By: Plenary Talks
Grooming behavior: insights on a honey bee defense mechanism against mites
Morfin N1, Mora A1, Harpur BA2, Hunt GJ2, Given K2, Fillier TA3, Pham TH3, Thomas RH3, Goodwin PH1, Guzman-Novoa E1
1University of Guelph, School of Environmental Sciences; 2Purdue University, Department of Entomology; 3School of Science and the Environment/ Boreal Ecosystem Research Initiative, Memorial University of Newfoundland,
Self-grooming is a behavioral immune response of honey bees (Apis mellifera) to the ectoparasite Varroa destructor. Self-grooming and associated traits (e.g. mite population growth and the proportion of mutilated mites), have been used in breeding programs to select for V. destructor resistant honey bees. In a recent study, self-grooming was used to evaluate colonies selected for low and high mite population growth (LVG and HVG). Differences in self-grooming between the selected genotypes included time of first grooming, number of differentially expressed genes (DEGs) and viral levels. The selection of resistant bees through self-grooming can be challenging, as the trait is affected by environmental stressors, such as the exposure to the insecticide clothianidin. Sublethal doses of clothianidin decreased the proportion of intense groomers. Also, the effect of the neurotoxic insecticide affected the lipid composition of the honey bee brain, including lipids related to energy metabolism and the stability of nicotinic acetylcholine receptors (e.g. CL18:3/18:1/14:0/22:6 and PC16:0/18:3). Additionally, genes associated with the pathway GPI-anchor biosynthesis were found differentially expressed, indicating an effect of clothianidin on neural processes affecting motor control and self- grooming. Self-grooming appears to be an effective quantifiable behavioral trait to study behavioral immunity and neural processes in honey bees.
Is DWV-B taking over from DWV-A, and does it matter?
Arguably the most serious threat to honey bees worldwide is Deformed wing virus (DWV), transmitted by varroa mites and found as two widespread genotypes, A and B. DWV is often associated with colony death and may account for the apparent increase in colony mortality over the past two decades. The originally described DWV genotype A (DWV-A) has been shown to have spread across the world ‘out of Europe’, likely accompanying the dispersal of varroa mites through transport of queens and colonies. A second genotype B (DWV-B) has more recently been described, a genotype that we have shown to be apparently more virulent in adult honey bees than DWV-A. Here I provide evidence for its rapid worldwide spread, which is likely not due to under-recording, as well as its marked increase in prevalence, not only in the USA but also in many European countries. Using evidence from my own group and others, I show that DWV-B may be spreading, potentially at the cost to DWV-A, and that it is likely spilling over into wild bee species. This is a cause of concern for the health of both honey bees and wild bee species in the coming years.
Chemical Ecology, Behavior and Nutrition
Mandible differences between high and low mite biters: a multifaceted approach
Farrell MC1, Harpur B2, Li-Byarlay H1,3
1Department of Agricultural and Life Sciences, Central State University; 2Department of Entomology, Purdue University; 3Agricultural Research and Development Program, Central State University
Varroa destructor mites present a major threat to honey bee (Apis mellifera) populations worldwide. Recent research showed a significant difference in mite-biting behavior from breeding stocks (ankle-biters) in Indiana when compared to commercial colonies to defend against Varroa mites. The mandibles of these bees are morphologically different in the long edge, and appear to be smaller in size therefore more efficient at mite removal. To examine the molecular mechanisms underlying the mandible differences, we are analyzing the transcriptome of the mandibles themselves at two developmental timepoints to look for candidate genes that regulate the differences in mandible morphology. In addition, we are examining metal ion incorporation into the mandibles of bees. Metal ion incorporation into insect cuticles directly influences their hardness in insects and other invertebrates, and could contribute to the morphological changes observed in high biting bees. Taken together, these data present a complete picture of a mechanism of mite resistance in honey bees. Our new knowledge in molecular mechanisms will provide unique information and foundation for future genetic research to improve breeding and selection of mite-resistant bees.
Exploring the role of beeswax foundation to promote comb honey production and economic profit for hobbyist beekeepers
Kittle S, Fudolig M, Wu-Smart J
University of Nebraska-Lincoln Bee Lab
Managing honey bees provides economic revenue either as the main source of income for commercial beekeepers or as supplemental income for many small-scale or hobbyist beekeepers. Beekeepers commonly generate profit from extracted liquid honey, however, the average price of honey ($5-8/lbs) can fluctuate greatly with the market. Hobbyists have to contend with lower prices and fewer opportunities to commercially sell their products and therefore cannot compete with larger operations. Comb honey, or honey that is still contained in beeswax cells, is a “higher quality” or value-added specialty product (averaging $15-20 per 12oz or 0.75lbs) because it is more labor intensive and energetically costly for bees to produce. These are also reasons why the production of comb honey decreased tremendously, particularly among larger operations, after extraction of liquid honey had been widely implemented.This experiment seeks to evaluate the role different amounts of wax foundation (full, half, or none) plays on encouraging bees to build comb cells and compares economic costs and benefits of using the three sizes to stimulate comb honey production.
Determining the mechanism of honey bee (Apis mellifera) premature self-removal behavior
Twombly Ellis J, Rangel J
Texas A&M University Entomology Dept
The honey bee (Apis mellifera) is an economically important pollinator and a tractable system for studying the behavioral consequences of eusociality. A sterile worker’s own genetic fitness is best served by acting in the interest of her colony, even if that behavior curtails her lifespan. Stressed honey bees typically leave the colony to forage early, which leads them to be unproductive foragers. Precocious foraging behavior can even lead to colony collapse when expressed at high levels. In this study, we tested the hypothesis that developmentally stressed honey bees remove themselves prematurely from their colony and subsequently die. To confirm that this behavior is a reaction to severe stress, and not caused by a parasite or pathogen, we stressed bees with either temperature stress or Varroa mite parasitization during pupation. Stressed bees, as well as control counterparts, were tagged upon emergence and introduced to an observation hive. We then observed the colony for premature self-removal of tagged workers. We found that stressed bees self-remove at a significantly higher rate than their unstressed counterparts. Stressed bees also have smaller hypopharyngeal glands than their unstressed controls, indicating that this is a stress driven behavior and potentially a form of extremely accelerated precocious foraging.
