Halyomorpha halys mortality and sublethal feeding effects following insecticide exposure

Abstract

The brown marmorated stink bug, Halyomorpha halys (Stal), is a highly polyphagous invasive pest. Increased use of broad-spectrum insecticides to manage H. halys has resulted in secondary pest outbreaks and disruptions to integrated pest management (IPM) programs. We evaluated H. halys mortality, molting, and feeding after exposure to insecticides in the laboratory. Five insecticides (four active ingredients), considered less risky to natural enemies, were compared to a pyrethroid insecticide and an untreated control. Compared to the control, only azadirachtin + pyrethrins significantly reduced egg hatch, while all insecticides caused significant direct mortality to 1st and 2nd instars 5 days after hatch (DAH). Bifenthrin quickly caused complete mortality of adults, and the only insecticide to statistically match this level of mortality was sulfoxaflor at 14 days after treatment (DAT). Azadirachtin + pyrethrins and sulfoxaflor significantly reduced the proportion of 1st instars that molted compared to the control. Adults that survived sulfoxaflor exposure produced significantly fewer feeding sites than the control. However, when taking into consideration both lethal and sublethal effects, all insecticides, except pyrethrins, resulted in significant reductions in feeding sites/individual compared to the control. This more complete estimate of efficacy (i.e., reduction in injury/insect), confirms the potential of several insecticides to reduce crop injury without the necessity of high direct mortality to H. halys.