Robert G. Danka

Standard methods for pollination research with Apis mellifera

Summary In this chapter we present a synthesis of recommendations for conducting field experiments with honey bees in the context of agricultural pollination. We begin with an overview of methods for determining the mating system requirements of plants and the efficacy of specific pollinators. We describe methods for evaluating the pollen-vectoring capacity of bees at the level of individuals or colonies and follow with methods for determining optimum colony field stocking densities. We include sections for determining post-harvest effects of pollination, the effects of colony management (including glasshouse enclosure) on bee pollination performance, and a brief section on considerations about pesticides and their impact on pollinator performance. A final section gives guidance on determining the economic valuation of honey bee colony inputs at the scale of the farm or region.

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.

Male reproductive parasitism: a factor in the africanization of European honey-bee populations.

Africanized drone honey bees (Apis mellifera) migrate into European honey-bee colonies in large numbers, but Africanized colonies only rarely host drones from other colonies. This migration leads to a strong mating advantage for Africanized bees since it both inhibits European drone production and enhances Africanized drone production.

Comparisons of pollen substitute diets for honey bees : consumption rates by colonies and effects on brood and adult populations

Summary Commercially available pollen substitute diets for honey bees (Apis mellifera L.) were evaluated for consumption and colony growth (brood and adult populations) and compared with pollen cake and high fructose corn syrup (HFCS). Two trials were conducted; the first for 3 months during the fall and winter and a second for 2 months in the summer. Three diets were tested in Trial 1 (Diet-1, Diet-2, and Diet-3 (liquid and patty form)) and Diet-2 and Diet-3 (patty) in Trial 2. In both Trials, Diet-2 and Diet-3 patty were consumed at rates that were comparable to pollen cake. Colonies consumed significantly less Diet-1 than the other diets. There was a significant relationship between the amount of diet consumed and the change in brood area and adult population size in both Trials. Colonies fed Diet-3 patty produced significantly more brood than those fed pollen cake or any other diet in Trial 1. The lowest brood production occurred in colonies fed Diet-1 or HFCS. Adult populations in colonies fed Diet-3 liquid or patty did not differ from those fed pollen cake, and were significantly larger than colonies fed Diet-1 or Diet-2. In Trial 1, when some pollen was being collected by colonies, Diet-2 and Diet-3 did not differ from pollen cake in brood or adult population growth.

Evidence of autogrooming as a mechanism of honey bee resistance to tracheal mite infestation

SUMMARYInfestations of tracheal mites (Acarapis woodi) were measured in honey bees (Apis mellifera) whose autogrooming ability was compromised by having legs or segments of legs amputated. Bees of two stocks, one more resistant (Buck-fast) and one more susceptible to tracheal mite infestation, were tested by performing amputations on uninfested, young (0–24 h) adult bees, exposing the treated bees to mites in infested colonies, then retrieving and dissecting the bees to measure parasitism. In both stocks, bees that had mesothoracic legs amputated had greatly increased mite abundances. However, the relative increase in infestation was greater in resistant bees. Mite infestation increased as more (0 vs. 1 vs. 2) mesothoracic legs were removed. In bees with only one leg removed, mite infestations were greater on the treated side. In subsequent tests with resistant stock bees only, removing the mesotarsi resulted in infestations equalling those found when entire mesothoracic legs were removed, but amputating ...

Variable Population Growth of Varroa destructor (Mesostigmata: Varroidae) in Colonies of Honey Bees (Hymenoptera: Apidae) During a 10-Year Period

Abstract We measured significant variation in the instantaneous growth rates for varroa mites, Varroa destructor (Anderson & Trueman) from 1993 to 2002 in Baton Rouge, LA. Mite population growth was monitored in colonies of honey bees, Apis mellifera L., with queens from miscellaneous U.S. sources that had not been selectively bred for varroa resistance. Mite populations were measured at the beginning and end of short field tests that started in the late spring of each year. Analyses of multiple regression showed that only the first two of the following regressors were linear predictors of r, the instantaneous growth rate: 1) percentage of reproducing female mites, 2) proportion of total mites in capped brood, 3) mortality of mites in brood cells, 4) growth of the bee population, 5) capped brood area at the end of a test, and 6) duration of the test. Analysis of commonality indicated that the percentage of reproducing female mites explained ≈26% of the total variation in r, and the proportion of total mites in capped brood explained 6%. The joint expression of both variables accounted for another 4%. Thus, residual error reflected most of the total variation in r, which suggested possible climatic or environmental effects on mite growth. The lowest growth rates occurred in three consecutive years of drought in Louisiana. Measures of ambient temperature and relative humidity correlated to growth of mite populations among different years. Reduced growth rates were probably the result of diminished reproductive rates by varroa mites during periods of hot and dry weather.

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.

Honey bees (Hymenoptera: Apidae) with the trait of varroa sensitive hygiene remove brood with all reproductive stages of varroa mites (Mesostigmata: Varroidae).

ABSTRACT Varroa sensitive hygiene (VSH) is a trait of honey bees, Apis mellifera L. (Hymenoptera: Apidae), which supports resistance to Varroa destructor Anderson & Trueman. VSH is the hygienic removal of mite-infested pupa. Bees selectively bred for VSH produce colonies in which the fertility of mites decreases over time. In addition, mite fertility decreases after infested brood is exposed to VSH bees for 1 wk. The purpose of this study was to decide whether the reduction in mite fertility is caused by selective removal of mites that produce offspring. Initially, we monitored changes in a small patch of capped brood during exposure to VSH bees at 2-h intervals through 60 h, which provided a reference for the subsequent experiment. The first test showed that VSH bees uncapped, recapped, and began to remove many pupae in ≈2 h. The approach in the second experiment was to compare the percentage of fertile mites from brood exposed to VSH bees for a 3-h period to the percentage of fertile mites in brood that was protected from hygiene by a screen. There were no significant differences in fertility between mites on pupae that were being removed by the bees and mites on protected pupae. These results suggest that neither egg-laying by foundress mites nor mite offspring are the stimuli that trigger hygienic removal of mite-infested pupae by VSH bees. It may be that hygienic activities such as the uncapping of brood cells inhibits or disrupts reproduction by varroa mites.

Nectar Robbery by Bees Xylocopa virginica and Apis mellifera Contributes to the Pollination of Rabbiteye Blueberry

Abstract 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.

REACTION NORM VARIANTS FOR MALE CALLING SONG IN POPULATIONS OF ACHROIA GRISELLA (LEPIDOPTERA: PYRALIDAE): TOWARD A RESOLUTION OF THE LEK PARADOX

Abstract 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 × 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 × 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.