Army Worms: How to Identify and Combat Them Efficiently (2023)

Army caterpillars are destructive garden pests that get their name because they travel in small armies of insects, consuming almost anything in their path.

But what exactly are army worms? And are there types of caterpillars? This article answers all of that and shows you how to control them effectively.

There are several species of fall armyworm, many of which have a distinct taste for a specific plant or vegetable. But some will eat anything green, red or yellow. They are most active at night and hide in plants and under garden debris during the day.

In their larval stage, fall armyworms attack a wide variety of crops and grasslands, sometimes moving en masse into new areas in a manner that, as the name suggests, resembles an army on the march.

Attack is primarily aerial, and gray moths often arrive under the cover of darkness to lay eggs. The biggest caterpillar invasion usually occurs after a cold, wet spring.

Read on to learn more about them, including the seven most common types of fall armyworm, what their host plants are, and how to effectively control these destructive pests.

What are army worms?

Army caterpillars are the larvae of moths that belong to the Noctuidae family. These night fliers lay eggs that hatch into tiny larvae that can reach 2 inches in length and curl up when startled.

Although they eventually become moths, most of the damage is caused by the worm-like larval stage. Army Worms have the appearance of an army battalion when encountered in large numbers. A severe infestation can wipe out your lawn grass in a matter of days.

Army caterpillars come in a variety of types, but all have a distinctive inverted Y-shaped mark on their heads.

Agricultural crops, grass blades from pastures, and cool season grasses serve as nesting sites. Plants of rice and maize varieties are more susceptible than others.

The common name "army caterpillar" comes from the fact that these insects often appear in large numbers when feeding in the early morning or late afternoon, or when migrating to the nearest host.

Life cycle of a military worm

Army caterpillars are prolific and respond to favorable conditions. Its eggs are deposited in loose masses on the crowns of seedlings and on the leaves of older plants.

Small caterpillars hatch in 5 to 10 days and feed for several weeks. There can't be too much damage during early development. However, more than 93% of the foliage is consumed after the fourth instar.

Sixth-instar larvae tunnel into the straw soil layer, where they pupate and hatch as adults 10 days later.

Typically, three or more generations are produced each season, just as you remove the caterpillars from your garden plants, another generation prepares to leave the soil to replace them, but some species of caterpillars can lay up to six times.

Female moths lay eggs en masse by the hundreds, preferring to lay them on brightly colored surfaces such as tree trunks, fence railings, the underside of branches, or even grass.

(Video) How to Get Rid of Armyworms (4 Easy Steps)

These egg masses are also light in color, ranging from white to off-white, with a hairy or moldy appearance. They will get darker over time. Like most caterpillars, they live where they eat, usually hatching on their food source.

In places with milder winters, such as the Deep South, caterpillars hibernate underground as eggs and pupae. In warm climates, they can be active all year round.

How to identify military worms

Markings on newly hatched caterpillars are often difficult to distinguish, with older larvae having prominent stripes along the length of the body with an inverted Y on the front.

Heerwürmer (Spodoptera frugiperda) are brown with yellow stripes and fall armyworms (small Spodoptera) are green with light stripes.

Adults are speckled gray moths (1-1/2 inch wingspan) with a small white dot in the center of each forewing and dark edges on the hindwings.

To find out how to identify the seven most common types of fall armyworm, read the next section of this article.

To use:Many areas are too cold to harbor caterpillars in the winter. But they are often driven north into these areas by strong winds and spring storms.

Fall armyworms cause severe defoliation in grasses and lawnsdon't southeast. Some of these moth-like caterpillars even migrate from the Caribbean.

The most common types of military worms (and what they feed on)

Several species of fall armyworm infest lawns and crops in the United States and around the world. Let’s look at the seven most common ones:

1. Common Army Track (True Army Track)

Common fall armyworms are usually grayish-green or grayish-brown and have long, dark stripes that run the length of their bodies.

The adult form of the white speckled moth, named for the whitish spots in the center of its wings, has small black dots along the wingtips.

This species is common in North, South and Central America, as well as in Southern Europe, Central Africa and Western Asia.

They prefer to eat all species belonging to the grass family, including wheat, barley, sugar cane, corn, sorghum, oats, rice and rye.

In addition, they can consume other types of crops such as sweet potatoes, alfalfa, artichokes, onions, celery, beans, peppers, cabbage, lettuce, carrots and cucumbers.

