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Scout for Black Cutworm, Other Early Crop Insect Damage

Scout for Black Cutworm, Other Early Crop Insect Damage

Agronomists in Missouri and other Corn Belt states advise farmers to check cornfields now.

Agronomists across the Corn Belt are reporting intensive moth trap counts of black cutworm.

Agronomists working at Syngenta sent a report out last week stating that cornfields in the states of Missouri, Illinois, Indiana, Iowa and Kansas are at possible risk. Growers are urged to scout fields now because black cutworm can cause substantial damage to growers' yield potential if not controlled early in the growing season. Infestations can lead to stand reductions of more than 70% in some sections of fields.

Moth trap counts are a good way to identify locations where eggs may have been laid as well as regions that are at higher risk of future damage from the newly hatched larvae that like to feed on young corn plants. Increased levels of moth flights are often the first sign of heavy egg-laying and possible infestations later in the season.

In southwest Missouri, some cornfields scouted by University of Missouri Extension agronomists were in the fourth and fifth leaf stage. Jay Chism, MU Extension agronomist, Lamar, reported that cutworm damage is no longer a concern for plants at that stage.  However, cornfields that are not that far along, such as in later planted areas in northern Missouri, need to be individually scouted for black cutworms. 

"I saw a little phosphorus deficiency likely due to the rain. I also saw a small amount of insect feeding, possibly brown stinkbug. Pictures have been sent off to confirm," Chism added. "Some fields are being re-planted, but individual scouting needs to be done is order to see the individual population of the field."

Wheat fields near Lamar were scouted on May 9 and according to Chism, most wheat was in the flowering stage and diseases were fading as the temperatures rose last week. "I saw a few aphids, but wheat is now at the stage that aphids are no longer a concern.  No armyworms or other harmful insects were seen," Chism noted.

Syngenta agronomists recommend scouting cornfields by checking 20 plants in five locations every 25 to 30 acres. If the total of damaged plants exceeds two percent and larvae are smaller than three-fourths of an inch in length, consider treating with an insecticide. As larvae and corn increase in size, the threshold can be raised to 5%; however, if the current stand is less than 15% below optimum, maintain the 2% threshold.

"Growers should be aware of the increased possibility for upcoming black cutworm infestations, especially in no-till fields with annual weeds," said Bruce Battles, Syngenta agronomy marketing manager. "Unfortunately, weather patterns across the Corn Belt this winter and spring have created field conditions in which black cutworm populations tend to proliferate.

Corn hybrids with the Agrisure Viptera 3111 trait stack have an in-seed defense against the multi-pest complex, which includes black cutworm, corn earworm, fall armyworm, Western bean cutworm, dingy cutworm, stalk borer and sugarcane borer, among others. Syngenta estimates damage from these pests costs U.S. corn growers 238 million bushels of corn and $1.1 billion in annual yield and grain quality losses.

For more information about the Agrisure Viptera 3111 trait stack, visit For the latest crop scouting reports in Missouri, contact your local MU Extension agronomist.

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