A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission.

The ectoparasite Varroa destructor is the greatest threat to managed honey bee (Apis mellifera) colonies globally. Despite significant efforts, novel treatments to control the mite and its vectored pathogens have shown limited efficacy, as the host remains naïve. A prospective solution lies in the development of Varroa-resistant honey bee stocks, but a paucity of rigorous selection data restricts widespread adoption. Here, we characterise the parasite and viral dynamics of a Varroa-resistant honey bee stock, designated 'Pol-line', using a large-scale longitudinal study. Results demonstrate markedly reduced Varroa levels in this stock, diminished titres of three major viruses (DWV-A, DWV-B, and CBPV), and a two-fold increase in survival. Levels of a fourth virus that is not associated with Varroa-BQCV-do not differ between stocks, supporting a disruption of the transmission pathway. Further, we show that when decoupled from the influence of Varroa levels, viral titres do not constitute strong independent predictors of colony mortality risk. These findings highlight the need for a reassessment of Varroa etiology, and suggest that derived stocks represent a tractable solution to the Varroa pandemic.

Social Apoptosis in Varroa Mite Resistant Western Honey Bees (Apis mellifera).

Honey bees are eusocial animals that exhibit both individual and social immune responses, which influence colony health. This is especially well-studied regarding the mite Varroa destructor Anderson and Trueman (Parasitiformes: Varroidae), a parasite of honey bee brood and disease vector. Varroa was introduced relatively recently to Apis mellifera L. (Hymenoptera: Apidae) and is a major driver of the catastrophic die-off of honey bee colonies in the last decade. In contrast, the original host species, Apis cerana Fabricius (Hymenoptera: Apidae) is able to survive mite infestations with little effect on colony health and survival. This resilience is due in part to a newly identified social immune response expressed by developing worker brood. Varroa infested female A. cerana brood experience delayed development and eventually die in a process called 'social apoptosis'. Here, an individual's susceptibility to Varroa results in colony level resistance. We tested for the presence of the social apoptosis trait in two Varroa resistant stocks of A. mellifera (Pol-line and Russian) with different selection histories and compared them to a known Varroa-susceptible stock (Italian). We assessed the survival and development of worker brood reared in either highly or lightly infested host colonies, then receiving one of three treatments: uninfested, experimentally inoculated with a Varroa mite, or wounded to simulate Varroa damage. We found that response to treatment was only differentiated in brood reared in lightly infested host colonies, where experimentally infested Russian honey bees had decreased survival relative to the mite-susceptible Italian stock. This is the first evidence that social apoptosis can exist in Western honey bee populations.

A non-activating diluent to prolong in vitro viability of Apis mellifera spermatozoa: Effects on cryopreservation and on egg fertilization.

A non-activating semen diluent does not cause motility or acrosomal reaction or capacitate the sperm cell. The effects of such a diluent on the viability of honey bee spermatozoa stored in ambient conditions were assessed 60 days pre-cryopreservation and 24 h post-cryopreservation. Seven variations of a Tris-based non-activating diluents (FEM1 - FEM7) were compared to samples treated with conventional activating diluent and untreated semen. Semen viability (membrane integrity) was assessed after short- and long-term storage at 14.0 ± 0.2 °C. The non-activating medium FEM7 contained more viable spermatozoa than the activating medium, 24 h after cryopreservation (67.6 ± 10.9% and ~4%, respectively). After 60 days, 22.0 ± 7.8% of spermatozoa was viable in non-activating medium versus 0.0 and 60.8 ± 12.3%, in conventional media and untreated controls, respectively. Hence FEM7 was used to cryopreserve bee semen and subsequently inseminate honey bee queens. The quality of brood produced by the queens was assessed 30-60 days after insemination. The percentage of worker-bee offspring (produced from successfully fertilized eggs) was ~75% for both the non-activating medium and the conventional extender medium. Our results indicate that a non-activating medium possesses significant advantage over the conventional activating medium if the semen requires storage after treatments such as cryopreservation. The percentage of female offspring (from fertilized eggs) produced by queens inseminated with semen diluted in either the activating or non-activating medium did not differ from one another.

Association Between Density of Foraging Bees and Fruit Set in Commercial Fields of Rabbiteye Blueberries (Ericales: Ericaceae) in Louisiana and Mississippi.