2. Armeewurm

Fall armyworm larvae are mostly brown in color with two distinctly lighter yellow stripes running down the sides, occasionally edged with white.

Compared to other fall armyworm species, these appear to be hairier. The moth has darker forewings and white hindwings with patterns on the forewings. Compared to women, men have more elaborate patterns.

(Video) How To Combat Armyworm in Your Lawn

Early fall and late summer see large fall armyworm populations across much of eastern and central North America and even into South America. The fall armyworm poses a significant threat to food security in Africa and is exacerbating the continent's problems of hunger and poverty.

More than sixty and possibly as many as eighty different plant species are consumed by the insatiable appetite of the fall armyworm. This includes most vegetables as well as forage and pastures, corn, alfalfa, soybeans, cotton and more.

It is also this particular fall armyworm species that has been linked to foliar damage in grasses such as tall fescue and Bermuda grass. In late summer and early autumn, fall armyworms emerge.

3. Northern Army Worm

Fall armyworm larvae are green and their bodies are usually striped. However, they have two wider stripes on their backs, separated by a lighter line, and their heads are brown. The moth's wings are grayish with a yellowish tinge.

These are common throughout Asia, including Sri Lanka, China, Japan, Southeast Asia, New Zealand, Australia and some Pacific Island countries.

Rice, corn and sorghum are the three most consumed grains. Other species of Gramineae can also be attacked by these pests.

4. Southern Army Worm

The larvae of the southern fall armyworm species have a grayish-green or dark green body and a reddish-brown head.

The larvae develop into a yellow-striped caterpillar with additional white or whitish stripes as they age. They darken until they appear grayish-black. The forewings are brown and the hindwings are whitish.

They are common throughout much of South and Central America and the Caribbean. In the United States, it is most commonly seen in the southern states.

Numerous plants, including avocado, beetroot, cabbage, carrot, citrus fruits, kale, eggplant, okra, peanuts, pepper, potato, sunflower, yam, tobacco, tomato, velvet bean and watermelon are the fall armyworm's home. They also eat weeds, but hogberry and pokeweed are their favorite varieties.

5. Army Worm Lawn

First appearing as light green larvae, the caterpillar eventually develops into green caterpillars with white and brown stripes on the sides.

Rows of semi-circular black dots can be seen along the white stripe on the sides. Adult moths have dark patterns and a grayish-brown color.

They can be found throughout the Pacific Islands and in the area between the Red Sea and India and from the Malay Peninsula to Australia.

Rice is the crop most susceptible to damage from this pest, but it also eats nuts, kale, kale, cauliflower, mustard greens, broccoli, beets, sugar cane, and a variety of grasses, including grass.

6. Beetworm

These caterpillars are greenish-brown in color and have long dark stripes on their backs. The hindwings of the adult moth are ivory or buff in color, while the forewings are mottled reddish brown.

Beet armyworm is a common agricultural pest that originated in Southeast Asia but has since spread around the world.

(Video) Army Worms Treatment |

Beet armyworms can affect a wide variety of crops including sugar and table beets, beans, asparagus, celery, potatoes, cotton, tomatoes, lettuce, peas, tobacco, grains such as wheat and corn, oilseed crops such as flax , many flowering plants and a wide variety of weeds.

7. African army worm

Interestingly, the oldest African larvae have different colors depending on whether they live singly or in large groups.

Caterpillars in groups are black or dark grey, individual caterpillars are green. As in all other species, the stripes run along the entire length of the body. The adult has gray-brown forewings, while the hindwings are whitish with visible stripes.

Africa and Asia are the most common regions where you can find them.

The African fall armyworm is almost entirely dependent on grasses for its diet, including the grasses found in cereal crops, pastures and pastures. It also affects most grain crops, including corn, sorghum, millet, rice and wheat seedlings, and oat seedlings.

According to research, just two larvae can swallow an entire 10-day corn plant, making this pest a serious threat to corn fields.

Army caterpillar damage

In spring, the larvae stay close to the ground and feed on grasses and other low-lying plants. At the end of the season, they migrate upwards to feed on the leaves and fruits of the plants.

The first signs of the presence of fall armyworms are their characteristic damage, where they chew through the leaves and leave garlands along the edges of the leaves.

