Acaricidal activity of essential oil from Mentha longifolia (Lamiaceae) against Varroa destructor (Acari: Varroidae) and its effect on Apis mellifera (Hym.: Apidae)

Varroa destructor Anderson & Trueman is one of the most important pests of Apis mellifera L. world widely. It causes great economic loss to the beekeeping industry through feeding on various developmental stages of bees and by transmission of pathogenic viral agents. Recently, application of chemical pesticides has led to the occurrence of mite resistance and contamination of hive products. Therefore, the objective of the current study is to evaluate fumigant toxicity of essential oil from Mentha longifolia L. against varroa mite and honey bee. Adult females of varroa mites were treated with different concentrations of essential oil (from 0.5 to 3.75 µl/l air) at 25°C and 40% RH in darkness for 10 h. Also, worker honey bees were exposed to concentrations of essential oil (from 0.62 to 6.25 µl/l air) in incubator set at 32°C and 45 - 50% RH in dark for 10 h. All experiments were conducted with four replications. The number of dead and live treated animals was counted each hour from commencement of exposure. Results showed that the mortality was increased as concentration and exposure time of the oil increased. Estimated LC50 value of M. longifolia treated on V. destructor 9 and 10 h after exposure was 2.05 and 1.65 µl/l air, respectively. However, LC50 values of the oil on A. mellifera at the same exposure times were 5.08 and 4.76 µl/l air, respectively. These findings indicate that varroa mite is more susceptible than A. mellifera. Therefore, more comprehensive experiments are necessary to find appropriate concentration and exposure time of M. longifolia essential oil in varroa mite control programs in apiaries.