Powdered sugar shake to monitor and oxalic acid treatments to control varroa mites (Varroa destructor Anderson and Trueman) in honey bee (Apis mellifera) colonies

Abstract

A practical method to control the destructive varroa mite, Varroa destructor Anderson and Trueman in honey bee colonies consisted of monitoring with powdered sugar and treatment with oxalic acid (OA). We tested mite populations within 28 honey bee colonies on adult bees by a using a powdered sugar shake method. Subsequently, the same colonies were treated with 2.9% oxalic acid and 31.9% sucrose-in-water solution (w/w) four times, with a final varroa treatment using Apistan strips. On average 66.10 ± 35.23% and 94.64 ± 9.56% mites were detected using this simple sugar shake method in August and October, 2015. Furthermore, positive correlations were found between relative number of infested honey bees detected by powdered sugar shake and washing bees with alcohol plus soapy water (r = 0.90 and r = 0.62). Temperature and humidity seems to be crucial in determining the effectiveness of the powdered sugar shake method. For control of the mites, four consecutive OA treatments performed during the winter months in colonies containing capped brood had an average of 228 ± 226.93, 167 ± 313.79, 92 ± 160.50, and 27 ± 42.19 varroa mortality, respectively. Combination of four successive OA applications by trickling onto adult bees between combs in situ, during warm temperate winter conditions ensured a cumulative efficacy of 98%. Based on this level of mortality, it can be concluded that using the powdered sugar shake method to establish adult bee infestation levels in colonies along with an OA treatment may provide adequate varroa control in certain situations.