The caterpillars "skeletonize" the leaves of lettuce, cabbage, beans and corn. With tomatoes, they make shallow grooves in the fruit. Corn is its preferred target. They feed on whorls of leaves and pierce their ears.

Sometimes removing the husk from an ear of corn in an infested field will reveal several worms burrowing into the core. Early season young corn is particularly susceptible to worm infestation.

Damage caused by fall armyworms includes the reduction of pastures suitable for grazing forage animals and ugly lawns for homeowners.

Caterpillar damage is most likely to occur from August to October, when populations are at their peak. It is not uncommon for the first reports of damage to be reported during periods of drought in early July.

How to get rid of army worms

If you don't have fall armyworm outbreaks, thank your natural enemies and predators, including birds, beneficial insects, and other larval predators.

If the number of pests is high, it indicates that these natural predators were killed by the same pesticides used to kill caterpillars. The absence of predators gives the growing pest a decisive advantage in your garden. So to control the caterpillars...

  • Avoid the use of harmful pesticides or practices that inadvertently destroy beneficial insects, your natural first line of defense.
  • To usepheromone trapsto monitor the arrival of moths. When you first observe them look for the distinctive white patch on their forewings, it's time to examine your plants more closely.
  • From early spring, check for larvae and signs of damage. Caterpillars usually feed on the underside of leaves and new shoots. Handpick the worms you find and don't be tempted to squash them between your thumbs. Instead, place them in a bucket of soapy water.
  • releasetrichogram waspsto parasitize each newly laid egg. These tiny beneficial insects, 1 mm or smaller, lay their eggs inside pest eggs and kill them before entering the herbivorous larval stage.
  • Other benefits likeChrysopa,ladybird,jtiny hackersThey feed on fall armyworm eggs as well as the young larval stage. Remember: beneficial insects help fight other harmful pests, including aphids, earwigs, conquest worms, cabbage worms, a variety of mites and insect eggs.
  • plant tooattract beneficial birds and insects. Birds are particularly fond of moths and extract larvae from grasses and plants. In the fall, mulch the soil and turn it over before placing so birds can pluck exposed pupae.
  • If you've had an infestation or are concerned that conditions, including a cool, wet spring, will encourage the worms, release them.useful nematodesin your soil These microscopic soil creatures feed on the eggs, pupae and larvae of up to 200 pests. They don't harm vertebrates or amphibians, they don't harm plants, bees or earthworms, and they don't threaten beneficial insects that, like the Trichogramma wasp, lay eggs on anything, not soil anywhere. Beneficial nematodes, however, kill fall armyworm eggs and pupae in the soil.
  • applications ofgarden dustalso known as Bacillus thuringiensis (Kurstaki) or OMRI listedMonterey Garden Insect Spray(espinosade) will kill the caterpillars.
  • As the season progresses,natural oil sprays for horticulturecan be used on plants that show signs of worm infestation. polyvalentNeemöl-SprayIt is effective on larvae and mites at different stages. It also prevents mold growth. Full coverage, including the undersides of leaves and connections to stems, is essential.
  • use quick actionorganic insecticideswhen the pest infestation becomes unbearable.
  • If the infestation is heavy, you can use insecticides that contain active ingredients such as spinosad, bifenthrin, cyfluthrin and cypermethrin. Avoid watering the area for 24 hours for maximum effect on the fall armyworm. For this reason, do not apply insecticide if rain is forecast in the next 24 hours. Read the insecticide label for application rates.

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Trichogramma Wasp This small 1/50 inch parasitic wasp preys on the eggs of leaf-eating caterpillars.

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(Video) How to Identify and Control Armyworms on Cannabis Plants
Ladybird This native species of ladybird is the best-known predator in the garden.

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Beneficial Nematodes These tiny worm-like parasites hunt and destroy over 230 different pests.

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Garden Powder Apply application when caterpillars are first noticed and repeat every 7-10 days or as needed.

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Garden Insect Spray (Spinosad) A potent insecticide recently discovered in the soil of a rum distillery.

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Neem Oil - RTU An easy-to-use, ready-to-spray formula that works both indoors and outdoors.

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Horticultural Oil A high quality paraffinic oil that breaks down quickly and has almost no toxicity.

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What is the fastest way to get rid of army worms? ›

Neem oil is effective at killing armyworms and other pests. Mix a solution of one to two teaspoons of pure neem oil in a spray bottle with a gallon of warm water and a teaspoon of liquid soap or insecticidal soap. Spray the solution on lawns and other affected areas like plants twice a week as a preventative measure.

