K-State entomologists warn of army cutworm surge in western Kansas

GARDEN CITY — Kansas State University Research and Extension agents are alerting western Kansas farmers and landowners to begin looking for a common springtime pest.

The army cutworm is starting to make an appearance in some wheat and triticale fields in the far western region of the state, said Anthony Zukoff, an entomologist at K-State.

“The army cutworm is … one of the first pests that producers need to start looking for in the spring,” Zukoff said.

Army cutworms also are commonly known by their adult name, miller moths. Zukoff said adult moths fly from the Rocky Mountains into western Kansas from late summer into fall. The moths spend two months laying eggs in fields, especially those that are freshly cultivated or seeded, which begin hatching in spring.

K-State entomologists say that female miller moths can lay up to 1,000 eggs. The cutworm larvae subsist on crop leaves until they grow into adult moths.

After hatching, army cutworm caterpillars immediately start to eat. Farmers can easily spot evidence of cutworms by looking for “windowpane” damage on leaves. The caterpillars will eat a small square portion out of the surface of the leaf, which resembles the shape of a windowpane.

“If your wheat stand came up thinner than usual during the fall, then you may be more susceptible to (the army cutworm),” Zukoff said.

The army cutworm is less pesky in eastern Kansas. Zukoff said the caterpillars are prone to diseases that exist within the moisture-rich soils farther east, however miller moths were observed in eastern Kansas last spring.

Last fall, a large number of miller moths were trapped by K-State entomologists as part of a monitoring effort established by Zukoff called the Kansas Insect Trapping Network. Almost 2,000 moths were caught in October at one location in western Kansas. Entomologists wrote online that, generally, trap counts of about 800 moths indicate significant caterpillar activity the following spring. Their goal is to collect more data as it’s only their second year for trapping insects.

“We don’t know the historic trends for some of these pests, so as we get multiple years of trap data, we can correlate that to potential outbreaks of army cutworms,” Zukoff said. “We can tell ag producers to be on their toes, and we can customize pest management recommendations with several years of data.”

The Insect Trapping Network currently includes local extension agents who are building and operating insect traps in their counties, but Zukoff said he has plans to expand the network to include ag producers and landowners.

One of the main questions K-State entomologists receive is about how to kill a particular pest. The K-State Entomology Department website offers an insect management guide for every crop and commodity. Zukoff said adult miller moths do not pose a threat to crops, only the young caterpillars, so ag producers don’t need to worry about spraying for the moths.

“That would be a waste,” Zukoff said. “We’ll get nightly waves of moths coming from new places. They’re just a nuisance we have to deal with for a few weeks.”