Eric C. Mussen

Effects of chlortetracycline of honey bee worker larvae reared in vitro

Abstract An in vitro method was developed for rearing worker honey bee (Apis mellifera L.) larvae to the adult stage. Average larval and postdefecation mortalities were 9.5% and 18.1% respectively. Larval and postdefecation development times were similar to worker brood reared in field colonies. Only 1 of 30 sampled adult bees exhibited queen or intercaste characteristics. The in vitro rearing method subsequently was used in studying the effect of the antibiotic chlortetracycline on larval growth and development. A general dose response was observed in mortalities of larvae fed diets containing 0.0025% to 0.05% chlortetracycline. At 0.0025%, larval and postdefecation mortalities were similar to the controls. At this concentration, chlortetracycline effectively reduced larval and postdefecation mortalities of larvae inoculated with 1 × 104 to 1.5 × 108 spores/ml of Bacillus larvae, the causative pathogen of American foulbrood disease. Chlortetracycline doses higher than 0.0025% retarded larval growth and development and caused precocious pigmentation in early larval instars.

Impact of Mediterranean Fruit Fly Malathion Bait Spray on Honey Bees

During a Mediterranean fruit fly eradication program (1980–1982) in northern California, two field studies were conducted to evaluate the impact of malathion bait spray on honey bees. Significant mortality of adult bees was associated with weekly applications, eventually reducing colony populations to levels that would cause economic loss and threaten winter survival of colonies. Flight activity was reduced greatly for 1 day after each predawn application. Brood mortality was not observed. Residual levels of malathion were 1.71 ± 0.37 ppm (range, 2.24–7.64 ppm) in trapped pollen and 2.22 ± 0.13 ppm (range, 0.78–5.28 ppm) in bees collected from entrance traps attached to hives within spray zones.

Effects of Selected Fungicides on Growth and Development of Larval Honey Bees, Apis mellifera L. (Hymenoptera: Apidae)

Abstract Laboratory studies were conducted to determine the effects of incorporating selected almond fungicides into the diet of larval honey bees, Apis mellifera Linnaeus. One-day-old larvae, from mixed Italian stocks, were grafted to basic larval diet or basic diet containing various fungicides. Experimental concentrations were calculated from field dose application rates of formulated product per hectare. Larvae were transferred to fresh diet daily and incubated in the dark at 35°C and 95% RH. After defecation, prepupae were moved into a dark incubator at 35°C and 75% RH. Mortalities of larvae, prepupae, and pupae were recorded daily. No larvae fed Captan, Rovral, or Ziram completed development to adults. In the case of Rovral, a novel amorphogenic effect was observed. There were no significant differences in total mortality between the controls and larvae fed Abound, Elevate, Flint, Rally, and Vangard.

The effects of azadirachtin on the parasitic mite, Varroa jacobsoni and its host honey bee (Apis mellifera)

SUMMARY We conducted a series of experiments under laboratory conditions to evaluate the feasibility of using a neem-based (Azadirachta indica) insecticide to control varroa (Varroa jacobsoni). The experiments included studies of anti-feeding effects of azadirachtin, the active ingredient of neem-based insecticides, on adult worker honey bees (Apis mellifera); toxicity of azadirachtin to adult workers, worker larvae and associated mites; and the effects of azadirachtin on female V. jacobsoni reproduction. Both commercially formulated and purified azadirachtin were used in the experiments. The results of adult feeding experiments showed that azadirachtin significantly reduced syrup consumption by worker bees (P < 0.05) and exhibited a dose response in mortality: with an oral LC50 of 10.87 μg/ml in mite-free bees, 13.69 μg/ml in mite-infested bees, and 41.87 μg/ml for associated mites. The topical LC50 of azadirachtin was 12.53 μg/ml in mite-free bees, 12.31 μg/ml in mite-infested bees, and 35.43 μg/ml in the associated mites. The results of larval feeding experiments showed that worker larvae were more sensitive to azadirachtin than adult worker bees: exhibiting an LC50 of 180.92 μg/ml to purified azadirachtin and 100.13 μg/ml to formulated azadirachtin. More than 90% of treated, normal-appearing, white prepupae and pupae showed precocious and abnormal pigmentation on their mouthparts and other appendages. LC50‘s of topical applications of formulated azadirachtin were 104.91, 99.12 and 171.37 μg/ml for mite-free worker larvae, mite-inoculated larvae and associated mites, respectively. In addition, feeding host larvae with azadirachtin significantly reduced the fecundity of mother mites (P < 0.001) as well as egg hatching rate (P < 0.001). However, more research is needed to evaluate the reproductive effects of azadirachtin on drones, queens, and varroa under hive conditions.