Field-scale data on the relationship between pollinator activity and fruit set are scarce for rabbiteye blueberries (Vaccinium virgatum Aiton). We measured the densities of Apis mellifera L. (Hymenoptera: Apidae), Habropoda laboriosa F. (Hymenoptera: Apidae), Bombus Latreille (Hymenoptera: Apidae) spp., and Xylocopa virginica L. (Hymenoptera: Apidae) in 7-21 commercial fields during each of 3 yr in Louisiana and Mississippi. Foraging bees were counted on 10 'Tifblue' bushes per field on 2 d during bloom, and the density of bees per flower was calculated based on the number of flowers open during the counts. Fruit set was measured 30 d after bloom. The impact of foraging activity on fruit set was inconsistent when densities of either all foragers or foragers of individual taxa were considered. Strong associations were observed only in 2001, with fruit set increased by H. laboriosa and Bombus and with a weaker contribution by A. mellifera. Floral robbery by X. virginica had no measurable negative effects. Populations of H. laboriosa were more consistent than those of other bees across sites. Managed colonies of A. mellifera were added at two densities (12.5 or 2.5 colonies per hectare) in seven fields each in 2001. These supplemental bees did not result in greater forager densities or fruit set in stocked fields. The observations show the challenge of field-scale pollination tests but provide an initial framework for rabbiteye blueberry growers to assess the availability of foraging bees early in bloom to help decide whether to add supplemental A. mellifera to try to enhance pollination if populations of non-Apis bees are low.

Larval Pollen Stress Increases Adult Susceptibility to Clothianidin in Honey Bees.

Neonicotinoid insecticides have come under scrutiny for their potential role in honey bee declines. Additionally, reduced access to forage in agricultural areas creates the potential for risk interactions with these pesticides in regions critical for honey production. In this study, we sought to determine whether sufficient access to pollen during larval development could mitigate stress associated with oral clothianidin exposure in honey bee adults. An apiary was established where pollen traps deprived half of the colonies of pollen, which was then supplemented to the others. Adults were fed 0, 10, 40, 200, or 400 µg/L clothianidin in the laboratory, and larval and adult lipids and superoxide dismutase (SOD) activities were compared between feeding treatments. Survival at sublethal concentrations of clothianidin was significantly reduced for adult bees reared in pollen deprived colonies. Adult SOD activity was affected by clothianidin dose but not larval feeding treatment, though within the pollen-deprived cohort, SOD was greater in controls than those fed clothianidin. Larval SOD differed between field replicates, with supplemented colonies having slightly higher activity levels during a period of pollen dearth, indicating that supplementation during these periods is particularly important for mitigating oxidative stress within the hive. Larval lipids were significantly higher in supplemented colonies during a substantial pollen flow, though adult lipids were unaffected by feeding treatment. These results suggest that during periods of pollen dearth, oxidative stress and adult worker longevity will be improved by supplementing colonies with locally collected pollen.

Effects of truck-mounted, ultra low volume mosquito adulticides on honey bees (Apis mellifera) in a suburban field setting.

Few studies have examined the impact of mosquito adulticides on honey bees under conditions that reflect actual field exposure. Whereas several studies have evaluated the toxicity of mosquito control products on honey bees, most have been laboratory based and have focused solely on acute mortality as a measure of impact. The goal of this study was to determine effects of routine applications of truck-based ultra-low volume (ULV) mosquito adulticides (i.e., Scourge, Duet, and Deltagard) on honey bees in a suburban setting. The mosquito adulticides used in this study were pyrethroids with active ingredients resmethrin (Scourge), prallethrin and sumithrin (Duet), and deltamethrin (Deltagard), in which resmethrin, prallethrin, and sumithrin were synergized with piperonyl butoxide. We measured and compared mortality and detoxification enzyme activities (esterase and glutathione S-transferase) from sentinel beehives within and outside of mosquito control areas. Concurrently, colony health (i.e., number of adult bees, brood quantity and brood quality) was compared throughout the study period. No significant differences were observed in honey bee mortality, colony health or detoxification enzyme activities between treated (five sprayed areas each received one to three insecticide treatment) and control sites (four unsprayed areas that did not receive insecticide treatment) over the seven week study period. However, our laboratory study showed that exposure to resmethrin, the active ingredient in Scourge, caused significant inhibition of esterase activity compared with the control group. Our findings suggest that proper application of truck based insecticides for mosquito control results in little or no exposure and therefore minimal effects on domestic honey bees.

Influence of Varroa Mite (Varroa destructor) Management Practices on Insecticide Sensitivity in the Honey Bee (Apis mellifera).

