A study of the efficacy of formic acid in controlling Varroa destructor and its correlation with temperature in Iran
R Bahreini, Gh Tahmasebi, J Nowzari and M Talebi
European honey bee (Apis mellifera) colonies infested with varroa (Varroa destructor) were used to compare the effect of treatment with tau-fluvalinate (Apistan) and formic acid (65%) during a 3-year period from 1998 to 2000. Twenty colonies were divided into 5 treatment groups, each with 4 replications. The groups were treated with either tau-fluvalinate (AP) or four applications of 20 ml (for a total of 80 ml (FA80)), 30 ml (FA120), 40 ml (FA160) or 50 ml (FA200) of 65% formic acid per colony applied over 16 days. The percentage mite mortality due to experimental treatment was determined using the sticky board method. Total mite mortality in the treatment groups over the 3-year period was 93.25% in the AP group, 60% in FA80, 75% in FA120, 59.5% in FA160 and 69.55% in FA200. Treatment with formic acid was as effective as Apistan only in the third year when comparatively high ambient temperatures were recorded during sampling periods; in year 3 the average temperature was 19.44 °C and mite mortality was 83% (AP), 89.25% (FA80), 95.25% (FA120), 75.67% (FA160) and 92% (FA200). In years one and two, mite mortality was higher in the Apistan group than in all formic acid groups, but none of the formic acid groups differed from one another. The there was a significant (r = 0.0181) correlation between formic acid mite mortality and temperature, but no such relationship (r = - 0.05) between mite mortality and relative humidity.
honey bees, Apis mellifera, Varroa destructor, formic acid, tau-fluvalinate, control methods, temperature