Assessing Honey Bee (Hymenoptera: Apidae) Foraging Populations and the Potential Impact of Pesticides on Eight U.S. Crops

ABSTRACT Beekeepers who use honey bees (Apis mellifera L.) for crop pollination services, or have colonies making honey on or in close proximity to agricultural crops, are concerned about the reductions of colony foragers and ultimate weakening of their colonies. Pesticide exposure is a potential factor in the loss of foragers. During 2009–2010, we assessed changes in the field force populations of 9–10 colonies at one location per crop on each of the eight crops by counting departing foragers leaving colonies at regular intervals during the respective crop blooming periods. The number of frames of adult bees was counted before and after bloom period. For pesticide analysis, we collected dead and dying bees near the hives, returning foragers, crop flowers, trapped pollen, and corn-flowers associated with the cotton crop. The number of departing foragers changed over time in all crops except almonds; general patterns in foraging activity included declines (cotton), noticeable peaks and declines (alfalfa, blueberries, cotton, corn, and pumpkins), and increases (apples and cantaloupes). The number of adult bee frames increased or remained stable in all crops except alfalfa and cotton. A total of 53 different pesticide residues were identified in samples collected across eight crops. Hazard quotients (HQ) were calculated for the combined residues for all crop-associated samples and separately for samples of dead and dying bees. A decrease in the number of departing foragers in cotton was one of the most substantial crop-associated impacts and presented the highest pesticide risk estimated by a summed pesticide residue HQ.

Effects of high fructose corn syrup and probiotics on growth rates of newly founded honey bee colonies

Summary Honey bees are agricultures major pollinator. As such, they are often heavily managed in order to ensure that they thrive in unproductive environments, or are at their strongest at times of the year that are abnormal given their life history. Within this context, supplemental feeding is critical. There is currently debate among commercial beekeepers as to what sort of carbohydrate feed is best for bees. Blends of high fructose corn syrup (HFCS) are easiest to use, and cheapest, but there are some possible health concerns for the bees. Commercial suppliers of HFCS also suggest that some of their blends work better than sucrose for building up colonies. Here we test these issues by determining whether newly established packages grow faster, and are healthier, when fed either sucrose solution or a HFCS blend. In addition, we also test whether antibiotic treatments, commonly administered to prevent bacterial diseases, impact colony health at the critical foundation stage, and whether feeding probiotics alleviates these impacts. Overall, we found no negative health effect associated with HFCS feeding. Significantly, we found that colonies grew faster and appeared healthier when fed the HFCS blend. We also found no negative effects on colony growth associated with antibiotics application, and no beneficial effects associated with probiotics treatment. This work suggests that HFCS blends are suitable and productive as large scale feeds, even at times when the colonies are strongly dependent on supplemental feeding.

Ultrastructure of the freeze-etched spore of Ascosphaera apis, an entomopathogenic fungus of the honeybee Apis mellifera.

Abstract The freeze-fractured outer surface of the spore wall of Ascophaera apis is covered with granules which are 21.5 nm in diameter. The cross-fractured spore wall consists of subunits which are 9 nm in diameter. The inner surface of the spore wall is granular and has many stud-like projections measuring approximately 120 nm long × 26 nm wide. The convex face of the spore membrane carries many particles as well as many depressions which are complementary to the projections on the inner surface of the spore wall. The nucleus possesses double nuclear membranes which contain numerous well-defined nuclear pores. In the cytoplasm of the spore there are many mitochondria which have well-defined cristae and many particles on the internal membranes. The sporoplasm contains many lipid droplets which possess concentric smooth-surfaced lamellae.

Effects of Contact and Ingestion Exposure to Formulated CheckMate® LBAM-F and Unformulated LBAM Mating Pheromones on Adult Worker Honeybees, Apis mellifera (Hymenoptera: Apidae)

ABSTRACT Acute 7-day toxicity tests evaluating adverse effects from contact and ingestion exposure to light brown apple moth (LBAM) pheromones and time-released microencapsulated LBAM pheromones in CheckMate® LBAM-F (Checkmate) were conducted on newly emerged honeybees (less than 24 h old). Contact studies exposed bees to 1× and 10× the CheckMate label application rate. Ingestion studies exposed bees to CheckMate formulations, and active (pheromone) ingredients (a.i.) at 0.1%, 1.0%, and 10% concentrations by weight in solid food. Bees ingested approximately 39% of their body weight during the tests. Mortality ranged from 2–10% in three of four contact and ingestion exposure trials. Trial 1, which utilized a different feeding design, showed higher mortality in both control and test replicates (9–28%). One-way ANOVA tests indicated no significant difference in mortality between control and treatment replicates in the four trials. Bees were subjected to one-time CheckMate contact exposures of up to 0.49 mg/kg-bee, and average pheromone and formulation ingestion exposures of up to 56 (0.1%), 611 (1.0%), and 6,282 (10%) mg/kg-bee-day. LBAM pheromones and microencapsulated pheromones proved to be non-toxic to honeybees when sprayed with 10× the field application rate, or when ingested in food at concentrations of up to 10% by weight.

In vitro activity of 15-azasterol (A25822B) against chalkbrood pathogen Ascosphaera apis in the honey bee

The antifungal agent 15-azasterol A25822B was examined for effects on the growth and development of Ascosphaera apis. The minimum inhibition concentration (MIC) of azasterol against A. apis was 1 μm. Growth and development of A. apis was completely controlled at this concentration. At a concentration of 0.01 μm growth of A. apis was retarded and although sporocysts were formed developing spores were not be able to reach maturation. A major effect of azasterol at this low concentration was the accumulation of lipid in the hyphae, sporocysts and immature spores. In addition it caused a conformational change in mitochondria and damage to the spore membrane structure. On the basis of these results, further investigations of azasterol for the treatment of chalkbrood disease in the honey bee are warranted.