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Armyworms Guide

Identify

Inspect

Treat

Prevent

What Do Armyworms Look Like?

Armyworms are the caterpillar (larval) form of several moth species. As caterpillars, they can cause significant damage to lawns, gardens, crops, and forage grasses. These pests can be highly destructive during their larval stage.

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Armyworms Characteristics

Color

Armyworm caterpillars are typically dark brown, black, or green with distinctive stripes of white, orange, brown, or sometimes yellow running the length of their bodies. A unique upside-down "Y" marking on their head segments makes them easy to identify.

Common Types of Armyworms

There are several species of armyworms, each with slight visual differences but often displaying similar stripes. Each type may prefer different plants for feeding:

  • Fall Armyworms: Known to be the most damaging to home lawns and golf courses, their damage is typically noticeable in late summer or early fall.
  • Yellowstriped Armyworms: These caterpillars are more general feeders, attacking a wide range of crops, including fruits and flowers.
  • Beet Armyworms: Green in color, these caterpillars prefer fruit crops and are less common in the U.S. than fall armyworms.
  • True Armyworms: Primarily attracted to weedy grasses, these pests can also damage fruit and vegetable crops.

Size

Armyworm larvae (caterpillars) grow up to 1.5-2 inches long at their largest stage. They hatch from small clusters of 50-150 eggs, which are typically green or white and hidden on the underside of leaves, though they may also be found on surfaces near grassy areas.

Armyworm moths typically have a wingspan of about 1.5 inches across.

Shape

Armyworms hatch from circular eggs laid in clusters near grassy areas. After hatching, they crawl or use silken threads to move, sometimes even catching a ride on the wind.

The larvae go through 5-6 growth stages, known as instars, before reaching their full size in about 10 days in warm weather.

At the end of their larval phase, armyworms form a protective pupa (cocoon) underground, which is about 1.25 inches long and reddish-brown to black in color.

After 1-2 weeks, the adult moth emerges. These moths typically have long antennae and two sets of wings that often display different colors and patterns.

Range

Armyworms are found across much of the United States, with a preference for the warmer climate of the Southern states. True Armyworms are more common east of the Rocky Mountains, and damage from these pests is often first reported in the southeastern U.S.

Armyworms are sometimes confused with cutworms, which also go through a caterpillar-like larval stage before transforming into a moth. Unlike armyworms, cutworms do not have the distinctive stripes that make armyworms easy to identify.

How to Check for Armyworms

Where Are Armyworms Found?

Armyworms are small caterpillars characterized by their distinctive body stripes and an inverted "Y" marking on their heads. Understanding where armyworms prefer to live, hide, and molt will make it easier for you to manage them on your property.

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Finding Armyworms Outdoors

To spot armyworms, check for them during dusk when they are most active feeding on plants in your lawn. During the daytime, armyworm larvae tend to hide in loose soil around plants, so you may need to dig around the soil to find them.

Pro Tip

To locate armyworms during the day, you can flush them out with soapy water. Mix 3 tablespoons of dish soap in a gallon of water, then pour the solution over a 3-foot square area. The soapy mixture will irritate their skin, causing the armyworms to emerge.

When to Find Armyworms

Armyworms are most active in late summer and early fall. They cannot survive cold weather and will typically be eliminated by the first frost. If you notice similar damage during cold weather, the culprit is likely a different pest.

Where to Find Armyworms

Fall armyworms are attracted to grasses like fescue, rye, bermuda, and bluegrass, but will also feed on other plants if available. They prefer lush, well-fertilized, and actively growing grasses. You may notice small dirt piles where the larvae have emerged from the soil.

Armyworms are most common in the southeastern U.S., but their adult moths can be carried by weather patterns to other parts of the country. In recent years, armyworm sightings have become more frequent across different regions of the U.S. If you suspect you have armyworms, it's best to confirm before they cause extensive damage.

Armyworm Damage to Look For

An armyworm infestation often causes a lawn to appear dormant, brown, or barren. Upon closer inspection, you'll see grass blades that have been chewed down to the stem. Some blades may show a "windowpane" effect with green leaf matter eaten away, while other blades might be entirely consumed.

