Effect of essential oils on Varroa mite infestation and reproduction

Compared to other acaricides, essential oils are more environmental friendly and cost effective agents for varroa control. In this study three essential oils, thymol, origanum, and clove oils in different formulations were examined for their effects on mite infestation and reproduction. Infestation rates of varroa mites in larval cells treated with neat clove oil, starch-encapsulated thymol, beta-cyclodextrin encapsulated thymol, and beta-cyclodextrin-encapsulated origanum oil were significantly lower than that of their controls. Actual fertility, actual fecundity, and actual reproductive rate of varroa mites in larval cells treated with thymol crystals and beta--cyclodextrin encapsulated origanum oil were significantly lower than values for control groups. However, potential fertility, potential fecundity, and potential reproductive rate of varroa mites were not significantly different among larval cells treated with the two oils and the control. These results suggest that thymol and origanum oil prevented some mother mites from initiating reproduction, but did not decrease the reproduction of these mites that were reproducing. Essential oils did not delay the development of mite offspring. We concluded that some essential oils (neat clove oil, starch-encapsulated thymol, beta-cyclodextrin encapsulated thymol, and beta-cyclodextrin-encapsulated origanum oil) reduced mite infestation and others (thymol crystals and beta-cyclodextrin-encapsulated origanum oil) affected mite reproduction. Exploring the possibilities of using sub-lethal doses of essential oils for mite control can reduce cost and chances of contamination, and slow down resistance development.