An unusual midsummer 2010 outbreak of cutworms that destroyed thousands of acres of alfalfa has many hay growers in Eddy County, NM, nervous about the chances the pests will stage a repeat performance this year.

“I’ve had a fair number of calls from growers who want to know if the cutworms will be back this year,” says county agriculture agent Woods Houghton. “All I can tell them at this point is that nobody knows. We didn’t expect them last year.”

Houghton points out that cutworms are typically a problem for alfalfa growers in his area in early spring or late fall. They’re also considered more of a concern in new-seeding fields.

Last year, though, the cutworms started showing up in Eddy County fields following a mid-July cutting. Mature alfalfa stands as well as new plantings were affected. By most estimates, 4,000-6,000 acres of alfalfa were completely defoliated.

“I’ve been doing this job for more than 30 years, and I’ve never seen anything like it,” says Houghton. “Typically, one or two cutworms per square foot is considered the economic threshold for treatment. But we were seeing 25-30 cutworms/square foot. And that was in the middle of the day. Usually, you never find cutworms in the daytime.”

He says growers concerned about a possible cutworm outbreak next season can try to head off problems by keeping weeds under control and cleaning up field edges. “You don’t want to leave a lot of organic matter out there where they can overwinter. The first rule of insect control is always sanitation.”

Running a tine harrow over fields might also help control outbreaks. “The cutworms generally pupate in the top 4” of soil,” he says. “Breaking up the top level of soil a little bit will expose the cutworms to cold and dry conditions. This year, that strategy might not be as effective because it hasn’t been that cold.”

As soil temperatures warm up this spring, growers will want to start scouting for cutworms. “Get a flashlight and look for them at night,” Houghton advises. “You want to try to find them while they’re still small. They’re harder to kill when they get bigger.”

He estimates that around 90% of the Eddy County acreage damaged by cutworms in 2010 was replanted. “A few growers decided to plant cotton because of high cotton prices and/or because it fit in with their normal crop rotations.”

Houghton will be among the speakers at the Southwest Hay & Forage Conference in Ruidoso, NM, later this week. Learn more about the conference.

To contact Houghton, call 575-887-6595 or email whoughto@nmsu.edu.