13 Natural Ways to Get Rid of Armyworms on Plants

Armyworms are the caterpillars of several kinds of moths. They get their name because large groups may move across fields or lawns while looking for food.

A few armyworms may cause little damage. However, a large group can quickly strip leaves from grass, corn, vegetables, and other plants. Young caterpillars are easier to control, so it is important to find them early.

This guide explains how to identify armyworms and control them with natural or lower-risk methods.

How to Identify Armyworm Damage

Armyworms often hide during the day and feed in the evening or at night. Check plants early in the morning or near sunset.

Look for:

• Ragged holes in leaves.
• Leaves with only the ribs or stalks left.
• Brown or bare patches in a lawn.
• Dark droppings inside corn whorls.
• Groups of caterpillars hiding under leaves or in plant debris.
• Egg masses covered with pale scales or fuzzy material.

Different armyworm species look different.

For example, a large fall armyworm often has a pale, upside-down Y-shaped mark on its head. It also has four dark spots arranged in a square near the rear of its body [1].

These marks can help with identification, but young caterpillars may be harder to recognize.

How to Get Rid of Armyworms Naturally

Below are natural, biological, and lower-risk ways to control armyworms. Results will depend on the armyworm species, its size, and how many are present.

1. Remove Them by Hand

Check your plants early in the morning or in the evening. Look under leaves, inside corn whorls, and near the base of damaged plants.

Wear gloves and pick off any caterpillars you find. Drop them into a container of soapy water. You can also remove leaves that hold egg masses and place them in a sealed bag before throwing them away.

Hand-picking works best in small gardens and when the infestation is still light.

2. Spinosad

Spinosad can control armyworms when they eat treated leaves. It often works best on small caterpillars.

Choose a product labeled for the plant and pest you are treating. Some spinosad products are approved for organic gardening, but others may not be.

Spray in the evening when bees are less active. Do not spray open flowers or allow the spray to drift onto nearby flowers. Spinosad can harm bees while the spray is still wet.

Follow the label for mixing, harvest times, and repeat treatments.

3. Encourage Parasitic Wasps

Tiny parasitic wasps are natural enemies of armyworms. Some species lay their eggs inside armyworm eggs or caterpillars. Their young then develop inside the pest, stopping it from reaching adulthood.

Grow small-flowered plants, such as dill, cilantro, sweet alyssum, and yarrow, to provide nectar for beneficial wasps. Avoid broad-spectrum insecticides because they can kill these helpful insects.

Commercially raised wasps, including some Trichogramma species, are available in certain places. These tiny wasps attack moth eggs, including the eggs of some armyworm species.

However, you must release the correct wasp at the right time. Results will depend on the armyworm species, the crop, and your location.

Ask a local agricultural adviser before releasing them. Biological control works best as part of a larger pest-management plan.

4. Neem-Based Products

Neem-based insecticides may slow the feeding and growth of young armyworms. However, they may not control large caterpillars or a heavy infestation.

Choose a product labeled for the crop and pest you are treating. Neem products come in different forms and strengths, so follow the label mixing rate.

Test the spray on a few leaves first. Wait one or two days to check for damage before treating the whole plant. Apply it in the evening and avoid spraying open flowers, bees, or other helpful insects.

Keep children and pets away while you mix and apply the product. Do not let them enter the treated area until the spray has dried or for as long as the label directs.

5. Bacillus thuringiensis (Bt)

Bacillus thuringiensis, or Bt, is a bacterium used in some biological insecticides.

For armyworms, choose a product made to control leaf-eating caterpillars. The label may list Bacillus thuringiensis subsp. kurstaki, often shortened to Btk.

The caterpillar must eat Bt, so cover the leaves that the armyworms are feeding on. It works best on small, young caterpillars. Large armyworms are harder to kill.

Sunlight and rain can reduce its strength. Follow the label to learn when another application may be needed.

6. Check for Eggs and Young Caterpillars

Inspect your plants at least twice a week when armyworms are active. Check the tops and bottoms of leaves, young plant parts, and corn whorls.

Armyworm eggs are often laid in clusters. Some egg masses are covered with pale scales or fuzzy material. Remove the affected leaf or scrape the eggs into a container of soapy water.

Also look for tiny caterpillars feeding together. They are easier to control before they grow large and spread out.

