How to Get Rid of Armyworms on the Lawn

Army worm

An army of caterpillars marching across your lawn, ready for battle, is an intimidating sight. Armyworms are nasty and destructive creatures that can desolate your entire lawn in just a few days, making it almost impossible to grow healthy grass. Let’s learn how to get rid of these pests as fast as possible so you can reclaim your land.

Tip: Neglecting your lawn care can favor armyworms’ base camp operations. So in this article, we will give you some tips on how to prevent armyworms, how to notice when they first appear on your lawn, and how to deal with them using various methods.

What Are Armyworms?

The term armyworm can refer to a handful of species of caterpillars, such as the fall armyworm (Spodoptera frugiperda), the beet armyworm (Spodoptera exigua), or the yellow-striped armyworm (Spodoptera ornithogalli). 

Armyworms are the larval stage of adult moths. They live in most parts of the world and are one of the most common lawn pests in the United States. As their name suggests, they form large colonies that can be difficult to control if you don’t deal with them early. They feed on many plants, including flowers, fruit, and grass, that took you so long to grow.

Here’s what they look like:

  • Range from shades of brown, to gray, green, yellow, or black
  • Three white or yellow stripes down their back
  • Inverted Y-shape on their heads
  • Can reach up to 2 inches long

Pro Tip: Armyworms are easier to spot at night since they hide in debris during the day.

How to Get Rid of Armyworms (Organic Options)

Photo Credit: शीतल सिन्हा / Wikimedia Commons / CC BY-SA 4.0

One day, out of nowhere, you see something ominous in your yard: black strips slowly advancing towards your very own lawn. It’s the armyworm – massive in number and hungry for your beautiful grass. But worry not! We will teach you how to get rid of these creatures just in time.

You can pick and choose which of the following methods work best for you, but we recommend always combining the chosen method with proper lawn care, especially lawn mowing. 

Handpick the Armyworms

You have just noticed the first armyworm larvae on your lawn, and you don’t want it to become an infestation. The first thing to do is to handpick and destroy them. The best way to ensure they die is by dropping them in a bucket of soapy water. 

Handpicking might be enough if you have just a few armyworms on your lawn. However, slaughtering hundreds of them alone is not very efficient, so this is usually the first step in your armyworm counterattack. Just don’t forget to wash your hands and gardening tools after it to account for the eggs that might have stuck.

Maintain Your Lawn

Maintaining your lawn goes a long way when dealing with pests. 

For example, moths, the adult stage of armyworms, prefer laying their eggs in grass that is overgrown or not mowed regularly. In addition, tall grass can make it difficult for you and natural predators, such as birds, to find armyworms. 

Lawn care best practices to get rid of armyworms include:

  • Mowing: keeping your grass at the recommended height encourages lawn health and reduces the chances of armyworms. It can also help wipe out those you couldn’t remove by hand.
  • Thatch removal: removing thatch, that is, the tight layer of dead and living grass shoots, stems, and roots that accumulates on your lawn, helps eliminate larvae and eggs’ hideouts.
  • Leaf removal: during the day, armyworms hide in dead and dry leaves, so keeping your lawn clean can aid your extermination campaign.

Use Beneficial Insects

Ladybugs, lacewing, and minute pirate bugs are armyworm eggs’ worst nightmares. These beneficial insects can help you contain your armyworm infestation by working hard to eat as much of their eggs as possible. Not just that, but they also eat the young armyworm larvae as they hatch from their eggs, keeping the population down.

These little insects will happily eat any egg they see. You only have to place them around your plants every few days until all signs of armyworms disappear from your lawn, then keep up with regular maintenance as needed.

Trichogramma wasps are parasitic wasps that can also assist you. They lay their eggs inside armyworm larvae, killing them from within and preventing further infestation in the area. 

