Year-round gardening: Preparing for miller moth invasion

By: Kitty West Colorado Master Gardener
May 18, 2013

The activity: Preparing for miller moth invasion

Why: The spring of 2012 was the most memorable miller moth infestation in recent memory. The miller moth (Euxoa auxiliaris) found in Colorado is the army cutworm. The eggs are laid in late summer or early fall. Most eggs are laid in fields where vegetation is thick.

The new year starts with the immature cutworms (caterpillars) living in a semi-dormant state in our soils. As temperatures warm, they feed on a variety of plants and transition to the adult stage and leave the soil in search of nectar.

Miller moths prefer cool, humid regions, so they will migrate into higher elevations in summer. In August and September, the moths will make a reverse migration. When they return to lower elevations, they lay eggs in the soils and the process begins again.

The good news is the moths will not do any damage to your landscape, and they will leave before they lay any eggs.

How: There are a few techniques you can use to reduce the number of moths in and around your home.

1. Seal openings around windows and doors.

2. Turn off unnecessary lights at night. You may substitute yellow lights as moths aren't drawn to them.

3. Build a trap. Suspend a light bulb over a partially-filled container of soapy water. The moths will be attracted to the light and many will fall into the water and drown.

4. Keep your vacuum within easy reach. Use the hose attachment to suck up the moths when they light.

5. When adding or replacing plantings around the home, be aware that moths are attracted to certain plants: lilac, cherries, spirea, cotoneaster, horse chestnut and raspberry. These plants provide food (nectar) and shelter to the migrating moths.

6. Adult moths aren't very susceptible to insecticides.

When: Generally, the migration through our area begins in late May. But weather patterns affect the migration. The recent cold spell likely will push migration, which lasts about 5-6 weeks, back.

What's needed: Common items can be used to help reduce and/or remove the moths: light bulbs, dishwashing soap and a vacuum with a hose.

The last word: In researching, I found updated miller moth information from Whitney Cranshaw, Colorado State University Extension entomologist. In one article, he noted that the annual migration across the Front Range should be "well above average."


When you have questions, call the Master Gardener Volunteer Help Desk at 520-7684 or email CSUmg2@el Volunteers are available 9 a.m.-noon Monday through Friday.

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