Heather A. Higo

Worker honey bee ovary development: seasonal variation and the influence of larval and adult nutrition

We examined the effect of larval and adult nutrition on worker honey bee (Apis mellifera L.) ovary development. Workers were fed high or low-pollen diets as larvae, and high or low-protein diets as adults. Workers fed low-protein diets at both life stages had the lowest levels of ovary development, followed by those fed high-protein diets as larvae and low- quality diets as adults, and then those fed diets poor in protein as larvae but high as adults. Workers fed high-protein diets at both life stages had the highest levels of ovary development. The increases in ovary development due to improved dietary protein in the larval and adult life stages were additive. Adult diet also had an effect on body mass. The results demonstrate that both carry-over of larval reserves and nutrients acquired in the adult life stage are important to ovary development in worker honey bees. Carry-over from larval development, however, appears to be less important to adult fecundity than is adult nutrition. Seasonal trends in worker ovary development and mass were examined throughout the brood rearing season. Worker ovary development was lowest in spring, highest in mid-summer, and intermediate in fall.

The role of queen mandibular pheromone and colony congestion in honey bee (Apis mellifera L.) reproductive swarming (Hymenoptera: Apidae)

The roles of honey bee queen mandibular pheromone and colony congestion in the inhibition of swarming were investigated. Two colony siz.es were used: small, congested colonies and large, uncongested colonies. Both groups of colonies were treated with various dosages of the five-component, synthetic queen mandibular pheromone in the spring, and the extent and timing of swarming were followed. Most treatment groups received pheromone or a solvent blank (control) on a stationary slide; one group of the congested colonies received a pheromone treatment via an aerosol spray. The pheromone was not effective at delaying swarming in the congested colonies at any dosage applied on slides, but the aerosol spray-treated colonies swarmed significantly later in the season than the control colonies. The uncongested, pheromone-treated colonies exhibited a dose-dependent delay in swarming, with the highest dosage colonies swarming almost four weeks later than the control colonies. These results indicate an interaction between congestion and pheromone in the control of honey bee reproduction. While congestion may in itself be a factor stimulating swarming, these results are consistent with the interpretation that colony congestion reduces the transmission of queen pheromone within the nest, thereby removing the queen s pheromone-based inhibition of queen rearing and subsequent swarming by workers.

Lethal and Sublethal Effects of Imidacloprid on Osmia lignaria and Clothianidin on Megachile rotundata (Hymenoptera: Megachilidae)

Abstract We examined lethal and sublethal effects of imidacloprid on Osmia lignaria (Cresson) and clothianidin on Megachile rotundata (F.) (Hymenoptera: Megachilidae). We also made progress toward developing reliable methodology for testing pesticides on wild bees for use in pesticide registration by using field and laboratory experiments. Bee larvae were exposed to control, low (3 or 6 ppb), intermediate (30 ppb), or high (300 ppb) doses of either imidacloprid or clothianidin in pollen. Field experiments on both bee species involved injecting the pollen provisions with the corresponding pesticide. Only O. lignaria was used for the laboratory experiments, which entailed both injecting the bee’s own pollen provisions and replacing the pollen provision with a preblended pollen mixture containing imidacloprid. Larval development, emergence, weight, and mortality were monitored and analyzed. There were no lethal effects found for either imidacloprid or clothianidin on O. lignaria and M. rotundata. Minor sublethal effects were detected on larval development for O. lignaria, with greater developmental time at the intermediate (30 ppb) and high doses (300 ppb) of imidacloprid. No similar sublethal effects were found with clothianidin on M. rotundata. We were successful in creating methodology for pesticide testing on O. lignaria and M. rotundata; however, these methods can be improved upon to create a more robust test. We also identified several parameters and developmental stages for observing sublethal effects. The detection of sublethal effects demonstrates the importance of testing new pesticides on wild pollinators before registration.

Queen and pheromonal factors influencing comb construction by simulated honey bee (Apis mellifera L.) swarms

Summary: The influence of the queen and her pheromonal signal on comb construction was examined. We tested four treatments with newly hived packages of bees containing: 1) a mated queen, 2) a virgin queen, 3) no queen but with a dispenser containing synthetic queen mandibular pheromone (QMP), and 4) no queen and no pheromone. After 10 days, the comb produced by each colony was removed, comb measurements made, bees from the comb-building area collected, the size of the scales on the wax mirrors of the collected bees ranked on a scale of 0-4 and the queens removed and analyzed for QMP components. Queenless workers built substantially less comb and the comb they did build had significantly larger, drone-sized cells than for the other 3 treatments, indicating that both cell size and the quantity of comb built are mediated through the queen, particularly QMP. The observations of wax scale size suggested that QMP influenced comb building behaviour rather than wax scale production. These results support the idea that queenless honey bees can adopt a strategy of constructing drone-sized cells in order to increase reproductive fitness through male production following queen loss.

