How to Prevent an Armyworm Infestation

To prevent armyworms from infesting your lawn, avoid overwatering and overfertilization, remove weeds, thatch, and grass clippings, attract armyworms’ natural enemies, and apply preventive insecticides.

While none of these pest prevention methods is bulletproof, they can reduce the armyworm population and limit lawn damage. The more you mix, the easier it is to prevent an armyworm infestation on your lawn.

1. Don’t Overwater the Lawn

Dr. Shaohui Wu, assistant professor of Turfgrass Health at Ohio State University, says that moisture attracts armyworms.

“Under drought conditions as in this year, irrigated lawns are more attractive to the armyworm moths laying eggs.”

Don’t worry. You don’t have to let the lawn dry to keep armyworms at bay. Watering the lawn correctly is enough. Apply only the recommended amount of water (typically about 1 inch per week) for your turf type and wait for the grass to show signs of drought stress (wilting, grayish color, slow recovery after foot traffic) between watering sessions. 

Pro tip: Aerate compacted soil to ensure the water you apply reaches the roots and doesn’t pool on the soil surface.

2. Fertilize Only When Needed

Highly adaptable and picky eaters at the same time, armyworms munch on hundreds of different plants but prefer grasses and are attracted by good-quality material. Lush, succulent grass blades, supported by a high nitrogen boost, are a delicacy hard to resist. 

To prevent your lawn from becoming an armyworm’s favorite meal, avoid nitrogen applications during summer and postpone them in the fall when there is an armyworm alert in your area. If you need to use fertilizer, go for slow-release nitrogen products.

Learn more about armyworms and what they feed on from our guide, “What Are Armyworms?”

3. Mow the Lawn at the Right Height

Tall grass provides armyworms and other lawn pests with more moisture, food, and a safe shelter from birds looking to feed on them. To make the lawn less attractive and secure for armyworms, mow it regularly and at the height recommended for your turf type and season.

4. Keep the Lawn Free of Debris

Armyworms larvae use the thatch layer and fallen leaves as shelter to hide from intense sunlight, heat, and natural predators such as birds and bats. 

To leave them exposed and naturally limit their population, remove the thatch layer during their season (armyworms are most active in summer to early fall) and keep the lawn clear of fallen leaves when autumn comes.

Related articles:

• “5 Signs Your Lawn Has Excessive Thatch”
• “How Much Does Lawn Dethatching Cost in 2024?”
• “How Much Does Leaf Removal Cost in 2024?”

5. Collect the Grass Clippings

While armyworms don’t like to feed on dead grass, they enjoy munching on freshly cut blades. It’s like home delivery for them, so a lawn where grass clippings are always left on the ground can be very attractive for these pests. Grass clippings also keep the soil moist and make for a cozy shelter where armyworms can hide. Ensure you collect the clippings if you see signs of armyworms on your lawn.

6. Remove Weeds Around the Lawn

Armyworms feed primarily on grasses but often use broadleaf plants to lay their eggs. Remove all weeds in your lawn and nearby areas to reduce the number of places that might attract armyworm moths searching for a good place to nest.

7. Attract and Protect Natural Enemies

Birds, bats, ground beetles, ants, minute pirate bugs, and parasitic wasps are natural enemies of armyworms that can help you reduce their number. Attract these beneficial insects in your yard by growing trees, hedges, and flowering plants and installing bird feeders and fountains.

Be mindful when applying insecticides, no matter the reason. Only use them if necessary, choose a suitable product, and follow the application instructions. Apply only to infested areas to avoid killing natural predators that can help keep armyworms and other lawn pests under control.

8. Apply Preventive Insecticides

If you live in the South or frequently deal with armyworm attacks, apply insecticides preventively well before the first signs of infestation. Armyworms are most active in summer and early fall but can start reproducing in late spring if warm enough. April or May is a good time to start applying preventive treatments. 

Use insecticides with a prolonged residual effect that can stay active in the lawn for up to three months, such as products with chlorantraniliprole, methoxyfenozide, or diflubenzuron. 

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Dr. Shimat Joseph, associate professor of Turfgrass and Ornamentals at the University of Georgia, says newly planted grass is especially susceptible to infestation. “If you planted new sod, the sod is likely under stress and releases stress signals to attract FAW [fall armyworms] resulting in infestation.” 

9. Scout and Handpick Armyworm Eggs

Scouting and handpicking armyworm eggs across and around the lawn is a practical way to prevent infestation. They look like fuzzy, cottony patches, with each egg mass having, on average, 100 to 200 eggs. 

Those laid in turfgrass can be difficult to spot, but often armyworm moths lay egg masses on structures around the lawn, such as fences, light posts, outdoor furniture, the patio, the house walls, etc., where they are more visible. 

Once collected, put them into a vial with ethanol or a bucket of soapy water, where you mix 1 or 2 tablespoons of dish soap for each gallon of water.

10. Plant an Armyworm-Resistant Lawn

You can increase your lawn’s resistance to armyworm attacks by mixing more cultivars of the same grass species and planting grass cultivars that hinder armyworm growth.

While the mechanism is not yet understood, a study on St. Augustine cultivars shows that armyworms thrive on lawns with a single cultivar but experience slower growth, changes in the female-to-male ratio, and lower chances to reach adulthood in mixed lawns. Study results suggest mixing at least four different cultivars for the best results.

In another study, fall armyworm larvae failed to survive to the pupal stage when fed on Emerald or Cavalier Zoysiagrass. Their larval development was also prolonged when fed on the DALZ8501, Royal, El Toro, Crowne, and Palisades cultivars of zoysiagrasses. Why does this matter? The longer the life cycle, the fewer armyworm generations there are to attack the lawn.

Related articles:

• “How to Choose the Right Grass for Your Lawn (8 Factors to Consider)”
• “The Best Types of Sod for Your Lawn”
• “How to Plant and Grow Grass Seed in 9 Steps”

FAQ About Armyworm Prevention

What Attracts Armyworms?

Armyworm moths are attracted to moist areas with plenty of food suitable for laying eggs. Young and succulent turfgrass in newly installed sod or freshly seeded lawns is especially attractive to these pests. Moths are also attracted to light.

What Are the Early Signs of Armyworms in Your Lawn?

Early signs of armyworms include grass blades with transparent areas or chewed along the margins and birds, skunks, or rodents hunting in your lawn. Small brown patches in your lawn can also be a sign of early infestation.

How Long Do Armyworms Stay Around?

Armyworms die when a freeze comes. Each generation of munching pests lives 30 to 60 days, and depending on where you live, you can have two to four generations or more in your area.

How to Get Rid of Armyworms?

You can use the following methods to get rid of armyworms in your lawn:

• Handpick the larvae and egg masses when in small number
• Apply a biological insecticide such as Bacillus thuringiensis or beneficial nematodes
• Spray natural insecticide with neem oil extract
• Apply synthetic pesticides such as pyrethroids and chlorantraniliprole

Learn more pest control methods from our guide, “How to Get Rid of Armyworms in the Lawn.”

Keep Armyworms Away!

Don’t allow armyworms to make your lawn their kitchen and pantry. Find a lawn care professional with LawnStarter and benefit from the best pest prevention and treatment methods. 

Tired of mowing and raking the lawn? LawnStarter pros can take care of all your lawn maintenance tasks and are only a few clicks away.

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