Montana and the surrounding region are currently observing large numbers of “miller” moths congregating near buildings at night where they are attracted to sources of light. Any type of moth that is abundant around homes have been called Miller moths. 

In Montana and surrounding states, it is typically the adult stage of the army cutworm, Euxoa auxiliaris. The larval caterpillar stage feeds on a variety of plants and crops during the spring season, and now in early summer the emerging adult stage migrates from the plains to higher elevations in the mountains. 

Later in the August and September the moths return to the plains to mate and lay eggs. During this annual migration, the moths can be a nuisance pest when they enter homes for shelter. They are attracted to lights, so some suggestions include turning off outdoor lights, sealing doors and windows, leaving an outbuilding lighted to divert them and considering yellow insect lights as they are less attractive.

Army cutworms lay their eggs during the fall season and the larvae overwinter. In the spring they can damage small grain and other crops. Where they decide to lay their eggs and winter survival of the larvae cannot be predicted, but the abundant moth population this year suggests producers should consider additional scouting in the spring of 2021 when the weather warms up. Cutworm outbreaks tend to cycle periodically, remaining low for several years then increasing and peaking for 2-3 years. 

A Montguide can be downloaded by clicking here.

Brought to you by: Brenda Richey, 

MSU Flathead Reservation Extension

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