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Cutworms Natural Insect Pest Control

Cutworms
Cutworms
Cutworms

Cutworms are the larvae of several species of night-flying moths.

The moths are brownish or gray with 1½-inch wingspans. The larvae are plump, gray or brown, hairless caterpillars often with shiny heads.

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 are common in or near grassy-weedy areas and areas previously planted in lawn.

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.

Target Plants: 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.

Organic Controls: 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.

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 drench 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.

Natural Predators: Beneficial Steinernema nematodes attack cutworms.  Insect predators include parasitic wasps, ground beetles, soldier beetles, predatory stinkbugs, and tachinid flies. Birds will eat cutworm caterpillars.

Scientific Name: Order Lepidoptera: Family Noctuidae

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