Evaluation of a formic acid formulation for the fall control of Varroa jacobsoni (Acari: Varroidae) in colonies of the honey bee Apis mellifera (Hymenoptera: Apidae) in a temperate climate

Formic acid and Apistan were compared as fall treatments for Varroa jacobsoni (Oudemans), a parasitic mite of the honey bee. Apis mellifera L. Treatment with Apistan resulted in an average mite mortality of 98%, whereas treatment with formic acid resulted in an average 56% mortality. Mortality was not correlated with the level of mite infestation for either treatment. The ratio of the coefficient of variation in mite mortality among colonies in the formic acid group to the coefficient of variation among colonies in the Apistan group was 43.28, indicating that Apistan is a more reliable control agent than the formulation of formic acid used in this experiment. Overall, only 63% of the 250-ml formic acid treatment evaporated during the 30-d treatment period, resulting in an average daily release of 5.26 g of formic acid, which is below that required for effective treatment. These results demonstrate that formic acid shows promise as an acaricide. However, considerable adjustments in the release characteristics of the delivery device must he made before it can Le recommended as a useful control tool.