I remember watching the movie A Bug’s Life and thinking how cute and cleverly portrayed the insects were. One of my favorite characters was the always-hungry caterpillar, Heimlich, all fat and happy. Of course, I saw this movie before college (and way before I took entomology), so I had no idea of how much of a nuisance caterpillars could really be.

Armyworm on turf

Fall armyworms eat grass in late summer and early fall, destroying its ability to photosynthesize.

Photo Credit: Charles T. Bryson, USDA Agricultural Research Service, Bugwood.org

Armyworm closeup

This Southern pest grows between 1 and 2 inches long.

Photo Credit: Alton N. Sparks, Jr., University of Georgia, Bugwood.org

Armyworm marking

Fall armyworms have a distinct “Y” shape marking on their head.

Photo Credit: Steve L. Brown, University of Georgia, Bugwood.org

In real life, we often find Heimlich and his caterpillar relatives (like fall webworms and tent caterpillars) taking up residence in treetops. We rarely expect our lawn to be attacked by them. But fall armyworms (Spodoptera frugiperda) are an insect pest many Southern homeowners face each year.

Where do these pests come from? Well, Col. Caterpillar and his army fly up from the Gulf Coast in spring (as adult moths) and generally become a “major” pain as they lay their eggs on turf around mid-July. Lt. larvae make rank in early fall, and that’s when the war begins. As fall armyworms dine on delicious blades of grass, the turf loses its ability to photosynthesize and can eventually die.

Even though populations vary from year to year, fall armyworms can be a devastating turf pest if damage isn’t diagnosed and treated early. You might notice an invasion of fall armyworms by the sudden death of your turf in early fall. Damage typically starts on a lawn’s edge and progresses rapidly across the yard. Catching these enemies before damage is severe is challenging but vital, because smaller, younger worms are more easily killed than large ones.

Fall armyworms typically feed in the early morning and late in the evening, so catching them in the act can be a task. If you suspect fall armyworm damage, try a soapy water drench on an affected portion of your lawn. Your weapon of choice should be a 2-gallon bucket of water and a healthy squirt of dish soap. The goal is to make soapy water, not a sudsy mess. Pour the mixture over a 2- by 2-foot-square area that’s “on the front line” of invasion, and wait a few minutes to see what emerges to surrender. Although the armyworms won’t come out of the ground with their hands up, you’ll be able to recognize them as foreign spies by the upturned “Y” marking on their foreheads.

Once you’ve found them, the battle’s on. If discovered early enough (while the worms are small), chemical treatment can be effective. Use only chemicals specifically labeled for fall armyworms according to the label recommendations and be prepared to treat more than once. (When in doubt, check with your local Cooperative Extension Office for advice.)

Believe me, it’s worth the battle if you’re willing to fight. We noticed these pests on our lawn a few years ago and treated immediately. And I totally freaked when I noticed that our neighbors had a corner of lawn dying, too. (I didn’t want them back in my yard again!) So, what did I do? You guessed it: I went over immediately with my bucket of soapy water and drenched their lawn to see if they had armyworms. And they did! I insisted my designated sprayer (AKA, my husband) offer to spray for them. Thankfully, our neighbors approved our method of attack, and we all celebrated our victory over the fall of armyworms! Long live the lawn!