Use of essential oils for the control of Varroa jacobsoni Oud. in honey bee colonies

Essential oils and essential oil components offer an attractive alternative to synthetic acaricides for the control of Varroa jacobsoni, They are generally inexpensive and most pose few health risks. Terpenes (mainly monoterpenes) are the main components of essential oils, comprising about 90 % of the total. More than 150 essential oils and components of essential oils have been evaluated in laboratory screening tests. Very few of them, however, have proven successful when tested in field trials. Thymol and thymol blended with essential oils or essential oil components offer a promising exception. Mite mortality obtained with these formulations typically exceeds 90 % and often approaches 100 %. In addition, residues in honey are low, even after long-term treatments. The exact conditions under which these formulations will yield reliable and effective control, however, have only been determined for certain European regions. Based on the available studies, relying solely on a single treatment with an essential oil or essential oil component is generally not sufficient to maintain mite populations below the economic injury level. Therefore, efforts are necessary to optimize the use of these substances and to incorporate them, along with other measures for limiting mite populations, into an integrated pest management strategy for control of Varroa jacobsoni. (C) Inra/DIB/AGLB/Elsevier, Paris.