Significant flights of black cutworm moths were reported in several counties of Illinois during mid-April. Based upon these captures of moths in pheromone traps, projected cutting dates are offered for the following counties: Champaign (May 20), Fayette (May 11), Logan (May 14), Madison (May 11), Pike (May 17), and Warren (May 18). Fields most at risk to economic infestations include those that are planted late and infested with winter annuals. Weedy fields are often targeted for egg laying by these strong migratory moths. Minor leaf feeding is often an early indicator of potential cutting that may ensue. Fields at greatest risk to economic loss are those in the 1- to 4-leaf stage of development.
Many Bt hybrids now provide various levels of protection against black cutworms. I encourage producers to view the Handy Bt Trait Table published by Drs. Chris DiFonzo (Michigan State University) and Eileen Cullen (University of Wisconsin) to determine if their Bt hybrid offers black cutworm protection. If a hybrid has been planted that does not offer black cutworm protection, producers are strongly encouraged to scout fields carefully for early signs of cutworm leaf feeding, potential cutting, and pay close attention to projected cutting dates. Rescue treatments can provide effective control for this pest if needed. Entomologists at Iowa State University provided a good discussion on economic threshold considerations for black cutworm several years ago. Even if a Bt hybrid has been planted and offers black cutworm protection — it may be worthwhile to scout fields to ensure this investment has paid dividends.
I offer my thanks to Kelly Estes, Cooperative Agricultural Pest Survey Coordinator, Illinois Natural History Survey, for providing these projected cutting dates for Illinois.