Expect ‘an abundance’ of miller moths in Colorado this year, CSU insect experts say

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Miller Moth

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FORT COLLINS, Colo. (KDVR) — Entomologists at Colorado State University say people in the Centennial state should expect “an abundance” of miller moths this year.

Also known as army cutworms, the insects are often called “miller moths” because fine scales easily rub off their wings. The scales are reminiscent of dusty flour on the clothing of grain millers.

After four consecutive years of below-average numbers, miller moths “should be noticeably more abundant in 2020,” according to CSU entomologists Whitney Cranshaw and Frank Peairs, professors in the Department of Agricultural Biology and CSU Extension specialists.

The moths originate on the Plains of Colorado, Kansas and Nebraska and migrate west into the Rocky Mountains for the summer. They return to the Plains in September.

Cranshaw and Peairs said moths crossed into eastern Colorado during the first few days of May this year. Last year, they entered Colorado in late May.

“Peak moth flights may last five to six weeks, generally starting the last week of May or early June,” CSU said in a press release issued Thursday.

The moths have already damaged crops in Colorado, Kansas and Nebraska.

The entomologists say Front Range residents are seeing more moths due to relatively low moisture during the fall, winter and spring.

“It’s been drier this year than last, reducing the number of blooming flowers. Plus, a freeze in mid-April killed blossoms from plants that would normally be in peak bloom in early to mid-May. With fewer flowers available to the insects during their migration, they tend to concentrate in areas with larger numbers of flowering plants – usually, irrigated landscapes, including yards and gardens,” CSU said.

The moths will leave the Front Range as nighttime temperatures continue to rise. The researchers warn, however, that cool, moist weather could delay their departure.

Cranshaw said there is another moth migration currently happening along the Front Range: the alfalfa webworm, “a smaller, mottled-gray moth that is very visible by day when walking across a yard.”

Additional information about miller moths can be found on this factsheet written by Cranshaw and Peairs.

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