Part 2
DOI: https://doi.org/10.55406/ABRC.4.24.2
Pesticides and Acaricides
Control of Varroa destructor with Lithium Chloride: Efficacy and Side Effects
Rein, C1; Rosenkranz, P1; Traynor, K1
1 State Institute of Bee Research, University of Hohenheim, Germany
The parasitic mite Varroa destructor remains the greatest threat to honey bee health. Once established in a country, beekeepers must typically treat against Varroa to keep the colony alive. New, highly effective and easy to apply varroacides with limited unwanted side effects are thus highly desired. Lithium chloride (LiCl) has shown excellent potential as a new treatment agent, as feeding this compound to bees in syrup or candy results in high Varroa mortality yet is easy and safe to use with no pesticide residues in honey. We investigated the onset of the toxic effect in cage trials using individual bees parasitized by single mites. Within 24 hrs of starting the 50 mM LiCl feeding, 78% of the mites died, whereas within 48 hrs 95% mortality was achieved. A colony-level Summer treatment in brood-free colonies eliminated 77-98% of the mites, depending on the LiCl feeding duration. Unfortunately, lithium disturbs the development of the honey bee brood, leading to concentration dependent brood removal of up to 61%. Further investigations are needed to find an application method to minimize this brood loss. The combination of a brood break and treatment with LiCl remains an effective and practical control method.
Get those fleas off my bees!: Exploration of the isoxazoline class as possible Varroa destructor control and safety towards honey bees (Apis mellifera)
St. Amant, J1; Jack, C1
1Entomology and Nematology Department, University of Florida, FL, USA
Previous experiments have shown chemical resistance of Varroa destructor to commonly used active ingredients, such as amitraz and coumaphos. In order to find new active ingredients that reduce V. destructor populations in honey bee (Apis mellifera) colonies, we examined the acute toxicity of isoxazoline insecticides. Isoxazolines are commonly used to treat ticks and fleas on mammals through topical and oral routes. We evaluated afoxolaner, fluralaner, sarolaner and lotilaner on V. destructor and honey bees by using direct application methods. These values were compared to amitraz, coumaphos, a solvent control and a positive control (dimethoate). Fluralaner (LD50 = 0.065 ng/V. destructor) was the most toxic isoxazoline insecticide and only 2× less toxic than amitraz (0.036 ng/ V. destructor). Fluralaner and lotilaner were 126× and 2× more toxic to V. destructor than to honey bees. Sarolaner and afoxolaner were more toxic to honey bees than to V. destructor. Our results suggest that fluralaner demonstrates some promise as a treatment option due to its high toxicity to V. destructor and its relatively low toxicity to honey bees. Further research should be conducted to study the long-term impacts of isoxazoline insecticides on honey bees and possible impacts within honey bee colonies.
The utility of honey bee larval toxicity bioassays for the safety evaluation of a pesticide
De Souza, D; Feken, M; Tome, HVV; Schmehl, D
The exposure of immature honey bees to a pesticide during their development may result in mortality and developmental effects. Pesticide safety evaluations in some countries and regions rely on OECD standardized laboratory test protocols, with two of those designed to assess acute (single day) and chronic (multiple day) exposure to honey bee larvae. These tests have historically prioritized assessing larval honey bee mortality. The quantitative evaluation of growth and development (e.g., development rate) are currently not included in standardized test procedures which may potentially limit the sensitivity of the test to detect sublethal effects. The goals of our current study were to determine whether chronic toxicity tests with immature honey bees consistently result in a higher toxicity measurement than the acute single day exposure tests, and whether adult emergence weight measured in chronic toxicity tests is a more sensitive indicator of pesticide effects to honey bee larvae than mortality alone. To address our first goal, we compared acute and chronic larval toxicity data for 43 pesticides. To address our second goal, 46 chronic toxicity studies that measured both survival and adult emergence weight were analyzed to determine which study measurement resulted in the most sensitive indicator of a pesticide effect. Our analysis determined that the chronic toxicity test design adequately covers all immature stages, and that the weight of emerged adults was a more sensitive indicator than mortality of treatment-related effects in 22% of the analyzed studies. Further effort is needed to develop a standardized method for measuring the weight of emerged adults, as well as other possible sublethal endpoints, and to link those measurements in the laboratory with the protection goals of bees (e.g., survival and colony growth).
Physiological and Reproductive Changes in Honey Bee Female Castes Following Direct Colony Exposure to Insecticides
Valizadeh Gever, B1; Caren, J2; Huand, L2; Zhu, L2; Amiri, E1
1Delta Research and Extension Center, Mississippi State University, Stoneville, MS, USA
2USDA-ARS, Pollinator Health in Southern Crop Ecosystem Research Unit, Stoneville, MS, USA
Honey bee queens are thought to be protected from environmental stresses via physical and social barriers in their colonies. However, they can indirectly be exposed to pesticides. In this study, we assessed the effects of three widely used insecticides—Acephate, Bifenthrin and Chlorantraniliprole— on worker bees, to investigate their indirect impact on the physiology and reproductive traits of queens as well as the eggs they produced. Using RT-qPCR we measured the expression of several detoxification and immune genes in workers, queens and produced eggs after insecticide exposure. Our findings revealed distinct effects of these insecticides on honey bee female castes. Acephate significantly decreased esterase level in exposed worker bees at all time intervals, while Biofinthrin elevated acetylcholinesterase content 12 h after exposure. Altered gene expression by these insecticides emphasizing their intricate effects on honey bee workers and queen tissues. Even the expression of several genes has changed in the produced eggs. Acephate caused adverse effects on the reproductive traits of queens, reducing the egg size and number as well as the queen weight. Our results indicate that insecticides can indirectly cause negative impact on queen physiology and reproduction through exposed worker bees. Even the effects can potentially extend to the next generation.
