Trials of a new compound to control Varroa destructor, an ectoparasite of honey bees (Apis mellifera)

Infestation of bee colonies (Apis mellifera) by varroa mites (Varroa destructor) is a significant cause of colony loss, particularly during winter months in Canada. Currently, beekeepers have a limited number of tools available to treat bee colonies for varroosis. Varroa mites have 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 on previous laboratory screening assays, we discovered a new acaricidal substance, 1-allyloxy-4-propoxybenzene, referred to as 3c {3,6}. From 2019 through 2024 we conducted field trials in the southern British Columbia and northern Alberta to evaluate the efficacy of this acaricide under a range of environmental conditions. These experiments showed efficacy levels of up to 94.6 ± 1.2% , using a 6-week treatment period with release devices impregnated with 8 – 10 g of 3c {3,6}. These studies showed 3c {3,6} as being safe for honey bees, having few measurable negative effects on adult bee or brood development. Results will be discussed comparing the efficacy of 3c {3,6} over various applications, as well as target animal safety for bees, and residue deposition in beeswax and honey.