Acaricidal activity of essential oils for the control of honeybee (Apis mellifera) mites Tropilaelaps mercedesae under laboratory and colony conditions

Abstract

Tropilaelaps spp. mites are considered a major parasite of honeybees. In this study, essential oils (EOs) of 11 plant species were evaluated for acaricidal activity under laboratory and field conditions. Five adult mites per petri dish and ten adult worker bees per plastic cup cage were exposed to different concentrations of each essential oil (0.1, 0.5, 1.0, 5.0, and 10.0% (v/v)). The essential oil of Piper betle (betel) showed the highest acaricidal activity in laboratory testing. Additionally, most EOs showed low toxicity to adult honeybees in a lab assay. Piper betle, Amomum krervanh, and Zanthoxylum limonella were then tested in whole colonies using cardboard strips soaked in 10 mL of each essential oil at various concentrations, every week for 4 weeks. Amomum krervanh at 10% (v/v) and P. betel at 5.0% (v/v) decreased mite populations after 30 days. We further tested grease and a sponge as application methods to deliver A. krervanh, with no significant impact on mites. Although several essential oils demonstrated acaricidal activity against Tropilaelaps under laboratory conditions, the EOs tested did not significantly reduce mites under colony conditions. Therefore, the concentration and colony delivery methods of these promising EOs warrant further investigation.