How to Get Rid of Armyworms

Wake up to a patchy, chewed-up lawn? Armyworms may be the culprit. Knowing how to get rid of armyworms fast is the key, because these pests attack in large numbers and can devastate a lawn seemingly overnight.

The best strategies include removing them manually, applying organic or chemical insecticides, encouraging natural predators, and practicing good lawn care.

In this article, we’ll talk about how to detect them and, of course, how to halt their march across your lawn. If the job feels like too much, Lawn Love’s lawn treatment service can take it off your plate.

Signs you have armyworms

You likely have armyworms if you see fast-spreading brown patches, chewed or scalped grass blades, and green-to-black striped caterpillars with an inverted Y on their heads. Detection is the key to stopping them before they do too much damage. Here are the main things to look for:

Distinctive damage patterns

Armyworm damage can present in any of the following ways:

• Bare or brown patches

• Grass that looks scalped

• Visible worms and frass (small black droppings)

• A lot of birds feeding on your lawn

• Transparent grass blade tips

• Moths flying around your property

Ben McGraw, professor and program coordinator of Turfgrass Science at Pennsylvania State University, says armyworm damage on a lawn has a distinct pattern.

“Eggs hatch and caterpillars drop down, feeding outward in a pack,” McGraw says. “Damage usually progresses across the lawn, so homeowners could also look for damage on edges near where moths are likely to place their eggs.”

Their appearance

Armyworms are green, brown, or black and sport distinctive white, brown, or orange stripes along their bodies. They grow 1 to 2 inches long, have a smooth, cylindrical body, and have an inverted Y-shaped marking on their heads.

Behavior

Armyworms typically appear in late spring to early summer, hatching and feeding voraciously for a few weeks, eventually emerging as moths that lay eggs and start the cycle again.

They don’t burrow into the soil, so you won’t have to dig to find them. By day they hide in thatch, dense turf, or at the base of plants; at night they move onto the grass blades and soil surface to feed.

Kyle Koch, associate extension educator and insect diagnostician at the University of Nebraska–Lincoln, says armyworm eggs have a unique appearance.

“Egg masses are pretty distinct and conspicuous with a moldy or fuzzy appearance,” he says. “Adult females will lay eggs on just about any object in the landscape and especially like vertical objects.”

To confirm hidden larvae before treating, try a soap-flush test: Mix a couple tablespoons of dish soap into a gallon of water and pour it over a suspect patch. Irritated armyworms wriggle to the surface within a few minutes.

True to their name, armyworms move in large groups, consuming grass, flowers, vegetables, and fruit throughout the Southern and Southeastern U.S. These little eating machines cause rapid turf damage, stripping an area the size of a football field in just 2 to 3 days.

Armyworms can be a tough pest to handle for beginners. If it sounds overwhelming to get rid of armyworms yourself, Lawn Love can connect you with a local pest removal expert.

Natural ways to get rid of armyworms

Armyworms may be tough, but you can fight back without harming your lawn or the environment. Try these natural methods to keep them in check.

Handpick

Start at one end of your lawn, then work your way across, section by section. Carefully examine the grass and leaves for any signs of armyworms. Check in the thatch layer and at the base of the grass blades. When armyworms come out to feed, you’ll see them crawling along the blades or on the soil surface.

As you spot them, pick them off and drop them into a bucket filled with soapy water to drown them. Check your lawn every few days, ideally in the early morning or late evening when armyworms come out. Keep doing this until you stop finding them.

When to handpick armyworms: Early in an infestation, when armyworm numbers are low, typically in late May through June in the southern regions and June through July in northern areas.

Use natural enemies

To continue on the natural path, encourage armyworm predators in your yard.

Birds, parasitic wasps, ground beetles, ladybugs, lacewings, and spiders can all help remove armyworms naturally from your lawn. Some eat the pests outright, while others, like parasitic wasps, lay eggs inside the armyworms so larvae can finish the job.

I once spotted an absolute bird frenzy in my parents’ backyard, something I’d never seen before. There were dozens of robins pecking at the ground, and I couldn’t understand why, so I called my dad over. Turns out, they were feasting on an all-you-can-eat buffet of armyworms.