Beneficial Insects that can help with your army defense strategy, and how to get them:

  • Ladybugs: You can try attracting them naturally by providing water sources in the form of damp paper towels or by providing shelter with ladybug houses (a wooden box you can easily DIY, with some raisins or sugar water inside). You can also buy them on Amazon; they’re usually cheap.
  • Lacewing: These insects like nectar, so planting nectar-rich flowering plants is a good idea. Your ladybug house can also attract them.
  • Minute pirate bugs: Pirate bugs also like flowers, shrubs, and ornamental plants, so you may be able to draw them by planting these.
  • Parasitic wasps (Trichogramma wasps): Even if you plan on buying these wasps to release on your lawn, it’s better to have herbs or flowers that have the pollen or nectar they need nearby, such as dill and cilantro, so they stay where they were released.

Introduce Beneficial Nematodes

Beneficial nematodes are microscopic worms that help destroy various pests. They are practical, natural, and safe to use, which makes them a perfect tool against insects that live on the soil surface and don’t reach the root, such as armyworms. Nematodes work like invisible bodyguards walking around your lawn, protecting it from invaders.

They work by eating the armyworm from the inside out until they run out of food or nutrients. Once this happens, the armyworms simply die off, leaving no trace except for their empty shells, which eventually crumble away. Nematodes are safe for humans and pets, so there’s no need to worry about them spreading or becoming a problem in your home. 

Common species that target armyworms include Steinernema carpocapsae and Heterorhabditis bacteriophora. They can be ordered online or at your local garden supply store. 

Note: Do not use beneficial nematodes combined with beneficial insects, since they can also prey on those insects.

Apply Bacillus Thuringiensis

Bacillus thuringiensis, or Bt for short, is a bacteria that naturally occur in the environment, and are safe for humans and other animals. Still, they can kill the armyworm in its larval stage within 48 hours of infection. The specific strain that targets armyworms is Bt aizawai and Bt kurstaki.

The bacteria will die shortly after they have been applied to your lawn. Hence, there shouldn’t be any concern about them getting into the water supply or other areas where they might affect different species. The only downside is that it’s not entirely effective against other pests. So you may want to consider using another pest control method if you’re dealing with a mixed infestation.

Apply Neem Oil

Another effective natural pesticide is neem oil. Neem oil inhibits armyworms’ life cycle by disrupting the absorption of carbon dioxide from the air of the plant they feed on. Therefore, spraying neem oil on your lawn can hinder the growth of armyworms, controlling their population.

However, neem oil isn’t ideal for large areas because it requires multiple applications every few weeks until no more armyworm caterpillars appear. So you might want to do this only if you have a small yard.

How to Get Rid of Armyworms (Inorganic Options)

Photo Credit: K-State Research and Extension / Flickr / CC BY 2.0

Synthetic pesticides are designed to kill only certain types of pests, so they usually don’t harm animals or plants if appropriately used. Some pesticides can even help your lawn by killing off harmful bugs like armyworms while leaving the beneficial ones alone.

However, it’s essential to always read the label carefully when buying a pesticide or insecticide product. This way, you know exactly how to apply it and what it will do to your yard or garden. In addition, most pesticides require you to wear protective clothing and gloves and keep children and pets away from the treated area until it has dried completely.

There are two types of insecticides that can be used against armyworms:

IGR Insecticides

This insecticide inhibits the armyworm’s growth cycle. It usually works better for tiny larvae. Some examples are:

  • Carbaryl
  • Chlorantraniliprole
  • Methoxyfenozide

Pyrethroid insecticides 

This type of insecticide can kill quickly upon contact, and for that, they require a pesticide applicator license. Some examples include: 

  • Beta-cyfluthrin
  • Gamma-cyhalothrin

It’s also important to note that some pesticides are more toxic than others, and some have been banned in the United States. If you have questions about what chemicals are safe for your family, talk to your local pest control expert. They can recommend effective pesticides that won’t harm any human or pet.

How to Prevent Armyworms

Man using a dethatcher
Photo Credit: Agri-Fab, Inc. / Wikimedia Commons / CC0 1.0

If you’re trying to get rid of armyworms, you might be tempted to think that once they’re gone, that’s it. But here’s the thing: they’ll just keep coming back if you don’t take care of your lawn. So here are some lawn care best practices that can help prevent armyworms from appearing again on your lawn.

