A gel formulation of formic acid for control of Varroa destructor

Abstract

Two formulations of a starch-based gel containing 85% formic acid were evaluated to control Varroa destructor in bee hives. Gels were poured in polyethylene-wrapped plates provided with release areas from 10 to 300 cm2 to regulate evaporation. In a laboratory test, at 32 ŶC and 40-60% r.h., evaporation rate of the plates, expressed as weight loss, was determined over 45 days. A selected formulation and release areas of 16, 32, and 64 cm2, allowing evaporation of about 10 g per day, were used in field tests. In June and July 2004, plates were placed inside honey bee (Apis mellifera) hives in Tlalmanalco (State of Mexico) and Cordoba (State of Veracruz, Mexico). Weight loss of the plates was measured together with their effectiveness in V. destructor control and their possible effects on adult and brood population, presence and activity of the queen bee, and quantity of food supplies. Mean daily evaporation of formic acid ranged from 8 to 12 g in both locations. None of the treatments had negative effects on bee population and food supplies, but three queens were lost, apparently due to excessive handling. Mean effectiveness in reducing the Varroa population was about 73%. Treatment with formic acid in a gel formulation is considered to be economically sound and practically feasible.