Recommendations for oxalic acid application and treatment intervals for reduction of Varroa destructor populations in western honey bee (Apis mellifera) colonies
Prouty, C1; Abou-Shaara, HF1,2; Stanford, B1,3; Ellis, JD1; Jack, C1
1Entomology and Nematology Department, University of Florida, FL, USA
2Department of Plant Protection, Damanhour University, Egypt
3Florida Department of Agriculture and Consumer Services, Division of Plant Industry, FL, USA
We investigated which method of oxalic acid (OA) application (dribbling, fogging or vaporizing) was the most effective at reducing Varroa destructor infestations (Experiment 1) and sought to improve upon this method by determining the application timing that resulted in the greatest mite reduction (Experiment 2). We used Api-Bioxal and maintained 40 honey bee colonies (10 per treatment) in both experiments. Experiment 1 colonies included: 1) dribbling 50 ml of 3% OA solution, 2) vaporizing 4 g solid OA, 3) using an insect fogger supplied with 2.5% OA dissolved in ethyl alcohol and 4) an untreated control. After three weeks, only the vaporization method reduced mite infestations and resulted in significantly increased brood amounts and numbers of adult bees. In Experiment 2, all colonies were treated with four applications of OA via vaporization at 4 g OA/colony and groups were separated by treatment intervals at either three day, five day or seven day intervals. We observed that five day and seven day intervals significantly reduced mite populations from pretreatment levels over that of the controls and three day intervals. Our data demonstrate the efficacy of OA in reducing V. destructor infestation, particularly vaporizing 4 g every five to seven days as the most effective method of application.
Evaluation of a stabilized oxalic acid formulation (VarroxSan) for control of varroa mites (Varroa destructor) during Summer honey production season
David, IA1; Hopkins, BK1
1Department of Entomology, Washington State University, Pullman, Washington
To provide an efficient Varroa control strategy for U.S. beekeepers in the United States (U.S.), this research investigated the potential effects of a stabilized OA product (VarroxSan). Label information indicates this product slows down the release of OA for about 42 to 56 days in the colony; this slowdown (extended-release) ensures mites are eliminated once they emerge from brood cells and reduces the need for multiple reapplication treatments. This product was tested for efficacy, toxicity and significant residue in four treatments in infested colonies over the Summer (60 hives). Results were compared to the industry standard dose of formic acid (FormicPro) and to a no-treatment control. Follow-up hive inspections, egg emergence, mite counts from alcohol wash and sticky cards, and honey and wax samples were investigated during the treatments. We found that VarroxSan performed as well as FormicPro, lasting longer, and thus reducing the frequency of apiary visits. Successful registration of this product would create a long-lasting, labor-saving, alternative and valuable IPM tool.
Effect of an insecticide-fungicide tank mix on honey bee visitation in blooming soybean fields
Johnson, LHP1; Hearon, LE1; Lin, CH1; Lindsey, LE2; Johnson, RM1
1Department of Entomology, The Ohio State University, OH, USA
2Department of Horticulture and Crop Science, The Ohio State University, OH, USA
Soybeans and honey bees have a mutually beneficial relationship where nectar is provided in exchange for pollination that can improve yield. However, pesticide use on soybeans during bloom could disrupt this relationship by harming bees and reducing yield increases from pollination. The aim of this project was to document the impact on bee foraging and soybean yield resulting from a pesticide application made at different times of day, mid-day and in the late afternoon, at different times of year, during peak bloom and after bloom has ended. To do this, we sprayed soybean plots individually with a mixture of Fastac insecticide and Fitness fungicide using a backpack sprayer. Honey bee activity data within each plot was documented through use of an audio recording device sensitive enough to pick up honey bee buzzing. Audio files were then dissected for instances of bee buzzing by a specially trained machine learning model. Yield data was obtained through harvesting soybean plants and measuring the plot weight, plot moisture and test weight. The honey bee visitation was analyzed through an analysis of variance. Yield data was analyzed through the use of a t-test. The timing of the pesticide application did not have a significant effect on honey bee visitation or on soybean yield. This may be due to the soybean plots being too small for honey bees to differentiate between them.
Effects of oral exposure to combinations of the insecticide acetamiprid and the fungicide triflumizole on honey bees
Foster, AJ1; Johnson, RM1
1Department of Entomology, The Ohio State University, OH, USA
Some fungicides, specifically sterol biosynthesis inhibitors (SBIs), are known to have synergistic effects with insecticides on honey bees (Apis mellifera). We performed a chronic oral bioassay of the neonicotinoid insecticide acetamiprid on honey bees, with one group additionally exposed orally to the SBI fungicide triflumizole for a single day. After the end of the ten-day bioassay, the surviving bees were fed untreated syrup and mortality was recorded daily until the bees naturally expired. The 10-day mortality was analyzed with both a traditional probit model and a General Unified Threshold model of Survival (GUTS). Both models found no difference between the mortality of the fungicide-fed and non-fungicide-fed groups. Kaplan-Meier survival curves over the entire lifetime of the bees (a maximum of 36 days) were also analyzed. The lowest observable effect concentration (LOEC) for the triflumizole-fed bees was 10 mg/L while the LOEC for bees fed only insecticide was 50 mg/L. Previous studies have found large synergistic effects of triflumizole and acetamiprid applied topically, while this study found only subtle effects. This may be due to the low water solubility of triflumizole limiting the concentration that can be used in the bees’ food.
Using Low-Risk Adjuvants to Improve Varroa Control in Managed Honey Bee Colonies
Shannon, B; Johnson, RM
Beekeepers must apply chemical treatments (miticides) to manage varroa and maintain colony health. Unfortunately, many treatments are ineffective due to miticide resistance or low efficacy. The goal of this research was to increase the efficacy of miticidal active ingredients using bee-safe adjuvants. Adjuvants are a group of compounds used in plant pesticide applications to increase the spreading and penetration of a pesticide through the waxy cuticle of leaves and may act in a similar way to increase miticide penetration through varroa mite cuticle. Laboratory cage trials were performed with a formulation of Swedish sponges saturated with a mixture of glycerin solvent, a miticidal active ingredient (oxalic acid, clove oil or fenpyroximate), and an adjuvant (Ecostep BC-12®, Ecostep SE-11®, Ecostep AE-13®, Ecostep CE-13®, or Silwet L-7500®). Field trials used Swedish sponge strips with oxalic acid combined with Ecostep BC-12®. Both experiments included a solvent control and active ingredient control. Cage trial results showed an average efficacy of 96% of oxalic acid plus Ecostep BC-12® adjuvant, compared to 76% efficacy of oxalic acid control and 28% efficacy of the solvent control. Field trials determined a statistically significant decrease in mite loads in ethanol washes after treatment for the oxalic acid plus adjuvant treatment, but not for the oxalic acid control or the solvent control. Additionally, the oxalic acid plus adjuvant combination showed a trend for greater total mite drop per full box of bees over the treatment period than for the oxalic acid control and was significantly greater than solvent control. The improved delivery and increased efficacy of miticides through combination with adjuvants could improve the formulation for oxalic acid and other varroa control products to help beekeepers maintain healthy hives.
