Effects of environmental and agronomic factors on soil-dwelling pest communities in cereal crops

• Our study documents factors that affect wireworms in the Pacific Northwestern USA.
• Wireworms were more abundant in spring wheat compared to winter wheat.
• Native grassland habitats serve as good reservoirs for wireworms.
• Soil moisture and acidification strongly mediate wireworm communities.
• Understanding landscape-scale distributions of wireworms can improve IPM.

Characterizing the composition of pest communities across variable cropping landscapes is critical for developing integrated management programs due to variation across species in their ecology and impacts on crops. Wireworms, the soil-dwelling larvae of click beetles, have resurged as major pests of cereal crops in the Pacific Northwestern United States, but knowledge of the composition of wireworm communities across cereal-growing landscapes remains limited. Here, we conducted a large-scale field survey of wireworms across a broad region in the Pacific Northwest. We identified a total of 13 wireworm species across samples taken from 160 fields in Washington, Oregon, and Idaho. The most common species were Limonius infuscatus, L. californicus, and Selatosomus pruininus, which together represented approximately 90% of collected larvae. Wireworm communities were more abundant and diverse in spring wheat and conservation reserve program compared with winter wheat fields. Interestingly, L. californicus was the only species that was more abundant in cultivated wheat crops than in native grass fields, suggesting that this species persists in crop habitats throughout its life cycle and thus might exert stronger impacts on winter crops compared to other species. Our results indicate that Limonius species are distributed mostly in the intermediate and higher precipitation zones or in irrigated fields, while S. pruininus is confined to drier regions. As the dominant wireworm species, the diversity of wireworm communities, and total wireworm abundance varied across crops, landscapes, and climatic regions, management practices should vary across regions for maximum effectiveness.