Optimization of the use of 'Apilife VAR' to combat Varroa jacobsoni Oud in honey bee colonies

'Apilife VAR' has been developed to combat Varroa jacobsoni in bee colonies. It consists of a Vermiculite plate which is loaded with about 20 g of a mixture of thymol (76%), eucalyptol (16.4%), menthol (3.8%) and camphor (3.8%). The purpose of these tests was to examine the efficiency of the product in the following conditions: a) duration of the treatment: 4 or 8 weeks; b) dosage in Swiss hives; twice 1 plate, twice 1/2 plate or once 1 plate; c) formulation: with or without camphor; d) disposition of the plates in Swiss hives, directly on the brood combs or on a fine-meshed grid positioned on the combs; e) disposition of the plates in Dadant and Ritter hives: directly on the combs (above) or under the bottom grid (below). Problems related with bee toxicity, concentration of the components of the product in the air of the hive and residues in the bee food and honey have also been examined. In the Swiss hive the average efficiency of 'Apilife VAR' was 97.7% after 8 weeks of treatment and 93.7% after 4 weeks of treatment. The difference was not significant. Twice 1 plate was the best dosage in the Swiss hive. The difference of formulation (with or without camphor) did not influence the results of the treatment (table I). The fine-meshed grid between the brood comb and the plate did not change substantially the efficiency of the product as long as the bees did not cover the grid with propolis. In the Dadant and Ritter hives the treatment from below was not efficient enough (table II). The treatment from above had an efficiency of 97.1% in the Ritter hives and of 89% in the Dadant hives.