Tropilaelaps mercedesae management: Combining cultural and chemical control methods
Tokach, R1; Chuttong, B2; Aurell, D1; Williams, G1
1Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
2Meliponini and Apini Research Laboratory, Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai, Thailand
Tropilaelaps mercedesae is a parasitic mite that severely impacts the European honey bee (Apis mellifera). Tropilaelaps mites can outcompete Varroa mites and overwhelm colonies more rapidly. While T. mercedesae is native to Asia, it has recently expanded its geographic range and has the potential to devastate the U.S. honey bee industry if introduced. Our research exploited the dependence of Tropilaelaps mites on honey bee brood by combining a cultural control (brood break) with additional chemical controls to develop an eradication method in the event of U.S. introduction. We compared four treatment groups: 1) brood break; 2) brood break + formic acid (FormicPro®); 3) brood break + oxalic acid dribble; and 4) untreated control. Mite drop on sticky boards and infestation of worker brood cells were used to measure mite infestation. Honey bee population was also assessed. We found that mite levels rapidly increased over 60 days in control colonies but were kept to minimal numbers in all other treatment groups. All treatments were extremely effective and could be helpful to managing Tropilaelaps. However, no treatment exhibited 100% efficacy, so additional measures may be needed to eradicate Tropilaelaps mites from colonies if an introduction is observed.
Concurrent treatment with amitraz and thymol for Varroa management
Aurell, D; Bruckner, S; Wall, C; Williams, G
Beekeepers have limited tools to manage Varroa mites and prevent severe damage to their honey bee colonies. Several registered treatments exist, but many U.S. beekeepers use an emulsifiable concentrate formulation of amitraz (AEC), because it reportedly controls Varroa more rapidly and effectively than registered treatments. We hypothesized that a concurrent treatment with two registered Varroacides could exceed the Varroa control of Apivar(R) alone, and could match or exceed Varroa control by AEC. To test this, we treated test colonies with a combination of Apivar(R) and Apiguard(R), and treated positive-control colonies with Apivar(R) or AEC. Based on worker brood infestation after 21 days of treatment, AEC and combination treatments provided more rapid Varroa control than Apivar(R) alone; AEC provided the most rapid control of Varroa on adult bees. After 42 days of treatment, Varroa infestations were not significantly different. Bee populations in combination and Apivar(R) treatments were compromised compared to the AEC treatment, which we attribute to brood damage and slower control of Varroa, respectively. Our results indicate that rapid Varroa control is a valuable treatment characteristic, and that Apivar(R) and Apiguard(R) can be combined for rapid control, but treatment timings or procedures should be optimized to avoid compromising colony strength.
Pesticide exposure in migratory beekeeping for pollination and honey production in Northwestern U.S.
Zhang, G; Kuesel, R; Olsson, R; Hopkins, B
The Northwestern U.S. is the primary production region for a variety of specialty crops as well as many other seed crops, which heavily depend on honey bee pollination. However, honey bees are continuously exposed to various pesticides when they are moved from one crop to another for pollination. The evaluation of spatiotemporal pesticide exposures in migratory beekeeping will help beekeepers comprehend the impact of pesticides and make appropriate management decisions accordingly. We repeatedly tracked pesticide exposures to six groups of 24 hives in 2022 (144 colonies studied) and six groups of 16 hives (96 colonies studies) in 2023, each group being located at an apiary. The general migratory routes and timeframes included: Feb-Mar for almond pollination in California, April-May for tree fruit pollination (apple, cherry, blueberry) in Washington, Jun-Jul and Aug-Sept for seed crop pollination (sunflower, canola, carrot, onion) and honey production (buckwheat, pasture, forest) in Washington. The preliminary results from the 2022 study suggest spatiotemporal patterns in overall pesticide exposure levels that the lowest exposure levels were found in almond pollination, and highest exposure levels were found during tree fruit pollination. Exposure levels declined during June to September when honey bees were engaged in pollinating seed crops and producing honey. Fungicides were the dominant pesticide source of pesticides exposures in quantity throughout the growing season.
Chemical Ecology, Behavior and Physiology
The impacts of sterol biosynthesis inhibitory fungicides on honey bees
Chakrabarti, P1,2; Walt, H1; Sagili, RR2
1Dept. of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS, USA
2Dept. of Horticulture, Oregon State University, Corvallis, OR, USA
With increasing fungicide use in agriculture, it is imperative that we examine their impacts on beneficial arthropods such as the bee pollinators. In this particular study, two azole group fungicides were tested for their toxicity and their impacts on honey bee physiology. The doses selected were those reported across North American apiaries as residues across various hive matrices. Targeted lipidomics approach and qPCR were used to examine the impacts of these fungicides on the physiology of the honey bees examined under laboratory conditions.
Indirect exposure to a juvenile hormone analog affects honey bee (Apis mellifera) reproductive behaviors, hatching, and ovarian protein expression
Fine, JD; McAfee, A
Pesticide exposure and queen loss are major causes of honey bee colony loss, yet little is known regarding the effects of agrochemicals on honey bee reproduction. Here, we present the results of a two-generational study wherein queens were exposed to commonly used insect growth disrupting pesticides (IGDs) through their retinue of worker bees. Queen performance and worker responses to queens were tracked under IGD exposure, then the queen attendance behaviors of the exposed queens’ offspring was assessed to identify patterns that may contribute to long-term colony health and stability. The positive control, novaluron, resulted in deformed larvae hatching from eggs laid by exposed queens, but, curiously, eggs laid by queens exposed to pyriproxyfen, a juvenile hormone analog, hatched at higher rates relative to the control queens’ eggs. The pyriproxyfen exposed queens’ larvae developed into worker progeny with increased responsiveness to queens. Additionally, pyriproxyfen exposure affected the expression of proteins in the queens’ ovaries. These results and efforts to further investigate potential hormetic effects of queen exposure to pyriproxyfen at the colony level will be discussed in this presentation.
GCMS study of the lipid composition of fermenting bee bread
Becher, J; Duffy-Matzner, J; Olson-Manning, C
This work proposes that the lipid composition of bee bread will change during the fermentation process. The target lipids include monosaccharides, fatty acids and fatty acid derivatives, which should be present at high levels and are of particular interest due to their diverse roles in cellular functions. Bee hives around the Sioux Falls area were surveyed during the Summer of 2022 and the surrounding plants were also recorded. Samples of pollen and bee bread were collected over three consecutive weeks which correlates to the predicted fermentation time for bee bread and then frozen until examination. Nine compounds that should be present in significant amounts in the ethanolic extraction layer were chosen to react with BSTFA (N, O-bis(trimethylsilyl)trifluoroacetamide) to serve as standards. Ethanolic extractions of the ground bee bread were treated with BSTFA and analyzed via a GCMS method published by Isidorov. Retention times were compared to the standards to determine if the concentrations vary over the different fermentation periods. In the one location studied so far, the composition of bee bread does change over time, but not in a consistent pattern in composition.
