Evaluation of natural compounds and different delivery systems for controlling the ectoparasitic mite Varroa destructor (Anderson & Trueman) in honey bee (Apis mellifera L.) colonies
The toxicity of natural compounds to 'Apis mellifera' and to their parasitic mite, 'Varroa destructor' was determined in the laboratory. Thymol, origanum oil and clove oil were the most toxic and selective products with LC50S of 56.1 g/vial, 56.1 g/vial, and 90.9 g/vial, respectively. Several materials and solvents were tested as candidate carriers for their ability to release a natural, volatile acaricide at a uniform rate, for different periods of time. Absorbent pads (Dri-Loc®, Cryovac Company, New Jersey, USA), gelatin, and powdered product were selected as acaricide carriers for short, mid, and long-term treatments, respectively. New formulations of thymol, origanum oil and clove oil were dissolved in ethanol plus mineral oil and applied with several delivery methods in honey bee colonies to evaluate their efficacy as spring and fall varroa-mite control treatments. The best results were obtained with thymol, delivered using a pad soaked in gelatin, mixed with powdered sugar, or infused in vermiculite sponges, during early fall; levels of mite control ranged from 97.4 to 99.2%.