Sublethal treatment of insect growth regulators induces precocious foraging and alters collected pollen quantity in honeybees
Deeter ME, Corby-Harris V
USDA-ARS, The University of Arizona
Commercial honey bee colonies have experienced rapid declines in the past two decades due to a synergy of stressors, such as pesticides. Chronic stress can have lasting physiological changes in worker bees, such as the accelerated depletion of internal nutrient stores. Experimental reductions in abdominal lipid have been linked to a behavior known as precocious foraging, wherein worker bees forage earlier in their adult lifespan. Precocious foragers have been speculated to be less effective, but the relationship between precocious foraging and reduced pollination services requires further investigation. In this study, we found that bees treated with sublethal quantities of pyriproxyfen, an insect growth regulator, forage earlier than untreated controls. Additionally, we found that bees treated with another insect growth regulator, spirodiclofen, return with less, yet fattier, pollen than untreated controls. Our results suggest a slight yet significant reduction in forager yield due to pesticide stress, an effect that can further compromise colony health.
A mixed-use landscape in Virginia provides sustained foraging resources for honey bees
Ohlinger BD, Schürch R, Couvillon MJ
Poor nutrition due to habitat loss has gained attention as a possible stressor contributing to the well-reported declines in managed honey bee colonies. Scientists, policymakers and concerned citizens have coordinated their efforts to mitigate habitat loss by providing supplemental forage for hungry bees. However, additional information related to the temporal and spatial availability of honey bee forage can help to develop management plans that better meet their needs. We used dance decoding to monitor honey bee foraging from April – October in 2018 and 2019 within a mixed-use landscape in Virginia. We aimed to 1)identify temporal trends in communicated foraging distance and 2)identify attractive land characteristics within our study area. We observed a 63% increase in communicated foraging distance in June 2018 and a 64% increase in communicated foraging distance in June 2019; however, median yearly communicated foraging distances were relatively low in both 2018 (727 m) and 2019 (694 m). Additionally, honey bees expanded their foraging into distant forested areas during June in 2018 and 2019, indicating that forests provided quality forage during this time. Taken together, our results suggest that our relatively diverse study area provided sustained floral resources throughout the two honey bee foraging seasons.
You are what you eat: Effect of Fall feeding regimen on the overwintering success and gene expression
profiles of honey bees
Underwood RM, Döke MA, Ortiz-Alvarado Y, Koru BY, Giray T
Penn State University; University of Puerto Rico in Rio Piedras
In Fall, beekeepers generally remove stored honey from managed honey bee hives and replace it with artificial feed. This feed, which is often sucrose syrup (SS), high fructose corn syrup (HFCS), or invert syrup (IS), is a much-needed carbohydrate source that will sustain the colony over the Winter. In this study we examined the effect of these feeding regimens on colony survival and molecular markers of metabolic health in workers. Full-sized colonies were either allowed to keep their honey (control) or have their honey removed and replaced by one of the three artificial feeds (SS, HFCS, or IS) in Fall. In March, overwintered adults and newly emerging, callow worker bees were sampled from each feeding regimen. Overwintering success was significantly higher in colonies that kept their honey and those that were fed IS compared to those that were fed HFCS or SS. Moreover, vitellogenin and ILP-2 were up-regulated while ILP-1 and JHamt were down-regulated in brain samples of bees that consumed honey or SS relative to those that were fed HFCS or IS. These findings were consistent across overwintered and callow worker samples, the latter of which had no direct access to the feed available in the colony.
Flowers contributing to colony weight gain and honey production in an agriculturally intensive Midwestern landscape
McMinn-Sauder H, Lin C-H, Eaton T, Johnson R
Department of Entomology, The Ohio State University
The Ohio agricultural landscape includes a variety of sources for honey bee forage, including crop plants, weeds, and supplemental plantings. Currently, there is little understanding of the complementarity of these resources in the honey bee diet. This study aims to identify the flowers contributing most to colony honey production in agriculturally intensive regions of Ohio, with specific focus on soybeans as a resource and the dietary contribution of pollinator plantings. Colonies at twenty-four apiaries in north-central Ohio were monitored in 2020 and 2021. Broodminder hive scales were used to track colony weight continuously, capturing periods of honey production. Nectar samples were collected from apiaries monthly and pollen metabarcoding was used to identify the plants contributing most during periods of colony weight gain. Results indicate colonies at all sites gained weight during soybean bloom with nectar samples composed largely of Trifolium (clover) and Glycine (soybean) nectar. In addition, Vitis (grapevine) pollen was detected frequently in samples during this period. This study provides insight into nectar resources for bees in this landscape and identified periods of nectar dearth. These dearth periods can then be targeted in supplemental plantings to include blooming flowers, maximizing honey bee colony health and productivity in this landscape.
Improving honey bee tolerance to Deformed wing virus infection by optimizing macronutrient ratios within artificial diets
Payne AN1, Lau PW2, Garcia C1, Gomez J1, Boncristiani HF3, Rangel J1
1Department of Entomology, Texas A&M University; 2USDA Pollinator Health in Southern Crop Ecosystems Research; 3Inside The Hive Media & Consulting, Inc.
It has been shown that the health of honey bees infected with pathogens can be improved by ensuring proper nutrition. However, commercially available pollen substitutes vary widely in their macronutrient protein (P) to lipid (L) ratios, and it is unknown what target ratio can help bees better deal with pathogen infection. The purpose of this study was to determine what P:L ratio had a positive impact on the survivorship, physiology, and overall health of honey bees infected with a common honey bee pathogen: Deformed wing virus (DWV). We conducted cage assays where both infected and non-infected cohorts of bees were fed one of four diet treatments: a high P: low L diet (40P:10L), a low P: high L diet (20P:30L), an intermediate diet ratio at which non-infected honey bees were previously found to self-select for (30P:20L), or no diet whatsoever. Differences in diet consumption, survivorship, pathogen load, and physiology were compared between our different experimental groups. The purpose of this study is to identify at what macronutrient ratio honey bees can better tolerate infection with a viral pathogen in order to better tailor commercially available pollen substitutes for managed colonies on altered and changing landscapes.
Stockpiling pasture legumes and forbs for late Summer honey bee forage on non-irrigated pastures
Melathopoulos, A, Kincaid, S., Ates, S
Department of Horticulture, Oregon State University
Western Oregon is home to over 80,000 honey bee colonies. While honey and pollen flows are adequate through to the end of July, beekeepers have difficulty preparing colonies for Winter owing to a lack of forage in the latter half of the Summer. We have been working together with the National Honey Board to develop late-Summer bloom in dairy and sheep pasture systems, where pastures are grazed during Winter and Spring and are currently left dormant during the dry Summer. We investigated the nectar output in pastures where we incorporated perennial forages (forage chicory, hubam sweet clover and birdsfoot trefoil) and self-regenerating annual forages (balansa and berseem white clover), following Spring closures from sheep grazing on non-irrigated pastures. In spite of severe drought, we demonstrated tremendous nectar output from the self-regenerating annual forages. On the other hand, the bloom from perennial legumes was lower than expected.