The impacts of sicklepod extracts on honey bees
Whilden, ME; Ziming, Y; Te-Ming, PT; Chakrabarti, P
Sicklepod is a weed that is native to the United States, and it is commonly found in agricultural settings. This plant naturally contains toxins, including anthraquinones. Anthraquinones are widely spread throughout the environment and have been shown to be effective avian and deer repellants. Because honey bees can encounter anthraquinones when plants, such as soybeans, are sprayed with these extracts, this study was conducted to evaluate anthraquinone’s effect on honey bees. A lab cage experiment was run, exposing honey bees to sicklepod extracts through sugar syrup and a gradient of doses were used. Consumption of sugar syrup, daily survival in the lab cages and honey bee physiology are being assessed to understand such impacts.
Age-related Honey Bee Physiology and Colony Health
Nearman, A; vanEngelsdorp, D
Understanding the colony-level physiological responses to known risk factors may lead to the ability to predict colony mortality. Given the relatively short lifespan of individual bees and the close association between chronological age and task performance, physiologies that can identify bees by chronological age could potentially detect these colony-level responses. In an initial experiment I identify six physiologies whose binary presence or absence are strong candidates for identifying the age demographic profile in a sample of bees: hypopharyngeal gland development, quantities of Malpighian tubules, rectum color and size, debris in the venom sac and melanized sting gland tissue. Applying these physiologies to models that predict bee age suggests an overall accuracy of roughly 90%. To test the hypothesis that shifts in age demographic could detect response to risk factors, I then applied these methods to a retrospective study on 230 colonies with known health outcomes. Here I demonstrate that changes in the prevalence among age-related physiologies were associated with overwinter mortality or known risk factor exposures, such as queen events and Varroa. Last, I apply the age-predictive models to the retrospective study and demonstrate that changes in age demographic associate with a near doubling of mortality rates.
Increased flower density but not more flowers boosts honey bee recruitment signals
Carr-Markell, MK; Gull, L; Zhou, A; Donaldson-Matasci, MC
Nectar quality affects whether a honey bee forager will perform a waggle dance to advertise a patch of flowers, but relatively little is known about how flower distribution influences recruitment behavior. Here, we used arrays of artificial flowers to test whether 1) the spacing of flowers within a patch and 2) the total number of flowers within a patch would change two aspects of individual foragers’ behavior: 1) the number of dances performed and 2) the number of signals (waggle runs) per dance. We trained bees to visit our artificial flower arrays and individually marked each bee. We then presented the bees with three treatments: a high density/67-flower array, a low density/67-flower array or a high density/607-flower array. During both trials, one site served as a control for changes in weather and colony conditions, always presenting the same treatment. We analyzed the in-hive behavior of the marked bees that visited each array. Decreasing the density of flowers had a significant negative effect on both aspects of recruitment behavior. In contrast, the total number of flowers per array had no significant effect on either aspect of recruitment. We discuss the implications of these findings for designing bee-friendly plantings.
Imaging the honey bee peritrophic matrix
Webster, T; Tiwari, S
We found an effective method for examining the structure of an intact honey bee peritrophic matrix (PM), by fluorescence microscopy. The PM lines the midgut, and is responsible for protecting the epithelial cells from pathogens and abrasive particles. It serves also as a substrate for enzymes that digest pollen. This structure is secreted continuously in concentric layers by specialized epithelial cells. It then moves slowly to the rectum. When it is damaged by Nosema (Vairimorpha) infection or agricultural chemicals it may lose its functions for the bee. A damaged PM cannot be removed intact from the midgut. Instead, the midgut is removed from the bee, placed in 1% sodium dodecyl sulfate to lyse the midgut cells, and incubated for 2 h in a microcentrifuge tube at 37°C. The tube is inverted periodically to dislodge the remnants of the midgut cells. The supernatant is removed, and replaced with water three times, leaving only the PM. The PM is then stained with calcofluor white and examined by fluorescence microscopy. Calcofluor stains the chitin in the PM, and fluoresces vividly with emission and excitation maxima at 380 / 475 nm.
The Weak Worker Hypothesis: a new framework for understanding differences in individual and group division of labor.
Herman, JJ1; Walton, A1; Rueppell, O1
1Department of Biological Sciences, University of Alberta, Edmonton, Canada
Here I give an explanation and preliminary results of a framework for understanding division of labor that we call the “Weak Worker Hypothesis”. This research aims to test, specifically in Apis, if group level stress-mitigating behaviors are initiated and/or conducted primarily by individuals that are weakest to the given stressor. As preliminary results, I will present on colony heat stress in relation to individual fanners, colony cooling in relation to warming clusters, and colony food scarcity and individual starvation resistance. Further, I will suggest other colony level traits/responses that we may test in the future, as well as the possibility to compare and contrast to other social insects.
Determining the colony level impact of honey bee premature hive exit behavior in a field setting
Twombly-Ellis, J; Rangel, J
The Western honey bee, Apis mellifera, is both an economically important pollinator and a tractable system for studying the intricacies of eusociality. Honey bees are currently being challenged by multiple stressors, which act concomitantly to affect colony health. For instance, our research has documented the existence of a novel premature hive exiting behavior (PHEB) in response to developmental stress. This behavior leads to young bees dying shortly after emergence and draining colony resources. To understand the potential effects of PHEB on a colony level we conducted a field study with colonies that are allowed to PHEB and colonies that are not in order to observe their long-term survival and growth. We used eight colonies in each group. The control group was left untouched while the treatment had the PHE bees replaced each week for three months. We observed their colony dynamics during those three months as well as after. We found that both treatment groups had similar weights. However, the treatment group with the replaced PHE bees had lower mite loads and better survivorship than their control counterparts. This demonstrates that this premature hive exit behavior could have negative impacts on long-term colony survival.
