The sight of a fall armyworm (FAW) can instantly strike fear in the hearts of homeowners and turfgrass managers alike. After the record damage caused by the insect in 2021, that fear is not misplaced. But it is important to understand the normal patterns of this destructive pest so that if conditions align for those numbers again, we’re ready to identify and treat the problem properly.

• Description

Fall Armyworms begin their life cycle as clustered egg masses on flat surfaces such as fences, signs, and buildings. When the eggs hatch, the tiny caterpillars that emerge will drop to the ground and start feeding – on the turfgrass surface they’ve landed on. They continue feeding until they pupate, usually a few weeks. They remain in the pupal case for a week or two, then emerge as adult moths. This process occurs and repeats typically between June and October.

• Damage

In general, armyworms prefer feeding on finer-textured grasses, but that is by no means the only crop affected. In outbreak years, such as 2021, damage was observed in many different grasses and agricultural crops. Damage from FAW often has a clear margin of affected vs. unaffected turf. You can easily see the actual caterpillars moving (army crawling) across the surface on which they feed.

• Management

Once you’ve confirmed the presence of FAW, ensuring that you treat for the correct life stage is of great importance. Treating with insecticide in the caterpillar stage is most effective, and the early stage of growth (approximately 1/2 inch in length) is best.

Finding the right product is essential – consult with a local extension agent or a turf professional for more in depth advice for your specific situation.

Photo Credit: Frank Peairs, Colorado State University,, CC BY 3.0 US <>, via Wikimedia Commons