Found throughout North America, it’s more likely you’ll see the damage caused by cutworms before you see the cutworms themselves. Cutworms hide under litter or soil during the day and come out in the dark to feed on plants. They typically attack the first part of the plant they encounter, usually the stem, often of a seedling, and cut it down; hence the name cutworm.
Cutworms are the larval stage of large, brownish-gray moths with wingspans of approx. an inch and a half. There are numerous species of cutworms, each affecting certain parts of plants in specific ways.
Cutworms are usually green, brown, grey, or yellow with shiny heads, stout, almost greasy appearance, soft-bodied caterpilla
rs, often with longitudinal stripes, measuring 1-2 inches in length.
Some species overwinter as pupae; adults emerge in spring as it warms up and lay eggs on grass or soil surface from mid-spring to early summer. Eggs hatch in 5-7 days, larvae feed on plants or grass and pupate for 3-5 weeks, before a new batch of adults emerge. Other species overwinter as eggs that hatch during the first warm days and feed on early seedlings. Usually 1-2 generations per year.
Cutworms will feed on low-growing perennials, seedlings, annuals, root vegetables, flower and vegetable seedlings, transplants including tomatoes, bell peppers, eggplant, cabbage, cauliflower, beets, kale, broccoli etc.
Cutworm damage is unmistakable: plants are severed at or near the surface of the soil or small seedlings are completely consumed. They do their dirty work in the night, and attack early vegetable and flower seedlings and transplants. Very rarely they may climb up mature plants and chew on leaves. During the day, cutworms can be found curled up below the soil surface beside damaged plant stems.
Organic Control and Prevention of Cutworms
1. Protect seedlings with collars: The best way to get protection from cutworms is to place a paper, cardboard, plastic or metal collar around your seedlings and transplants. Collars should be 3-4 inches tall and should fully circle the stem of the plant enabling it to grow. Press the collars at least an inch down into the soil. A lot of gardeners use toilet paper rolls, plastic soda bottles, tuna cans and other household items to make these collars.
2. Cultural practices: Remove weeds and grassy areas from your garden and from the areas around your garden to cut back on places for moths to lay their eggs. Cutworms eat and lay eggs on many varieties of plants, not only crops. Deep plowing, digging, or tilling in the fall and again in spring before planting will kill and expose laid eggs and overwintering larvae.
3. Scout and handpick: Scout the garden every morning early in the season, especially when you have seedlings out
in the garden. If you see cutworm damage, dig slightly around the base of the affected plant with a stick until you find the cutworm, usually within 2-3 inches from the stem. You could also go hunting for them in the night with a flashlight, when you may find them chomping away at stems or crawling along soil surfaces near plants.
4. Mulching: Mulch plants with oak leaves, crushed eggshells, cedar mulch, vulcanite sand, damp wood ashes or diatomaceous earth to act as irritating physical barriers.
5. Apply parasitic nematodes to the soil which is an effective control for cutworms. Purchase nematodes from a trusted source and ask a local expert before engaging in such a solution.
6. Bt (Bacillus thuringiensis), a widely available bio-insecticide is an effective caterpillar killing bacterium that can be used against cutworms. Mix Bt with moist bran and molasses and spread around plants.
7. Beneficial insects: Tachinid flies, trichogramma wasps and braconid wasps help control cutworms by parasitizing the eggs. Toads, moles, shrews, blackbirds, meadowlarks, ground beetles, lacewings, spiders and firefly larvae will feast on cutworms in your garden. Catch and release a few toads as an inexpensive way to control cutworms.
8. Delay planting your garden for a couple of weeks if possible. After the initial outburst early in spring, the number of cutworm larvae decreases and great damage can be avoided by starting seedlings inside and delaying planting outside for as long as viable.
9. Sprinkle used coffee grounds around your plants. Although there is no science to support this, the Old Farmer’s Alamanac reports that used coffee grounds repel cutworms.
10. Purchase and set up electronic bug zappers, as they can help nab the adult moths.
11. Sprinkle cornmeal around the garden. It is said that cutworms love cornmeal but can’t digest it and end up bloating.
12. Cutworms would rather starve than eat plants treated with extracts of pineapple weed or sagebrush, according to Greg Salloum, a student at University of British Columbia.