Norroa™ as a dsRNA biopesticide for Varroa destructor: insights from New Zealand research on mode of action, field efficacy, non−target effects, and social acceptance

(hereafter varroa), a globally distributed parasitic mite and a key driver of honey bee colony losses. Here, we review laboratory, field, and social research conducted in New Zealand that has enhanced understanding of vadescana, a dsRNA biopesticide targeting calmodulin gene expression in varroa, and its commercial formulation Norroa™. Laboratory studies using mini-hive systems demonstrate that vadescana can suppress mite reproduction, primarily through disruption of embryonic development. Varroa calmodulin and calmodulin-like gene expression was suppressed. Vadescana does not appear to affect adult mite survival. Field trials in commercial beekeeping operations in both the North and South Islands have shown that vadescana can be used to manage varroa populations and maintain low infestation levels for extended periods. The efficacy of this biopesticide in maintaining low mite populations was comparable to synthetic miticides under some conditions, but variability was observed across sites, infestation levels, and management contexts. Importantly, New Zealand-based studies indicate no or minimal impacts of vadescana on honey bee larval and adult survival, foraging behaviour, colony growth, and honey production. Bioinformatic and experimental assessments have predicted a low risk of adverse effects on non-target organisms associated with beehives. Finally, we discuss remaining challenges and future directions, including resistance management, optimisation of application strategies, incorporation into varroa integrated pest management programmes, and the need for international regulatory harmonisation. Collectively, the greatest utility of Norroa™ appears to lie in maintaining low mite populations and supporting integrated pest management programmes, rather than functioning as a stand-alone, knock-down treatment under high varroa infestation pressure.