Cutworms: How to Prevent and Get Rid of Cutworms Effectively
How to identify and effectively control cutworms using proven, organic and least-toxic methods.
Cutworms are general feeders that can cause a lot of damage to a wide variety of crops in your home garden, including broccoli, kale, and cauliflower.
Many species of cutworms from the night-flying moth family Noctuidae are found in home gardens across the United States. The larvae commonly feed on plant stems at or below ground, eventually cutting them down.
If you’ve been wondering exactly what cutworms are, or how or when to identify them, this guide is perfect for you. We’ve also included tips and tricks on how to prevent an infestation in the first place, as well as how to get rid of cutworms that might be infesting your yard at this very moment.
What are Cutworms?
The term ‘cutworm’ is used for the larvae of a number of moth species.
Adult moths lay eggs on plant debris from spring through fall with some species’ eggs emerging in spring and summer and others in fall. Those that hatch in the fall spend the winter in the ground or in a woodpile and come out to feed in the spring.
These pests cause the most damage early on in the gardening season when the cutworms emerge after overwintering and then feed on young seedlings.
Cutworms are caterpillars, but they are often mistaken for the grubs of beetles such as Japanese beetles.
How to Identify Cutworms?
Since cutworms consume such a wide array of fruits and vegetables, young seedlings and transplants are especially vulnerable to attack by these pests. Cutworms can be found by moving through your garden at dusk or in the evening and looking at the bases of plants. They prefer cloudy days as well.
There are several varieties, and they can range in color from gray to pink to green to black, and their length can reach up to two inches. They come in solid, spotted, and striped patterns. When they’re not moving, they usually curl up. Cutworms are nocturnal, feeding only at night and hiding during the day.
One of the most common species of cutworms is the black cutworm (Agrotis ipsilon). They grow into the dark sword-grass moth, that has small dark spots on its body.
Peridroma saucia saucia, or variegated cutworms, are another widespread species. They have brown spots and a thin white stripe down the middle of their backs.
Depending on where you live, you may also come across Army Cutworms, Bristly Cutworms, Bronzed Cutworms, Claybacked Cutworms, Clayhill Cutworms, Dingy Cutworms, and Pale Western Cutworms.
Generally, though, adult cutworms are moths of dark-wing colors. They are usually brown or gray and get to be about 1½ inches long with a 1½-inch wing length. Keep an eye out for the adults, because the females will lay eggs in dry soil after they mate.
Cutworm caterpillars (larvae) are stout, soft-bodied, gray, or dull brown caterpillars (1-2 inches long) that curl up when at rest or disturbed. They feed at night and burrow into the soil during the day.
Adults are dark gray or brown, night-flying moths (1-1/2 inch wingspan) with ragged blotches or stripes on their wings. They do not damage plants.
Note: Pest populations vary greatly from year to year. When numerous, cutworms can destroy up to 75% of a crop.
Life Cycle of a Cutworm
Most species pass the winter in soil or under garden waste as young larvae. In the spring, as temperatures warm, they become active and begin feeding on plants at night remaining hidden during the day.
The larvae molt several times and when fully grown pupate in the soil (late spring). Within one week moths emerge and begin laying hundreds of eggs mostly on stems and leaves. One to five generations per year, depending upon the species.
Note: Overwintering larvae and the first generation in the spring are the most damaging. A few species pass the winter as pupae or hibernating moths.
Damage Caused by Cutworms
Cutworms can attack a variety of plants since they are general feeders. Vegetables such as asparagus, beans, cabbage, and other crucifers, carrots, celery, corn, lettuce, peas, peppers, potatoes, and tomatoes are among their favorite foods to consume.
A few species also feed on turfgrass. Cutworms feed by curling their bodies around the stem. This feeding results in the plant being cut just above the soil surface.
Damage occurs at night when caterpillars feed by clipping off seedling stems and young plants near or just below the soil surface. Often, an entire row of newly planted garden vegetables will be cut off during the night.
Different cutworm species will climb plants doing damage to foliage, buds, and shoots. Cutworms are also known to gouge potato tubers. Late-season cutworms will tunnel in fruit.
Cutworms, like their close cousins armyworms, will also frequently attack turf grass. The damage they inflict on grass — cutting off blades at the crown — is usually more dispersed than damage from armyworms. Cutworms favor golf courses where they cause ‘ballmark’ pockets of dead and missing turf both on fairways and putting greens.
How to Get Rid of Cutworms
Losing precious transplants once to cutworms is all most people require to implement preventive measures as part of an Integrated Pest Management plan.
There’s little more heart-breaking than coming out to the garden one morning to find the seedlings you started months ago indoors have been severed at the root.
Preventive Measures for Cutworms
- Before planting a new garden remove weeds and plant debris that might feed and shelter developing larvae.
- Turn the soil after fall clean up then give birds and other predators a chance to pick off the expose larvae and pupae.
- Mow as closely as possible to the edge of your garden to give cutworms less to feed on and less shelter near your plants.
- A three-foot wide (or more) bare-soil strip between your lawn and your garden plants makes it harder for larvae to reach your plants. It also gives you more of a chance to spot them.
- Wait as late as possible before setting out starts. Cutworms go on the move early in the growing season. Give them a chance to starve before you put out dinner.
- Place cardboard collars (or milk containers with the bottom cut out) around transplant stems at planting time. Be sure to work the collar into the soil at least an inch or two.
- Plant sunflowers along the edge of your garden. Sunflowers are a favorite target of cutworms. The plants will attract the larvae giving you a chance to pick them from the ground before they head to your corn.
Dealing with Cutworm Infestations
- The presence of many birds feeding in the yard may indicate cutworms in your turf.
- Handpick caterpillars after dark. This is often most productive following a rain or thorough watering.
- Slow the progress of worms, who don’t like navigating dry soil, by watering in the morning then cultivating your garden’s walkways lightly to a depth of an inch or so. This cultivated soil will dry quickly while trapping moisture beneath it. Do not use mulch which gives the worms shelter.
- Beneficial nematodes released in moist, spring soil will attack and destroy cutworms living underground. They’re especially beneficial to apply during the season after cutworms have been a problem.
- At the first sign of moths, release trichogramma wasps weekly for three consecutive weeks to parasitize cutworm eggs.
- Spreading a line of diatomaceous earth around the base of plants sets up a barrier to larvae. Diatomaceous earth, the fossilized, abrasive remains of prehistoric sea life, literally lets you draw a line in the dirt that’s deadly to any larvae that pass over.
- Scatter bran or corn meal mixed with Monterey Bt (Bt-kurstaki) and molasses on the soil surface to attract and kill caterpillars. Eco-Bran will also kill caterpillars that feed on it.
- In case of severe infestations, look for insecticides with ingredients such as carbaryl, cyfluthrin, and permethrin. It’s recommended to apply the pesticide in the evening before cutworms venture out for their evening feeding session. It should be applied to the stems or leaves for climbing cutworms.
Note: Gardens that were covered in grass or weeds the previous season are especially attractive to this pest.
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