Nutritional and pheromonal environment interact with hormonal regulation of honey bee worker longevity
Walton, A1; Corby-Harris, V2; Rueppell, O1
1Department of Biological Sciences, University of Alberta, Edmonton, Canada
2Carl Hayden Bee Research Center, USDA-ARS, AZ, USA
Hormones are major regulators of honey bee social biology that respond to multiple internal and external conditions to affect behavior, development and physiology. Adipokinetic hormone (AKH) is found widely in insects and stimulates the release of nutrient stores in the fat body. Yet, AKH’s role in honey bees remains predominantly unknown and controversial. We investigated the role of AKH and the adipokinetic hormone receptor in mobilizing worker bee nutrient stores and the subsequent effects on longevity. Here we present our findings on how AKH and the AKH receptor may contribute to the regulation of a honey bee worker’s nutritional investments in her own reproductive physiology and how the mobilization or retention of these stores affect how long she lives. Moreover, we examined the effects of AKH in the context of queen presence and absence to illuminate the interactions between queen pheromone (QMP) and hormonal modulation of worker physiology, and to better understand how the social context of the colony influences worker nutrient investment strategies. This work contributes to an understanding of how conserved nutrient sensing and mobilizing pathways regulate cooperation in honey bees and other social Hymenoptera.
Clustering Together to Characterize Winter Brood Production
Tsuruda, J; Barlett, L; Cook, S; Goblirsch, M; Jack, C; Rinkevich, F; Rogers, S; Tokach, R; Williams, G
Understanding the dynamics of brood production is key to effective colony management, including effective control of Varroa mites and nutrition. Specifically, the presence and amount of capped brood is a key consideration when using chemical treatments for mites. However, since inspection intervals lengthen during the Winter, our understanding of activity and brood production is not as deep as during the active, warm season. Given the variability of Winter conditions across the United States, a collaborative effort of researchers and Extension personnel (seven land-grant universities, one statewide cooperative extension system and five USDA ARS labs) came together to jointly monitor the amount of capped brood in their colonies from mid-October 2022 to the end of February 2023. Every two weeks, the number of frames of capped brood were measured, along with the number of frames of bees and management tactics were measured and recorded. The data were reported on a website so beekeepers and researchers could better understand what occurs in their colonies during the Winter and when management decisions could be most effective. This study continues with several more collaborators, including beekeepers, during the Winter of 2023-2024.
Seasonal changes in queen quality and worker-queen interactions in subtropical honey bee colonies
Carroll, MJ; Brown, NB; Anderson, KE
Workers maintain a viable resident queen throughout the year under variable conditions despite marked changes in queen signaling and productivity. We examined seasonal changes in queens and their supporting workers from colonies in warm subtropical regions. In contrast to queens from more temperate areas, these queens display nearly continuous oviposition through Winter and mid-Summer forage dearths. Retinue workers tended queens similarly through the months despite considerable variation in QMP signaling and brood productivity. Queen signaling of the QMP components 9-HDA, 9-ODA and HOB, (measured as residues recovered from retinue worker bodies) were lower in January than other months. Notably, residues of HVA, a QMP component associated with mated queens, were sharply higher in January when colony brood rearing substantially increases. Unlike queens from colder regions, these queens did not display early Winter atrophy of ovaries but maintained egg-laying potential through overwintering. Queens showed seasonal changes in relative nutrient allocations to reproductive and non-reproductive tissues (ovaries and fat bodies). Queens stored less protein and lipid in ovaries and more lipid in fat bodies during Winter compared to warmer months. The absence of seasonal differences in worker interactions with queens reflect continuous brood rearing efforts and queen oviposition throughout the year.
Hangry bees: When pollen deprivation, stock and parasitization collide
Walsh, E1; Avalos, A1; Simone-Finstrom, M1; Ihle, K1; Lau, P2
1Honey Bee Breeding, Genetics, and Physiology Unit, USDA-ARS, LA, USA
2 Pollinator Health in Southern Crop Ecosystem, USDA-ARS, MS, USA
Honey bees (Apis mellifera) encounter environmental stressors constantly, but it is unrealistic to evaluate the impact of individual stressors on phenotype when colonies realistically encounter multiple at any given time. In this study, we looked at how multiple stressors (pollen deprivation and parasite/disease state) interact and ultimately impact temperament. Temperament—especially aggression or defensiveness— is commonly thought to be dependent on genetic background, but our results show that environmental stressors also play a role in the resulting behavior as measured by aggression assays. Furthermore, we see that honey bee stock (Italian and Russian stocks were used in this experiment) also plays a role and is likely additionally impacted by Nosema parasitization. Ultimately, these stressors have a synergizing effect which results in a noticeable change in bee behavior, thus impacting the beekeeper. These results should be kept in mind when selecting apiary locations, stock of bees and end goal of keeping bees.
Vg-like gene expression varies with age and task
O’Brien, S; Pigott, E
The multifunctional protein Vitellogenin (Vg) is a key regulator in many aspects of honey bee social behavior and life history regulation, ranging from division of labor and foraging preferences to anti-inflammatory functions and cellular immunity. In recent years, three homologues of Vg have been identified in honey bees and other hymenopterans arising from ancient duplications: Vg-like A, B, and C. Despite the importance of Vg itself, very little follow-up work has been done on its homologues in honey bees. In ants, Vg-like A has been demonstrated to have a functional role in brood care and division of labor and Vg-like C is associated with foraging behavior. In honey bees, it has been suggested that Vg-like A may retain the anti-inflammatory, antioxidant and storage roles of Vg, while Vg-like B may have a role in protection from oxidative damage. Here, we fill an essential knowledge gap by separating the roles of chronological age from behavioral task in the expression of the Vg-like genes. We found that while Vg-like A expression is associated with nursing behavior, expression of Vg-like C is associated with chronological age.
Environment and Ecosystem Interactions
Evidence revealing interactions between honey bees and non-flowering plants.
Miller, MS1 ; Alger, S1 ; Borch, B1 ; Burnham, PA2 ; Lagasse, H3 ; Barrett, C1 ; Patel, N3
1Plant and Soil Science Department, University of Vermont, VT, USA
2Biology Department, University of Vermont, VT, USA
3Biology Department, Trinity College, CT, USA
Ferns and mosses lack the coevolved relationships with animals, such as honey bees, upon which flowering plants rely for dispersal. Instead, the dispersal of fern and moss spores is thought largely to be passive, with spores landing close to the parent plants and hence limiting dispersal distance. Here, we explore the possibility of moss and fern spore dispersal by honey bees via passive encounters during foraging trips. Bee-collected pollen and nectar samples were collected from five apiaries in Vermont from May-September and analyzed for plant genetic composition. Moss (family Bryaceae) and fern (family Osmundaceae) DNA were observed in 12.5% of nectar samples. Individual pollen loads and flower samples were evaluated for spore presence using microscopy. We found that 58% of pollen loads contained moss and fern spores, while 21% of flowers harbored fern spores. Pollen loads were plated onto Knops media and maintained until germination was observed. Moss spores successfully germinated on 33% of plates. Our preliminary findings suggest that bees likely encounter spores incidentally while foraging for nectar, pollen or water. But, even the occasional passive dispersal of spores may have implications for the distribution of ferns and mosses. Our findings suggest that honey bees may play a larger role in spore dispersal than previously thought.