Developing a methodology to detect honey bee foraging using bioacoustics analysis
McKenzie H, Johnson R, Lin C-H
Department of Entomology, The Ohio State University
Detecting bees in crop fields is critical for assessing pollination activity and for choosing appropriate time periods to apply pesticides to minimize bee exposure. There are currently several methods for detecting pollinator presence and activity, including pan traps, manual collection, and visual observation. However, there are limitations to the utility of existing methods, including the bias of pan traps against large bees and the limited duration of observation possible using manual approaches. I am developing a methodology to record the audible wingbeats of foraging honey bees (Apis mellifera) in soybean (Glycine max) fields and quantify periods of honey bee foraging by identifying the wingbeat frequency specific to honey bees, 234±13.9 Hz. I outline the technological and practical challenges of this new methodology, as well as how those challenges might be addressed and overcome by future work. Successful refinement of this methodology would provide a useful tool for measuring activity of honey bees and other flying insects in other crops or ecosystems.
Nutritional triggers of migration and swarming in Apis cerana
Klett K, Ihle K, Spivak M
My goal is to understand the physiological mechanisms underlying swarming and migration in Apis cerana. Apis cerana undergoes a yearly colony growth period, culminating in swarming. Conversely, A. cerana colonies undergo migration, in which the entire colony moves to a new location when resources become scarce. I tested potential nutritional triggers of swarming in Apis mellifera in Minnesota before testing them on A. cerana. Reproductive swarming is a complex, multi-stage group decision. A reduction in queen pheromone dispersal and crowding have been identified as triggers of swarming, yet causal mechanisms have not been demonstrated. I hypothesize that protein intake via pollen collection, and resulting nutritional status in individual bees, may be physiological triggers of swarming. I marked 7d and 14d old bees weekly, for two months, from colonies that eventually swarmed or did not swarm. I weighed pollen collected in traps over a 24 hr period every week and measured quantities of vitellogenin using qPCR as a nutritional indicator. After repeating this experiment with A. cerana, I will test the hypothesis that colony migration, in contrast to swarming, may be triggered by a reduction in protein intake, leading to the movement of the colony to areas of higher resource availability.
Pests, Pathogens and Beneficial Microbes
Effects of plant natural products on honey bee (Apis mellifera) health and gut microbiota
Martin A, Simone-Finstrom M, Ricigliano V
Louisiana State University, Dept. of Entomology
Honey bees are exposed to many different plant derived compounds both naturally (e.g. propolis, phytochemicals in nectar and pollen) and via management (added essential oils in dietary supplements or for treatments). Since animal microbiota are influenced by host phytochemical ingestion, more research is necessary to understand these dynamics in honey bees. This project aims to understand how phytochemicals may modulate the gut microbiota and what these changes could mean for bee health. Cages of newly emerged bees were provided sucrose syrup containing different concentrations of i)Brazilian or ii)Louisiana propolis extract, or iii)lemongrass, iv)spearmint, or v)thyme oil and pollen paste ad libitum for seven days. Control syrups contained either emulsifiers, kanamycin, or just sucrose. Abdomen samples were collected on day 7 and day 14 for microbiota analysis via taxon-specific bacterial 16S rRNA quantification and culture-based approaches. Bees fed sucrose, Brazilian propolis, and lemongrass had the longest median lifespans while bees fed thyme and spearmint had the shortest. Results of the influence of these diets on gut microbial communities will also be presented. The results will help elucidate the impacts of naturally-encountered and beekeeper-applied phytochemicals on honey bee physiology and health.
Developing a method for rearing Varroa destructor in vitro
Johnson BL, Jack CJ, Ellis JD
University of Florida- Department of Entomology & Nematology – Honey Bee Research & Extension Laboratory
Varroa destructor is a significant mite pest of western honey bees (Apis mellifera). Developing a method to rear and maintain populations of V. destructor in vitro would provide year-round access to the mites, allowing scientists to study its biology, behavior and control more rapidly. In this study, we determined the impact of various rearing parameters on V. destructor survival and reproduction in vitro. To do this, we collected V. destructor from colonies, placed them in gelatin capsules containing a honey bee larva, and manipulated the following conditions experimentally: rearing temperature, colony source of honey bee larva, behavioral/developmental stages of V. destructor and honey bee larva, and mite:bee larva ratio. Varroa destructor survival was significantly impacted by temperature, colony source of larvae, and mite behavioral stage. In addition, V. destructor reproduction was significantly impacted by mite:larva ratio, larval developmental stage, colony source of larva, and temperature. The following conditions optimized mite survival and reproduction in vitro: using a 4:1 mite:larva ratio, beginning the study with late stage uncapped larvae, using mites collected from adult bees, setting the rearing temperature to 34.5°C, and screening larval colony source. Ultimately, our data can be used to improve V. destructor in vitro rearing programs.
DO NOT ENTER: Keeping small hive beetles at bay through olfactory cues
Roth MA, Lahondère C, Gross AD
Small hive beetles (Aethina tumida) are invasive pests that enter Apis mellifera colonies and inflict feeding damage. Apis mellifera colonies emit many volatiles, including the key alarm pheromone component isopentyl acetate (IPA); A. tumida adults use these volatiles to locate hives. We hypothesize that one way to keep A. tumida adults from invading apiaries is to obscure responses to IPA through use of repellent molecules, which we are testing at antennal and behavioral levels through electroantennography and olfactometry. Thus far, electroantennograms (EAGs) have been performed using IPA and several repellent volatiles (paraffin oil control). EAG results allowed for calculation of half-maximal effective concentrations (EC50) for IPA (5.6ppm), picaridin (16.6%), piperidine (15.9%), pyrrole (1.19%), and pyrrolidine (0.26%). Mixing EC50 values of IPA and picaridin have resulted in significantly reduced responses compared to IPA alone. Dual-choice olfactometers are now being used to compare beetle behavior to EAG results. Thus far, slight preference for IPA was observed, while pollen patty (12g) was significantly attractive. Additionally, when 10mg of pyrrolidine were added to filter paper atop 12g of pollen patty, beetles significantly avoided this treatment. Ultimately, repellent compounds could mask attractive volatiles, preventing A. tumida adults from discovering apiaries.
