Acaricidal activity of Swietenia mahogani and Swietenia macrophylla ethanolic extracts against Varroa destructor in honeybee colonies

The alcoholic extracts of leaves and stem bark of Swietenia mahogani showed the highest acaricidal activity against Varroa mites with weak or no effect on honey bees. This study suggested that the use of natural plant extracts or their products as ecofriendly biodegradable agents could be of high value for the control of Varroa mite. [Display omitted] ► Swietenia mahogani and Swietenia macrophylla extracts were tested for their acaricidal effect against Varroa mite. ► The highest reduction rate of infestation was observed with S. mahogani leaves extract. ► All the tested extracts showed less or no effect on honey bees. ► Plant products can be used as ecofriendly biodegradable agents to control Varroa mite. The acaricidal (miticidal) activity of 90% ethanolic extracts of leaves and stem bark of Swietenia mahogani and Swietenia macrophylla were tested against Varroa destructor mite. Four concentrations were used over two different time intervals under laboratory and field conditions. In general, it was noticed that the acaricidal effect based on mortality and LC50 of all tested extracts against the Varroa mite was concentration and time dependant. The acaricidal action against Varroa mites was relatively the least for the S. macrophylla stem bark extract at 500ppm concentration after 48h while it reached 100% and 95% in case of S. mahogani bark and S. macrophylla leaves, respectively. The% infestation with Varroa in colonies treated with the different extracts at various time intervals showed that the rate of infestation decreased to 0.0% after 12days from the beginning of treatments with 500ppm of S. mahogani leaves extract compared to 0.79% decrease after treatment with Mitac, a reference drug (60mg/colony). The rate of infestation in case of treatments with S. mahogani bark, S. macrophylla leaves and S. macrophylla bark was decreased to 0.11%, 2.41% and 1.08%, respectively. The highest reduction was observed with S. mahogani leaves extract followed by S. mahogani bark. All the tested extracts showed less or no effect on honey bees at the different concentrations and at different bioassay times. This study suggested that the use of natural plant extracts or their products as ecofriendly biodegradable agents could be of high value for the control of Varroa mite.