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Moths among us

Moths cling to a porch light in Fargo. Forum Communications Co. file photo

They eat crops, can destroy trees, and turn bed sheets into perfect renditions of the Charlie Brown ghost costume.

And if you live in the Midwest, chances are you're seeing a lot more of them this year than in the past.

Moths - butterflies' ugly, and maybe misunderstood, stepsiblings - are out in abundance lately, and they have the relatively mild winter and warm months that followed to thank for it.

"Because of the generally early spring throughout the Great Plains, along with strong southerly winds, we have three moth species in abundance right now," said Dr. Gerald Fauske, research specialist at North Dakota State University's Department of Entomology. "While we always have them in the spring, now they are here in greater abundance as well as earlier than normal."

The three species are the army cutworm, variegated cutworm and armyworm.

"They're getting a head start this year that they haven't had in previous years," Fauske said.

Fauske, who also is the collection manager at NDSU, gave brief breakdowns on each suspect moth.

Army cutworm: Overwinters as partially grown larvae. They finish feeding (often on winter wheat) early in spring, pupate and become adults. This is a resident species that migrates to high elevations in the Rocky Mountains to spend the hot summer months and then returns to the Great Plains in the autumn to lay eggs. There is only a single annual generation.

Variegated cutworm: Cannot tolerate freezing conditions, and so overwinters to the south of our area. Moths immigrate annually into our area, and their larvae can be pests in vegetable gardens and on non-cereal crops.

Armyworm: Another species that cannot tolerate freezing temperatures and is an annual immigrant from the southern U.S. The larva of this species feeds on a wide variety of cereal and broad-leaved crops. Both of these latter two species will have one generation in the northern Great Plains (or two in longer seasons) per year before being killed off by the first major frost. However, because both these species do have additional generations further south, and because there is a constant influx of moths, larvae and adults of both the armyworm and variegated cutworms can be found throughout the summer months.

A throw of the dice

Coincidentally, none of the moths pose much of a threat to area residents. Army cutworm, variegated cutworm and armyworm all enjoy the warm glow of a porch light, and "if the moth is coming to a light, it's not one that attacks clothes," Fauske said.

Even farmers, whose cereal crops would be hardest economically hit in the presence of an infestation, have stopgaps in place to hinder moth caterpillars from getting out of hand.

Fauske said scouting takes place for early season insects, such as cutworms, and if numbers of caterpillars per square yard of crop surpass the economic threshold, farmers know it's time to spray pesticides. Before those thresholds, it doesn't pay to take such decisive action.

But given the already higher than normal numbers, is there a chance for the moth population to increase even more - maybe to unheard of levels?

"Not much, but the possibility is on the board and most years it's not even on the board," Fauske said. "It's sort of like, with the extra numbers and earlier appearance, we've already got one favorable dice throw.

"There's always the chance something unexpected can happen."

Much like their appearance in the first place, how well the moths propagate largely relies on the weather.

"If it's cool and wet, or just wet at the wrong time, we won't have anything to worry about. But if we stay warm and dry, the potential rapidly increases," Fauske said.

For the army cutworm, any damage they might have caused already has been done as the larvae hatch early and feast on fresh spring growth. Once morphed to moths, they migrate to the Rockies in the summer before returning in the fall to lay eggs.

Fauske said the army cutworm moths hanging around now are the results of last year, therefore their real impact won't be known until next spring.

As for the variegated cutworm and armyworm, they pose a bit more of a threat.

"In both cases, there is a continuous immigration through the year, and you can often find larvae all year, especially with armyworms," Fauske said. "The armyworms have potential to be harmful."

Again, any supposed impact from an outbreak would be dependent on a perfect storm of variables. Even then, the first killing frost takes care of most moths, Fauske said, although more can blow in on southern winds.

For now, it would seem the multitude of moths pose nothing more than a mild nuisance and, at most, a slight inconvenience as they bump and flutter around the dining room chandelier.

"Plus, they're great bird food," Fauske said.

For more information on moths, including a North Dakota moth guide created by Fauske, visit the NDSU Entomology Department website at