Field trials of the novel varroacide, 1-allyloxy-4-propoxybenzene, against Varroa destructor in Western Canada

Varroa destructor is an ectoparasite of western honey bees (Apis mellifera), substantially damaging managed colonies worldwide. Various chemical "varroacides" have been developed to help beekeepers combat infestations of these mites. Nevertheless, treatments may induce non-target toxicity in bees and humans, and their application can be laborious and hazardous. Moreover, widespread varroacide usage has seen the emergence of resistant mite populations, necessitating the need for new treatment options. The dialkoxybenzene, 1-allyloxy-4-propoxybenzene (codenamed 3c{3,6}), has previously been shown to induce paralysis and death of varroa in laboratory experiments, and capable of reducing varroa infestations in full-sized bee colonies. Our study sought to comprehensively investigate 3c{3,6} as a varroacide by optimizing dosages, treatment schedules and application methods across two sets of parallel experiments in Western Canada. Colonies treated with 3c{3,6} were compared to untreated negative controls and positive control colonies treated with the thymol-based commercial product, Thymovar. Across all experiments, 3c{3,6} had mite-killing efficacy comparable to Thymovar, being consistently greater than the untreated colonies, though efficacy varied between years. Treatment with 3c{3,6} did not impact food stores or bee populations. As treatment efficacy varied with dosage and application method, additional studies will be required to optimize 3c{3,6} treatment regimens for potential commercial use.