Longevity and foraging performance of honey bees treated with an RNAi-based Varroa destructor biopesticide

RNA interference (RNAi) technology is a novel approach for Varroa destructor mite control. In this study, we investigated the effects of vadescana, a new dsRNA-based treatment, on bee longevity and foraging behaviour. Vadescana treated hives were compared to hives treated with a conventional miticide strip treatment, amitraz, and to untreated hives. Field bee hives were equipped with a radiofrequency identification (RFID) system and newly-hatched bees were tagged with RFID chips, allowing automated tracking of forager movements in and out of the hives. We found individual lifespan to be different for all treatments, with untreated bees having the shortest average survival times. Bees from amitraz-treated hives had the longest lifespans, with bees from vadescana-treated hives intermediate. Foraging behaviour analysis showed that vadescana treatment increased foraging activity. Bees were also recorded to drift between neighbouring hives and rob hives even in distant apiaries. Throughout the trial, mite numbers were monitored with bottom board counts and remained lowest for the vadescana treatment group. Our results highlight how parasitism with Varroa destructor is damaging to bees, reducing their foraging performance and longevity. Vadescana treatment in contrast, increased longevity and foraging activity in treated bees.