Effects of emerald ash borer specific gene silencing using RNA interference on soil communities

The emerald ash borer (EAB) (Agrilus planipennis Fairmaire) is an invasive wood- boring beetle from Asia that primarily feeds on ash trees (Fraxinus spp.). Since its invasion of North America, EAB threatens the functional extinction of ash with damages and management costs projected to reach $900 million by 2054. Current management strategies have been insufficient to prevent EAB’s spread, highlighting the need to advance innovative approaches like RNAi, which has demonstrated efficacy against EAB in laboratory and greenhouse trials. Double-stranded RNA targeting heat shock 70-kDa protein (hsp) induces EAB mortality, systematically disperses and persists in planta, and causes no phenotypic effects for several ash-associated insects. We evaluated the environmental and nontarget effects of dsHSP, focusing on soil communities. In laboratory soil incubation assays, dsHSP was recovered up to 8 h post-treatment. Exposure of the collembolan Folsomia candida to dsHSP-treated soil had no effects on adult survival or body length, but increased reproduction. Field foliar applications of dsHSP on ash trees produced no consistent effect on collembolan abundance, while Shannon diversity, hymenopteran, and acarian abundance were minimally impacted. dsHSP was not recovered from soil near treated trees, validating our field design. In the laboratory, soil prokaryotes showed little response in community diversity or composition.