To make your yard a hotspot for armyworm enemies, plant native plants and nectar-rich flowers and minimize pesticide use as much as possible. Consider adding shrubs, trees, and mulch areas to make your landscape even more attractive to armyworm natural predators.

When to use them: As a long-term control strategy to keep armyworms from becoming a major problem. However, if armyworms have already taken over, this alone won’t cut it. You’ll likely need to add biological or chemical treatments.

Read more:

• 26 Beneficial Insects for the Lawn and Garden

• Beneficial Birds You Want in Your Yard

Use beneficial nematodes

• Estimated cost: Around $20 to $40 for a package, depending on the quantity

• How fast they work: Typically, it takes a few days to see results. Longer if the infestation is large.

• What to use to apply them: A sprayer or watering can, usually mixed with water according to the instructions.

• When to use them: When the larvae are actively feeding in the soil or in the thatch layer, usually during warm, moist conditions. Nematodes are sensitive to direct sunlight, so choose an overcast day for application.

Tiny, naturally occurring, soil-dwelling worms, beneficial nematodes enter armyworms’ bodies and release bacteria that kill them from within. They’re a safe, eco-friendly armyworm treatment that won’t harm pets, kids, or helpful insects like bees.

Opt for host-specific species like Heterorhabditis bacteriophora or Steinernema carpocapsae that eat only armyworms. This protects non-target beneficial insects and boosts your chances of success.

Use Bacillus thuringiensis (Bt)

• Estimated cost: Between $15 and $45, depending on the size

• How fast it works: 2 to 3 days after application

• What to use to apply it: Garden sprayer

• When to use it: At the first signs of small armyworm larvae before they reach later stages. In the early or late parts of the day.

Bt is a bacterium naturally found in the soil. It produces toxins specifically harmful to caterpillars, including armyworms.

“To be impacted, susceptible insects must consume Bt toxin crystals,” says Eric Vinje of Planet Natural Research Center. “Unlike toxic insecticides that target the nervous system, Bt works by generating a protein that hinders the digestive system of the insect, effectively starving it,” Vinje adds.

Whether you choose Bt as a spray, granules, or powder, always follow the label instructions. Apply it early or late in the day since ultraviolet (UV) light can weaken its effectiveness.

Plant fragrant flowers

• Estimated cost: From $1 to $15 depending on plant type and size

• When to use them: As a long-term control strategy

Companion planting is a good way to keep armyworms at bay without using harsh chemicals. Certain herbs and flowers repel pests because they produce strong scents or release chemicals. These include garlic, onions, basil, dill, cilantro, marigolds, and lavender.

Chemicals that eliminate armyworms

Chemicals are usually more potent and work faster than organic pest control, but there are downsides to them. Chemicals are generally indiscriminate, meaning they affect plants and animals you don’t want harmed, so use them carefully.

Some of the best insecticides for armyworms include the 4 below.

Insecticide	How fast it works	Best for
Pyrethroids	A few hours, with residual control	Fast knockdown of active infestations
Spinosad	1 to 2 days	A lower-toxicity option for pets and kids
Carbaryl	A few hours	Large, heavy infestations
Chlorantraniliprole	Feeding stops within hours	Long residual, preventive control

Pyrethroid products

• Estimated cost: It depends on the product and quantity. Typically, you can expect to pay from $50 to $150.

• What to use to apply them: Backpack or handheld sprayers

• When to use them: At the first sign of infestation, in the early morning or late afternoon

Pyrethroids kill armyworms on contact. They’re especially effective when armyworms are actively feeding on grass and other plants.

As broad-spectrum insecticides, pyrethroids can also kill beneficial insects like ladybugs and bees, so use them carefully around pollinators.

Look for products with these active ingredients:

• Bifenthrin, Cutter Backyard Bug Control Spray

• Permethrin, Bonide Eight Insect Control Yard and Garden

• Lambda-cyhalothrin, Martin’s Cyonara Lawn and Garden

Spinosad

• Estimated cost: $20 to $30 per bottle, though prices vary

• What to use to apply it: Sprayer or watering can

• When to use it: Apply in the early morning or evening when pollinators are less active and when armyworms are feeding. Wait 7 days before reapplying.