Stable carbon and nitrogen isotope ratios in healthy and Nosema-infected honey bees
Kamminga K, Webster T
College of Agriculture, Community and the Sciences, Kentucky State University
Nosema ceranae infection in honey bee workers was studied through the measurement of stable carbon and nitrogen isotopes. For this study, mixed-age honey bees were collected and maintained in an incubator at 32°C. Bees were fed 50% sucrose solution with Nosema spores. At days 0, 6, 9, 12, and 26 post-inoculation (DPI), sixty bees were removed from each cage and anesthetized. Newly emerged bees were also analyzed. Sixty midguts from each group were placed by tens in microcentrifuge tubes and crushed with a pestle to release spores. Spore numbers were counted on a hemocytometer. The pellet tissue was dried and sent to the University of Arkansas Stable Isotope Laboratory for isotope analysis. Through ANOVA, we found significantly higher δ13C at 6, 9 12, and 26 DPI than for newly emerged and uninfected bees. However, δ15N was lower for newly emerged bees than for the mixed aged bees at 0 through 26 dpi. Statistically significant positive relationships of δ13C and δ15N with increasing spore counts were also found through linear regression. This indicates that the developing N. ceranae aggressively incorporates carbon as it develops. This result conforms to published literature which states that parasites are isotopically more enriched than their host.
Three’s a crowd: How honey bees respond to infection with Lotmaria passim and Nosema ceranae
MacInnis C1,2, Guarna MM2, Luong LT1, Pernal SF1
University of Alberta and Agriculture and Agri-Food Canada
Nosema ceranae and Lotmaria passim are two digestive tract parasites of the honey bee that have been associated with honey bee colony losses in Canada, the U.S., and Europe. Unfortunately, honey bee colonies are often co-infected with these parasites, and we have little information regarding how the two parasites interact to affect honey bee health. We have investigated the effect of both parasites (single and mixed infections) on honey bee mortality, humoural defense response, and foraging behavior. Results of a mortality experiment suggest that L. passim is less virulent than N. ceranae, with individuals inoculated with only L. passim surviving 10.4 days longer than those inoculated with only N. ceranae. Interestingly, mixed infections also appeared less virulent than N. ceranae alone, with individuals inoculated with both parasites surviving 0.75 days longer than those inoculated with N. ceranae only. We will also discuss the effect of single and mixed infections on individual honey bee behavior.
Comparative quantification of honey bee (Apis mellifera) associated viruses in wild and managed colonies
Dickey M, Rangel J
The most detrimental threat to honey bee (Apis mellifera) health is the ectoparasitic mite Varroa destructor, which is linked to sizeable colony losses worldwide. Varroa is also a prolific vector of several honey bee-associated viruses. Wild honey bee colonies live in feral conditions and are thus not treated for Varroa control, which has enabled the natural selection of mite tolerant bees. To date, there is limited information about virus prevalence in wild Africanized honey bee (AHB) populations. The Welder Wildlife Refuge (WWR) is a unique site to study the viral landscape of wild AHBs in the Southern U.S. The goal of this project is to quantify honey bee-associated viruses in a wild population of AHBs, compare the presence of these viruses to that in the nearest managed apiaries. In 2013 we detected the presence of Deformed wing virus (DWV), Black queen cell virus (BQCV), and Lake Sinai virus (LSV). In 2016 we detected the presence of DWV, BQCV, and Sacbrood virus (SBV). All samples that tested positive for viruses contained extremely low copy numbers in both years. This study provides us the first information on the presence and levels of honey bee-associated viruses in a wild population of AHBs.
The effect of hygienic behavior, viral co-infection and blueberry pollination on the development of European foulbrood in honey bees in Michigan
Fowler P, Schroeder D, Kevill J, Milbrath M
Michigan State University
European foulbrood (EFB) has been an increasing problem for Michigan beekeepers. Here we examine the role that blueberry pollination, hygienic behavior, and viral co-infection play in the development of EFB. In May of 2020, 60 queen-right hives were selected from a commercial beekeeping operation in Michigan and split into two locations: in blueberry fields for pollination or a distant holding yard, away from blueberries. Hygienic testing was performed on each hive and workers were collected for viral testing and hive health metrics and EFB disease status were gathered three times over the season. We found high levels of viral co-infection, with no clear links to health outcomes. No statistically significant difference was found in the development of clinical disease between the two groups with 61% (17/28) of the colonies in the holding yard developing moderate to severe disease over the course of the season compared with 69% (20/29) of those in blueberry pollination. No relationship was found between hygienic behavior and colony health. This suggests that blueberry pollination is likely not an important factor in the development of European foulbrood and hygienic behavior is not important in preventing the development of this disease.
Hygienic Behavior in Feral and Managed Honey Bees (Apis mellifera) in Response to Parasitic Mites (Varroa destructor)
Mukogawa B, Nieh, J
UC San Diego
Varroa destructor is threatening both managed and feral Apis mellifera colonies worldwide. Some studies suggest feral colonies may have increased resistance to V. destructor because of their increased immunocompetence and due to disruption of V. destructor reproductive cycles through their more frequent swarming. Additionally, Africanized colonies have also been shown to demonstrate increased hygienic behavior by removing more dead/infected brood and grooming more intensely, making them potentially more Varroa resistant in subtropical areas. This study aims to understand whether there are differences in hygienic behavior between feral and managed A. mellifera. We wish to understand why, despite not being treated, feral colonies are able to survive with Varroa. Interestingly, there are few observed differences between the autogrooming behavior of managed and feral colonies through behavioral lab assays. And similarly, there are no differences in their mite biting behavior. However, there is a common trend of honey bees biting off specific mite legs (pedipalps) more than other legs—which may be a strategy to reduce mite infestations. These findings may help us understand how feral A. mellifera colonies combat V. destructor infestations.
Comparison of individual hive and apiary-level sample types for spores of Paenibacillus larvae in Saskatchewan honey bee operations
Zabrodski MW, DeBruyne JE, Wilson G, Moshynskyy I, Sharafi M, Wood SC, Kozii IV, Thebeau J, Klein CD, de Mattos IM, Sobchishin L, Epp T, Ruzzini AC, Simko E
University of Saskatchewan
Three commercial honey bee operations in Saskatchewan with outbreaks of American foulbrood (AFB) and recent or ongoing antibiotic use were sampled to detect spores of Paenibacillus larvae. We compared spore concentrations in different sample types within individual hives, assessed the surrogacy potential of honey collected from honey supers in place of brood chamber honey or adult bees within hives, and evaluated the ability of pooled, extracted honey to predict the degree of spore contamination identified through individual hive testing. Spore concentrations in unaffected apiaries were significantly different from AFB affected apiaries in one of three operations. Only a few hives were responsible for the majority of spore contamination in any given apiary. For individual hive samples, brood chamber honey was best for discriminating clinically affected apiaries from those unaffected (p = 0.001). Honey super honey positively correlated with both brood chamber honey (rs = 0.76, p < 0.0001) and bees (rs = 0.50, p < 0.0001) and may be useful as a surrogate for either. Spore concentrations in pooled, extracted honey have predictive potential for overall spore contamination within each operation and may have prognostic value in assessing the risk of future AFB outbreaks at the apiary (or operation) level.