Field Evaluation of Neem and Canola Oil for the Selective Control of the Honey Bee (Hymenoptera: Apidae) Mite Parasites Varroa jacobsoni (Acari: Varroidae) and Acarapis woodi (Acari: Tarsonemidae)

Abstract Neem oil, neem extract (neem-aza), and canola oil were evaluated for the management of the honey bee mite parasites Varroa jacobsoni (Oudemans) and Acarapis woodi (Rennie) in field experiments. Spraying neem oil on bees was more effective at controlling V. jacobsoni than feeding oil in a sucrose-based matrix (patty), feeding neem-aza in syrup, or spraying canola oil. Neem oil sprays also protected susceptible bees from A. woodi infestation. Only neem oil provided V. jacobsoni control comparable to the known varroacide formic acid, but it was not as effective as the synthetic product Apistan (τ-fluvalinate). Neem oil was effective only when sprayed six times at 4-d intervals and not when applied three times at 8-d intervals. Neem oil spray treatments had no effect on adult honey bee populations, but treatments reduced the amount of sealed brood in colonies by 50% and caused queen loss at higher doses. Taken together, the results suggest that neem and canola oil show some promise for managing honey bee parasitic mites, but the negative effects of treatments to colonies and the lower efficacy against V. jacobsoni compared with synthetic acaricides may limit their usefulness to beekeepers.

Bumble bees influence berry size in commercial Vaccinium spp. cultivation in British Columbia

We studied the abundance, diversity, and dispersion patterns of managed and wild bee (Hymenoptera: Apoidea) populations in commercial highbush blueberry and cranberry (Ericaceae: Vaccinium corymbosum L., Vaccinium macrocarpon Ait.) fields in the Fraser Valley of British Columbia, and assessed their potential as pollinators of these crops by determining which groups of bees had the greatest impact on percent yield and mass of berries. Bumble bees were evenly distributed within both crops. Other wild bee species were well distributed in blueberry fields but generally remained at edges of cranberry fields. Percent berry yield was not related to bee abundance for any group of bees, nor was species diversity correlated with berry mass. Blueberry mass and cranberry mass were related to abundance of bumble bees but not to that of honey bees or other wild bees. Bumble bees are recommended as potential alternative pollinators of these crops.

Comparison of Release Mechanisms for Botanical Oils to Control Varroa destructor (Acari: Varroidae) and Acarapis woodi (Acari: Tarsonemidae) in Colonies of Honey Bees (Hymenoptera: Apidae)

Abstract Two major parasitic pests threaten honey bee populations, the external mite Varroa destructor and the internal mite Acarapis woodi (Rennie). Varroa are beginning to develop resistance to the main chemical defense fluvalinate, and alternative control methods are being pursued. Previous studies have shown that botanical oils, especially thymol, can be effective. Six release devices for either thymol or a blend of botanical oils known as Magic 3 were tested in beehives. The release devices were as follows: (1) low density polyethylene (LDPE) sleeves filled with Magic 3, (2) Magic 3-infused florist blocks, (3) thymol infused florist blocks, (4) a canola oil and thymol mixture wick release, (5) a plastic strip coated with calcium carbonate and Magic 3, and (6) an untreated control. There were significant decreases in varroa levels with the use of Magic 3 sleeves, but brood levels also decreased. Tracheal mite levels significantly decreased with the Magic 3 sleeve treatment, the Magic 3 florist block treatment, and the thymol canola wick treatment. A second experiment showed that changing the location of Magic 3 sleeves in the colony did not detrimentally effect brood levels, but also did not effectively control varroa mites.

Development of a bioassay to test the orientation behaviour of the honey bee ectoparasite, Varroa jacobsoni.

SUMMARY A bioassay was developed to test various aspects of the orientation behaviour of the honey bee ectoparasite, Varroa jacobsoni The bioassay arena consisted of a petri dish, 60 mm in diameter, in which live honey bee larvae and previously frozen adults were used as hosts. Bioassays were conducted in a dark incubator at 32°C for 60 min. Greater numbers of mites parasitized worker larvae than drone larvae, but this trend was not significant. Mites of various ages given a choice between nurse bees and fifth instar worker larvae preferred nurse bees at all ages of mites tested, excluding newly emerged mites. When given a choice between a nurse bee and a pollen forager, V. jacobsoni did not show a preference, and similarly when given a choice between a nurse bee and an adult drone no preference was observed. Finally, when given a choice between a nurse bee extracted with hexane and a non—extracted nurse bee, V. jacobsoni preferred the non-extracted host.

The effects of honey bee (Apis mellifera) queen mandibular pheromone on colony defensive behaviour.

SUMMARY Honey bee (Apis mellifera) queen mandibular pheromone (QMP) influences many aspects of worker behaviour and physiology. We observed that synthetic QMP seems to calm colonies and reduce stinging, suggesting a role for QMP in managing colony defensive behaviour. We assessed defensive responses of colonies that were queenright, queenless or supplemented with two forms of synthetic QMP (liquid QMP on glass slides or Bee Boost® synthetic lures) by counting stings on a leather patch and the number of responder bees at colony entrances. Colonies with queens showed decreased defensive behaviour when exposed to liquid QMP; colonies without queens and exposed to liquid QMP had no change in the number of stings but a decrease in the number of guard bees. Bee Boost had no effect on colony defensive behaviour in colonies with or without queens. The ability to reduce defensive behaviour with QMP could have positive implications for commercial beekeeping, especially in context with Africanized bees, should an effective release device be developed.