How to Get Rid of Armyworms

Wake up to a patchy, chewed-up lawn? Armyworms may be the cause. Few pests pack the destructive power of armyworms, so named because they attack in large numbers and can devastate a lawn seemingly overnight.

The key to preserving your lawn is knowing how to get rid of armyworms. 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.

Signs you have armyworms

Armyworms are caterpillars that feed on grass and plants and can devastate a yard overnight. Detection is the key to stopping them before they do too much damage. Here are some things to consider:

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

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. During the day, they often hide under grass thatch, in dense turf, or near the base of plants to avoid the sun. At night, they come out onto the grass blades and soil surface to feed.

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 can consume nearly three-quarters of their weight in plant material daily, snacking mostly at night but never truly taking a break during the day.

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

• Where to buy them: Local nurseries, online retailers, and farm supply stores
• Estimated cost: Around $20-$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.

Depending on how bad the problem is, you may have to reapply beneficial nematodes until the armyworms are gone.

Use Bacillus thuringiensis (Bt)

• Where to buy it: Garden centers, nurseries, and online retailers
• 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 the 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.

Once an insect ingests Bt, it stops eating within hours and typically dies in a few days, either from starvation or a damaged gut, Vinje notes. This makes it extremely effective. 

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

Plant fragrant flowers

• Where to buy it: Garden centers, nurseries, and online retailers
• 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.

Add the plants strategically around your yard. You can mix them in with the veggies that armyworms target (cabbage, carrots, and lettuce), place them along the borders of your garden, or group them together to boost their scent and make them more effective.

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:

Pyrethroid products

• Where to buy them: Garden centers, nurseries, and online shops
• Estimated cost: It depends on the product and quantity. Typically, you can expect to pay from $50 to $150.
• How fast they work: A few hours after application, they start paralyzing the armyworms. They have good residual control that lasts for several days to weeks, depending on the weather.
• 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 & Garden
• Lambda-cyhalothrin – Martin’s Cyonara Lawn & Garden

Spinosad

• Where to buy it: Garden centers, nurseries, and online shops
• Estimated cost: $20 to $30 per bottle, though prices vary
• How fast it works: Within 1 to 2 days
• 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 cutworms 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 or armyworms, causing paralysis and death within a day or two. What’s great about spinosad is that it kills armyworms without harming beneficial insects like bees. Due to its low toxicity, it’s also a better choice for households with pets and kids.

Carbaryl

• Where to buy it: Most garden centers and online stores
• Estimated cost: Anywhere from $20 to $200, depending on the quantity
• How fast it works: Within a few hours and stays on plants for 3 or 4 days
• What to use to apply it: A sprayer or dust applicator
• When to use it: Early in the season or when you first spot cutworm damage

According to the Texas A&M AgriLife Extension, 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

• Where to buy it: Agricultural supply stores, garden centers, online retailers
• Estimated cost: Varies based on formulation and quantity. For example, 10 mg can cost $30, while 100 mg can run $115.
• How fast it works: Armyworms stop eating within hours of ingestion and die within a few days.
• 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.

Researchers at the Texas A&M AgriLife Extension note that this general-use insecticide provides several weeks of residual control, depending on how heavily you apply it.

In fact, a 2011 study in the Florida Entomologist journal showed that chlorantraniliprole was one of the rare insecticides still killing over 40% of armyworms even 28 days after application.

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.

Emilinate 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.

Read more: Broadleaf Weeds vs. Grassy Weeds: How to Tell Them Apart

FAQ about ways to eliminate armyworms

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, you can hire a pest control professional in your area to manage the problem. A local lawn care professional can also keep your lawn and surrounding vegetation in great shape.

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Main Photo Credit: Jeanne Menjoulet | Flickr | CC BY 2.0