Since Varroa mites may cause devastating losses of honey bees through direct feeding, transmitting diseases, and increasing pathogen susceptibility, chemical and mechanical practices commonly are used to reduce mite infestation. While miticide applications are typically the most consistent and efficacious Varroa mite management method, miticide-induced insecticide synergism in honey bees, and the evolution of resistance in Varroa mites are reasonable concerns. We treated colonies with the miticide amitraz (Apivar®), used IPM practices, or left some colonies untreated, and then measured the effect of different levels of mite infestations on the sensitivity of bees to phenothrin, amitraz, and clothianidin. Sensitivity to all insecticides varied throughout the year among and within treatment groups. Clothianidin sensitivity decreased with increasing mite levels, but no such correlation was seen with phenothrin or amitraz. These results show that insecticide sensitivity is dynamic throughout the 5 months test. In-hive amitraz treatment according to the labeled use did not synergize sensitivity to the pesticides tested and this should alleviate concern over potential synergistic effects. Since IPM practices were largely ineffective at reducing Varroa mite infestation, reliance on chemical methods of Varroa mite management is likely to continue. However, miticides must be used judiciously so the long term effectiveness of these compounds can be maximized. These data demonstrate the complex and dynamic variables that contribute to honey bee colony health. The results underscore the importance of controlling for as many of these variables as possible in order to accurately determine the effects of each of these factors as they act alone or in concert with others.

Genetics, Synergists, and Age Affect Insecticide Sensitivity of the Honey Bee, Apis mellifera.

The number of honey bee colonies in the United States has declined to half of its peak level in the 1940s, and colonies lost over the winter have reached levels that are becoming economically unstable. While the causes of these losses are numerous and the interaction between them is very complex, the role of insecticides has garnered much attention. As a result, there is a need to better understand the risk of insecticides to bees, leading to more studies on both toxicity and exposure. While much research has been conducted on insecticides and bees, there have been very limited studies to elucidate the role that bee genotype and age has on the toxicity of these insecticides. The goal of this study was to determine if there are differences in insecticide sensitivity between honey bees of different genetic backgrounds (Carniolan, Italian, and Russian stocks) and assess if insecticide sensitivity varies with age. We found that Italian bees were the most sensitive of these stocks to insecticides, but variation was largely dependent on the class of insecticide tested. There were almost no differences in organophosphate bioassays between honey bee stocks (<1-fold), moderate differences in pyrethroid bioassays (1.5 to 3-fold), and dramatic differences in neonicotinoid bioassays (3.4 to 33.3-fold). Synergism bioassays with piperonyl butoxide, amitraz, and coumaphos showed increased phenothrin sensitivity in all stocks and also demonstrated further physiological differences between stocks. In addition, as bees aged, the sensitivity to phenothrin significantly decreased, but the sensitivity to naled significantly increased. These results demonstrate the variation arising from the genetic background and physiological transitions in honey bees as they age. This information can be used to determine risk assessment, as well as establishing baseline data for future comparisons to explain the variation in toxicity differences for honey bees reported in the literature.

Functionality of Varroa-resistant honey bees (Hymenoptera: Apidae) when used for western U.S. honey production and almond pollination.

Two types of honey bees, Apis mellifera L., bred for resistance to Varroa destructor Anderson & Trueman, were evaluated for performance when used for honey production in Montana, and for almond pollination the following winter. Colonies of Russian honey bees and outcrossed honey bees with Varroa-sensitive hygiene (VSH) were compared with control colonies of Italian honey bees. All colonies were managed without miticide treatments. In total, 185 and 175 colonies were established for trials in 2010-2011 and 2011-2012, respectively. Survival of colonies with original queens or with supersedure queens was similar among stocks for both years. Colony sizes of the Varroa-resistant stocks were as large as or larger than the control colonies during periods critical to honey production and almond pollination. Honey production varied among stocks. In the first year, all stocks produced similar amounts of honey. In the second year, Russian honey bees colonies produced less honey than the control colonies. V. destructor infestations also varied among stocks. In the first year, control colonies had more infesting mites than either of the Varroa-resistant stocks, especially later in the year. In the second year, the control and outcrossed Varroa-sensitive hygiene colonies had high and damaging levels of infestation while the Russian honey bees colonies maintained lower levels of infestation. Infestations of Acarapis woodi (Rennie) were generally infrequent and low. All the stocks had similarly high Nosema ceranae infections in the spring and following winter of both years. Overall, the two Varroa-resistant stocks functioned adequately in this model beekeeping system.

