Spinetoram exposure disrupts survival of flower bugs and leads to population collapse in orchards

Abstract

The increasing use of reduced-risk insecticides in orchard management has raised concerns regarding their potential risk to beneficial arthropods. Depending solely on acute short-term effects tends to underestimate the risks posed by spinetoram to natural enemies. Limited information is available on the long-term consequences of low exposure to spinetoram on natural enemies. The survival and predation of Orius strigicollis gradually decreased with the increase in spinetoram exposure rate, and the preoviposition periods were prolonged above 0.208 g a.i. ha-1. However, the adult lifespan, reproductive rate, population parameters, intrinsic rate of increase, finite rate of increase, and net reproductive rate were reduced, while the transformation rate was increased with the increase in spinetoram exposure rate. The population size and predation potential of O. strigicollis at 0.104 g a.i. ha-1 were higher than other treatments but did not differ from those of the control. Field residue monitoring showed that the peak residue levels of spinetoram on Eriobotrya japonica and Bidens alba flowers were 0.525–0.589 g ha-1 and 0.139–0.148 g ha-1, respectively, and it required at least 28 and 9 days, respectively, for the residue levels to dissipate to a level with no toxic effect on O. strigicollis. Therefore, the sublethal effects resulting from trace residues is the primary factor responsible for O. strigicollis population collapse. We provide insights for mitigating the negative impacts of spinetoram on O. strigicollis and for integrated pest management development.