Genetics and Evolution
Breeding Varroa mite resistant honey bees in Canada
De la Mora A, Emsen E, Morfin N, Kelly P, Borges D, Eccles L, Goodwin P; Guzman-Novoa E. University of Guelph The mite Varroa destructor is considered the main threat to honey bee health worldwide. In Ontario, V. destructor is responsible for most overwinter colony losses (>80%). V. destructor also is a vector of the deformed wing virus (DWV) that is transmitted to the bees. This dual parasitism shortens the lifespan of infested bees and contributes to the collapse of colonies. Beekeepers control mite infestations using synthetic miticides, but the mites soon develop resistance to their active compounds, compromising their efficacy. Accordingly, it is necessary to have alternative control strategies. One way of reducing the impact of V. destructor and DWV parasitism is to breed Varroa-resistant strains of honey bees. We are implementing a bee breeding program in Ontario, Canada, to select for lower and higher rates of V. destructor population growth (LVG and HVG, respectively), monitoring infection rates of DWV. Collaborative institutions are the Ontario Queen Breeders Association, the Ontario Beekeepers Association, and the University of Guelph. Preliminary results show a six-fold difference in mite population growth between the LVG and HVG colonies. Additionally, DWV levels and winter colony mortality are significantly lower in LVG colonies than in HVG colonies.
Genetic Progress Achieved during 10 Years of Selective Breeding for Honey bee Traits of Interest to the Beekeeping Industry
Maucourt S, Fortin F., Robert C., Giovenazzo P.
Genetic improvement programs have resulted in spectacular productivity gains for most animal species in recent years. The introduction of quantitative genetics and the use of statistical models have played a fundamental role in achieving these advances. For the honey bee (Apis mellifera), genetic improvement programs are still rare worldwide. Indeed, genetic and reproductive characteristics are more complex in honey bees than in other animal species, which presents additional challenges for access to genetic selection. In recent years, advances in informatics have allowed statistical modelling of the honey bee, notably with the BLUP-animal model, and access to genetic selection for this species is possible now. The aim of this project was to present the genetic progress of several traits of interest to the Canadian beekeeping industry (hygienic behavior, honey production and spring development) achieved in our selection program since 2010. Our results show an improvement of 0.30% per year for hygienic behavior, 0.63 kg per year for honey production and 164 brood cells per year for Spring development. These advances have opened a new era for our breeding program and sharing this superior genetic available to beekeepers will contribute to the sustainability and self-sufficiency of the beekeeping industry in Canada.
How many species of honey bees (Apis) are there?
School of Environmental Sciences, University of Guelph
At least 178 forms of honey bees have been given species names since Carl Linnaeus first named Apis mellifera in 1758. Subsequently, most of those taxa were combined until, by 1986, there was general agreement that there are just 4-5 species of Apis: the single species A. mellifera of Europe and Africa and 3-4 species in Asia—the dwarf honey bee, giant honey bee, and eastern hive bee. However, expanded research of the honey bees across Asia has led to recognition of between 7-14 species, with the number depending on the species concept that one follows. Several genetic studies over the last 15 years suggest that there is justification for 14+ species. The fallacy of basing species on male genitalic differences will be reviewed. Species concepts and how they influence our understanding of the diversity within the genus Apis will be briefly explained. Several exciting biological situations will be highlighted, as well as the future for understanding honey bee diversity.
Population Genomics of Managed and Feral Honey Bees
Carpenter MH, Harpur BA, López-Uribe MM
Purdue University Department of Entomology; The Pennsylvania State University
Humans have intentionally selected, bred, and managed animals for over 15,000 years. In some cases, human-mediated selective pressures have generated subsets of the original populations containing unique phenotypes and genotypes: domesticated species. Honey bees (Apis mellifera) are a unique case because their reproductive strategy is rarely subjected to human control, allowing free mating between managed colonies and their sympatric feral or wild counterparts. Therefore, it is unknown if feral honey bees constitute a genetically distinct population from managed honey bees, or if feral stocks are escapees from nearby managed colonies. To answer this question, we conducted whole-genome re-sequencing on five managed stocks from across the United States and three known feral populations. We found that feral and managed stocks are closely related on the mitochondrial level, but whole genome sequencing reveals significant differences in genetic differentiation and ancestry.
A Tale of Two Stocks; Variance in chalkbrood symptoms between domestic honey bee (Apis mellifera) stocks
Walsh E1, Paillard M2, Giovenazzo P2, Pernal S1
1Beaverlodge Research Farm, Agriculture and Agri-Food Canada; 2Centre de Recherche en Sciences Animales de Deschambault
Chalkbrood is a common fungal disease that affects honey bee (Apis mellifera) brood, and is caused by the cosmopolitan heterothallic fungus, Ascosphaera apis. Chalkbrood can cause serious economic damage to beekeeping operations, particularly when colonies are already stressed. There are no chemical treatments registered for chalkbrood disease control in Canada or the USA, and as such, prevention and control of the disease must be achieved through best management practices. Because A. apis spores are common and the active fungus may be asymptomatic, it can be difficult for beekeepers to know the prevalence of the disease in their colonies or beekeeping operation. Consequently, the use of highly-resistant honey bee stocks capable of mitigating chalkbrood infections are critical to prevent significant disease outbreaks, such as those reported by Canadian beekeepers during blueberry and cranberry pollination. We assessed social immunity traits—namely propolis production and hygienic behaviour—in various stocks of bees and determined their effect on chalkbrood expression. Our results indicate variability in chalkbrood symptoms across stock types. Hygienic behaviour differed between both stocks, with our Quebec stock averaging 84.03%+/- 3.9% and our Albertan stock averaging 69.48%+/-4.35%. However, neither propolis envelope nor hygienic behaviour were affected by disease status in this experiment.
Don’t put all your honey on one stock: The role of genetics in virus and mite resistance
Cambron LD, Underwood RM, Given JK, Harpur BA, López-Uribe MM
The Pennsylvania State University; Purdue University
Honey bee viruses impact individual and colony health, and can be difficult to treat within and between colonies. One approach for fighting pathogens is to actively select for resistance traits. However, while several genetic stocks are available, there is a need for data-driven recommendations based on stock performance so beekeepers can make informed decisions about which stocks to introduce into their operations. To measure intra-colony variation and compare genetic stocks, we tested colonies from one of 10 apiaries located in Pennsylvania that were requeened in June (40 queens per stock) in a blind study where neither the beekeepers nor the molecular biologist had information about the origin of the stocks. Preliminary data shows a strong effect of colony on viral genes, and a significant difference between genetic stocks for expression levels of Deformed Wing Virus, Black Queen Cell Virus, and expression of the mite biting gene neurexin. These findings show a difference in virus and grooming genes between genetic stocks. Further analysis of the remaining colonies will provide detailed information on stock performance which will help beekeepers obtain healthier bees, best suited for the operation, and decrease colony and profit losses.