7. Use a Soap Flush to Check a Lawn

A soap flush can help you find armyworms hiding in grass. It is a testing method, not a complete armyworm treatment.

Mix one or two tablespoons of mild liquid dishwashing detergent into one gallon of water. Pour it evenly over about one square yard of lawn.

Watch the area for several minutes. Caterpillars hiding in the grass or near the soil may crawl to the surface. Count and identify them before choosing a treatment.

Dishwashing detergent may harm some grasses, especially during hot or dry weather. Test a small area first. Rinse the area with clean water after you finish counting the insects.

Do not use this mixture as a spray for garden plants. Insecticidal soap is also unlikely to give dependable control of armyworms because it must cover the caterpillars directly.

8. Clean Up Plant Debris and Disturb the Soil

Remove heavy weeds, dead leaves, and crop remains that may shelter caterpillars. Do not leave badly infested plant material lying beside the garden.

Some armyworm species form pupae in the soil. Lightly turning the top layer of soil after harvest may expose these pupae to birds and other predators.

Avoid deep or frequent tilling. It can damage soil structure, earthworms, and other helpful organisms.

9. Welcome Insect-Eating Birds

Many birds eat caterpillars and may help lower armyworm numbers. Place a clean birdbath near the garden and change the water often.

You can also grow native plants that provide seeds, fruit, shelter, or nesting places. Choose plants that are native to your area because some kinds of ivy and honeysuckle can spread too aggressively.

Birds can help control armyworms, but they may not stop a large infestation on their own.

10. Garlic and Pepper Spray

Garlic and hot pepper mixtures are sometimes used as homemade pest repellents. However, there is limited evidence that they can control a serious armyworm infestation.

Blend four cloves of garlic and two hot peppers with two cups of water. Let the mixture sit overnight. Strain it through a fine cloth, then add enough water to make one quart of spray.

Test the mixture on a few leaves. Wait one or two days before spraying more of the plant. Stop using it if the leaves become spotted, curled, or burned.

Wear gloves and eye protection when preparing and applying the spray. Keep it away from your face, children, and pets. Do not spray flowers, bees, or other helpful insects.

Use Bt, spinosad, or another labeled armyworm product if the homemade spray does not work.

11. Beneficial Nematodes

Some beneficial nematodes may infect armyworm caterpillars or pupae when the pests are in or near moist soil. They do not normally control eggs attached to plant leaves.

Results depend on the nematode species, soil temperature, soil moisture, and the armyworm species present. They may be more helpful for lawn pests than armyworms feeding high on plants.

Choose a product labeled for the pest you are treating. Apply it exactly as directed and keep the soil moist for the time stated on the package.

12. Protect Natural Predators

Ground beetles, predatory bugs, spiders, lacewings, earwigs, and some lady beetles may eat armyworm eggs or small caterpillars. Parasitic flies and wasps may also attack them.

Grow a mix of flowering plants and leave some safe shelter for these helpful animals. Avoid spraying broad-spectrum insecticides across the whole garden.

Natural predators can reduce pest numbers, but they may not stop a large outbreak quickly. Combine their help with regular plant checks, hand-picking, and a labeled treatment when needed.

13. Wood Ash and Chili Powder

Some farmers place a small amount of clean wood ash or chili powder inside corn whorls to discourage fall armyworms. However, results vary, and these materials may not control a serious infestation.

Use only cool ash from clean, untreated wood. Never use ash from painted or treated wood, charcoal briquettes, household garbage, or glossy paper.

Use only a small amount of ash. Too much can damage leaves, add salts to the soil, and raise the soil’s pH. Do not use wood ash around plants that need acidic soil.

Wear gloves, eye protection, and a dust mask. Keep wood ash and chili dust away from your eyes, mouth, and lungs. If the treatment does not work, choose a labeled armyworm product.

After choosing a control method, you may also want to identify the armyworm species in your garden. The following descriptions cover some of the most common types.

Types of Armyworms

The name “armyworm” is used for several kinds of moth caterpillars. They do not all look alike or feed on the same plants.

Correct identification can help you choose the best treatment. The species below are some of the armyworms that may damage crops, pastures, or lawns.

1. Beet Armyworm (Spodoptera exigua)

The beet armyworm came from parts of Asia but is now found in many warm areas around the world, including North America and the Caribbean.

