Comparative laboratory toxicity of neem pesticides to honey bees (Hymenoptera : Apidae), their mite parasites Varroa jacobsoni (Acari : Varroidae) and Acarapis woodi (Acari : Tarsonemidae), and brood pathogens Paenibacillus larvae and Ascophaera apis

Laboratory bioassays were conducted to evaluate neem oil and neem extract f or the management of key honey bee (Apis mellifera L.) pests. Neem pesticid es inhibited the growth of Paenibacillus larvae (Ash, Priest & Collins) in vitro but had no effect on the growth of Ascophaera al,is (Olive & Spiltoir ). Azadirachtin-rich extract (neem-aza) was 10 times more potent than crude neem oil (neem oil) against P. larvae suggesting that azadirachtin is a ma in antibiotic component in neem. Neem-aza, however, was ineffective at cont rolling the honey bee mite parasites Varroa jacobsoni (Ouduemans) and Acara pis woodi (Rennie). Honey bees also were deterred from feeding on sucrose s yrup containing >0.01 mg/ml of neem-aza. However, neem oil applied topicall y to infested bees in the laboratory proved highly effective against both m ite species. Approximately 50-90% V. jacobsoni mortality was observed 48 h after treatment with associated bee mortality lower than 10%. Although topi cally applied neem oil did not result in direct A. woodi mortality, it offe red significant protection of bees from infestation by A. woodi. Other vege table and petroleum-based oils also offered selective control of honey bee mites, suggesting neem oil has both a physical and a toxicological mode of action. Although oils are not as selective as the V. Jacobsoni acaricide ta u-fluvalinate, they nonetheless hold promise for the simultaneous managemen t of several honey bee pests.