A Metagenomic Survey Investigating Viral Spillover Between Bumblebees and Honey Bees
McKeown, DA; Evans, E; Mendel, B; Helgen, J; Spivak, M; Schroeder, DCS
In the context of apiculture, viruses are well known as major contributors to colony collapse, primarily for the European honey bee, Apis mellifera. There are concerns that viral infections within apiculture systems can spread, or spillover, to wild bee populations. In North America, the question of spillover is especially important, given that the widely cultured A. mellifera is non-native, and therefore has the potential to introduce novel diseases to native bees. We investigated spillover between A. mellifera and native Bombus spp. with metagenomic screening in Minnesota, with sampling repeated monthly during the Spring and Summer from 2021 to 2023. The viromes of A. mellifera and Bombus were composed of distinct viruses, which indicated that no spillover occurred during our study, regardless of the proximity to the A. mellifera colonies. Despite A. mellifera commonly containing Deformed Wing Virus (DWV), Black Queen Cell Virus (BQCV), Sacbrood Virus (SBV), Lake Sinai Virus (LSV) and Acute Bee Paralysis Virus (ABPV), Bombus only possessed two other novel viruses.
Properties of spotted lanternfly honeydew honey, a new varietal resulting from an introduced invasive insect
Underwood, R; Kotlar, P; Ozturk, F
The spotted lanternfly (SLF), Lycorma delicatula, was first detected in Berks County, Pennsylvania in September 2014 and has since spread to 13 additional states. This invasive planthopper feeds on the phloem of over 170 plant species. In the adult stage, lanternflies aggregate on tree trunks and excrete large quantities of honeydew. This sugary liquid is subsequently collected by honey bees and stored in the hive as honey. Beekeepers raised the alarm about a dark, smoky, earthy honey found in hives in SLF quarantine zones in Fall 2019. Samples of this honey were tested for possible pesticide residues from SLF control efforts; dinotefuran, imidicloprid and triclopyr. These pesticides are not found often and were at exceedingly low levels when they were present. DNA testing of the honey proved positive for SLF. Ailanthone, a chemical produced by a favorite tree, Ailanthus altissima, was found at varying levels. Tests of the health properties of this honey have shown that it is highly medicinal, with zones of inhibition exceeding that of manuka honey in lab tests. Informal taste tests by the general public show that this honey is well liked by approximately 90% and highly disliked by the remaining 10%. This new varietal is a boon to beekeeping, as it saves beekeepers the time, effort and money required for Fall feeding when lanternflies are abundant in an area.
Identification of and response to the first documented invasive population of the yellowlegged hornet, Vespa velutina, in the Americas
Bartlett, LJ1,2; Hoebeke, R1,3; Wares, J2,3; Freeman, B2,3; Delaplane, KS1
1Department of Entomology, University of Georgia, GA, USA
2Odum School of Ecology, University of Georgia, GA, USA
3Georgia Natural History Museum, GA, USA
Updates on the ever-evolving case of Vespa velutina in Savannah, GA including genetic analysis, control and eradication efforts, detection and tracking tactics, collaboration with neighboring states and bee labs, and plans for future control, eradication or mitigation. In 2023, five colonies were found, all in GA. Single instances of individuals were found across the river in SC. Preliminary genetic analysis suggests a single queen from either its native range in south China or from the invasive populations in Korea or Japan. All located nests are within <4 miles of a central point, but evidence suggests some nests remained undiscovered and began producing reproductives.
Honey bee (Apis mellifera) foraging preferences are negatively correlated with Alfalfa leafcutting bee (Megachile rotundata) productivity in Virginian landscapes
Couvillon, MJ; Campbell, CD; Ohlinger, BD; Malone, S; O’Rourke, ME; Taylor, SV; Schürch, R
Honey bees may serve as bioindicators of habitat quality because we can observe, decode, map and analyze the information encoded in the waggle dance, which allows us to know where and when bees are collecting high quality forage. Previously, we measured honey bee foraging for two years (2018-2019) by dance decoding at three sites in Virginia. Here we use that data to predict the success of a non-Apis bee, the Alfalfa leafcutting bee (Megachile rotundata), in these same landscapes. We installed 15 nest boxes at each of the three sites, stocked with nesting materials and 160 cocoons, at a range of honey bee foraging propensities. From May-August 2021, we monitored the boxes and collected relative floral abundance data. We found that there was an overall negative relationship between honey bee foraging probability and Alfalfa leafcutting bee productivity (p < 0.001), where areas of higher honey bee foraging were associated with lower leafcutting bee productivity. This surprising result is in the opposite direction to our original hypothesis. Additionally, M. rotundata productivity varied by site and was positively associated with clover abundance. These data demonstrate that honey bees as bioindicators may be species and context-specific and possibly even in the opposite direction.
Validation of honey bees as bioindicators for native bees
Schürch, R; Ostrom, R; Ohlinger, BD; O’Rourke, ME; Couvillon, MJ
Honey bees have been proposed as bio-indicators for themselves and for other insect pollinators. The rationale is that honey bees are optimal foragers that can scout a landscape and find the best spots to forage at any given time. Because they are generalist foragers, where they find food, the landscape should generally be good for pollinators, and native bees in particular. Since we can study where honey bees forage by observing their waggle dances, we hypothesized that we could then assess the landscape for suitability for native bees by decoding where honey bees have foraged. Here we tested this idea using more than eleven thousand waggle dances across three landscapes in Virginia. Specifically, we tested if honey bee foraging predicted native bee abundance and diversity in Blacksburg, Winchester and Suffolk, Virginia. Over two seasons, in 2021 and 2022, we surveyed native bee health using sweep nets, blue vane traps and bee bowls in landscapes that had previously been assessed by honey bees. We find mixed evidence for a relationship between honey bee foraging and native bee population health. We discuss this evidence in relation to native bee traits such as social organization, generalist vs. specialists and nesting modality.
