RESUMO
Background: Ecto-parasite, varroa mite, (Varroa destructor), is the primary pest affecting the apiculture sector globally in various regions. Aim: This study examined the toxicity of nine essential oils to Apis mellifera L. and the acaricidal impact of those oils against V. destructor. Methods: The acaricidal effects of nine essential oils, extracted from plant materials were used. In the screening experiment, 10 mg of the active ingredients of the plant material extracts were prepared in an alcohol solution with concentrations of 5%, 10%, and 15%. For each type of plant extract, five female V. destructor were transferred to a Petri dish with five worker bees incubated at 70% humidity and 33°-34° for 2 days, for each treatment four replicates were used compared to the control. Forty-eight hours following treatment, the number of dead and live mites was counted to determine the mortality rate. In the second assay experiment, the best five essential oils of the previous experiment were selected to re-assess their effectiveness on varroa mites and honeybee workers by using a concentration of 15%. Five females of V. destructor were transferred to a Petri dish with 10 adult bees and treated with the solution of the selected oils. Five replicates and control treatments were taken for each sample simultaneously. Dead and live bees were counted for each replicate at 48 hours after treatment. Results: There were no significant differences between the concentrations used of each oil on the rate of death of mites, and its effectiveness ranged between 70.0% and 53.3% compared to the control groups. In addition, the best oil used was bitter melon, with a death rate of 80% at a concentration of 15%, while peppermint oil showed the lowest death rate of 45% at a concentration of (5%). However, all these treatments were statistically highly significant compared with the natural death rate in control (2%). In the second test, the results of the statistical analysis indicated that there were highly significant differences (P0.05 <0.0001) in the average numbers of dead varroa mites compared to the control when using a 15% concentration of five selected oils. On the other hand, there was no statistically significant difference in the honey bee workers' mortality rate between the treatment and control groups (P0.05 <0.3390), and it was relatively low for all treatments except the basil oil, where the bee mortality rate was 16% compared to the control (10%). Conclusion: It is clear from this experiment that bitter melon oil can be used to control varroa mites and it can be considered safe for honey bees as well as for the environment.