The grooming behavior between European Honey Bees and Asian Honey Bees
Belton H1, Luo S2, and Li-Byarlay H1,3
1Department of Agricultural and Life Sciences, Central State University, 2Institution for Apicultural Research, Chinese Academy of Agricultural Science, 3Agricultural Research and Development Program, Central State University
The grooming behavior of honey bees is one of beneficial traits for breeding. Worker bees can perform either auto-grooming individually or allo-grooming as a group in a colony. High levels of grooming can help to remove mites (Varroa destructor) from the body of worker bees. Asian honey bees (AHB, Apis cerana) as original hosts of Varroa mites may display a higher level of grooming behavior than European honey bees (EHB, Apis mellifera). But it is unknown whether the foster environment affects the grooming behavior when workers of one species are placed in the colony of the other species. Hence, we designed two experiments using colored fluorescent powders to induce grooming behavior and observed the 8-day old worker bees. In the first experiment, results showed that AHB workers spent more time on allo-grooming as a group than EHB workers, which is consistent with previous reports. In our second experiment of foster environment, interestingly, the environmental change in the colony level affected the auto- and allo-grooming behavior of workers in both species after they were placed in the foster colonies. These results show that both genetics and environment may affect the grooming behavior of honey bees.
Beekeeping Management, Education and Outreach
Thinking inside the box: building beehives that stimulate propolis collection and support honey bee health
Shanahan M, Simone-Finstrom M, Spivak M
Department of Entomology, University of Minnesota
Wild honey bee (Apis mellifera) colonies coat the rough inner surfaces of hollow tree cavities with propolis, a substance comprised primarily of plant resins. The resulting “propolis envelope” serves both structural and therapeutic functions inside the hive. Previous studies have shown that the presence of a propolis envelope leads to both individual and colony-level health benefits through the modulation of immune gene expression and increased colony strength. However, the smooth surfaces of the standardized wooden bee boxes currently used in beekeeping do little to stimulate bees to build a propolis envelope. As such, propolis has yet to be implemented as a tool to boost colony health in real-world beekeeping operations. In this study, we compared multiple hive textures for their ability to stimulate propolis deposition in stationary and migratory beekeeping contexts. We then examined effects on immune gene expression, colony health, and honey production. Our results provide support for the implementation of rough box hives as a means to stimulate propolis collection and support colony health in both stationary and migratory beekeeping contexts.
Times they are a’ changin’ – A decade of documenting changes in beekeeping practices
Steinhauer N, Wilson M, Fauvel AM, vanEngelsdorp D
University of Maryland, Department of Entomology
A principle aim of the Bee Informed Partnership (BIP) is to monitor the health of U.S. managed honey bee (Apis mellifera) colonies. We do this through various citizen science programs including survey and active field sampling. The Annual Colony Loss Survey taught us that between dead-outs and the combining and splitting of colonies, the average turnover – or “loss” – of colonies in a calendar year is 40% (Bruckner et al. 2021). The risk of colony loss varies by season, operation type, year, and region, but also according to the management practices beekeepers use (Steinhauer et al. 2021). Honey bees face many stressors, but good management offers a chance to prevent or rectify some of them. Survey results indicate that management of the ectoparasitic mite Varroa (Varroa destructor) in particular is associated with very different outcomes (Haber et al. 2019). BIP also employs effectiveness trials (pragmatic trials) using our networks of both backyard and commercial beekeepers to estimate the effect of different practices under “real world” conditions. However not all beekeepers are as likely to employ Varroa management (Thoms et al. 2018). Still, a decade of survey points to some encouraging shifts in beekeeper’s practice, possibly the result of extensive extension efforts.
Spotted lanternfly honeydew honey: a unique new varietal from an introduced invasive insect
Underwood RM, Zhu F, Urban J
The Pennsylvania State University
The spotted lanternfly (Lycorma delicatula; SLF) is an introduced planthopper from Asia that was discovered in the U.S. in Pennsylvania in 2014 and has since spread to several other states. This invasive species feeds on phloem and excretes copious amounts of honeydew, which is attractive to honey bees (Apis mellifera). Control measures include application of the systemic insecticides dinotefuran and imidacloprid to SLF adults’ preferred host, tree-of-heaven (Ailanthus altissima). Lanternflies feed on treated trees and, thus, can produce honeydew that contains pesticide residues, exposing non-target insects to these insecticides. Additionally, lanternflies feeding on tree-of-heaven as adults sequester the quassinoid ailanthone, which is known to impart a bitter taste in components of tree-of-heaven. If SLF honeydew contains this substance, it could explain the unusual taste of the honey that is being produced in SLF-infested areas. We have determined that the presence of SLF, and its associated chemical controls are leading to production of honeydew-based honey that can contain dinotefuran metabolites, imidacloprid, and ailanthone. However, contaminants have not been detected at levels of concern for honey bee or human health. As SLF have spread, so have reports of this distinct honey, so beekeepers should be made aware of this association.
Can irradiated royal jelly be used to rear Apis mellifera in vitro?
Standley JM, Ellis JD
University of Florida- Department of Entomology & Nematology – Honey Bee Research & Extension Laboratory
The ability to rear Apis mellifera workers in vitro is an important method used to study the effects of pesticides, nutrition, hormones, etc. on bee development. In this assay, bee larvae feed on an artificial diet that includes royal jelly (RJ) often sourced internationally, raising concerns about pathogen spread. These concerns may be mitigated by irradiating the RJ prior to use, though this could affect RJ’s value in an artificial diet. The purpose of our study was to determine if A. mellifera can be reared in vitro on a diet containing RJ irradiated at 25 kGy. Twelve-hour-old larvae were collected from eleven colonies and fed a diet containing untreated RJ, irradiated RJ, or an irradiation control. Statistically fewer larvae survived to adulthood when fed irradiated RJ (71%) than when fed untreated RJ (85%) or the irradiation control (78%). Feeding on irradiated RJ did not affect bee developmental time, though weight at emergence was reduced over that of the control group. Our data demonstrate that A. mellifera workers can be reared on a diet that includes irradiated RJ, but that additional diet refinements may be necessary to improve survival of these individuals to levels experienced by larvae feeding on untreated diet.