Prevalence and co-occurrence of honey bee-associated pathogens in native bees and wasps
Deutsch, K1; Graham, JR2,3; Boncristiani, HF2,4; Bustamante, T2,5; Mortensen, AN2,6; Schmehl, DR2,7; Wedde, AE2,8; Lopez, DL9; Evans, JD9; Ellis, JD2
1Department of Entomology, Cornell University, NY, USA
2Entomology and Nematology Department, University of Florida, FL, USA
3Planet Bee Foundation, CA, USA
4Inside The Hive Media, Consulting Inc.
5Independent collaborator
6The New Zealand Institute for Plant and Food Research Limited
7Bayer CropScience LP
8Driscoll’s Global R&D
9Agricultural Research Service, United States Department of Agriculture
Recent research has demonstrated that pathogens associated with honey bees are shared by other pollinators and can negatively affect their health. We surveyed honey bees and 15 native bee and wasp species for 13 pathogens traditionally associated with honey bees. We found at least one honey bee-associated pathogen in 53% of native bee and wasp samples. The most widely distributed and commonly detected pathogens were Nosema ceranae (detected in 18% of native bees and wasps), Melissococcus plutonius (24%), Ascophaera apis (9%), Deformed wing virus (8%) and Black queen cell virus (9%). The prevalence of viruses was generally higher in honey bees than in native bees and wasps. However, the prevalence of M. plutonius and A. apis was significantly higher in some native bee species than in honey bees. Often, multiple pathogens occurred in a single individual for many bee/wasp species (including honey bees), with some species having up to four pathogens co-occurring in a single individual. Our data do not tell us about the impact the identified pathogens may have on native bee and wasp health. Yet, trends in pathogen prevalence are the first step toward evaluating the risk posed by pathogen spillover between managed and native pollinators.
Modeling floral diversity suggests a dilution effect for RNA viruses in transmission between honey bees and bumblebees
Burnham, PA1; Alger, SA2
1 Biology Department, University of Vermont, VT, USA
2 Plant and Soil Science Department, University of Vermont, VT, USA
Both managed and wild bees face a growing number of threats including the spread of RNA viruses between and within bee species. For example, RNA viruses, as well as some other shared pathogens, have been shown to be transmitted between honey bees and bumblebees through the use of shared flowers. As a bridge of transmission, understanding the roles that floral abundance, diversity and composition play in modifying transmission rates is an important step in reducing transmission on the landscape. Flower species are known to harbor viruses differentially. These nonuniform distributions coupled with bee’s nonrandom foraging strategies (such as floral constancy) may provide a mechanism for flowers to influence transmission through dilution or amplification effects. In this study, we used an agent-based modeling approach to test how bee and floral abundance, bee foraging strategies and floral diversity influenced transmission of a DWV-like virus. We found that transmission was reduced when modeled in diverse landscapes as compared to monocultures providing evidence for a dilution effect in this system. Increased floral abundance also reduced transmission in both bumblebees and honey bees by reducing the likelihood of bees of both genera visiting the same flower. Finally, when bees exhibited higher levels of floral constancy, transmission was further reduced. These results indicate that disease reduction in bee species could be accomplished by managing floral landscapes. By increasing floral diversity and abundance, we may not only improve forage and habitat for bees and other animal species, but also decrease virus transmission. Future empirical studies that build on our results should test this theory in the field and aim to provide guidelines surrounding flower planting and management strategies.
American Bison as Bee Habitat Engineers
Red-Laird, S; Gardner, S
The modern agricultural practice of monoculture which creates habitat loss, and an overuse of pesticides and other synthetic chemicals is connected to staggering losses of honey bee (Apis mellifera) colonies. What if a major solution for bee loss is a bison burger? Holistically managed bison herds are currently being utilized to mimic the historical ecological impact these animals had on the pre-colonial Great Plains. We theorize the trophic rewilding of the landscape at the 28,000-acre 777 Bison Ranch – which is grazed by a herd of over 2,400 American bison (Bison bison) and 1,124 honey bee colonies – has restored nutrient dense habitat for bees. To understand the potentially synergistic or mutualistic interactions between honey bees, native bees and bison we have installed multi-year vegetation and pollinator monitoring areas at the ranch. These efforts will examine bee nesting frequency, bee habitat, bee communities and flower pollen availability and nutritional content. Findings from our project could positively influence future conservation, policy and land management decisions for both bees and bison.
Bees, Bean, and the Golden Forage: Improving Honey Bee Health with Mustard Cover Crop in Soybean Agricultural Systems
Lin, C-H1; Hearon, L1; Jasinski, J2; Johnson, RM1; Li-Byarlay, H3
1Department of Entomology, The Ohio State University, OH, USA
2Department of Extension, The Ohio State University, OH, USA
3Agricultural Research Development Program, Department of Agricultural and Life Sciences, Central State University, OH, USA
Honey bee colonies in soybean growing regions often benefit from the brief surge of nectar flow produced by immense fields of soybean flowers in mid-Summer. However, this same landscape could also exhibit an extreme dearth when soybeans are not in bloom. Mustards (Brassica juncea) can be grown to flower when soybean is out of bloom to provide pollen and nectar. Mustards also produce glucosinolates with antimicrobial activity that could control pathogens. We tested if mustards planted as a cover crop could provide both supplemental floral resources and an antimicrobial effect against the fungal gut pathogen Vairimorpha (formerly Nosema) in honey bees. One acre of mustards was planted at four locations in April, terminated in July and replanted in August. The timing of mustard planting provided peak blooms in June and September, typical periods with few floral resources in soybean-dominated regions of Ohio. Mustard pollen made up over 50% of pollen collected by honey bee colonies near blooming mustard fields, which also exhibited a reduction in Vairimorpha spore counts in early Summer. Laboratory studies are underway to isolate the effects of mustard pollen on Vairimorpha. Incorporation of bee-friendly cover crops, such as mustards, in soybean cropping systems could be an effective approach to improve pollinator health in the agroecosystem.
Comparing the critical temperature maximum of wild and managed honey bee (Apis mellifera) populations
Twombly-Ellis, J; Harpur, BA; Rangel, J
Honey bees (Apis mellifera) contribute $16 billion dollars annually to the world’s economy. Despite their importance, we see annual losses of managed populations around 30% due to pests, parasites and pathogens. Furthermore, beekeepers also worry about a changing climate and how to mitigate additional colony losses associated with this factor. One avenue that is understudied is populations of wild honey bees that are scattered throughout the U.S. They live without any human intervention and as such they have been allowed to locally-adapt to their environment. There is a large population of wild honey bees located at the Welder Wildlife Refuge (WWR) near Sinton, Texas, that has been free-living for over thirty years. I compared the critical temperature maximum of three different populations: the wild population at the WWR, a managed population that has been allowed to adapt to local environmental conditions and managed colonies that were purchased from California. To test these differences, we made a temperature rig to expose individual honey bees to an increase in temperature at the rate of 0.25°C/min. We found no significant difference in the Ctmax between treatment groups. This indicates that perhaps managed colonies can handle acute temperature stress similar to wild colonies.
