Influence of no‐tillage practices and later planting date on the pea leaf weevil, Sitona lineatus, in pea, Pisum sativum

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AbstractThe pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is a periodic pest of pea, Pisum sativum L. (Fabaceae), in the Palouse region of northern Idaho and eastern Washington, USA. Previous work on‐station and in commercial pea fields showed initial adult weevil colonization was greater in conventional‐tillage than in no‐tillage fields. Increased surface residue of no‐tillage systems results in cooler soils with greater available moisture typically resulting in later planting dates for conventional‐tillage fields. Cereal residue, a characteristic of the region's no‐tillage systems, and planting date were investigated as potential inhibitors of adult pea leaf weevil colonization and feeding on peas via field experiments in 2005 and 2006. Plots without cereal residue and early‐planted plots had greater weevil abundance. Early‐planted peas had greater weevil feeding injury compared to late‐planted peas. The presence of cereal residue did not significantly impact injury levels. A laboratory choice‐test with peas grown in conventional‐tillage and no‐tillage fields indicated greater adult weevil feeding damage on conventional‐tillage‐grown peas. A separate laboratory choice‐test using peas planted 10 days apart demonstrated greater adult weevil feeding injury on early‐planted peas. However, adjusting for available leaf edge resulted in no differences between treatments in either choice test, indicating crop availability and plant apparency during peak weevil colonization rather than plant factors resulting from growing conditions likely explain greater injury on peas planted early and under conventional‐tillage in the field.