Mow Regularly

Lawn mowing is one of the best ways to keep armyworms out of your lawn. Mowing can mechanically destroy some larvae, and it helps reduce armyworms’ primary food source (grass), which will make it less attractive to them.

Dethatch to Get Rid of Debris

Armyworms like to use debris as a strategic hideout, so removing thatch from your lawn at least once a year can go a long way towards keeping your property free of them.

Apply Preventive Insecticide

If you live in the Southeast area or any other common area for armyworms and you notice an overlap in their generations, you might want to consider spraying insecticides around your lawn every few months. This way, they won’t even consider coming near it. Insecticides containing methoxyfenozide or diflubenzuron have the longest residual and will persist the most in the soil.

Aerate Your Soil Annually

Soil compaction can hinder water drainage, and some armyworm species prefer laying their eggs on wet areas, so aerating your soil once a year can help prevent armyworms and make your lawn healthier. 

You can check if your soil needs aeration by performing the screwdriver test: if the screwdriver digs into the soil easily, you probably don’t need aeration just yet; if it’s difficult to penetrate the soil, you may need to aerate it.

Pay Attention to Watering

Most lawn care experts recommend watering regularly to prevent armyworms because they prefer dry and warm turf.

However, a recent study showed that although higher humidity hinders armyworms’ development, so does dryness, which leads to water loss in the egg and pupal membranes.

However, droughts could bring more damage than good to your lawn and end up killing both the armyworms and your plants, and that is the last thing you want. For that, it’s better to keep your soil moist.

Signs of Armyworm Damage

fall armyworm damage
Photo Credit: Shim / Pixahive / CC0 1.0

Armyworm damage can be hard to spot if they’re at the beginning of their infestation, but we’re here to help you with that. Here are the signs of the damage caused by armyworms:

  • Brown patches and brown spots. These patches may look like someone has spilled coffee on your lawn or may be large enough to resemble a streaking pattern. They’re usually shaped like circles or elongated ovals. 
  • Ragged blades. Armyworms eat the tips of each blade of grass before moving onto another section of your yard where there are still blades left untouched by them. 
  • Lacy or transparent blades. Young armyworms will leave the tips of the grass blades transparent as they eat away at the turf. 
  • Bare soil. You may notice that some areas of your lawn have been wholly eaten down to bare soil.

If you notice any of these signs on your turfgrass—especially if they appear overnight—it could mean that you have an infestation of armyworms, so look closely at it.

FAQ About Armyworms

1. Does dish soap kill armyworms?

Yes! Prepare a bucket with a gallon of water and a teaspoonful of a dish soap of your choice, and throw all the armyworms you have managed to pick into the bucket. The soap will kill all of them within minutes.

2. Do armyworms just go away?

Armyworms will eventually go away on their own after about 2 weeks, but your lawn will suffer as a result. That is because after they eat away your lawn until there’s nothing left, they move down to the ground and pupate for about 10 days. Once they’re ready, they turn into moths and go out on a mission: seeking out new lawns to lay eggs on. 

3. Will grass come back after armyworms?

The good news is that most grass types will come back after armyworm infestation, but not immediately. You will have to take good care of your lawn. Treating the soil with nitrogen fertilizer might help the grass grow back quickly.

When to Hire a Professional

Taking care of a large number of armyworms on your lawn by yourself can be a lot of work, but you don’t have to win this battle alone. If you are not feeling up to the task, there’s no shame in hiring a professional. Find a lawn care pro near you who can take this burden off your back! 

Main Image Credit: uacescomm / Flickr / CC0 1.0

Maria Isabela Reis

Maria Isabela Reis

Maria Isabela Reis is a writer, psychologist, and plant enthusiast. She is currently doing a PhD in Social Psychology and can't help but play with every dog she sees walking down the street.