Does the western honey bee (Apis mellifera; Apidae) have a reliance for Chinese tallow tree (Triadica sebifera; Euphorbiaceae)?
Standley, JM; Abbate, A; Chakrabarti, P.; Bennett, M; DeGrandi-Hoffman, G; Corby-Harris, V; Gaffke, A; Lau, P; Williams, G
The Chinese tallow tree (Triadica sebifera) is considered an invasive species in the USA that many landowners struggle to manage. Well-known by beekeepers as a nectar producing tree, we wanted to determine the extent to which honey bees forage on tallow. Therefore, we collected corbicular pollen and unripened honey (honey from uncapped cells) during its bloom period in late Spring: 13 colonies (locations: southern and east-central Alabama) were sampled in 2022, whereas 93 colonies (locations: southern and east-central Alabama and Mississippi) were sampled in 2023. Additionally, pollen and nectar were collected directly from tallow inflorescences from four locations (northern Florida, east-central Alabama and southern/northern Mississippi) in Spring 2023 to assess nutritional qualities. Preliminary data demonstrated tallow pollen and nectar foraging by honey bees during the sampling period. Future work will analyze the samples collected in 2023, thereby broadening the knowledge gap the role tallow provides for the honey bee in the U.S. southeast.
Landscape impacts on commercial honey bee hive health and mortality
Kuesel, R; Zhang, G; Olsson, R; Hopkins, B
Honey bee colonies managed commercially for pollination services and a Fall honey harvest incur high hive mortality for reasons not completely understood. Commercial Washington beekeepers often transport their colonies by truck to California’s San Joaquin Valley for almond pollination in early Spring. Colonies then return to Washington and continue a series of moves between fruit and vegetable seed crops, before ending in a forage landscape with late-season nectar flow. We know this movement incurs stresses in many forms (e.g. excessive heat or cold during long-distance movement and repeated contact with pesticides), but food availability at each pollination event may play a role in whether hives grow or collapse. The WSU honey bee team followed select commercial colonies across the 2022 and 2023 seasons to track their health at each pollination event. By analyzing metrics of colony health with linear mixed-effects models, we expected to find some health metrics are correlated with quantifiable facets of the landscape including coverage and diversity of cropland and non-crop vegetation. However, at this time we have not found consistent correlations. Continued analysis may help us understand a potential cause of hive mortality and can help beekeepers better decide equitable prices to charge for pollination services.
From Dawn to Diet; Are Honey Bees Right for Pumpkins?
Walls, C; Couvillon, MJ; Kuhar, T; Roulston, T; Yang, S; Wilson, J
Honey bees (Apis mellifera L.) are widely documented pollinators of plants in the genus, Cucurbita. Cucurbita pepo, including pumpkins, require bee pollinators to move pollen from male to female flowers for fruit to set. Pumpkin growers often establish honey bee pollination contracts based on current agricultural recommendations. This study examines the frequency of honey bees in pumpkin fields across VA using visual observations, bowl trapping, vacuum sampling and camera trapping methods. Through these field observations honey bees were found to be infrequent even with hives on sight. Low numbers of honey bees observed in the field raises concerns about honey bee health and nutrition in this pollination dependent system, as recently released work shows that pumpkin pollen is toxic to other bee types. As such, we conducted a feeding trial where bees were supplied only Cucurbita pepo pollen for 10 days to observe if changes in bees’ microbiome had occurred. Ultimately, the results from this study will allow us to revisit pumpkin pollination recommendations, ideally, to the benefit of both the producers and the bees. These studies contribute to a growing body of evidence that honey bees may not be the suitable bees to add into a pumpkin system.
Oxidative Stress Levels in Two Pollinators from Three Different Landscapes
Briscoe, K; Li-Byarlay, M; Rehan, S; Li-Byarlay, H; Johnson, R
It is well known that different environments can lead to stress in pollinators. Two important pollinators in agriculture are honey bees (Apis mellifera) and small carpenter bees (Ceratina calcarata). Different landscapes: conventional, organic, roadside utilize different pesticides and management practices for pest control. The roadside landscape is a control for minimum application of herbicides and management. Oxidative stress (OX) is a state of imbalance between antioxidants and reactive oxygen species, which are the byproducts of oxidative phosphorylation in the mitochondria. It is unknown whether the differences in these landscapes affect the oxidative stress of pollinators. Conventional farms offer the most exposure to pesticides, which have been related to increased stress levels. We hypothesized that honey bees and small carpenter bees (SCB) from conventional farms would experience the highest levels of OX. Results from the Thio Barbituric Acid Reactive Substances (TBARS) assay indicated that honey bees and SCB of organic, conventional and roadside landscapes experienced lowest to highest OX levels. While this is not representative of the presumed outcome, previous research has shown that feral bees have a tolerance to high stress levels. The same could be true of honey bees and SCB from roadside landscapes, where the conditions imitate natural habitats. Organic farms use naturally derived pesticides and moderate management practices, likely contributing to their lower levels. Examining how these pollinators are affected by different farm landscapes can reveal the benefits and detriments of their corresponding management practices. This will hopefully lead to streamlined practices that are healthier for pollinators.
Bottom-up effects of agricultural management practices on bee health
Lau, P
To maximize agricultural production, farmers and land managers have adopted various land management strategies to increase crop yield and profitability. These management practices, including conservation tilling and cover cropping, in agroecosystems can affect soil health, plant physiology and yield. For bees, the agricultural landscapes present a unique nutritional landscape, which can be altered by the management practices farmers implement to improve yield. Few studies have addressed possible changes in the nutritional landscape from a pollinator’s perspective. Our objective is to use an integrative approach to understand how changes in the abiotic environment can indirectly affect bee health through multiple trophic levels. We tested how different combinations of cover crops, including clover, rye and vetch, can affect soil health and corn pollen nutritional quality. We also tested how different conservation tillage practices affect soil health and the pollen and nectar cotton produced. Understanding the patterns and mechanisms of such bottom-up processes is critical for the development of predictive models of the effects of habitat-altering events on ecology, and more generally, to develop an understanding of how the abiotic environment affects ecosystems.
