Essential oils from Humulus lupulus as novel control agents against Varroa destructor

Abstract

Humulus lupulus, commonly known as hops has widely been used in breweries globally, however, the acaricidal properties of H. lupulus derived products could also be a novel and interesting avenue of study against insect pests. We tested the antiparasitic activity of H. lupulus essential oils against the honeybee mite Varroa destructor, and its bioactivity against the honeybee Apis mellifera. The hop varieties used in this study were Cascade, Victoria, Spalt, and Mapuche. The essential oils were extracted from flowers by hydrodistillation and then characterized by CG-MS. We evaluated the toxicity of hop essential oils against mites, adult bees (A. mellifera) and larvae, and whether the oils were an attractant or repellent to mites. The major components of the oils for all varieties were β-myrcene, myrcene, beta-farnesene, alpha, and beta cariophylene. Bioassays revealed that essential oils from all the varieties were toxic to the V. destructor mite. Victoria essential oil was the most toxic to V. destructor. The oils did not act as a repellent or attractant to the mites, and the bee (A. mellifera) mortality associated with complete exposure to the essential oil application was moderate to low. The results presented here provide promising results for the application of essential oils from hops grown in South America as an alternative method for controlling the honeybee mite Varroa destructor.