Improving ipm strategies by monitoring and identifying Plum curculio strains in Illinois

Plum curculio (PC), Conotrachelus nenuphar (Herbst.) (Coleoptera: Curculionidae), is a native pest of peaches and apples that causes significant damage as an internal fruit feeder. Effective control depends on precise timing between adult emergence and egg laying, but inconsistent monitoring tools and limited understanding of local strain dynamics complicate management.
PC has two distinct strains: the univoltine northern and bivoltine southern strain. Historically, Illinois was assumed to harbor only the northern strain, but no molecular evidence confirmed this. This study aimed to evaluate monitoring tools, identify strains, and assess lure performance in Illinois peach orchards.
In 2023, trunk traps baited with benzaldehyde lures were deployed in commercial peach orchards. While the traps intercepted PCs early in the season, none were captured in mid-summer. In 2024, both methyl salicylate and benzaldehyde lure, each combined with Grandiosic acid were tested. However, no fruit was produced that year due to an early frost and no PC adults were caught during the monitoring period.
To complement the field study, a laboratory Y-tube olfactometer assay was conducted to test lure attractiveness in presence of fruit. Results revealed a decreased attractiveness of lures when fruit was present. Molecular analysis of captured adults revealed both wCne1 (northern) and wCne3 (southern) strains, suggesting the southern strain PC is expanding northward, which has important management implications. This study highlights the importance of identifying PC strain, testing lure combinations and integrating monitoring into IPM programs to improve spray timing, reduce pesticide use, and minimize crop losses in Illinois peach orchards.