Made from soil bacteria, spinosad is a natural insecticide that effectively controls armyworms. You can find it as granules, sprays, dusts, and pellets.

Spinosad attacks the nervous system of armyworms, causing paralysis and death within a day or two. It is very highly toxic to bees while wet, so apply it when pollinators are inactive; it poses little risk once the spray has dried. Its low toxicity to mammals also makes it a better choice for households with pets and kids.

Carbaryl

• Estimated cost: Anywhere from $20 to $200, depending on the quantity

• What to use to apply it: A sprayer or dust applicator

• When to use it: Early in the season or when you first spot armyworm damage

Carbaryl has long been used to control armyworm populations in various settings. Like its counterparts, it attacks the pest’s nervous system.

Because it is very potent, carbaryl eliminates large armyworm infestations but can also hurt beneficial insects, pets, and humans on contact. Use it extremely carefully and only when absolutely necessary.

Chlorantraniliprole

• Estimated cost: Varies based on formulation and quantity. For example, 10 mg can cost $30, while 100 mg can run $115.

• What to use to apply it: A broadcast spreader or sprayer, depending on the formulation.

• When to use it: As soon as you detect armyworms

Another effective insecticide against armyworms is chlorantraniliprole. It affects armyworm muscles, causing them to stop feeding and die.

This general-use insecticide provides several weeks of residual control, depending on how heavily you apply it.

How to help your lawn recover from armyworms

Once the armyworms are gone, your lawn needs help bouncing back. The soil and roots are usually still alive, so most grass recovers with a little care.

Keep watering deeply and consistently to help stressed grass push out new growth. Warm-season lawns often regrow from their crowns and runners, while thinner cool-season lawns may need overseeding to fill bare spots.

Hold off on heavy foot traffic while the grass is weak, and give it a light feeding once you see fresh green blades. Patience pays off here, since a healthy lawn usually knits back together within a few weeks.

Lawn maintenance practices to prevent armyworms

Good lawn care isn’t about the appearance of your yard alone. Healthy, thick grass resists disease and is less attractive to pests like armyworms.

Proper mowing

In your fight against armyworms, determine a good mowing routine and stick to it. Mow according to your grass type (warm-season grass or cool-season grass), and don’t remove more than one-third of its height. Shorter grass is less inviting to armyworms as it doesn’t represent a good food source or a good habitat for laying eggs.

Proper irrigation

I recommend giving your grass between 1 and 1.5 inches of water per week (an irrigation system can make things easier). Water deeply but infrequently to boost root strength and grass health. Also, avoid excessive moisture that may attract armyworm larvae.

Eliminate thatch

Regular dethatching using a power rake or vertical mower removes the layer of dead grass where armyworms hide and lay eggs.

For cool-season grasses, dethatch in early fall or spring when the lawn is actively growing; for warm-season grasses, dethatch in late spring to early summer. Keep thatch below 1/2 inch thickness by dethatching annually if your lawn is prone to armyworm infestations.

Read more:

• How Much Does Lawn Dethatching Cost?

Get rid of weeds

Eliminate weeds regularly through hand-pulling, spot treatment with herbicides, or using pre-emergent herbicides in early spring before weed seeds germinate. Focus particularly on broadleaf weeds and grassy weeds that provide alternative food sources and shelter for armyworms.

Maintain a consistent weeding schedule every 2 to 3 weeks during the growing season, paying special attention to lawn edges and areas adjacent to gardens where armyworms often first appear before moving into turfgrass.

FAQs

Don’t let armyworms ruin your landscape

Armyworms can destroy your landscape in the blink of an eye. To keep them in check, remove them manually, apply organic or chemical insecticides, and maintain your yard.

But if time isn’t on your side or this task seems daunting, one of Lawn Love’s local lawn care pros can keep your lawn and surrounding vegetation in great shape.

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Main Photo Credit: Armyworm on a leaf | Jeanne Menjoulet | Flickr | CC BY 2.0