days, depending on soil type, pH, and moisture content. Reapply as needed.
Permethrin is corrosive and can cause irreversible eye damage. Avoid contact with eyes, and wear proper eye protection during application. Read and follow all label instructions for the legal and appropriate use of any pesticide.
Studies have indicated that soil-dwelling entomopathogenic nematodes have potential to provide some control of pupating SHB. Some species of these nematodes are commercially available from biological suppliers for use in the soil under and around bee hives. It is not yet evident whether these nematodes are effective in all soil types, or if they can persist through drought or overwintering conditions in all areas, however, they may be useful as part of an overall integrated pest management plan.
Because of insufficient scientific evidence on the efficacy of this control method, specific recommendations for the use of nematodes cannot be made at this time.
Chemical Treatment in the Hive
The chemical coumaphos (sold as Checkmite+ for varroa control) is the only pesticide registered for in-hive treatment of small hive beetles. Consult your local Cooperative Extension office or Department of Agriculture for specific recommendations in your state.
- Use 1 strip of Checkmite+ per hive.
- Treatments should not be applied while surplus honey is being collected.
- Do not place honey supers on a hive until 14 days after Checkmite+ strip has been removed, or treat hives after honey has been harvested.
- Prepare a 4x4” piece of corrugated cardboard by removing the paper surface from one side, and cover the smooth side with duct tape or shipping tape to prevent the bees from tearing up or removing it.
- Cut a single strip of Checkmite+ in half and staple both pieces to the corrugated side of the cardboard.
- Chemical resistant gloves must be worn while handling strips – do not use leather bee gloves when handling this product!
- Insert the cardboard square, strip side down, onto the center of the bottom board, or above the inner cover if screen bottom board is used.
- Beetles will seek shelter in the corrugations and contact the strip. Bees should not be able contact the pesticide.
- Leave treatment strips in place for a minimum of 42 days, but no more than 45 days.
- Dispose of strips according to label directions.
- Do not treat the same colony with coumaphos more than 2 times in one year.
These instructions are a presented as a general guideline. Users are responsible for reading and following all label instructions for the legal and appropriate use of any pesticide.
- Cabanillas, H. E. & P. J. Elzen. 2006. Infectivity of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) against the small hive beetle Aethina tumida (Coleoptera: Nitidulidae). Journal of Apicultural Research 45: 49-50.
- Ellis, J.D., C.W.W. Pirk, H.R. Hepburn, G. Kastberger & P.J. Elzen. 2002. Small hive beetles survive in honeybee prisons by behavioral mimicry. Naturwissenschaften 89: 326-328.
- Ellis, J.D., S. Spiewok, K.S. Delaplane, S. Buchholz, P. Neumann, & W.L. Tedders. 2010. Susceptibility of Aethina tumida (Coleoptera: Nitidulidae) larvae and pupae to entomopathogenic nematodes. Journal of Economic Entomology 103: 1-9.
- Hood, W.M. 2004. The small hive beetle, Aethina tumida: a review. Bee World 85: 51-59.
- Sanford, M.T. 2003. Small Hive Beetle. University of Florida IFAS Extension publication ENY-133.
- Skinner, J.A. 2002. The Small Hive Beetle: a New Pest of Honey Bees. University of Tennessee Agricultural Extension Service publication SP 594.
- Torto, B., R.T. Arbogast, D. Van Engelsdorp, S.D. Willms, D. Purcell, D. Boucias, J.H. Tumlinson & P.E. Teal. 2007. Trapping of Aethina tumida Murray (Coleoptera: Nitidulidae) from Apis mellifera L. (Hymenoptera: Apidae) colonies with an in-hive baited trap. Environmental Entomology 36:1018-1024.
- Fig 1. (left) Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, bugwood.org; (right) Natasha Wright, Florida Department of Agriculture and Consumer Services, bugwood.org.
- Fig 2. James D. Ellis, University of Florida, bugwood.org.
- Fig 3. Jon Zawislak, University of Arkansas Division of Agriculture, Cooperative Extension Service, www.uaex.edu.
- Fig 4. James D. Ellis, University of Florida, bugwood.org.
- Fig 5. James D. Ellis, University of Florida, bugwood.org.
- Fig 6. Chris Bryan.
Download a printable
fact sheet from the
University of Arkansas
Division of Agriculture
Has research been done on honey bees comparing 5.4 mm comb cell size with 4.9 mm? I have heard that small cell (4.9 mm) beekeeping can control varroa mites.
Below is a listing of research into European honey bees on small cell combs. Three of the articles (1, 2, and 5) deal with small cell and varroa mites. All three conclude that small cell does not help the bees deal with varroa mites, or otherwise reduce varroa mite numbers. Article #3 shows that small cell combs do not reduce tracheal mites. Study #4 is unrelated to small cell's effect on parasitic mites and shows that smaller combs do result in smaller bees, when measuring specific morphological characters.
- Berry, J. A., Owens, W. B., and Delaplane, K. S. (2010). Small-cell comb foundation does not impede Varroa mite population growth in honey bee colonies. Apidologie 41: 40-44.
