Impact of insecticides on the invasive Halyomorpha halys (Hemiptera: Pentatomidae): analysis of insecticide lethality.
The efficacy of 37 insecticide treatments against adult Halyomorpha halys (Stål) was established based on exposure to 18-h old dry insecticide residue in laboratory bioassays. Individual adult H. halys were exposed to an insecticide residue for 4.5 h and then monitored daily for survivorship over a 7-d period. The proportion of dead and moribund insects was used as an estimate of overall insecticide efficacy against H. halys immediately after the exposure period and over the 7-d trial. Among all materials evaluated, 14 insecticides exhibited increasing efficacy, in which the percentage of dead and moribund insects (used as a measure of insecticide efficacy) increased by >10% after 7 d. By contrast, insecticide efficacy values of eight insecticides declined by >10% (based on recovery of adults from a moribund state) over the 7-d period with most belonging to the pyrethroid class. In this study, the efficacy value of neonicotinoid, acetamiprid, showed the greatest decline from 93 to 10% over 7 d. A lethality index (scale of 0-100) was developed to compare insecticides based on quantifying the immediate and longer-term effects of insecticide exposure on H. halys. Among all materials evaluated, dimethoate, malathion, bifenthrin, methidathion, endosulfan, methomyl, chlorpyrifos, acephate, fenpropathrin, and permethrin yielded the highest values (>75) because of a high degree of immediate mortality with very little recovery. Our results provide baseline information regarding potential of candidate insecticides against adult H. halys and highlight the need to consider longer-term effects in establishing overall efficacy ratings against this invasive species.