Field Guide     Pest Management     Cutworms

Cutworms

CROPS IMPACTED: Asparagus, beans, cabbage, carrot, celery, corn, grapes, lettuce, pea, pepper, potato, sugar beets, sweet corn, and tomatoes

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Family: Noctuidae

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About Cutworms

The name cutworm originates from their larvae, which cut down young plants from below the soil surface as they feed on the roots. There are also varieties of cutworm that can climb plants eating the foliage, buds and shoots of host plants. Adult Cutworms are night-flying moths that do not cause damage.

Cutworms Reproduction and Life Cycle

Some cutworms migrate to warmer weather and other varieties over-winterize their eggs and larvae. Moths mate and then lay eggs from early spring to late summer/fall depending on the variety. Female moths are able to lay hundreds of eggs in small clusters. They typically lay these eggs on low-growing plants and or on plant residue. Once hatched, cutworm larvae can grow up to 2 inches long and can go through as many as 3 generations per year. The development of the cutworm is greatly affected by the weather, and more specifically rainfall.

Cutworms Identification and Habitat

Identification

Cutworms are typically quite distinct from each other. Their colouring can vary from brown, tan, black, gray, green and even pink. Some varieties of cutworms are one colour, where others can have stripes or spots on them. Larvae can also be glossy or shiny and others can appear dull. Cutworm larvae are soft and fat, and roll up into a “C” shape when disturbed. Fully mature adults are grey, brown or black night-flying moths that are about 1 inch long. They have a wingspan up to 1 ½ inches across, with their front wings typically darker with a pattern on them and lighter hind wings with no pattern.

Varieties

  • -Black cutworm (Agrotis ipsilon)
  • -Dark-sided cutworm (Euxoa messoria)
  • -Dingy cutworm (Feltia jaculifera)
  • -Bronzed cutworm (Nephelodes minians Guenee)
  • -Glassy cutworm (Apamea devastator)
  • -Variegated cutworm (Peridroma saucia)
  • -Army cutworm (Euxoa auxiliaris)
  • -Granulate cutworm (Agrotis subterranea)

Habitat

It is important to know that the population of cutworms can greatly vary from year to year, depending on the weather. Cutworms can be active throughout the summer but are normally not a problem after spring. Migrating moths lay their eggs on the soil and when these larvae hatch they are able to climb to feed on the plants leaves, buds and fruits. Native or overwintering cutworms live in weedy areas, grassy fields and pastures. Typically cutworms become a problem when weeds are present in the fall after harvest and also if the following fall and winter is mild. In this case, a large number of cutworms are able to survive the winter to eat the vegetables in the spring. Overwintered larvae feed on foliage and small roots until they reach ½ an inch long, at this point they emerge. For the most part cutworm’s damage happens in the chewing of vegetable seedlings below the soil line early in the growing season when the plants are quite small with tender tissue. Asparagus, beans, cabbage, carrots, celery, corn, grapes, lettuce, peas, peppers, potatoes, sugar beets, sweet corn, tomatoes and more of the crucifer family are common hosts for cutworms. Although, many cutworms will eat a variety of herbaceous plants including turf grass.

Cutworms Management and Control Methods

Management

When scouting for cutworm infestation, regularly check areas that you suspect are infested during the late afternoon and evening when cutworms are most active. You can also check your plants in the morning when the damage is still fresh and easy to see. Keep an eye out for wilting plants that have cuts near the bass. You can also detect droppings; to do so, run your hand over the soil, rolling over soil clumps and other places where cutworms may be hiding within a square area of the damage.

Note: it is much easier and more effective to control cutworms when they are small larvae. For some plants like celery, peppers and tomatoes, monitoring may have to be continued until vegetables are harvested.

Cultural Control

Keeping cutworms under control can be done by removing weeds and plant residue, minimizing the egg-laying sites and young weeds that small cutworms feed on. Make sure to till your land before planting and again in the fall as this will kill and expose the overwintering larvae. Tilling will also remove the plant residue to help discourage the laying of eggs.

Another cultural control method for dealing with cutworms is to place cardboard or aluminum foil collars around transplants. This will create a physical barrier that prevents the cutworm larvae from feeding on your desired plants. It is important that some of the collar is underneath the soil line and some of it is above ground. This technique should be able to prevent most cutworm species from eating your plants.

Chemical Control

If you are looking for an insecticidal control of cutworms, it is best done by contact chemicals. For the most effective treatment apply insecticides in the evening. Depending on the severity of the infestation, it might be best and much more economical to just treat the patches that are infested rather than the entire field. There are 3 common contact insecticides that are effective in controlling cutworms. These chemicals are carbaryl, cyfluthrin and permethrin, which have medium to long residual effects.

Sources

http://www.omafra.gov.on.ca/IPM/english/onions/insects/cutworms.html#advanced

http://www.extension.umn.edu/garden/insects/find/cutworms-in-home-gardens/

http://www.gov.mb.ca/agriculture/crops/insects/cutworms-field-crops.html