While other pests can cause similar damage, performing a soap flush test can help confirm the presence of armyworms.

Before hatching into caterpillars, armyworms lay small, round eggs on flat surfaces near grassy areas. These eggs usually hatch within two days, marking the beginning of the armyworm invasion.

Now that you know where to look for armyworms, check out the next section of this guide to learn how to treat your lawn for armyworm infestations.

Armyworm Treatment Guide

Armyworms can cause rapid and extensive damage to your lawn or grassy areas, particularly when the larvae are near maturity. These caterpillars consume more vegetation in their final days than throughout the rest of their lifecycle. Prompt treatment is crucial to minimize damage.

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Step1 Liquid Insecticide Treatment for Lawns

How to Get Rid of Armyworms
Liquid insecticides containing chlorantraniliprole, bifenthrin, or permethrin are effective in stopping armyworm infestations. When you spot armyworms and visible damage, applying a liquid insecticide is the quickest way to address the problem.

Application Tips:

  • Apply the product in the late afternoon or evening, as armyworms are most active at night.
  • If possible, mow the affected area before application. This can kill some larvae and help the product penetrate deeper.
  • Always wear protective clothing: gloves, long sleeves, long pants, goggles, and closed-toe shoes.
  • Wait at least 24 hours before watering, irrigating, or mowing after applying for optimal results.
  • Apply the insecticide to the entire affected lawn or property, but check the product label to ensure it’s suitable for full lawn coverage or specific usage requirements.

Products we recommend for Step 1

Step2 Use a Natural or Biological Insecticide for Grazing Areas

In pastures and grazing areas, using a natural insecticide may be the best approach. Products like Drexel Malathion 5EC are effective for controlling armyworms without requiring animals to be removed from the area.

For food-producing areas, biological insecticides such as Spinosad can effectively manage armyworm populations, especially when applied early in the infestation process, right after the larvae hatch in late summer.

It’s essential to consult the product label to ensure proper mixing and application methods. Biological products can offer a range of application techniques, so find the best fit for your situation.

Now that you know how to treat for armyworms, the next section of this guide will focus on How to Prevent Armyworms in Your Yard.

Be sure to continue reading to understand how to identify armyworms and learn more about the lifecycle of these pests.

Armyworm Prevention Guide

How to Prevent Armyworms from Infesting Your Property

Armyworm moths typically hatch in the spring or early summer. If you notice an unusually high number of ash-gray, two-toned moths near lights or other attractants, it’s time to start monitoring your grassy areas for potential armyworm damage. Additionally, you may see more birds than usual gathering on your lawn, as they feed on armyworm larvae.

While natural predators often help reduce moth populations, armyworms may still lay clusters of up to 200 tiny eggs on plants, structures, or landscaping elements. Here are some steps you can take to reduce the appeal of your lawn to armyworm invaders.

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Step1 Reduce Excess Thatch

Armyworms often seek shelter in the loose thatch of a lawn, and early signs of damage may be visible before the larvae move into the grass.

By raking away thatch, you remove daytime shelter for the hungry caterpillars and make it easier to spot them during your lawn inspections. The reduced thatch also helps expose armyworms that are hiding close to the soil.

When fall arrives, aerating or turning over your soil can help uncover armyworm pupae that may be overwintering. Birds and other beneficial predators will feed on these exposed cocoons.

Step2 Maintain Your Lawn

A healthy lawn is your best defense against insect pests like armyworms. Well-maintained turf is more resilient to damage and will recover faster if armyworms do strike.

To maintain a healthy lawn:

  • Water conservatively—avoid overwatering, especially during heavy rains. Armyworm larvae prefer warmer, drier soil, so keep your lawn at a consistently damp level to make it less attractive to them.
  • Mow your grass to the recommended height (usually between 2 and 3 inches). Avoid cutting it too short, as this stresses the turf.

Step3 Apply a Preventative Insecticide

A long-lasting insecticide applied during the spring and summer can provide early protection against armyworm infestations. Always consult the product label for the correct application rates and instructions.

Products we recommend for Step 3

Explore the other sections of this pest control guide to confirm the presence of armyworms and understand where they prefer to live. These insights will help ensure that your prevention efforts are as effective as possible.

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