APICULTURE AND SOCIAL INSECTS 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) ADONY P. MELATHOPOULOS, MARK L. WINSTON, ROBIN WHITTINGTON, HEATHER HIGO, AND MONIQUE LE DOUX Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6 J. Econ. Entomol. 93(3): 559Ð567 (2000) ABSTRACT Neem oil, neem extract (neem-aza), and canola oil were evaluated for the manage- ment of the honey bee mite parasites Varroa jacobsoni (Oudemans) and Acarapis woodi (Rennie) in Þeld 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 (-ßuvalinate). 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 efÞcacy against V. jacobsoni compared with synthetic acaricides may limit their usefulness to beekeepers. KEY WORDS Varroa jacobsoni, Acarapis woodi, Acaricide, mite, neem, canola oil THE PARASITIC Varroa [Varroa jacobsoni (Oudemans)] and tracheal [Acarapis woodi (Rennie)] mites threaten the honey bee, Apis mellifera L., industry worldwide. These two mites have severely reduced the number of healthy colonies (Matheson 1994, Kraus and Page 1995, Finley et al. 1997) available for beekeeping and pollination, a service valued at over $10 billion annually in North America alone (Robin- son et al. 1989, CAPA 1995). Honey bees are highly susceptible to Varroa, and colony death follows 1Ð2 consecutive years of infestation (Martin et al. 1998, Downey et al. 2000). Damage caused by tracheal mites varies considerably with environmental conditions (Eischen 1988, Eischen et al. 1989, Harbo 1993, Frazier et al. 1995) and colony genetics (Page and Gary 1990), but epidemic colony losses of up to 70% and severely reduced colony productivity have been reported (Eis- chen 1987, Otis et al. 1988, Eischen et al. 1989). Al- though it is unclear if Old World honey bee stocks have adapted to tracheal mites (Bailey and Ball 1992, Frazier et al. 1995), dual infestation with Varroa may result in rapid colony decline even in regions where tracheal mites are not considered a problem on their own (Downey et al. 2000). Currently, the management of Varroa relies on the synthetic acaricides -ßuvalinate and ßumethrin (py- rethroids) (Ferrer-Dufol et al. 1991), amitraz (ami- dine) (Herbert et al. 1988b, Wilson et al. 1998), and coumaphos (organophosphorothioate) (Milani and Iob 1998, Ellis et al. 1998, Wilson et al. 1998). Varroa have developed tolerance to these synthetic acari- cides in many areas (reviewed in Milani 1999), and acaricide residues have appeared in honey and wax products (reviewed in Wallner 1999). Tracheal mites, by contrast, have been successfully managed in North America without synthetic acari- cides. Management of tracheal mites relies exclusively on naturally derived acaricides, speciÞcally, menthol (Cox et al. 1986, Herbert et al. 1988a, Delaplane 1992), formic acid (Hoppe et al. 1989, Feldlaufer et al. 1997) and vegetable seed oil (Delaplane 1992, Sammataro et al. 1994, Calderone and Shimanuki 1995). Use of these natural products has largely overcome the problems associated with synthetic acaricides. To date there have been no cases of acaricide resistance, and al- though residues have been found in honey and wax, they are generally less persistent than the synthetic products used to manage Varroa (Li et al. 1993, Wall- ner 1999). Although natural acaricides have also been screened for activity against Varroa, and include or- ganic acids (Hoppe et al. 1989, Kraus and Berg 1994, Feldlaufer et al. 1997) and thymol (reviewed Imdorf et al. 1999), they are not as effective or consistent as synthetic products. As a consequence beekeepers continue to rely heavily on synthetic formulations for the control of Varroa. 0022-0493/00/0559Ð0567$02.00/0  2000 Entomological Society of America by guest on December 7, 2015 http://jee.oxfordjournals.org/ Downloaded from