High-resolution linkage analyses to identify genes that influence Varroa sensitive hygiene behavior in honey bees.

Varroa mites (V. destructor) are a major threat to honey bees (Apis melilfera) and beekeeping worldwide and likely lead to colony decline if colonies are not treated. Most treatments involve chemical control of the mites; however, Varroa has evolved resistance to many of these miticides, leaving beekeepers with a limited number of alternatives. A non-chemical control method is highly desirable for numerous reasons including lack of chemical residues and decreased likelihood of resistance. Varroa sensitive hygiene behavior is one of two behaviors identified that are most important for controlling the growth of Varroa populations in bee hives. To identify genes influencing this trait, a study was conducted to map quantitative trait loci (QTL). Individual workers of a backcross family were observed and evaluated for their VSH behavior in a mite-infested observation hive. Bees that uncapped or removed pupae were identified. The genotypes for 1,340 informative single nucleotide polymorphisms were used to construct a high-resolution genetic map and interval mapping was used to analyze the association of the genotypes with the performance of Varroa sensitive hygiene. We identified one major QTL on chromosome 9 (LOD score = 3.21) and a suggestive QTL on chromosome 1 (LOD = 1.95). The QTL confidence interval on chromosome 9 contains the gene 'no receptor potential A' and a dopamine receptor. 'No receptor potential A' is involved in vision and olfaction in Drosophila, and dopamine signaling has been previously shown to be required for aversive olfactory learning in honey bees, which is probably necessary for identifying mites within brood cells. Further studies on these candidate genes may allow for breeding bees with this trait using marker-assisted selection.

Functionality of Varroa-resistant honey bees (Hymenoptera: Apidae) when used in migratory beekeeping for crop pollination.

Two types of honey bees, Apis mellifera L. (Hymenoptera: Apidae), bred for resistance to Varroa destructor Anderson & Trueman were evaluated for performance when used in migratory crop pollination. Colonies of Russian honey bees (RHB) and outcrossed bees with Varroa-sensitive hygiene (VSH) were managed without miticide treatments and compared with colonies of Italian honey bees that served as controls. Control colonies were managed as groups which either were treated twice each year against V. destructor (CT) or kept untreated (CU). Totals of 240 and 247 colonies were established initially for trials in 2008 and 2009, respectively. RHB and VSH colonies generally had adult and brood populations similar to those of the standard CT group regarding pollination requirements. For pollination of almonds [Prunus dulcis (Mill.) D.A.Webb] in February, percentages of colonies meeting the required six or more frames of adult bees were 57% (VSH), 56% (CT), 39% (RHB), and 34% (CU). RHB are known to have small colonies in early spring, but this can be overcome with appropriate feeding. For later pollination requirements in May to July, 94-100% of colonies in the four groups met pollination size requirements for apples (Malus domestica Borkh.), cranberries (Vaccinium macrocarpon Aiton), and lowbush blueberries (Vaccinium angustifolium Aiton). Infestations with V. destructor usually were lowest in CT colonies and tended to be lower in VSH colonies than in RHB and CU colonies. This study demonstrates that bees with the VSH trait and pure RHB offer alternatives for beekeepers to use for commercial crop pollination while reducing reliance on miticides. The high frequency of queen loss (only approximately one fourth of original queens survived each year) suggests that frequent requeening is necessary to maintain desired genetics.

Expression of Varroa sensitive hygiene (VSH) in commercial VSH honey bees (Hymenoptera: Apidae).

We tested six commercial sources of honey bees, Apis mellifera L. (Hymenoptera: Apidae), whose breeding incorporated the trait of Varroa sensitive hygiene (VSH). VSH confers resistance to the parasitic mite Varroa destructor Anderson & Trueman by enhancing the ability of the bees to hygienically remove mite-infested brood. VSH production queens (i.e., queens commercially available for use in beekeepers' production colonies) from the six sources were established in colonies which later were measured for VSH. Their responses were compared with those of colonies with three other types of queens, as follows: VSH queens from the selected closed population maintained by USDA-ARS for research and as a source of breeding germplasm, queens from the cooperating commercial distributor of this germplasm, and queens of a commercial, mite-susceptible source. The reduction of mite infestation in brood combs exposed to test colonies for 1 wk differed significantly between groups. On average, colonies with VSH production queens reduced infestation by 44%. This group average was intermediate between the greater removal by pure ARS VSH (76%) and the cooperators' breeding colonies (64%), and the lesser removal by susceptible colonies (7%). VSH production colonies from the different sources had variable expression of hygiene against mites, with average reduced infestations ranging from 22 to 74%. In addition, infertility was high among mites that remained in infested cells in VSH breeder colonies from ARS and the commercial distributor but was lower and more variable in VSH production colonies and susceptible colonies. Commercial VSH production colonies supply mite resistance that generally seems to be useful for beekeeping. Resistance probably could be improved if more VSH drones sources were supplied when VSH production queens are being mated.

