Laboratory evaluation of miticides to control Varroa jacobsoni (Acari : Varroidae), a honey bee (Hymenoptera : Apidae) parasite

A laboratory bioassay was developed to evaluate miticides to control Varroa jacobsoni (Oudemans), an important parasite of the honey bee, Apis mellife ra L. Bees and mites were exposed to applications of essential oil constitu ents in petri dishes (60 by 20 mm). The registered mite control agents tau- fluvalinate (Apistan) and formic acid also were evaluated as positive contr ols. Treatments that caused high mite mortality (>70%) at doses that produc ed low bee mortality ((30%) were considered mite selective. The six most se lective of the 22 treatments tested (clove oil, benzyl acetate, thymol, car vacrol, methyl salicylate, and Magic3) were further evaluated to estimate L DS, values and selectivity ratios (A. mellifera LD50/V. jacobsoni LD50) at 24, 43, and 67 h after exposure. Tau-fluvalinate was the most selective tre atment, hut thymol, clove oil, Magic3, and methyl salicylate demonstrated s electivity equal to or greater than formic acid. The effect of mode of appl ication (complete exposure versus vapor only) on bee and mite mortality was assessed for thymol, clove oil, and Magic3 by using a 2-chambered dish des ign. Estimated V. Jacobsoni LD50 values were significantly lower for comple te exposure applications of thymol and Magic3 suggesting that both vapor an d topical exposure influenced mite mortality, whereas estimated values for clove oil suggested that topical exposure had little or no influence on mit e mortality. These results indicate that essential oil constituents alone m ay not be selective enough to control Varroa under all conditions, but coul d be a useful component of an integrated pest management approach to parasi tic mite management in honey bee colonies.