Gard W. Otis

Influence of Pollen Diet in Spring on Development of Honey Bee (Hymenoptera: Apidae) Colonies

The effects of changes in spring pollen diet on the development of honey bee, Apis mellifera L. (Hymenoptera: Apidae), colonies were examined in a 3-yr study (2002-2004). Pollen-supplemented and pollen-limited conditions were created in colonies every spring, and brood rearing and honey yields were subsequently monitored throughout the summer. In all 3 yr, colonies that were supplemented with pollen or a pollen substitute in the spring started rearing brood earlier than colonies in other treatment groups and produced the most workers by late April or early May. In 2002, these initial differences were reflected by a two-fold increase in annual honey yields by September for colonies that were pollen-supplemented during the spring compared with pollen-limited colonies. In 2003 and 2004, differences between treatment groups in the cumulative number of workers produced by colonies disappeared by midsummer, and all colonies had similar annual honey yields (exception: in one year, productivity was low for colonies supplemented with pollen before wintering). Discrepancies between years coincided with differences in spring weather conditions. Colonies supplemented with pollen or a substitute during the spring performed similarly in all respects. These results indicate that an investment in supplementing the pollen diet of colonies would be returned for situations in which large spring populations are important, but long-term improvement in honey yields may only result when spring foraging is severely reduced by inclement weather. Beekeepers should weigh this information against the nutritional deficiencies that are frequently generated in colonies by the stresses of commercial management.

Inspection and feeding of larvae by worker honey bees (Hymenoptera: Apidae): Effect of starvation and food quantity

Honey bee larvae are frequently inspected and, sometimes, provided with food by adult workers, but the stimuli that elicit the important task of food provisioning have never been investigated. Larvae with their food experimentally deprived received more frequent inspection and feeding visits from nurse bees than normally fed larvae, suggesting that there could be a “hunger signal.” Food-deprived larvae with artificially supplied larval food received the same rate of feeding visits from nurse bees as did normally fed larvae but still received more inspection visits. These results suggest that stimuli eliciting feeding are different from those for inspection. They also support the hypothesis that worker bees deposit food in a larval cell only when the quantity of food is below a certain minimum threshold that is perceived during larval inspections. A model is presented regarding the stimuli from larvae that result in worker feeding behavior.

Timing of production of winter bees in honey bee (Apis mellifera) colonies

Summary. Little is known about the development of the overwintering population of honey bees (Apis mellifera) colonies in temperate climates. Colonies were subjected to one of four requeening treatments: requeened in mid-summer with a mated, virgin or colony-reared queen, or left with the original queen (control). Worker survival in cohorts of newly emerged bees introduced to colonies in late summer and fall was followed until all marked bees had died. Winter bees were reared over a relatively similar length of time in all treatments, but they appeared earlier in control colonies compared to requeened colonies. The gradual increase in proportion of winter bees over time was similar among treatments, but requeened colonies lagged behind control colonies. The bulk of winter bees appeared much earlier in control colonies than in colonies that were requeened. This response demonstrates that cues within the colony (i.e., differences due to requeening) are perceived by workers as part of the conditions that influence summer bee or winter bee status.

Dwindling pollen resources trigger the transition to broodless populations of long‐lived honeybees each autumn

Abstract 1. Each autumn in northern regions, honeybee colonies shift from populations of short‐lived workers that actively rear brood to broodless populations of long‐lived winter bees. To determine if dwindling pollen resources trigger this transition, the natural disappearance of external pollen resources was artificially accelerated or delayed and colonies were monitored for effects on the decline in brood‐rearing activity and the development of populations of long‐lived winter bees.

Azadirachtin: An Effective Systemic Insecticide for Control of Agrilus planipennis (Coleoptera: Buprestidae)

ABSTRACT The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive pest discovered in North America in 2002, is now well established and threatens ash (Fraxinus spp.) trees throughout the continent. Experiments were conducted to 1) examine the efficacy of an alternative natural pesticide, azadirachtin, to control emerald ash borer, and 2) determine foliar uptake and dissipation patterns after systemic injections of azadirachtin into trunks of small (2.2 cm diameter at breast height [dbh]), uninfested green ash trees. We found no evidence of mortality of adult beetles. In contrast, fewer larvae completed their development at dose levels ≥1.7 mg (AI)/cm dbh and development ceased beyond the second instar at dose levels ≤13.6 mg (AI)/cm dbh. Substantial concentrations (11.2 µg/g dry mass [SD = 7.55]) of azadirachtin were present in leaves within 7 d of treatment. After rapid initial uptake, concentrations in leaves declined logarithmically during the 55 d after injection. A similar pattern was observed in a separate experiment that examined the uptake and translocation of azadirachtin in larger green ash trees (22 cm dbh) treated with 250 mg (AI)/cm dbh with the EcoJect injection system. In another experiment, recently infested plantation green ash trees treated with doses ≥40 mg (AI)/cm dbh had significant reductions in adult emergence ≈1 yr postinjection. Given the inhibition of larval development, reduction of adult emergence, and the occurrence of foliar residues at biologically active concentrations, we conclude that azadirachtin is effective in protecting ash trees from emerald ash borer.

