Luta contra Varroa destructor Anderson & Trueman: avaliação de estratégias biotécnicas e bioquímicas com o óleo de Mentha cervina L.

Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia

Varroa destructor Anderson & Trueman is a parasitic mite of the honeybee Apis mellifera L. This species is originated from Asia, being invasive in Europe and other regions, where it causes heavy losses to beekeeping. In this work we have two main objectives: In the first part, the effect of excluding the queen’s egglaying activity as a biotechnical control measure integrated with the chemical treatment against varroa is tested. In the second part of the study, laboratory trials were conducted using essential oil extracts of Mentha cervina L. to test its acaricide effect on the varroa. Two application methods were used, with direct application of the oil in a sponge allowing the varroa mites to contact the volatiles, and by through oil encapsulation in order to release volatiles more gradually. Different doses were tested on both methods. The exclusion of the queen in the colonies led to a significant increase in the efficacy of the chemical treatment. However, there was great variability between colonies, and some colonies ran the risk of getting orphaned, which undermines the viability of the method. The essential oil of Mentha cervina had a lethal action on the varroa, evidenced by both methods. Mortality after 2 hours of exposition to volatiles varied between 70% and 95%, varying with the dose and method. Encapsulation revealed better results expressed in mite mortality. Intermediate doses were shown to be sufficient, on the contrary the higher doses showed a lethal effect on bees also. Further, it was recorded that the volatiles released after about 30 to 60 minutes of exposure in the sponge had a higher acaricidal effect, suggesting that the monoterpenes with higher molecular weight, are probably the most relevant affecting the varroa mite.