You have to be a little worried about worms that have organized into an army, right?
Right. These battalions of lawn pests can eat through a lawn practically overnight, leaving it dead, dead, dead.
Luckily, Idaho’s cold winters tend to keep armyworms from being a bigger problem here than in other parts of the country.
But a small problem doesn't mean no problem. We’ve seen them in their pupae and larvae stages while digging in the dirt, and Idaho farmers report seeing them in their fields.
So they’re here. How can you get rid of armyworms in your Idaho Falls lawn? Let’s take a look.
Armyworms in Idaho Lawns: What They Are & Why They’re a Problem
You might expect a pest called an “armyworm” to march across your lawn in perfect formation. The truth is just as destructive — these striped caterpillars (larvae of the fall armyworm moth) can devour large sections of grass in days.
While Idaho’s winters keep their numbers lower than in southern states, warmer seasons and milder winters have made sightings in Idaho Falls and surrounding areas more common.
They’re bad news.
Fall Armyworm Lifecycle and Lawn Damage
While adult moths live only about two weeks, they make the most of it — a single female lays up to 2,000 eggs. Once those eggs hatch, the caterpillars spend 2–4 weeks eating their way through lawns before burrowing into the ground to pupate.
By the time an armyworm reaches full size (about 1–1.5 inches), it’s hungrier than a high school football player after practice. These pests chew the green tissue off grass blades, leaving behind thin, brown patches that spread quickly.
Then, almost as suddenly as they arrived, they vanish underground to transform into moths — starting the cycle all over again.
How to Identify Armyworms in Your Idaho Lawn
You’ll recognize them by:
- Length: 1–1.5 inches
- Color: Green, brown, or black
- Distinctive features: A wide black stripe down each side and an upside-down Y on the head
Spotting them early is the key to saving your lawn.
Signs of Armyworm Damage in Idaho Lawns
Not sure if you’re dealing with armyworms? Look for these signs:
- Brown patches or thinning areas that appear overnight
- Ragged, chewed grass blades that look frayed or shredded
- Increased bird activity (they’re snacking on the caterpillars)
- Visible caterpillars crawling through the grass
Best Time of Year to Treat Armyworms in Idaho
In Idaho Falls, and surrounding communities, armyworm activity is most likely during late summer and early fall — especially in warm years.
Preventive lawn insect treatments applied in spring stop larvae from hatching and feeding, protecting your grass before damage begins.
How to Kill Armyworms in Your Lawn?
It takes a high-quality insecticide that kills all white grub species. So armyworms are another great reason to control grubs.
Yes, grub control controls grubs, those icky white, C-shaped pests that can cause sections of your lawn to die overnight.
But it can also keep armyworms from invading your lawn, destroying it overnight, and costing you money to completely re-seed.
The trick is to kill these lawn pests before they hatch and start to chow down, so we apply preventive lawn grub control in the spring to nip them in the bud. The insecticide is absorbed by the grass. When lawn insects eat the grass blades or roots, they die.
Help Control Armyworms in Idaho with a Healthy Lawn
You can help prevent these pests by establishing healthy turf. While professional treatments give you the best defense, healthy lawn care habits make your yard less inviting to pests:
- Mow taller (around 3–3.5 inches) to protect grass crowns and shade the soil
- Water deeply and less often to encourage deep root growth
- Fertilize regularly to keep turf thick and resilient
Bugs hate a thick, healthy lawn. So your best line of defense is to keep your grass thick, lush, and healthy with an annual lawn care maintenance program that supports strong roots.
Protect Your Lawn from Armyworms with Lawn Buddies
Idaho armyworms on the march might not be invading your nightmares (spiders are another story, right?) but it’s worth protecting your lawn against these ravenous lawn pests.
We’ve got your back — targeted grub control treatment is included in our complete lawn care package, and other summer lawn pest control is available to customers signed up for our 6-step complete lawn care program.
Help prevent insect lawn damage by making sure your lawn is healthy in the first place.
Make it easy on yourself. Choose an Idaho Falls, ID professional lawn care service that bundles your yard’s most-needed treatments into one convenient, no-fuss plan.
Got a few minutes? That’s all you need to get started. Just fill out the form on this page, call us at (208) 656-9131 or read more about our services. Then you can kick back and relax in your healthy, thriving yard.
Image Source: armyworm moth