A comparison of the host preference of monarch butterflies (Danaus plexippus) for milkweed (Asclepias syriaca) over dog‐strangler vine (Vincetoxicum rossicum)

Observations in the field indicate that monarch butterflies will oviposit on dog‐strangler vine, an invasive introduced species in the same family as milkweed (Asclepias spp.), the principal larval host of monarchs. The potential impact of this behaviour depends on the strength of the preference of monarch adults to oviposit on these two hosts and the relative ability of larvae to survive on each. We determined the preference for milkweed vs. dog‐strangler vine of ovipositing adults and first instar larvae in choice and no‐choice tests. We also compared the ability of larvae to consume, develop, and survive on either host. In the presence of both hosts, adults exhibited a strong preference to oviposit on milkweed over dog‐strangler vine (mean 80.7 eggs compared to 0.4 eggs over 48 h, respectively). In the absence of milkweed, adults ceased oviposition (mean 0.9 eggs in 48 h), but resumed oviposition when the dog‐strangler vine was replaced with milkweed (mean 99.1 eggs in 48 h). Given a choice between hosts over 24 h, 92% of larvae moved to milkweed leaves and consumed 3.94 cm2 of milkweed leaves compared to 2% of larvae that moved to dog‐strangler vine and consumed negligible amounts of leaf material (0.01 cm2). Without a choice, larvae on dog‐strangler vine never consumed more than mean 0.02 cm2 larva−1 in a 24‐h period, did not develop beyond the first instar, and died within 96 h. We obtained no data in support of an effect of the presence of dog‐strangler vine on monarch butterfly populations.

Standard methods for tracheal mite research

Summary The honey bee tracheal mite (HBTM) Acarapis woodi (Rennie) (Acari: Tarsonemidae) is an obligate endoparasite of honey bees. First described from the Western (European) honey bee Apis mellifera L., this mite species was initially observed when honey bee colonies on the Isle of Wight, UK were dying between 1904 and 1919 (Rennie, 1921). Since then, this mite has been found in Europe, North and South America and parts of Asia, but its global distribution is not well understood. In this chapter, we outline protocols for collecting, detecting, identifying, diagnosing and measuring the infestation rates of A. woodi. We also describe methods to determine the damage threshold, outline several control measures, and describe methods for studying live mites.

DIFFERENCES IN DRONE CAPPINGS OF APIS CERANA AND APIS NIGROCINCTA

SUMMARYThe nature of the drone cell caps of Apis cerana and A. nigrocincta were examined in South and Central Sulawesi, Indonesia. All drone cells of A. cerana were capped with a hard conical cocoon structure; recently sealed cells also had an external wax capping. The hardened cocoon cap above drone pupae had a central pore. Drone cell caps of A. nigrocincta were sealed with a fragile thin wax capping. The hardened capping with pore typical of A. cerana was always absent from drone cappings of A. nigrocincta, regardless of the age of the drone brood. The significance of this finding is briefly discussed.

Comparative resistance in Buckfast and Canadian stocks of honey bees (Apis mellifera L.) to infestation by honey bee tracheal mites (Acarapis woodi (Rennie))

The results of bioassay and colony evaluation demonstrated that British and Texas Buckfast honey bee stocks had one-third to one-half the mean prevalence and abundance of tracheal mites as Canadian standard stock, indicating that Buckfast stocks are less susceptible to tracheal mites than Canadian standard stock. Hybrid Canadian and Buckfast stocks exhibited resistance characteristics similar to only one of their parental stocks, suggesting the colony has an unknown effect on the expression of a bees resistance to mites. A high correlation (rs=0.66) between abundance values from the bioassay and colony evaluations indicates that the bioassay can be used to screen bees for mite resistance.

Manipulating pollen supply in honey bee colonies during the fall does not affect the performance of winter bees

Each fall, honey bee (Apis mellifera L. (Hymenoptera: Apidae)) colonies in northern temperate regions rear a population of long-lived winter bees that maintains a broodless nest throughout the winter and resumes brood-rearing activities in the spring. Pollen supply in colonies is closely tied to this phenomenon; winter bees sequester large reservoirs of pollen-derived nutrients in their bodies and the brood-rearing capacity of colonies is dictated by the availability of pollen. We determined the effects of manipulating pollen supply during the fall on the number of winter bees present in colonies by spring, their mass and protein content before and after winter, and their capacity to rear brood during the spring. Colonies were either supplemented with or partially deprived of pollen during the fall, while a third group of colonies was not manipulated (control). We found that the performance of winter bees was not enhanced by supplementing colonies with pollen in the fall, nor did worker function suffer if pollen supply was restricted. Similar numbers of winter bees survived to spring in colonies and workers had similar physiology and brood-rearing efficiencies. These results suggest that beekeepers would not benefit by investing in fall pollen supplements to maximize colony growth in early spring.