Genetic detection and quantification of Nosema apis and N. ceranae in the honey bee.

The incidence of nosemosis has increased in recent years due to an emerging infestation of Nosema ceranae in managed honey bee populations in much of the world. A real-time PCR assay was developed to facilitate detection and quantification of both Nosema apis and N. ceranae in both single bee and pooled samples. The assay is a multiplexed reaction in which both species are detected and quantified in a single reaction. The assay is highly sensitive and can detect single copies of the target sequence. Real-time PCR results were calibrated to spore counts generated by standard microscopy procedures. The assay was used to assess bees from commercial apiaries sampled in November 2008 and March 2009. Bees from each colony were pooled. A large amount of variation among colonies was evident, signifying the need to examine large numbers of colonies. Due to sampling constraints, a subset of colonies (from five apiaries) was sampled in both seasons. In November, N. apis levels were 1212+/-148 spores/bee and N. ceranae levels were 51,073+/-31,155 spores/bee. In March, no N. apis was detected, N. ceranae levels were 11,824+/-6304 spores/bee. Changes in N. ceranae levels were evident among apiaries, some increasing and other decreasing. This demonstrates the need for thorough sampling of apiaries and the need for a rapid test for both detection and quantification of both Nosema spp. This assay provides the opportunity for detailed study of disease resistance, infection kinetics, and improvement of disease management practices for honey bees.

Reaction norm variants for male calling song in populations of Achroia grisella (Lepidoptera: Pyralidae): toward a resolution of the lek paradox.

Significant additive genetic variance often occurs for male advertisement traits in spite of the directional selection imposed by female choice, a problem generally known in evolutionary biology as the lek paradox. One hypothesis, which has limited support from recent studies, for the resolution of this paradox is the role of genotype x environment interaction in which no one genotype exhibits the superior performance in all environments--a crossover of reaction norms. However, these studies have not characterized the actual variation of reaction norms present in natural populations, and the extent to which crossover maintains genetic variance remains unknown. Here, we present a study of genotype x environment interaction for the male calling song in populations of Achroia grisella (Lepidoptera: Pyralidae; lesser waxmoth). We report significant variance among reaction norms for male calling song in two North American populations of A. grisella as measured along temperature, food availability, and density gradients, and there is a relatively high incidence of crossover of the temperature reaction norms. This range of reaction norm variants and their crossover may reflect the co-occurrence of plastic and canalized genotypes, and we argue that the different responses of these variants along environmental gradients may contribute toward the maintenance of genetic variance for male song.

Flight activity of USDA-ARS Russian honey bees (Hymenoptera: Apidae) during pollination of lowbush blueberries in Maine.

Flight activity was compared in colonies of Russian honey bees, Apis mellifera L. (Hymenoptera: Apidae), and Italian bees during commercial pollination of lowbush blueberries (principally Vaccinium angustifolium Aiton) in Washington Co., ME, in late May and early June in 2003 and 2004. Colonies of the two stocks were managed equally in Louisiana during autumn through early spring preceding observations in late spring each year. Resulting average populations of adult bees and of brood were similar in colonies of the two bee stocks during pollination. Flight during pollination was monitored hourly on 6 d each year by counting bees exiting each colony per minute; counts were made manually with flight cones on 17 colonies per stock in 2003 and electronically with ApiSCAN-Plus counters on 20 colonies per stock in 2004. Analysis of variance showed that temperature, colony size (population of adult bees or brood), and the interaction of these effects were the strongest regulators of flight activity in both years. Russian and Italian bees had similar flight activity at any given colony size, temperature, or time of day. Flight increased linearly with rising temperatures and larger colony sizes. Larger colonies, however, were more responsive than smaller colonies across the range of temperatures measured. In 2003, flight responses to varying temperatures were less in the afternoon and evening (1500-1959 hours) than they were earlier in the day. Russian colonies had flight activity that was suitable for late spring pollination of lowbush blueberries.

Environmental influences on flight activity of USDA-ARS Russian and Italian stocks of honey bees (Hymenoptera: Apidae) during almond pollination.

