If you live in Emerson and your lawn turned from green to straw-colored in a matter of days, it's worth ruling out armyworms. These caterpillars chew grass blades down to stubble, and when there are a lot of them, the damage moves across a yard surprisingly fast. The good news is that a healthy lawn usually grows back. Below, we'll cover what armyworms are, how to confirm them and what actually helps. If you'd like someone to look at your yard and tell you what's going on, our outdoor pest control team can start with an inspection.
What Armyworms Are
Armyworms aren't worms. They're the caterpillars of night-flying moths. The name comes from the way they behave: large groups feed together and, when they run out of food in one spot, they move on to the next like a marching army.
The type homeowners in New Jersey usually run into in lawns is the fall armyworm. It can't survive northern winters, so the moths fly up from the South each year. That's why the damage tends to show up in late summer and early fall, and why some years are much worse than others. Females lay fuzzy, gray egg masses on fences, siding, light-colored surfaces and plants near turf. The caterpillars that hatch feed for a few weeks, then drop into the soil to pupate.
How To Identify Armyworms
Full-grown fall armyworms are about an inch and a half long. Color varies from green to brown to nearly black, with light stripes running down the sides. Two features help most:
- An upside-down "Y" in a pale color on the front of a dark head.
- Four dark spots arranged in a square on the top of the body, near the rear end.
You'll rarely see them in the middle of a sunny afternoon. They feed most actively in the early morning and the evening and hide down in the thatch the rest of the time.
What The Damage Looks Like
Armyworm damage is easy to confuse with other lawn problems. This comparison can help you narrow it down before you spend money on the wrong fix.
| Armyworms | White Grubs | Drought Stress | |
|---|---|---|---|
| Grass blades | Chewed, ragged or eaten to stubble | Intact but wilted | Intact, dull and bluish before browning |
| Roots | Usually intact | Chewed; turf lifts up like carpet | Intact |
| How it spreads | Fast, often with a clear front line | Gradually, in irregular patches | In the sunniest, driest spots first |
| Other clues | Birds pecking at the lawn, caterpillars in a soap flush | C-shaped white larvae in the soil | Footprints stay pressed into the grass |
Lots of birds working one area of your lawn is a useful early clue. They're often feeding on the caterpillars. Sod webworms can also chew blades, so if the caterpillars you find don't match the description above, our guide to chinch bugs vs. sod webworms may help.
How To Check Your Lawn
The simplest test is a soap flush. Mix a squirt of dish soap into a bucket or watering can of water and pour it slowly over a small square of grass at the edge of the brown area, where green and brown meet. The soap irritates the caterpillars, and within a few minutes any that are present will crawl up to the surface. Do this in the morning or evening for the best results. If you see several caterpillars in a small patch, armyworms are a likely cause.
Are Armyworms Harmful?
Armyworms don't bite or sting, and they don't come indoors. They're a lawn problem, not a household one. For an established lawn, the damage is usually cosmetic. The caterpillars eat the blades, but the crowns and roots typically survive, so the grass greens back up with water and time. Newly seeded areas and fresh sod are different. Young grass has very little in reserve, and a heavy infestation can kill it outright.
How To Help Your Lawn Recover
Most of what works against armyworms is good lawn care. Here's a practical plan:
- Confirm before you treat. Do a soap flush first. If you don't find caterpillars, the problem is likely something else.
- Water the damaged area. Deep, occasional watering helps the crowns push out new blades once the caterpillars are done feeding.
- Watch new seed closely. If you overseeded in late summer, check those areas every few days during armyworm season.
- Reseed bare spots. Where grass doesn't come back, rake out the dead material and reseed when conditions are right.
- Keep the lawn healthy. Mowing at a proper height and watering deeply help grass tolerate feeding damage of all kinds.
If a soap flush turns up many caterpillars and the damage is still spreading, a licensed lawn care professional can tell you whether a treatment makes sense for your turf. Caterpillars that are already full grown are close to the end of their feeding, so timing matters.
When To Call A Professional
Call for help if you can't tell what's damaging your lawn, if brown patches keep growing after you've watered, or if new seed or sod is at risk. EcoFusion technicians can inspect your yard, identify the pest and tell you whether it's something our preventative pest control covers or a job for a lawn care specialist. Either way, you'll know what you're dealing with.
Armyworms can make a lawn look ruined in a week, but they usually move on and the grass usually grows back. Check with a soap flush, water the damaged areas, protect new seed and reseed what doesn't recover. If your Emerson lawn keeps losing ground and you're not sure why, EcoFusion Pest Control can take a look.