Suitability of the shrub-steppe habitat of eastern Washington for Halyomorpha halys (Hemiptera: Pentatomidae)

Authors: Hepler, James; MILLS, NICHOLAS - University Of California Berkeley; SMYTHEMAN, PETER - Washington State University; BEERS, ELIZABETH - Washington State University

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2023
Publication Date: 10/25/2023
Citation: Hepler, J.R., Mills, N.J., Smytheman, P., Beers, E.H. 2023. Suitability of the shrub-steppe habitat of eastern Washington for Halyomorpha halys (Hemiptera: Pentatomidae). Environmental Entomology. 52(6):1152-1161. https://doi.org/10.1093/ee/nvad108.
DOI: https://doi.org/10.1093/ee/nvad108

Interpretive Summary: The invasive brown marmorated stink bug (BMSB), a major pest of tree fruit and other crops, is present across most of the Pacific Northwest (PNW). However, pest pressure in the major tree fruit growing centers in the semi-arid eastern parts of Washington State remains low, possibly due to unfavorable wild host plants and desert climate. In the laboratory, we attempted to rear complete generations of BMSB on common wild shrub-steppe PNW plants to determine whether these native plant communities are capable of nutritionally supporting development of this pest. Additionally, we used the resulting developmental data to model the impact of a PNW wild plant diet and high summer temperatures on BMSB population growth. While we found that BMSB could complete development on a wild PNW plant diet, it was clearly a suboptimal food source. Our models predict that a diet of PNW shrub-steppe plants dramatically reduces the population growth rate of BMSB, and that periods of high summer temperatures typical of the region impose further severe reductions. Our findings may explain the lack of significant pest pressure in the region’s tree fruit production areas and advance ongoing efforts to predict the threat of BMSB outbreaks on a local and regional scale.

Technical Abstract: The invasive brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), has spread throughout most of Washington State since its detection in 2012. While it has emerged as a major agricultural and nuisance pest in the Pacific Northwest (PNW) west of the Cascade Mountains, pest pressure in the major tree fruit growing areas in semi-arid northern and central Washington State remains low. The reasons for this are unclear, although, both biotic and abiotic conditions may be contributing factors. We evaluated the suitability of a common shrub-steppe/riparian corridor plant assemblage for supporting H. halys development from egg to adult in summer and fall through controlled feeding studies. Insects successfully completed development on this diet of PNW native plants, though it generally resulted in lower survivorship and adult weight and longer developmental times than a modified colony diet or a diet of known hosts from the eastern United States. These developmental data were used to parameterize stage-structured matrix models to predict the impact of diet and extreme heat events on H. halys population growth. The predicted net reproductive rate (R0) of H. halys was consistently and substantially reduced by a diet of PNW native plants, and heat shock imposed further severe reductions in R0. Our results suggest that the combined population effects of suboptimal plant host quality and regional heat waves may explain the lack of landscape-level H. halys pest pressure in semi-arid regions of the PNW.