BIP Bites; BIP Tech Transfer Team Teasers
Fauvel AM, Steinhauer N, Wilson M
Bee Informed Partnership – University of Maryland
The Bee Informed Partnership (BIP) Tech Transfer Team provides inspecting, diagnosing, sampling, reporting and consulting services to commercial beekeepers across the U.S. A decade after establishing the first Tech Team region, we can tease out some interesting data regarding consistently lower Varroa, and higher Nosema loads and prevalence in BIP Tech Team beekeeper participants compared to the APHIS National average, as well as significant increases in honey bee hygienic behavior scores in California queen breeders. In addition to Tech Team regular services, the honey bee health field specialists conduct real-world condition field trials with our vast commercial operation network in collaboration with a variety of beekeeping industry stakeholders. From indoor wintering studies, to testing effectiveness of products such as probiotics and miticides, field evaluation of new genetic honey bee lines and surveying Varroa-vectored viruses across the nation, the Bee Informed Partnership Tech Transfer Team will share a few preliminary results.
How does learning environment affect knowledge and adoption of Varroa IPM?
Bruckner S, Mahood J, Steinhauer N, Wilson M, Williams GR
U.S. beekeepers commonly cite the ectoparasitic Varroa mite (Varroa destructor) as a major threat to their honey bee (Apis mellifera) colonies. However, many beekeepers do not implement existing field-tested Integrated Pest Management (IPM) practices recommended by extension agents and scientists, possibly because existing information resources are not aligned with their preferred learning environment. This study aimed to: 1)assess how two learning environments affect beekeeper knowledge gain and behavior change concerning Varroa IPM, and 2)identify their preferred information resources. To achieve this, we recruited beekeepers from the Southeast U.S., half of which experienced a fully online learning environment, whereas the other half engaged in an in-person experience. We found that both learning environments resulted in short term knowledge gain, but more in-person participants intend to change their behavior concerning Best Management Practices in Varroa IPM. This aligned to beekeeper preferred learning environments − attending classes and instructed workshops. Furthermore, beekeepers predominantly sought information from their clubs and fellow beekeepers through informal discussions. These insights are useful in promoting knowledge gain and behavior change by small-scale beekeepers via tailored information resources and educational opportunities.
A Bee’s Eye View of Apiary Inspection: Updates on Honey Bee Health from the Apiary Inspectors of America (AIA)
Apiary Inspectors of America/Massachusetts Department of Agricultural Resources
Apiary Inspectors and Apiary Programs are the regulatory authority for enforcing the laws and regulations of certain honey bee pests, parasites and pathogens. Given this, inspectors are responsible for monitoring and ensuring honey bee health by conducting field visits to apiaries where they inspect, identify, diagnose, and provide recommendations for treatment of issues. Apiary Programs are dynamic, often with inspectors also serving as educators, researchers, state fair superintendents, and coordinators for other-bee related activities such as Managed Pollinator Protection Plans (MP3). This presentation will provide information on how researchers can work with Apiary Inspectors as well as updates on member and organizational efforts from the past year along with inspection data and observed trends related to honey bee health.
Pesticides and Acaricides
Pesticide risk during apple pollination differs between honey bees and native wild bees
Mueller T, Zhao C, Sossa D, Baert N, McArt S.
Department of Entomology, Cornell University
Bees in agricultural systems are exposed to a wide variety of chemicals, many of which are highly toxic and have been linked to pollinator declines. Little work, however, has looked at how bee taxa differ in their levels of pesticide exposure and resulting risk during crop pollination. We collected five bee taxa across 20 New York apple orchards during bloom, including managed honey bees (Apis mellifera) and bumblebees (Bombus impatiens), wild bumblebee queens (B. impatiens), wild ground-nesting bees (Andrena sp. and Melandrena sp.), and wild wood-nesting bees (Xylocopa virginica). All bees were quantified for 93 common pesticides using HPLC-MS/MS. We found that bee taxa differed in the quantity and composition of pesticides they harbored with honey bees having the greatest risk from exposure. We assessed which pesticides were driving risk in each of the bee taxa surveyed, as well as if the landscape and crops surrounding the orchard were a driver of pesticide exposure and risk for different bees.
Pesticide risk to honey bees and native bees in sweet cherry production of Oregon
Carlson E, Sagili R, Melathopoulos A
Oregon State University
Apis mellifera L. colonies in agricultural environments may stray from a crop and forage on wild plants and other nearby food sources. This leads to a complex pesticide risk profile that includes the products applied to the crop and the potential for honey bees to be exposed to chemicals applied to other attractive plants within their foraging radius. When a diverse pollen sample is tested for pesticides, it is difficult to ascertain where the chemicals originated in the landscape. While a test of the composite sample provides a holistic view of pesticide exposure over a given period, it does not allow scientists and land managers to identify high-risk areas of the landscape. In this study, we investigate pesticide risk to honey bees in sweet cherry fields. Twelve cherry orchard sites were sampled for pollen at early and peak bloom; samples were analyzed for over 250 pesticide residues. We then sorted composite pollen samples into each species and identified the major plant species within each color of pollen. These sorted samples were tested again for pesticides and compared to the original composite test, allowing identification of the plant species which disproportionately contribute pesticide risk to the composite sample.
An evaluation of honey bee (Apis mellifera L.) worker behaviors when exposed to a pesticide-contaminated environment
Tokach R, Smart A, Wu-Smart J
University of Nebraska-Lincoln
Honey bees exhibit age polyethism and thus have a predictable sequence of behaviors they express through developmental time. Pesticide exposure can lead to behavioral acceleration, resulting in younger workers transitioning to performing more risky colony tasks, including precocious foraging. This, in turn, can lead to an imbalance in the number of workers performing colony tasks and eventual colony failure. This research examines the relationship between environmental pesticide exposure and colony failure by observing the task-specific behaviors of worker honey bees in observation hives. More specifically, this study assessed potential changes in behaviors of similarly aged workers within two treatment groups: 1)colonies located near point-source pesticide pollution, and 2)colonies embedded within a typical agricultural environment (control). Cohorts of newly emerged sister workers were routinely paint-marked and randomly incorporated into separate treatment hives to establish similar population structures that contained a range of age-marked individuals from newly emerged workers to older foragers. In 2021, worker bee tasks were monitored and assessed on a total of eight colonies three times a week for a month to determine potential impacts of pesticide-contaminated environments on worker performance and age-specific tasks critical for normal colony functions.
