Urgent Call for Scouting: Black Cutworm Migration in the Midwest

As the black cutworm moths migrate into the Midwest, agronomists are urging farmers to scout their fields actively. Recent trapping reports from Illinois, Iowa, Ohio, and Wisconsin indicate rising moth activity, which marks the beginning of a critical period for corn crops.

Flight Monitoring

The trapping initiatives commenced on April 1st and will run until the end of May, focusing on black cutworm and armyworm populations across the Midwest. Kelly Estes, coordinator for the Illinois State Agricultural Pest Survey, states, “This data helps us know when moths start arriving and identifies potential areas for heightened insect pressure.”

Estes notes that significant black cutworm flights occur when eight or more moths are captured over two nights. “Large captures signal an increased risk of injury to corn, establishing a ‘biofix’ for degree day accumulation,” she adds.

While large captures indicate a risk, they do not guarantee immediate damage. Growers are advised to start scouting three to four weeks post-capture. Estes explains, “Our trapping program aids growers in understanding when and where the risk is elevated, serving as a forecasting tool.”

Scouting for Cutworm

No-till, strip-till, or fields with heavy winter annual weeds or cover crops are most susceptible to the black cutworm, highlights Ryan Gentle, an agronomy manager for Wyffels Hybrids. “These fields deserve priority attention,” he advises.

The initial signs of black cutworm damage manifest as leaf feeding on emerged corn or surrounding weeds. Larvae may cut weeds before moving onto corn. As they grow, they create irregular holes in corn seedlings and can sever the plants entirely. “If you dig, you’re likely to find a cutworm,” Gentle mentions.

Cutworms feed nocturnally and hide during the day, making early morning scouting optimal. “It’s crucial to assess the instar size of the cutworms along with the growth stage of the corn to forecast the potential for further cutting,” he adds.

Management Strategies

Some Bt traits, like Viptera and Herculex, offer protection, while many corn hybrid traits provide minimal to no defense against cutworms. Additionally, standard seed treatments can be inadequate if larvae grow larger. Gentle recommends that insecticide applications should be timely and asserts, “If scouting isn’t feasible, consider using a soil-applied insecticide or choose hybrids with effective traits, especially in areas with significant moth flights.”

A Warning for Armyworms

Farmers should also stay vigilant for armyworms, which migrate similarly and target wheat and grass crops. While their damage differs—they rarely cut plants like cutworms—they can cause rapid defoliation in fields, especially within cover crop or wheat systems.

As planting season intensifies, Estes emphasizes the importance of monitoring both pests. “Timely scouting is critical; you don’t want to discover damage too late,” she cautions. “A little diligence now can substantially protect yield down the line.”

Farmers can track moth flights for black cutworm and armyworm, along with projected cutting dates for Iowa, Illinois, and Wisconsin, at the Corn ipmPIPE website. Additionally, it’s advisable to consult state Extension services for further resources.

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