The larvae or caterpillars of some moths are called cutworms (Agrotis, Amathes, Peridroma, Prodenia spp.) because of the manner in which they cut down young plants as they feed. The adults are night-flying moths which feed on nectar, if at all, and do no damage.

Damage:

There are a great many species of cutworms. While they all feed on plants by chewing, they vary as to damage done and host plants preferred. Generally they destroy more of the plant than they eat. Their numbers vary greatly from year to year and, when numerous, may destroy as much as 75% of a crop. Cutworms injure plants in four major ways:

- Solitary surface cutworms cut off young plants at or slightly above or below the soil line, sometimes dropping the severed plants into their burrows. Because most of the plant is not eaten, these cutworms do great damage, attacking and felling new plants nightly. The black, bronzed, clay-backed and dingy cutworms are in this group.

- Climbing species, usually the variegated and spotted cutworms, climb the stem of trees, shrubs, vines, and crops and eat the leaves, buds and fruit.

- Subterranean species, particularly the pale western and glassy cutworms, remain in the soil and feed upon roots and underground parts.

- Army cutworms occur in great numbers, consuming the tops of plants and then "marching" on to other fields.

Description:

The many species of cutworms can be quite distinct. Many are stout, smooth, soft-bodied, plump caterpillars. These vary from brown or tan to pink, green or gray and black. Some are all one color, others spotted or striped. Some larvae are dull, others appear glassy. The adults are generally very robust brown or black moths showing various splotches, blotches or stripes in shades of gray, brown, black or white.

Life Cycle:

Most cutworms pass the winter as partially grown larvae. Thus they are already large, voracious feeders when transplants and seedlings are set out in the fields. A few species pass the winter as pupae or hibernating moths. Overwintering cutworms may live under trash or bark, in clumps of grass or in earthen cells in the soil. These cutworms become active and begin feeding as the weather warms in spring, remaining hidden under debris or in the soil and feeding at night. Many species continue to feed well through June, then pupate in the soil to emerge later as moths. Normally there is only one generation per year. The moths crawl from their brown pupal cases in the soil and climb up through the soil, following the tunnel made by the burrowing larva. If this tunnel is blocked, the fragile moth cannot escape the soil. Cutworm abundance and development is greatly affected by weather, especially rainfall. The moths mate and lay eggs in late summer, beginning the next generation. The moths often seek out grassy or weedy areas to lay their eggs, which are usually deposited on plant stems or in the soil. One female may lay hundreds of eggs. The hatching larvae feed until cold weather and then hide for the winter in a sheltered, dry place.

Control:

Several cultural practices may offer some degree of control:

- Plow and fallow fields in mid- to late summer to prevent the laying of eggs.

- Plow in the fall to expose the larvae or deeply bury the pupae.

- Cultivate fields in the spring after vegetation has appeared and grown a few inches, then delay seeding to starve the cutworms.

- Plan rotations to avoid row or hill crops following a grassy sod. Plow sod fields in late summer or early fall the year before planting.

- Cultivate frequently to injure and expose hiding cutworms to predators.

- The construction of ditches and dusty furrows may interrupt armyworms.

- Place foil or paper wraps or cardboard collars around transplants; extend a few inches into the soil and several inches up the stem.

- Dig in the soil around damaged or adjacent plants in the row; find and destroy the cutworm.

- Plant a thick "trap crop" of sunflower, a favored host, around the perimeter of the garden; find and destroy attacking cutworms daily.

- Use a tanglefoot band on trees being attacked by climbing cutworms.

- Other suggested home remedies include catching and placing toads in the garden, wrapping onion stems around the stems of transplants, placing a ring of moist wood ashes around the plants, and placing a toothpick or 16d nail alongside each transplant stem. Chemical treatments are available as either homemade or commercial poison baits or as insecticide treatments directed to the soil surface or on and around the plants. Granular insecticide treatments, applied to protect the seed and developing seedlings from soil insects, are of little, if any, value in controlling cutworms.

Adapted from G.R Nielsen, University of Vermont Extension, 1999