Young caterpillars are pale green. Older ones may be green, brown, or almost black. They often have pale stripes running along their bodies.

Beet armyworms feed on many crops, including onions, scallions, corn, cabbage, tomatoes, peppers, beans, peas, potatoes, and ornamental plants.

2. Western Yellowstriped Armyworm (Spodoptera praefica)

The western yellowstriped armyworm is found mainly in western North America. Its range includes parts of western Canada, the western United States, and Mexico.

Older caterpillars are dark gray or black. They have a narrow yellow or orange stripe along each side and smaller pale lines on the back.

They feed on crops such as alfalfa, tomatoes, potatoes, corn, sugar beets, and some vegetables.

3. Yellowstriped Armyworm (Spodoptera ornithogalli)

The yellowstriped armyworm is found across much of North, Central, and South America. In the United States, it is most common in warmer areas but may appear farther north during the growing season.

Older caterpillars are dark gray or black. They have bright yellow or orange stripes along their sides and dark triangular marks on their backs.

They may feed on corn, tomatoes, beans, soybeans, cotton, tobacco, and many other plants.

4. True Armyworm (Mythimna unipuncta)

The true armyworm is also called the common armyworm. It is found in many parts of the world.

The caterpillar is usually greenish-brown to dark brown. It has long pale, orange, and dark stripes along its body. Its head is brown with a net-like pattern.

True armyworms prefer grasses and grain crops. They may attack corn, wheat, oats, barley, rye, and lawn grasses.

5. Southern Armyworm (Spodoptera eridania)

The southern armyworm is found in warm parts of North, Central, and South America. It may move into cooler areas during warm weather.

Its color can range from green to brown or almost black. Older caterpillars often have a pale line along the back and dark marks near the front of the body.

This pest feeds on many crops, including tomatoes, peppers, sweet potatoes, beans, corn, cotton, cassava, and tobacco.

6. African Armyworm (Spodoptera exempta)

The African armyworm is found mainly in sub-Saharan Africa. It also occurs in parts of the Middle East, Asia, Australia, and some Pacific islands.

Young caterpillars may be green. Older caterpillars often become dark brown or almost black, with thin pale lines along the body.

They mainly feed on grasses and grain crops, including corn, sorghum, millet, rice, wheat, sugarcane, and pasture grasses.

7. Fall Armyworm (Spodoptera frugiperda)

The fall armyworm is native to tropical and subtropical parts of the Americas.

It has spread into Africa, Asia, Australia, and other regions. It cannot survive cold winters in many areas, but adult moths can travel long distances.

Its color ranges from light green or tan to dark brown or black. An older caterpillar often has a pale, upside-down Y-shaped mark on its head. Near the rear, four dark spots form a square.

Fall armyworms prefer grasses. Corn is one of their most important food plants, but they may also attack sorghum, rice, millet, sugarcane, pastures, cotton, and some vegetables.

CABI describes it as a major pest that feeds on many crops but strongly favors maize and other grasses [2].

8. Oriental Armyworm (Mythimna separata)

The oriental armyworm is sometimes called the northern armyworm. It is found across many parts of Asia and also occurs in Australia, New Zealand, and some Pacific areas.

The caterpillar may be greenish, gray, or brown. It has several long dark and pale stripes that become easier to see as it grows.

It feeds mainly on grasses and grain crops, including corn, rice, wheat, barley, sorghum, and pasture grass.

9. Lawn Armyworm (Spodoptera mauritia)

The lawn armyworm lives in warm parts of Asia, Australia, the Pacific, and nearby regions.

Young caterpillars may be pale green. As they grow, they become darker and develop pale and brown stripes along their bodies.

They mainly feed on grasses. They may damage lawns, pastures, rice, oats, barley, and other grass crops.

See also: 13 Natural Ways to Get Rid of Cabbage Worms.

Takeaway

Check your garden often so you can find armyworms while they are still small. Look for egg masses, tiny caterpillars, ragged leaves, and dark droppings inside corn whorls.

For a small infestation, remove the eggs and caterpillars by hand. You can also protect birds, parasitic wasps, ground beetles, and other natural enemies.

If more control is needed, choose a Bt, spinosad, neem, or other product labeled for the crop and the armyworm you are treating. Follow every direction on the label.

Treating young caterpillars early usually gives the best results.