- Ellis, A. M., Hayes, G. W., and Ellis, J. D. (2009). The efficacy of small cell foundation as a varroa mite (Varroa destructor) control. Experimental and Applied Acarology 47(4): 311-316.
- McMullan, J. B., Brown, M. J. F. (2006). Brood-cell size does not influence the susceptibility of honey bees (Apis mellifera) to infestation by tracheal mites (Acarapis woodi). Experimental and Applied Acarology 39: 273-280.
- McMullan, J. B., Brown, M. J. F. (2006). The influence of small-cell brood combs on the morphometry of honeybees (Apis mellifera). Apidologie 37: 665-672.
- Taylor, M. A., Goodwin, R. M., McBrydie, H. M., and Cox, H. M. (2008). The effect of honey bee worker brood cell size on Varroa destructor infestation and reproduction. Journal of Apicultural Research 47(4): 239-242.
Frequently Asked Questions
Two "expert" bee researchers ponder a quandary: "well, what do you think?" Credit: Zach Huang
Beekeepers are almost by definition curious individuals. The nature of beekeeping, as with any environmental relationship, is complex. Even some of the most experienced beekeepers are confounded by the mysteries of a bee hive. That is what makes honey bee research a rewarding and never-ending journey.
Below is a list of commonly asked questions and links to the best answer at the time it was asked. As more information becomes available, perceptions shift, and may render a formerly correct answer invalid. The following list is only a starting point and one should always seek a second opinion on any difficult or important subject. Local knowledge is especially important as geographical variables cannot be resolved in this universal forum. If your question is not listed below, consider using the Ask an Expert function.
- Are there plants that produce nectar that is poisonous to either honey bees or humans?
- How can bees make honey from nectar that is poisonous to them?
- What is the life cycle of the bumble bee?
- How can farmers, gardeners, and applicators reduce risks of honey bee injury from pesticide application?
- What steps can beekeepers take to protect their colonies from pesticide injury?
- How can I tell the difference between small hive beetle larvae and wax moth larvae?
- What are wax moths and what kind of damage do they make in a hive?
- How many bee hives do I need to pollinate a crop?
- What causes purple brood?
- What is a "pollen bee" or a "non-apis" bee?
- Has research been done on comparing 5.4 mm comb cell size with 4.9 mm?
- What are small hive beetles and where did they come from?
- What is the best way to introduce a queen into a colony?
- What plants in my vegetable garden attract or need bees?
- What are some suggestions for keeping bears out of active beehives?
- What is causing the decline of honey bee populations?
- What is a toxic reaction to bee stings?
- What is the difference between a normal reaction to a honey bee sting and an allergic abnormal reaction?
- How long do worker honey bees live?
- Which pesticide formulations are least hazardous to honey bees?
- How many times does a queen honey bee mate?
- The drone has no father but has a grandfather. How is that?
- What crops do not require honey bee pollination?
- Why is honey different colors?
- I have bees in my house. How can I get rid of them without killing them?
- I have honey bees in a tree. Can I remove them and keep the bees?
- Will honey bee swarms in my yard move into a hole in the wall of my house?
- What is the basic life cycle of the fungus Ascosphaera apis that causes chalkbrood disease in honey bees colonies?
- Why do newly installed packages of bees seem to abscond more than well-established hives?
- How do honey bees use pheromones to communicate?
- How are queen bees raised and mated?
- Can a honey bee be born without the aid of a drone?
- Does honey have nutritional value?
- If honey is crystallized (solid) has it gone bad?
- What is Nosema disease?
- How do I know whether my bees have Nosema disease?
- How is Nosema disease treated?
- How do honey bees make wax?
- What are some ways to reduce the population of Varroa mites in honey bee colonies, without the use of pesticides?
- What is raw honey?
Honey Bee Lab and Organization Links
Male Melissodes bees apparently sleeping in a sunflower. Credit: Zach Huang
Many government agencies, private interest groups, and universities in the US and around the world work to better understand and protect honey bees and other pollinators. Many of these groups offer diagnostic or other services in honey bee health, while others feature informative resources for beekeepers, growers, gardeners, and other stakeholders.
Below is a selection of websites that offer compelling and trustworthy information or services in the areas of honey bee and pollinator health.
- USDA-ARS Bee Labs
- The Bee Informed Partnership
- Apiary Inspectors of America
- American Beekeeping Federation
- Eastern Apiculture Society
- Western Apiculture Society
- Heartland Apiculture Society
- American Association of Professional Apiculturalists
- Mid Atlantic Apiculture Research and Extension Consortium
- Pollinator Partnership
- The Xerces Society for Invertebrate Conservation
- Entomology Society of America
- International Bee Research Association
- State Beekeeping Laws in the USA
- Texas A&M Apiculture Program
- North Carolina State Apiculture Program
- University of Georgia Honey Bee Progam
- University of Florida Honey Bee Program
- Penn State University Center for Pollinator Research
- University of Minnesota Bee Lab
- Cornell University Hive and Honey Bee Library
- American Bee Journal
- Bee Culture
Honey Bees Disease and Pest Resources
Download a diagnostic manual for all honey bee ailments
Many diseases, parasites, predators, and conditions affect honey bee colonies.
