Use of oxalic acid to control Varroa destructor in honeybee (Apis mellifera L.) colonies

This study was carried out to determine the effects of oxalic acid (OA) on reducing Varroa mite (Varroa destructor) populations in honeybee (Apis mellifera L.) colonies in the fall. Twenty honeybee colonies, in wooden Langstroth hives, were used in this experiment. Average Varroa infestation levels (%) of the OA and control groups were 25.87% and 24.57% on adult workers before the treatments. The OA treatments were applied twice, on 3 November and 13 November 2006. Average Varroa infestation levels were 5.24% and 31.43% after the first application and 2.87% and 41.74% after the second application in the OA and control groups, respectively. Average efficacy of OA was 93.40%. No queens were lost, and there was no brood or adult honeybee mortality in any of the colonies during the experiment.