The Efficacy, Phytotoxicity, and Safety of Liquid Ethyl Formate Used to Control the Grape (Campbell Early) Quarantine Pest Pseudococcus comstocki

Abstract

Featured Application: Pseudococcus comstocki, a quarantine pest, was completely killed when fumigated with liquid ethyl formate (EF), without any phototoxicity or alterations in the internal condition of the grapes (Campbell Early), at EF 70 g/m3 for 4 h, 145.85 g h/m3 with a loading ratio of 10% at 5 °C. EF can be an alternative to methyl bromide (MB) in terms of safety in the workplace as well as preventing ozone depletion. Mealybugs found on grapes during quarantine in Korea are fumigated with methyl bromide (MB). However, MB is an ozone-depleting, highly toxic pesticide; therefore, the International Plant Protection Convention, a representative organization involved in quarantine, recommends using MB alternatives. We evaluated the feasibility of using liquid ethyl formate (EF), a new EF formulation, to control mealybugs (Pseudococcus comstocki) on grapes (Campbell Early). Large-scale tests and the comparative evaluation of EF and MB desorption from grapes were conducted during the simulated 72-h post-fumigation period. Dose–response tests showed that the EF concentration and time product causing 99% mortality (LCt99) at 5 °C was 47.36 and 145.85 g h/m3 for adults and eggs, respectively. EF treatment at 70 g/m3 for 4 h at 5 °C with a loading ratio of 10% achieved an LCt99 of 145.85 g h/m3 on P. comstocki, confirming EF efficacy on mealybugs without phytotoxic effects on grapes. EF fumigation may also be safer because EF concentrations were maintained at less than 100 ppm, the specified exposure limit of EF; meanwhile, those of MB were higher than the exposure limit (1 ppm). Therefore, liquid EF can be used as a safer alternative to MB in phytosanitary treatments of grapes to control P. comstocki.