In 2021, homeowners in Lancaster, Douglas and Sarpy Counties reported several to hundreds of peculiar, fuzzy egg masses laid on buildings, fence posts, and all other outdoor items. We instructed those people to wipe, scrape, scrub, or power-wash them off to prevent caterpillars from emerging. That year was considered the fall armyworm outbreak of 2021, and it was widespread from the southern US and across the entire Midwest.
This August, reports from Gage County about damage to turf and sightings of caterpillars made both horticulturists and entomologists stop and think: Are fall armyworms back? We received the email this week from the UNL East Campus Turfgrass Management Extension Educator, Amanda Folck, “we have A LOT of eggs!”
If you’ve seen several medium moths hanging around your landscape at night, they are the adults of migrating fall armyworm looking for a mate and a place to lay eggs. Several of them have been seen hiding in the turf during the day and flying about when homeowners mow.
Start looking for these signs, as well as getting down to the turf to see if you can see any of the caterpillars. These caterpillars will have a head capsule with an inverted “Y” shape and a few other characteristics.
Scouting
- Before applying insecticide to turf, it is best to perform a detergent flush test to determine if fall armyworm caterpillars are present
- According to Ohio State, both Joy and Dawn detergent work for the soap flush test.
- In a container, mix 1-2 tablespoons of liquid dish soap with 1-2 gallons of water
- Pour mixture over one square yard of damaged turf
- If present, larger caterpillars will emerge first, then smaller ones *Confirm they are fall armyworm using criteria above*
- If there are more than 10 armyworm caterpillars in the area sampled, proceed with treatment.
Management
- If you had your lawn treated in the spring for grubs with chlorantraniliprole, it should may be effective on fall armyworm during the summer.
- Young caterpillars can be treated with Bacillus thuringiensis kurstaki (Btk) or Spinosad, which are both organic options.
- Caterpillars that are less than 1/2” long can be treated with a synthetic pyrethroid, however this is broad spectrum insecticide, and will not bring your grass back to life if there is considerable damage.
- Mature caterpillars do the most damage and are difficult to control, therefore it may not be economical or effective to use an insecticide.
- After weeks of feeding, caterpillars pupate in the soil. During this period there is no reason for any treatment.
**When using pesticides always read and follow the label**
Fall armyworm cannot survive the cold winters here in Nebraska, so once we get our first frost, we are clear to start planning the steps to renovate and revive the lawn for next year.
Helpful resources to control fall armyworm:
Clemson University compiled list of active Ingredients, as well as product brand names that may be available to homeowners. To view, click here and scroll down to “Control” section.
Purdue University had a return of fall armyworms in 2024 and have also compiled a list of active ingredients for the treatment of fall armyworms. See Table 1.
