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

Abstract

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 LC 50 of 1 0.87 1-Jg/ml in mite-free bees, 13.69 IJg/ml in mite-infested bees, and 41.87 1-Jg/ml for associated mites. The topical LC 50 of azadirachtin was 12.53 IJg/ml in mite-free bees, 12.31 IJg/ml in mite-infested bees, and 35.43 IJg/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 LC 50 of 180.92 ng/ml to purified azadirachtin and 1 00.13 ng/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. LC 50 's of topical applications of formulated azadirachtin were 104.91, 99.12 and 171.37 ng/ml for mite-free worker larvae, miteinoculated 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. Downloaded by [RMIT University] at 02

Assessing delayed and acute toxicity of five formulated fungicides to Osmia lignaria Say and Apis mellifera

“…Neem oil contains many potentially bioactive constituents that vary among crude extracts (Schmutterer, 1995). Several neem-based insecticides were investigated for their anti-feeding effects on adult worker honey bees and for toxicity to A. mellifera workers and larvae (Naumann et al, 1994;Naumann and Isman, 1996;Melathopoulos et al, 2000;Peng et al, 2000), and applications were considered relatively safe to honey bee workers and larvae. Therefore, if direct exposure of bees is avoided, neem oil would be compatible with bees during the pollinating season.…”

The Effects of Four Insect Growth-Regulating (IGR) Insecticides on Honeybee (Apis mellifera L.) Colony Development, Queen Rearing and Drone Sperm Production

“…As neither azadirachtin nor tebufenozide are registered in the UK they were applied at the maximum rate shown not to result in anti-feedant properties (Peng et al, 2000), 1 mg ai/l azadirachtin and the maximum application rate 160 mg ai/l tebufenozide (BCPC 2001). Negative control solutions were 50% w/v sucrose.…”

Repellency of the oily extract of neem seeds (Azadirachta indica) against Varroa destructor (Acari: Varroidae)

“…Melathopoulos et al (2000a) and Peng et al (2000) directed their attention to determine acute toxicity of those products by a long term exposure (feeding, residual films or vapors) or topical application of high doses. More promising results were obtained by Whittington et al (2000) and Melathopoulos et al (2000b) by spray applications of neem extracts directly on bee colonies.…”

“…Melathopoulos et al (2000a, b) observed a reduction in the infestations of V. destructor and the tracheal mite Acarapis woodi Rennie, after feeding bees with sugar syrup mixed with a neem extract. A neem-based pesticide topically applied or mixed with sugar syrup, and supplied as food, exhibited acute toxicity on V. destructor as well as reduction in the proportion of fecund females and viability of eggs (Peng et al 2000). They also observed a reduction in V. destructor numbers when sprayed hives with neem oil; when neem oil with no AZ or other vegetable oils were used, V. destructor mortality in a lower proportion was achieved, meaning that mortality was due to the oil, and it also was caused by the AZ.…”