Evaluation of the botanical oils neem, thymol, and canola sprayed to control Varroa jacobsoni Oud.(Acari : Varroidae) and Acarapis woodi (Acari : Tarsonemidae) in colonies of honey bees (Apis mellifera L., Hymenoptera : Apidae)

The botanical oils neem, thymol, and canola were examined for control of pa rasitic mites (Varroa jacobsoni and Acarapis woodi) in honey bee (Apis mell ifera) colonies. Neem oil spray (5% solution) killed 90 +/- 6% of varroa mi tes, three times more than died in the untreated group. Thymol-oil spray (4 .8g thymol/L in 20% canola oil solution), thymol in vermiculite (3.6g/vermi culite block), and canola oil spray (20% solution) killed 79 +/- 8%, 68 +/- 6%, and 65 +/- 6% of the varroa mites, respectively. Colonies treated with the thymol-oil spray had a significantly lower tracheal mite infestation ( 1.3 +/- 7.5%) at the end of the treatment period than the untreated group ( 23.3 +/- 6.0%). All other treatments showed a slight but not statistically significant decrease in tracheal mite infestation levels, Neem and thymol-o il spray treatments were detrimental to bees, as they both had 50% queen lo ss, and colonies treated with neem oil had one-third as many adult bees and one-sixth as much brood as untreated colonies at the end of the experiment . However, both neem and thymol-oil spray treatments were as effective as c ommercially available formic acid against varroa mites. The negative effect s on bees may be remedied by changes in formulation, application technology , and season of application, Neem, thymol, and canola oil treatments provid e adequate control of varroa mites to be useful in an integrated pest manag ement approach. These natural products may have the added advantage of simu ltaneously reducing tracheal mite populations. Thus, continued research to develop application methods that do not cause bee mortality is warranted.