How to Kill Armyworms in Yard

There's nothing lovely about armyworms. Read on to know everything about these species of worms and how to treat and control them.
Phyllis McMahon
Phyllis McMahon
Research Writer
Phyllis teaches English Literature at a local college and loves writing in her free time. She’s also a great cook – her British beef Wellington is something the best res read more
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Chas Kempf
Chas Kempf
Expert Consultant
Chas works in a professional pest control company and knows all the nuances of this job. Also, he’s a fantastic tennis player and loves to organize BBQ parties for his fam read more
Last updated: August 20, 2023
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Even if you have never heard of armyworms, chances are that you have seen them, either in their caterpillar form or in their moth form. You may have just thought they aren’t a huge deal. But if you have ever seen the damage they can do, especially fall armyworms, then you know that they are nothing to sniff at and the question arises: how to kill armyworms?

Below we are going to look at armyworms and give you some information about armyworms and what to do if you have discovered that you have an infestation.

What Are Armyworms?

How to Kill Armyworms in Yard

An armyworm is a moth larva commonly found in the southeastern part of the United States. The hind wings of these moths are white, and the front wings are grey, with lighter and darker splotches. They lay their eggs in 50 or more clusters in tree leaves or at the host plants’ base.

When they hatch, those tiny caterpillars can be black, green or brown in color and they can grow from 1.5 to 2” long. You can identify them by their dark heads, which usually have a pattern on them that look like an upside-down Y. As they continue growing and they reach more than an inch in length, their bodies’ color change to a brown color with a white along their side and a head that is reddish-brown. Their life cycle’s around 28 days and there can be several generations in a single year.

Types of Armyworms

The fall armyworms are the ones that cause the most amount of damage to landscapes of homes. Other species include:

  • Beet armyworms
  • Western yellow striped armyworms
  • Yellowstriped armyworms
  • Bertha Armyworms

Habitat & Behavior

The behavior and habitat of the armyworm is going to depend on the species. However, we are going to talk about the specifics of the fall armyworm since that is the most destructive. It inhabits corn leaves’ undersides and grass weeds like ryegrass and bent grass. They’re usually found in big numbers, and they’ll migrate together.

In the North American continent, their generation is seasonal. It will die down during the colder months of winter.

Identifying Their Presence

How to Kill Armyworms in Yard
You can identify armyworms by the brown patches in the lawn and chewed grass.

Damage from armyworms will occur fast. Once they’ve hatched, these caterpillars keep on eating for two weeks. They’re most active during late evening and early morning in the summer and the early fall months.

Based on the infestation size, you might wake up and find you have dirt rather than a nice green lawn.

They also aren’t picky eaters. Therefore, they can attack a lot of types of plants as they’re migrating and looking for edible foliage. The larvae will leave some brown spots on your lawn. If you are seeing blades of grass that either appear ragged or chewed, chances are that you have an infestation of armyworms.

If you have worms in your house, they are most likely bed worms. Make sure you check out our article on how to get rid of bed worms in case you have this problem.

Signs You Have Damage from Armyworms

They’re sneaky. After they hatch, they’re going to weave nests that look similar to webs in the grass. They then use the tunnels so that they can hide from their predators throughout the day. During the nighttime, when animals such as birds are sleeping, they come and start to eat the grass. As they grow, they are going to go further up your grass blades. When they are adults, they are going to look for other sources of food. It’s hard to catch them red-handed since they’re active during the night.  It’s possible you’ll need to use a strong flashlight so that you can spot them well.

Below are some of the signs that you have problems with armyworms.

Brown Grass

How to Kill Armyworms in Yard

If you’ve tried to water and fertilize your grass without any success? If so, you may have armyworms, particularly if it happened quickly.

Ragged Grass Blades

Is your lawn looking like it was chewed? Or perhaps it looks like you went over it with a mower blade that’s dull? Armyworms might be the problem.

