Mysterious Eggs are Fall Armyworms (Outbreak 2021)

Homeowners in Lancaster, Douglas and Sarpy Counties this week are reporting several to hundreds of peculiar, fuzzy egg masses laid on buildings, fence posts, and all other outdoor items. If you’ve seen these on your property, wipe, scrape, scrub, or power-wash them off to prevent caterpillars from emerging. I’ve just been walking around my home each morning, wiping them off with a paper towel.

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.

Fall armyworm laying eggs on the exterior walls of a home

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.

Images courtesy of UNL Department of Entomology
  • If you had your lawn treated in the spring for grubs with chlorantraniliprole, it should be effective on fall armyworm.
  • 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.

For more A Bug’s Life profiles

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.

Jody Green, PhD
Extension Urban Entomologist at Nebraska Extension
Jody Green is the extension urban entomologist at Nebraska Extension in Douglas-Sarpy Counties. She specializes in structural, household, and health-related insect pests.
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