Plant extracts used for control of the parasitic mites Varroa jacobsoni (Acari: Varroidae) and Acarapis woodi (Acari: Tarsonemidae) in colonies of Apis mellifera (Hymenoptera: Apidae)

Natural products were evaluated as control agents for the tracheal mite Acarapis woodi (Rennie) and the Varroa mite Varroa jacobsoni (Oudemans) in colonies of the honey bee, Apis mellifera L. Test materials consisted of 1:1 (wt:wt) blends of thymol with cineole, citronellal, or linalool. Two, 25.0-g applications (rate 1) of each blend were applied to colonies infested with Varroa. A 2nd group of Varroa infested colonies received 2 x 12.5 g applications (rate 2). Each application was left in place for 14 d, during which time Varroa mites were collected on sticky boards placed on the bottom boards of the colonies. At the end of the 28-d treatment period, remaining mites were killed with fluvalinate and collected on sticky boards. Mite mortality in the colonies receiving thymol and cineole was 56.4 and 49.1% for rates 1 and 2, respectively, compared with a natural mite fall of 28.0% in control colonies. Two applications of each blend (rate 1) were applied to colonies infested with A. woodi in September. Mite prevalence values increased 28.3% in control colonies by the following May, but decreased 22.4% in colonies receiving thymol and citronellal. Our results suggest that the presence of brood seriously limits the efficacy of thymol-based control measures when they are applied as fumigants against Varroa. However, these products may be useful against the tracheal mite and may be an important component of an integrated pest management program for Varroa if used when brood levels are low.