Comparing Pesticide Delivery Methods for SWD Control

Three pesticide delivery methods were compared for efficacy in controlling spotted wing drosophila (SWD) – a new invasive pest in the United States. Airblast had the best field coverage, followed by helicopter and micro-spray chemigation. Foliage bioassays indicated that SWD mortalities were mostly similar between airblast and non-invasive micro-spray chemigation of Mustang Maxx^®. However, airblast provided a better coverage than micro-spray chemigation at harvest despite airblast’s economic levels of fruit drop and commensurate SWD control with Malathion. Foliar residue data supported the bioassay results. Furthermore, fruit residue analysis found micro-spray resulted in lower fruit chemical residues than airblast application. The data suggested micro-spray chemigation could provide season-long fruit protection by creating a toxic habitat resulting in a cumulative exposure while protecting ripening berries at or below maximum residue levels. The foliar residual bioassays indicated effective overall field toxicity was much lower than previously thought.  This is validated by the fact that no infested berries were discovered in the mistigation plots throughout the harvesting season. Among three delivery methods, micro-spray chemigation was advantageous over helicopter and airblast application in terms of cost and efficiency.