In addition to pages on eXtension.org, the following resources can guide you in the identification and treatment of these issues.
Diagnosis of Honey Bee Diseases; Shimanuki, H. and Knox, D. A.; USDA-ARS Agriculture Handbook Number 690; Download a .pdf of Diagnosis of Honey Bee Diseases
Additional websites for honey bee health information:
- University of Georgia Honey Bee Program
- Mid-Atlantic Apiculture Research and Extension Consortium (MAAREC)
- The Apiary Inspectors of America (AIA)
Metallic sweat bee (Augochlora pura). Photo by Philip Moore. Credit: Sam Droege
Honey bees (Apis mellifera) are but one species among thousands of different bees within the superfamily Apoidea. Honey bees are unique in their societal life cycle and storage of large food reserves; most bees are solitary, nest individually, and do not store surplus food. Honey bees are not native to America and were imported from Europe early on during colonization. Native bees have evolved with the existing flora and some have established intricate relationships with particular flowers. Conserving populations of native bees is important because they are valuable pollinators of many plant species, often performing pollination more effectively than honey bees.
Understanding some of the characteristics of native bees will help foster a positive environment for all bees. Below are a few articles that will help explain a bit about native bees.
Dance Language of the Honey Bee
Social behavior in bees has a number of advantages. One of the most important of these is the ability to quickly mobilize a large number of foragers to gather floral resources that may only be available for a short period of time. The ability to communicate location with such precision is one of the most interesting behaviors of a very interesting insect.
The recruitment of foragers from a hive begins when a scout bee returns to the hive engorged with nectar from a newly found nectar source. She begins by spending 30-45 seconds regurgitating and distributing nectar to bees waiting in the hive. Once her generosity has garnered an audience, the dancing begins. There are 2 types of bee dances: the round dance and the tail-wagging or waggle dance, with a transitional form known as the sickle dance.
In all cases the quality and quantity of the food source determines the liveliness of the dances. If the nectar source is of excellent quality, nearly all foragers will dance enthusiastically and at length each time they return from foraging. Food sources of lower quality will produce fewer, shorter, and less vigorous dances; recruiting fewer new foragers.
The Round Dance
The round dance is used for food sources 25-100 meters away from the hive or closer. After distributing some of her new-found nectar to waiting bees the scout will begin running in a small circle, switching direction every so often. After the dance ends food is again distributed at this or some other place on the comb and the dance may be repeated three or (rarely) more times.
The round dance does not give directional information. Bees elicited into foraging after a round dance fly out of the hive in all directions searching for the food source they know must be there. Odor helps recruited bees find the new flowers in two ways. Bees watching the dance detect fragrance of the flower left on the dancing bee. Additionally, the scout bee leaves odor from its scent gland on the flower that helps guide the recruits.
The Waggle Dance
As the food source becomes more distant the round dance is replaced by the waggle dance. There is a gradual transition between the round and waggle dance, taking place through either a figure eight or sickle shaped pattern.
Shown here is a dancing bee on a swarm. The marked bee has returned from a sugar water feeder. She is seen here being unloaded by a number of bees, and then begins to dance, which communicates the source of sugar water related to the current sun azimuth. This recording was produced at the University of California, Riverside by Kirk Visscher.
The waggle dance includes information about the direction and energy required to fly to the goal. Energy expenditure (or distance) is indicated by the length of time it takes to make one circuit. For example a bee may dance 8-9 circuits in 15 seconds for a food source 200 meters away, 4-5 for a food source 1000 meters away, and 3 circuits in 15 seconds for a food source 2000 meters away.
Direction of the food source is indicated by the direction the dancer faces during the straight portion of the dance when the bee is waggling. If she waggles while facing straight upward, than the food source may be found in the direction of the sun.
If she waggles at an angle 60 degrees to the left of upward the food source may be found 60 degrees to the left of the sun.
Similarly, if the dancer waggles 120 degrees to the right of upward, the food source may be found 210 degrees to the right of the sun. The dancer emits sounds during the waggle run that help the recruits determine direction in the darkness of the hive.
Source: The information in this article was taken from "The Dance Language and Orientation of Bees" by Karl von Frisch
A productive apiary with standard bee hive equipment on hive stands. Credit: The Food and Environment Research Agency (Fera), Crown Copyright
The modern bee hive was invented by the Reverend L. L. Langstroth, patented in 1852, after his monumental discovery of "bee space". Bee space describes the phenomenon that if a space less than 1/4 inch is left the bees fill it with propolis (a glue like substance produced from tree sap) and, when a space larger than 3/8 inch is left the bees fill it with comb. The majority of bee hives used today are still based on Langstroth's design.
Given the narrow range of tolerance with bee space, hive components must fit together tightly to limit excess or too little open space. Each manufacturer may produce bee hives slightly differently and combining components from different companies can cause problems. Careful research and experience with each company's components is important before investing in hive equipment. Below are articles to explain a few of the necessary hive equipment.