Differences in flight activity and in the percentages of pollen foragers between commercially managed honey bees, Apis mellifera L. (Hymenoptera: Apidae), of two stocks (USDA-ARS Russian, n = 41 colonies; and Italian, n = 43 colonies) were evaluated in an almond, Prunus dulcis (Miller) D. A. Webb, orchard in Kern Co., CA, during February and March 2002. Flight activity was measured by taking 1-min counts of bees exiting colonies on each of 9 d. Flight activity was best predicted with a model containing the effects of colony size (populations of adult bees and sealed brood), temperature, time of day, the interaction of adult bee population with temperature, and the interaction of adult bee population with time of day. Flight increased linearly with adult bee and brood population, had a quadratic relationship with temperature (increasing, but less so at higher temperatures), and had a quadratic relationship with time of day (decreasing, but less so at later times). Larger colonies had more response to changing temperatures and less response to different times of day than small colonies. Bee type had no direct influence on flight activity at any given colony size, temperature, or time of observation or when evaluated using a reduced data set retaining 34 Italian colonies and 32 Russian colonies whose mean sizes were equal. Overall, however, Russian colonies were less populous by about one-fourth and so fielded on average 71% of the foragers that Italian colonies did. Pollen collection was measured by capturing returning foragers on 4 d. The percentages of foragers with pollen were not different for the bee types.

Caste, sex and strain of honey bees (Apis mellifera) affect infestation with tracheal mites (Acarapis woodi).

Worker honey bees from genetic strains selected for being resistant (R) or susceptible (S) to tracheal mites typically show large differences in infestation in field colonies and in bioassays that involve controlled exposure to infested bees. We used bioassays exposing newly emerged individuals to infested workers to compare the propensity for tracheal mites to infest queens, drones and workers from R and S colonies. In tests with queens, newly emerged R and S queens were either simultaneously confined in infested colonies (n = 95 and 87 respectively), or individually caged with groups of 5-20 infested workers (n = 119 and 115 respectively). Mite prevalence (percentage of individuals infested) and abundance (foundress mites per individual) after 4-6 days did not differ between R and S queens. In another test, five newly emerged drones and workers from both an R and an S colony, and a queen of one of the two strains, were caged in each of 38 cages with 20 g of workers infested at 60-96% prevalence. Infestations of the R queens (n = 17) and S queens (n = 19) did not differ significantly, but R workers had half the mite abundance of S workers, while R drones received about a third more migrating mites than S drones. In tests to evaluate possible mechanisms, removal of one mesothoracic leg from R and S workers resulted in 2- to 10-fold increase in mite abundance on the treated side, but excising legs did not affect infestation of the corresponding tracheae in drones. This suggests that differences in infestation between R and S workers, but not drones, are largely determined by their ability to remove mites through autogrooming. If autogrooming is the primary mechanism of colony resistance to tracheal mites, selection for resistance to tracheal mites using infestation of hemizygous drones may be inefficient.

Nectar robbery by bees Xylocopa virginica and Apis mellifera contributes to the pollination of rabbiteye blueberry.

Honey bees, Apis mellifera L., probe for nectar from robbery slits previously made by male carpenter bees, Xylocopa virginica (L.), at the flowers of rabbiteye blueberry, Vaccinium ashei Reade. This relationship between primary nectar robbers (carpenter bees) and secondary nectar thieves (honey bees) is poorly understood but seemingly unfavorable for V. ashei pollination. We designed two studies to measure the impact of nectar robbers on V. ashei pollination. First, counting the amount of pollen on stigmas (stigmatic pollen loading) showed that nectar robbers delivered fewer blueberry tetrads per stigma after single floral visits than did our benchmark pollinator, the southeastern blueberry bee, Habropoda laboriosa (F.), a recognized effective pollinator of blueberries. Increasing numbers of floral visits by carpenter bee and honey bee robbers yielded larger stigmatic loads. As few as three robbery visits were equivalent to one legitimate visit by a pollen-collecting H. laboriosa female. More than three robbery visits per flower slightly depressed stigmatic pollen loads. In our second study, a survey of 10 commercial blueberry farms demonstrated that corolla slitting by carpenter bees (i.e., robbery) has no appreciable affect on overall V. ashei fruit set. Our observations demonstrate male carpenter bees are benign or even potentially beneficial floral visitors of V ashei. Their robbery of blueberry flowers in the southeast may attract more honey bee pollinators to the crop.