How do you detect army worms? ›

Signs/Damage of Armyworms: Small brown lawn patches are often the first clue of an armyworm problem. The pests may leave grass blades ragged or chew just the green layer, creating a transparent "windowpane" look. Grass may be sheared to the ground, creating bare spots in your lawn.

How do you control an armyworm infestation? ›

Apply a fast knock down liquid insecticide to the leaf of a recently mown lawn during the afternoon. Repeat applications may be necessary over the coming weeks to ensure the Armyworm is completely eradicated. When the Armyworm become active again in the evening they will eat at the recently treated leaf.

What is the best way to treat army worms? ›

Treat Early for Best Control

An armyworm infestation. If this happens in your yard, you can control armyworms with an insecticide. Apply Ortho® Bug B Gon® Insect Killer for Lawns if you find armyworms in your lawn—they're surface feeders so you should be able to spot them in the turf.

Will grass grow back after armyworms? ›

In most cases, the long-term health of grass is usually not affected and the grass will recover with proper care. However, in the case of a severe case of armyworms that were not detected and treated early enough, overseeding and/or re-sodding may be needed in order to repair the damage.

Where do armyworms hide during the day? ›

Remember, during the day, armyworms hide in soil cracks or under clods and crop residues. Occasionally they may be found in the whorl of the plant during the day. Armyworms usually feed only at night. To sample for armyworms, examine 20 consecutive plants in each of at least 5 random locations in the field.

What time of day are army worms most active? ›

They are most active on turf in early morning or late afternoon/early evening, but they may feed any time of the day. On tall, unmowed turf, fall armyworms are obvious when feeding on foliage during the day (Figure 1).

How do you keep armyworms out of your yard? ›

How to Prevent Armyworms From Coming Back
  1. Aerate your lawn annually. ...
  2. Regularly water your lawn. ...
  3. Cut your grass no shorter than two inches and keep weeds and wild grasses to a minimum.
  4. Fertilize. ...
  5. Check for armyworm moths and grubs regularly.
May 18, 2021

How do I fix my lawn after armyworms? ›

After you've applied your insecticide treatments, we recommend applying starter fertilizer to your lawn the next day. Continue to water your lawn each morning for several days to promote a healthy recovery. In most cases, the long-term health of grass is usually not affected and the grass will recover with proper care.

What is the natural enemy of army worms? ›

Biological Control

Natural enemies can provide good control of armyworms in many fields. Predators include bigeyed bugs, spiders, minute pirate bugs, damsel bugs, assassin bugs, and lacewings. The parasitic wasp, Hyposoter exiguae, is the most important of at least 10 parasites attacking this pest.

Does mowing help get rid of army worms? ›

Mow the lawn

Plus, when you cut the grass, you can destroy some of the eggs that are already there. Already have an armyworm infestation? Mowing the lawn can still help. Mowing exterminates some armyworm caterpillars in your lawn and cuts back the survivors' food source.

How long does it take for a yard to recover from army worms? ›

Your brown lawn may look bad for a couple of weeks, but in most cases the turf will recover. There is a good chance that some areas may see two generations this fall, so keep an eye out for the voracious feeders.

What is the best product for killing army worms? ›

The best chemical treatment for Armyworms is Bifen LP and Reclaim IT. Conduct a full broadcast of both products on your lawn and garden to achieve control.

Do armyworms come back every year? ›

There are several species of armyworms that are present every year in the Midwest, however, economic infestation usually do not occur on an annual basis.

How long do armyworms stay in your yard? ›

occur each year and typically the life cycle from egg to adult takes 28 days. The life cycle can be extended if cooler temperatures occur and can last up to several months. Armyworms in the spring and summer occur in more distinct groups than later in the season.

What causes armyworm infestation? ›

Each year, fall armyworm moths, carried by air currents, make their way from southern Florida, southern Texas, and Central and South America. The size and timing of the initial moth flights are two factors that influence the outbreak potential of this pest. Droughty conditions are favorable for the fall armyworm.

How do you tell if Army worms are in your yard? ›

Signs that you may have army worms include evidence of skeletonised leaves, chewed leaf tips, scalloping of grass leaves along the margins, or complete defoliation of the plant. Larvae faeces, known as frass, is also a sign of army worm infestation. These may look like tiny green-yellow pellets within the lawn.

