How to Get Rid of Armyworms

Written by AZ Animals Staff
Published: September 17, 2021
Image Credit natthawut ngoensanthia/
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Armyworms are pests that can destroy any farm field, pasture, yard, or garden they come across with their hunger. True to their name, they march into vegetation. If you think you have armyworms, it’s necessary to know how to control them. But not all pests are the same and not all methods work on every type, so here’s more information about how to get rid of armyworms.

#1: Recognize Armyworms

Before learning about how to get rid of armyworms, you first need to make sure it is the armyworms you are dealing with. Let’s go over their appearance and what their effects look like.

First and most importantly, armyworms aren’t worms. They’re caterpillars. Measuring about 1 and 3/4 inches and up to 2 inches long, there are seven common types. Here are the common names for each of the seven species followed by their scientific names and their appearance:

  • Common armyworm, true armyworm, or white-speck moth (Mythimna unipuncta): Greying-brown or green-brown in color with long, dark stripes, its moth form has tiny black dots on the outside of its wings and white specks which its name refers to.
  • Northern armyworm, Oriental armyworm, or rice ear-cutting caterpillar (Mythimna separate): The larvae have long, greenish stripes of a lighter line and two wider stripes on either side, and their heads are brownish. The adult moth has a greyish color with yellow-tinged wings.
  • Southern armyworm (Spodoptera eridania): The blackish-green or grey-green larvae have reddish-brown heads, maturing to develop long, yellow stripes and off-white or white stripes, darkening into a greyish-black undertone. The adult moths have a brown body, brown forewings, and off-white rear wings.
  • Fall armyworm (Spodoptera frugiperda): This hairier species is mostly brown in color with bright yellow, long stripes which may sometimes have white borders. The adult moth has a darker, patterned forewing and a white rear wing.
  • Beet armyworm, asparagus fern armyworm, small mottled willow moth (Spodoptera exigua): The greenish-brown larvae have dark, long stripes on their upper sides, while adult moths are brownish with reddish-brown spotted forewings and beige or ivory rear wings.
  • Lawn armyworm or paddy swarming caterpillar (Spodoptera mauritia): Beginning as pale green larvae, it matures into a green color on its back with long brown and white stripes. The adult moths have dark patterns with greyish-brown undertones.
  • African armyworm, nutgrass armyworm, Okalombo, or Kommandowurm (Spodoptera exempta): There’s no one color with this species because its color depends on whether it is solitary or in a group. The single larvae are green, while the ones in a group are dark grey or black. Both have dark, long stripes. Adult moths have grey-brown forewings, off-white hindwings, and veining patterns.

The fall, common, and southern armyworms are species that exist in North America, including the United States. It is the fall armyworm you’re most likely to encounter chewing up plants in your yard or pasture. Plus, this particular chomping chaos-wreaker tends to sneak up on you, making it even more important to notice an infestation early on and prepare accordingly. Regardless, methods for getting rid of them will be the same.

The fall armyworm is the most common armyworm found chewing plants in yards or pastures.

kale kkm/

#2: Use a Pest Control Method for Armyworms

Finding a method that works for you will empower you in your pest control. It’s best to go with the least invasive and potentially dangerous method as possible first, and then continuing with additional methods:

Method 1: Common Organic Remedies

One organic remedy is a liquid spray or powdered form of Bacillus thuringiensis var. kurstaki, also called BT for short. You might find the liquid spray available as Monterey BT and the powdered version available as Garden Dust. BT will poison armyworms as well as many other types of caterpillars. A spinosad spray like Monterey Garden Insect Spray works similarly. So does an azadirachtin spray like Azatrol EC, but you can instead use neem oil which has the same active ingredient, Azadirachtin, and it will be just as effective.

Method 2: Beneficial Insects or Birds in The Enviroment

You can benefit your small ecosystem by providing food for the armyworm’s natural predators. Ladybugs, lacewings, ground beetles, and predatory wasps are sold as beneficial insects for biological pest control. Alternately, you can set up bird feeders and nests to attract the local birds.

Method 3: Insecticide

When all else fails, it’s time to bring out the insecticide. Use IGR insecticide to interrupt the army worm’s growth cycle and control small armyworms, and pyrethroid insecticide for small to medium-sized armyworms. Note that IGR insecticide does not require a license to use, but pyrethroid does. You might want to mix them for fast-acting results plus lasting after-effects.

#3: Prevent Armyworms From Setting Up Camp Again

You are most likely to experience armyworms if you have wild grasses, any of the several flower species they feed on, or either the following plants and crops:

  • alfalfa
  • artichoke
  • asparagus
  • avocado
  • barley
  • bean
  • beets
  • broccoli
  • cabbage
  • carrot
  • cauliflower
  • celery
  • citrus
  • cole cropes
  • collards
  • corn
  • cotton
  • cowpeas
  • cucumber
  • eggplant
  • flax
  • kale
  • lettuce
  • maize
  • millet
  • mustard
  • nutsedge
  • oats
  • okra
  • onion
  • parsley
  • peas
  • peanut
  • pepper
  • potato
  • rapessed
  • rice
  • rye
  • sorghum
  • soybeans
  • sugarcane
  • sunflower
  • sweet potato
  • tobacco
  • tomato
  • turnip
  • velvet bean
  • watermelon
  • wheat
Corn is a major crop armyworms feed on.

Fabian Putruele/

It’s not enough to know how to get rid of armyworms once you have an infestation of them, though, you also need to know how to prepare your yard or pasture to stop them from returning. Floating row covers can prevent armyworms from laying eggs. Also, diatomaceous earth can deter them from moving in on your grasses, crops, and flowers.

Armyworms are just one possible type of common pest you might encounter in your yard or pasture. If you check to make sure you are dealing with armyworms and you are, you need to know how to eliminate them properly. Common organic remedies, beneficial insects and birds, and insecticide are possible methods to help you get rid of them and save your vegetation.

Next Up: What Animals in North America Hibernate?

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AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.