Cutworms are the larvae of various species of night-flying brown or gray moths. Cutworms chew the tender, young stems, and leaves of almost all vegetable crops. Control cutworms early in the season by handpicking, trapping, or exposing them to predators such as birds.
Cutworms feed at night on young plants, usually severing the stem at or just below the soil line causing the plant to fall over. Cutworms can completely consume seedlings. During the day, cutworms rest in the soil at the base of plants; they are usually found curled up into a C-shape.
Cutworms emerge in spring to feed at night. The moths are brownish or gray with 1½-inch wingspans. The larvae are plump, gray or brown, hairless caterpillars often with shiny heads.
One cutworm can chew through the stems of several seedlings and transplants in one night. Cutworms also climb on plants to chew leaves and buds. Several generations of cutworms can live in a garden in one growing season.
Cutworm larvae are shiny, smooth gray, or dull brown caterpillars, 1 to 2 inches long, with shiny heads. Some cutworms are variegated with yellow spots down the center of the back. When disturbed, cutworms curl into a C-shape.
Moths that lay cutworm eggs are brown or gray with a wingspan of about 1½ inches and stripes on their forewings. The moths fly at night and lay white eggs on host plants or in the soil. Newly hatched larvae feed on vegetable and flower leaves and then retreat into the soil during the day where they curl beside plant stems. Cutworms can chew through stems or completely consume small seedlings. They can climb into plants and eat leaves and buds.
Cutworms can be found throughout the United States and Canada. In far northern regions, one or two generations of cutworms can be expected each year; in southern regions, there can be six generations or more per year. Eggs hatch in 5 to 7 days and larvae feed on grass and plants for 3 to 5 weeks before pupating in the soil. Eggs and pupae can overwinter in the soil.
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Cutworms are common in or near grassy-weedy areas and areas previously planted in lawns.
Adult cutworm moths emerge in spring after overwintering as pupae. They lay eggs in the soil or on grass blades. Eggs hatch 5 to 7 days later. Then larvae cutworms feed on seedlings, grass, and plant leaves for 3 to 5 weeks before burrowing into the soil to pupate.
There are several generations of cutworms each year, and several moth species produce cutworms.
Cutworms can be found throughout North America.
Scientific Name: Order Lepidoptera: Family Noctuidae
Cutworms attack most early-season vegetable and flower seedlings, shoots, and transplants.
Feeding habits and damage
Cutworms chew stems and leaves of young plants. They severe seedlings and leave them lying on the ground. They sometimes consume entire small plants.
Protect seedlings and transplants from damage by using cutworm collars. A collar can be made of cardboard, plastic, or a small tin can with both ends removed. Press the collar an inch into the soil, leaving an inch or two exposed. The collar will exclude cutworms from the plant stem. Cultivation can expose cutworms to cold and birds. A drench containing Steinernema parasitic nematodes can be poured into planting beds; the nematodes will attack cutworms.
Put collars made of paper, cardboard, plastic, aluminum foil, or tin around transplant stems at planting. Bottomless Styrofoam cups, waxed-coated paper cups, or yogurt cups can be placed around seedlings. Push the collars into the soil until about half of the collar is below soil level and at least 2 inches above soil level, then check to make sure there are no cutworms inside the collar. Leave the collars in place all season or until plants are too large to be damaged by cutworms.
Cultivate to expose larvae
Cultivate the planting beds two or three times lightly before sowing seeds or setting out transplants, especially where cutworms were a problem during the past season. Turning the soil will expose cutworm larvae. You can handpick cutworms or leave them exposed for birds to eat.
Where it appears cutworms have been active—where seedlings or transplants have been attacked, use a trowel or garden fork to sift the soil lightly near the base of plants to uncover hiding cutworms or pupae. Cutworms will burrow down about 2 inches below the soil surface. Crush or drop them in a can of soapy water. The best time for handpicking cutworms is early in the morning or at night with a flashlight.
Traps and lures
Insect traps that contain floral lures can attract moths and catch them before they lay eggs on plants. This will stem future generations of cutworms but will not control pupae or cutworms already living in the soil.
Apply parasitic Steinernema nematodes in the soil around crops. These beneficial microscopic wormlike animals get into the insides of cutworms, armyworms, corn rootworms, and fire ants and release a bacterium that paralyzes and kills the insects. They are not harmful to humans. Beneficial nematodes are available at garden centers and come in a gel or medium that can be added to your garden soil.
Apply an insecticide or bait containing carbaryl, such as Sevin, around the bases of undamaged plants in beds where stems have been cut; weekly reapplication will be necessary,
Set out transplants later in the season after moths are no longer active in the garden.
Organic control calendar
Here is what you can do seasonally to control cutworms:
- Before planting: Clear planting beds of garden debris and cultivate the soil to expose cutworm pupae, eggs, or caterpillars. Cultivate seedbeds twice at least 14 days before planting to turn up cutworms and pupae for birds to eat. Scatter moist bran mixed with Bacillus thuringiensis var. kurstaki and molasses a week before setting out transplants or drenching the soil with neem or a solution of insect parasitic nematodes. Encourage or introduce natural predators such as parasitoid wasps, ground beetles, soldier beetles, predatory stinkbugs, and tachinid flies.
- At planting time: Avoid exposing seedlings to the main population of cutworms by planting later in the season. Spread diatomaceous earth around young seedlings to deter cutworms. Protect transplants by placing a stiff paperless collar around each plant; push the collar 1 to 2 inches into the soil and let it extend 1 to 2 inches above the soil level to exclude cutworms. Cultivate the soil to expose cutworms to birds or handpick and destroy the larvae.
- While crops develop: Apply Steinernema beneficial nematodes to kill cutworms in garden beds. Use a garden fork to sift through the soil where cutworms are active; crush them or drop them into a can of soapy water. Use a flashlight to find cutworms feeding at night; handpick and destroy them
- After harvest: Clear the garden of all dead plants and plant debris. Cultivate the soil to expose eggs and pupae to the cold and birds.
Beneficial Steinernema nematodes attack cutworms. Insect predators include parasitic wasps, ground beetles, soldier beetles, predatory stinkbugs, and tachinid flies. Birds will eat cutworm caterpillars.
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