Toxicity of Spray Adjuvants and Tank Mix Combinations to Adult Honey Bees
Shannon B, Walker E, Johnson R
The Ohio State University
Spray adjuvants are a diverse group of agrochemicals that are added to pesticide tank mixes to improve the function of spray application. There is concern that significant honey bee colony losses that are reported during and after almond bloom in California are related to adjuvant and pesticide exposure during almond pollination. The aim of this research was to determine if adjuvants and field-relevant mixtures of adjuvants and pesticides applied during almond bloom can cause increased mortality in adult worker honey bees exposed to simulated spray applications. This study established the acute toxicity, expressed as LC50, of different adjuvants and adjuvant tank-mix combinations. Spray application was performed using a Potter Spray Tower on 3-day-eclosed adult worker honey bees. Tested adjuvants included Dyne-Amic, Kinetic, Surf-90, Induce, Cohere, Liberate, Activator 90, Nu Film P, LI 700, Choice, Latron B, and Attach; tested fungicides included Pristine, Tilt, Vanguard, and Luna Sensations; and tested insecticides included Intrepid. Results showed substantial bee toxicity of some adjuvants applied alone at field relevant levels. Results also showed a trend in increased toxicity of some adjuvants when applied as a tank mix with some pesticides. There is evidence that the toxicity of an adjuvant is related to a relatively higher application rate recommended on the label.
Novel method for Varroa destructor management: utilizing worker brood to control mite populations in honey bee colonies
Reams T, Rangel J
Texas A&M University
Parasitization of Apis mellifera by the mite Varroa destructor is one of the main causes for the decline of honey bee health worldwide. To reproduce, a female mite enters the comb cell of a bee larva before it is capped, undergoes development and reproduction within the cell, and exits the cell as the bee emerges. Varroa mites have shown a preference for invading drone cells during the reproductive phase, but will invade worker cells throughout the year, as the population of mites within a hive escalates. A mechanical method for mite control is the removal of capped drone brood, but this can only be done when drone larvae are widely present in the hive. Our study involves the manipulation of nurse bee visitations of worker cells by starving worker brood for several hours. We then measured the mites’ invasion rates of starved and non-starved (untreated) worker brood. Our results show that starved worker brood have increased mite invasion compared to non-starved worker brood. These results show that starved worker brood could be more attractive to Varroa mites, and could be used as a potential control method throughout the summer, when drone larvae are not widely present in the colony.
Predicting the long-term effects of metal pollutants on the honey bee colony: A comparison of modeling approaches
Ricke D, Johnson R
The Ohio State University
Honey bees are regularly exposed to metals in the environment. Unlike pesticides, metals never break down, allowing them to accumulate in colonies over time. In contrast, our understanding of the effects of metals on honey bees is based on relatively brief laboratory assays. Consequently, there’s interest in modeling approaches that can leverage short-term toxicological data collected from individuals to predict the cumulative effects of metals and other toxic substances on whole colonies. For the present study, we compare two approaches for predicting the long-term effects of metals on honey bees: a “traditional” approach based on dose-response curves and a state-of-the-art model of survival (the General Unified Thresholds Model of Survival, GUTS). Specifically, we compare how well each approach predicts the results of 20-day chronic toxicity assays using data from standard (10-day) assays. We then compare the predictions of each approach in the background of a preexisting colony population model. We’ve found that GUTS outperformed the traditional approach for two metals (Cd and Li) when predicting 20-day survival in the lab. Results were equivocal for a third metal (Zn). In addition, GUTS tended to predict lower rates of colony population growth under exposure to metals. These results indicate that prevailing approaches for predicting toxic effects may underestimate effects that accumulate over time.
Efficacy of new compounds against Varroa destructor and their safety to honey bees (Apis mellifera)
Jack C, Kleckner K, Demares F, Rault L, Anderson T, Carlier P, Bloomquist J, Ellis J
University of Florida
Acaricides used to control Varroa destructor are becoming increasingly ineffective due to resistance issues, prompting the need for new compounds that can be used by beekeepers. Ideally, such compounds would be highly toxic to Varroa while maintaining a relatively low toxicity to bees. We characterized the lethal concentrations (LC50) of amitraz, matrine, FlyNap®, carbamate 421, carbamate 408 and dimethoate (positive control) for Varroa using a glass vial assay. Additionally, the test compounds were applied to honey bees using an acute contact toxicity assay to determine the adult bee LD50 for each compound. Amitraz was the most toxic compound to Varroa, but carbamate 421 was nearly as toxic (within 2-fold) and the most selective due to its low bee toxicity, demonstrating its promise as a Varroa control. While carbamate 408 was less toxic to honey bees than amitraz, it was also 4.7-fold less toxic to the mites. Matrine was relatively non-toxic to honey bees, but also not effective against Varroa. FlyNap® was ineffective at killing Varroa and was moderately toxic to honey bees. Additional Tier 2 and Tier 3 testing is required to determine if carbamate 421 can be safely used as a Varroa control in honey bee colonies.
The causes of variability in honey bee residual toxicity tests
Swanson L, Bucy M, Melathopoulos A
Oregon State University
Residual toxicity statements on pesticide labels are informed by tests, whereby treated foliage is harvested at specified intervals of weathering to determine whether honey bee contact with this foliage results in mortality (EPA Ecological Guidance 850.3030). The information is of considerable importance to both beekeepers and pesticide applicators to determine whether toxic products sprayed at dusk would dissipate by the following morning. I completed a meta-analysis of 31 papers consisting of 1,299 individual residual toxicity trials of 136 insecticide active ingredients. I estimated the residual toxicity for each active ingredient by calculating RT25 (i.e., weathering time taken for cage mortality to be reduced to 25%) and determined sources of variation in experimental protocols that influenced RT25 values. I reported on discrepancies in RT25 values calculated from the literature compared to values recently published by the Environmental Protection Agency (EPA). I investigated whether discrepancies were the product of variation in the parameters of the test. I found that the age of bees used in test cages (R2= – 0.48) were associated with bee mortality and may be responsible for discrepancies from EPA results.
Apple orchards feed and contaminate bees during, but even more so after bloom
Steele T, Schürch R, Couvillon M
Honey bees provide vital pollination services to many crops such as apples. Previous studies have focused on the impact of bees on orchards during bloom, but fewer studies have examined the reciprocal relationship of orchards on honey bees, particularly across the entire foraging season. We investigated honey bee foraging in orchards in Northern Virginia by mapping 3,710 waggle dances across two years concurrent with pesticides analysis on the forager collected pollen. We found that bees foraged mostly locally (< 2 km), with some long-range events occurring in May after bloom (both 2018 and 2019) and in Fall (2019). The shortest communicated median distances (0.50 km and 0.53 km) occurred in September in both years. We determined that honey bees forage more within apple orchards after the bloom (29.4% an 28.5% foraging) compared to during bloom (18.6% and 21.4% foraging). This post bloom foraging also exposed honey bees to the highest cumulative concentration of pesticides compared to other times (2322.89 ppb pesticides versus 181.8 during bloom, 569.84 in late Summer, and 246.24 in Fall). Therefore, post bloom apple orchards supply an abundance of forage, but also the highest risk of pesticide exposure, which may have important implications for future management decisions.