A new acaricidal compound against Varroa.

Infestation of bee colonies (Apis mellifera) by varroa mites (Varroa destructor) is a significant cause of colony loss, particularly during the winter months in Canada. Currently, beekeepers have a limited number of tools available to treat bee colonies for varroosis. These mites have also quickly developed resistance to a number of registered compounds with acaricidal activity (i.e. fluvalinate, coumaphos, amitraz), while remaining treatment options often pose health hazards to beekeepers, require special devices for application, or have variable efficacy. As such, alternative control strategies are urgently required, particularly those that involve novel compounds. Based previous laboratory and field testing, we have discovered a new acaricidal substance, 1-allyloxy-4-propoxybenzene, referred to as 3c {3,6}. In 2019, 2021 and 2022 we conducted large scale field trials in the southern British Columbia and northern Alberta to evaluate the efficacy of this acaricide under a range of environmental conditions, in comparison to a thymol-based treatment and untreated colonies. In 2019 and 2021, field experiments during fall months showed mite control efficacy levels of up to 81.1 ± 2.9% , using a 4 week treatment period and release devices impregnated with either 4 or 5 g of 3c {3,6}. These studies also showed no measurable negative effects of the active compound on adult bee or brood development. Results will be discussed comparing the efficacy of 3c {3,6} with variation in amount of active ingredient applied to colonies, the duration of exposure and the type application device.