What are armyworms attracted to? ›

Adult true armyworm moths are attracted to fields that contain living ground cover, which include fields with grassy weeds or cover crops such as rye or grass. Fields that are minimum, no-till, or contain a cover crop should be scouted for true armyworms in May and June (Fig. 1).

Do armyworms live in the soil? ›

Cutworms and armyworms are active from mid-March to October. They feed on leaves and crowns and may cut off plants near the soil surface. Larvae feed at night and hide in the thatch layer or in a burrow in the soil during the day. Turfgrass may be closely clipped around aeration holes, which larvae commonly occupy.

How do I protect my plants from army worms? ›

A cheaper option would be the use of garlic, which also garlic has anti-feedant properties and can also repel most pests. Mix 85g of crushed garlic with 50ml of vegetable oil and add 10ml of liquid soap. Mix 50ml of the garlic and vegetable oil emulsion with 1l of water, shake thoroughly before spraying.

Is there a preventative for army worms? ›

Treating Fall Armyworms. There is no "over the counter" preventative treatment available to homeowners for FAW in the egg, pupa, or moth stages. However, insecticide is available to homeowners for preventing them when they're in the larva/caterpillar stage, which is when they are doing their damage.

How long are armyworms active? ›

After a preoviposition period of three to four days, the female normally deposits most of her eggs during the first four to five days of life, but some oviposition occurs for up to three weeks. Duration of adult life is estimated to average about 10 days, with a range of about seven to 21 days. Figure 6.

Do army worms like wet grass? ›

Improve your lawn's drainage if it has any wet spots as armyworms like to lay their eggs in damp patches of grass. Inspect sod before laying it down to be sure that there are no armyworms present.

How does dish soap get rid of armyworms? ›

Physically purging your lawn or garden might be enough to bring a limited invasion under control. Pick off the armyworm from the plant by hand and then drop it into a bucket of soapy water—liquid dish soap is perfectly fine. The soapy water solution will ensure the armyworms die.

Will a yard recover from army worms? ›

How Can I Help My Lawn Recover? After an infestation, your grass blades may be chewed up, but here's the good news: Armyworm feeding doesn't hurt the all-important plant crowns. Your lawn should bounce back with the right plan.

How long does it take for army worms to destroy a yard? ›

It is not uncommon for an army of armyworms to destroy an entire lawn or field within a few days. As the armyworm feeds, they leave brown patches in the lawn that appear to be heat, drought, or chemical stress.

Do army worms just go away? ›

This means that your lawn will recover from armyworm damage. It will take some time, it might even be next spring before it recovers, and it is certainly going to look bad in the mean time…but it WILL recover nonetheless.

What eats army worms? ›

Birds, fire ants, wasps, and other natural enemies consume fall armyworm eggs and larvae. The action of natural enemies can reduce the numbers of armyworms before noticeable damage occurs.

What is the lifespan of armyworms? ›

Duration of adult life is estimated to average about 10 days, with a range of about seven to 21 days. Figure 6. Typical adult male fall armyworm, Spodoptera frugiperda (J.E. Smith).

What time of day is best to spray for armyworms? ›

Apply insecticides early or late in the day, because the caterpillars are more active at these times. Use as large a spray volume as you can (20 gallons by ground or 3 to 5 by air, if possible).

How often should I treat my lawn for army worms? ›

Apply nematodes in the early morning, late afternoon, or on an overcast day because nematodes are sensitive to sunlight. Re-apply every two weeks until your armyworm infestation ends.

Do army worms go away in winter? ›

Fall armyworms are unusually susceptible to cold, and populations are thought to die out each winter except in the southern region of Texas. Infestations of fall armyworms often occur during “outbreak years”, when exceptionally high populations of the insects survive the winter and make their way north.

Can you mow over army worms? ›

Leave the lawn alone for three days.

After you apply liquid insecticide to your lawn, it is important to avoid mowing and watering for at least three days. This gives the insecticide time to work.

What plants repel armyworms? ›

Desmodium and Brachiaria grass are high quality animal fodder plants. The leguminous greenleaf desmodium becomes repellent, emitting a blend of compounds that help push armyworms away from maize while Brachiaria Mulato II grass around field edge produces chemicals attractive to the pests.


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