Bare Spots

It isn’t unheard of that armyworms leave bare patches on the lawn like a swarm of locusts came through. If you are seeing this, you have armyworms.

Areas That are Dug Up or Have Holes

Animals such as birds, possums, raccoons, and skunks tear up the grass so they can eat armyworms. Armyworms are pests to you but animals love eating them. Moles especially enjoy a snack of armyworms. It might be good for now, but in the long run moles are a problem too. Check our guide on how to get rid of moles if that’s your case.

How to Kill Army Worms in Your Grass

One of the things that you want to do is to make sure that you are taking care of the armyworms in your lawn. Below are some things that you can do to kill the armyworms in your lawn.

Bacillus thuringiensis

Products with this can control larva of the armyworms and not harm beneficial insects. It can be purchased in spray form or in a concentrated form that must be applied using tank sprayers. It’s recommended to re-treat using this since the residue only remains on the turf for fewer than 48 hours and it will wash away when it rains.

Neem oil

This great oil is something that works on a lot of pests including armyworms. Mix 1-2 teaspoons of it in 1-gallon warm water and then put it into your spray bottle. Add 1 tsp insecticidal or dish soap and spray this solution on affected areas such as your lawn two times per week to prevent the problem. There are other non-toxic and natural options in our guide on the best pet-safe ant killers, so check it out.

Diatomaceous earth

How to Kill Armyworms in Yard

This has sharp particles inside it. This makes it very uncomfortable for the armyworm grubs. It makes them feel like they are crawling through really small razor blades. The good news is that it won’t harm wildlife or pollinators.

Remove larvae by hand

If you want to know how to kill army worms in your garden, this is an easy way to do it. If you catch it quickly enough, you can remove the armyworms from your plants simply with your hand. Simply drop them into soapy water after removal and that will kill them. Any plants that are affected from the garden and avoid composting them. then wash any gardening tools. This is going to reduce the spread of any undetected eggs. This is also an option if you want to know how to kill army worms naturally. This isn’t something that you would do if you want to remove them from your pasture or a larger area.


This is another option when you are trying to get rid of armyworms in your lawn. Products that contain this are easy to use. Simply make sure that you read the directions and protect yourself.

Prevention Measures

One of the best things that you can do to avoid armyworms is to prevent the problem in the first place. Below are some of the things that you can do for preventative measures.

  • Regularly monitor your grass, looking for any brown grass patches, blades with the tips that were eaten off, and birds that are picking at the yard.
  • Mix soap and water, and then pour it over a spot on the lawn. This will let you know if you have caterpillars in the yard. They should come to the top if there’s an infestation.
  • Mow & water the lawn on a regular basis since this is going to make your lawn not as attractive.
  • Remove thatch and grassy weeds. This is going to make it a lot less hospitable for the larva and eggs.
  • Turn off outdoor lights close to your house during night. Moths are attracted to light, so when there isn’t any light, the moths won’t come to the area and lay their eggs.


Can army worms harm humans?

Although they’re not directly harmful to humans, they do cause a lot of crop destruction. The fall variety are the most destructive, since they feed for 2 seasons.

Are there any natural enemies of armyworms?

There are a variety of predators that will prey on armyworms. Some of them include:

  • Bigeyed bug
  • Spiders
  • Minute pirate bug
  • Damsel bug
  • Assassin bug
  • Lacewing
  • Parasitic wasp

What do armyworms eat?

The adults of armyworms feed on the nectar of plants and they don’t threaten plants. However, the larvae will feed mostly on grass and sometimes will cause damage to corn, forage grasses, turf grasses, and rice.

Final Thoughts

As with any kind of pest, one of the best ways that you can control and prevent a lot of damage from armyworms is to find that you have a problem quickly. Otherwise, you may discover that you have a lush lawn one day and a big bare spot where your lawn was the next, grab your head and ask yourself: how to kill armyworms?

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