Comparison of three bioassay methods to estimate levels of tarnished plant bug (Hemiptera: Miridae) susceptibility to acephate, imidacloprid, permethrin, sulfoxaflor, and thiamethoxam

Authors: Portilla, Maribel; Luttrell, Randall; Parys, Katherine; Little, Nathan; Allen, Clint

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2018
Publication Date: 8/28/2018
Citation: Portilla, M., Luttrell, R.G., Parys, K.A., Little, N., Allen, K.C. 2018. Comparison of three bioassay methods to estimate levels of tarnished plant bug (Hemiptera: Miridae) susceptibility to acephate, imidacloprid, permethrin, sulfoxaflor, and thiamethoxam. Journal of Economic Entomology. 1-10. https://doi.org/10.1093/jee/toy244.
DOI: https://doi.org/10.1093/jee/toy244

Interpretive Summary: The tarnished plant bug, TPB, is highly polyphagous insect feeding on many wild and cultivated crops some of which could be considered unsprayed refuges for susceptible genotypes. However, are often bottlenecked on agricultural crops receiving routine insecticide applications. Concerns for evolving insecticide resistance and reliability of research methods to explain poor control of this pest in agricultural crops have been expressed nearly as long as organic insecticides have been used in the United States. Various studies utilizing a variety of bioassay methods have been developed over the years to potentially explain these field situations. This research was conducted for a better understanding relationships among the different assay methods and develop monitoring procedures more predictive of field activity, we initiated studies in 2015 to compare the activities of several commonly used insecticides in two of the most common assay methods to that of TPB exposed to cotton in dipped assays with plants grown in the greenhouse.

Technical Abstract: A laboratory colony of tarnished plant bugs (TPB) reared solely on a meridic diet was exposed to acephate, imidacloprid, permethrin, sulfoxaflor and thiamethoxam in dose-response experiments using floral-foam, glass-vial, and dipped leaf assays. Results indicated that different assay methods produced different relative results across the different insecticides. Dose- and time-response regression models also indicated that length of exposure of TPB to insecticide treated plant tissue is important. Time of exposure required to reach an LC90 at estimated recommended field rates suggested that the recommended lower field rate of acephate (0.56 kg ai/ha) would reach an LC90 of exposed TPB between 48 and 96 h post initial exposure. An LC90 of TPB exposed to permethrin (0.11 kg ai/ha) was not predicted from the regression modes over the 168 h observation; lower recommended applications rates of imidacloprid (0.053 kg ai/ha), sulfoxaflor (0.053 kg ai/ha) and thiamethoxam (0.042 kg ai/ha) reached projected LC90s between 96 and 168 h of exposure. Collectively, the results of this study corroborate current existing procedures for tracking TPB resistance to insecticides, but also illustrate the importance of additional field studies that empirically associate assay results to projected field control.