How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PESTS

Cutworms include a number of species of dull gray to brown, medium-sized to large (up to 2 inches when full grown) caterpillars. Most cutworms curl up into a C-shape when disturbed. All normally feed close to the soil surface cutting off seedlings or damaging leaves resting on the ground. Most feeding occurs at night; during the day cutworms are usually found just below the soil surface or under dirt clods. First instar cutworms of some species may be found feeding on the leaf surface.

Adult cutworm moths have dark gray or brown front wings with irregular spots or bands and lighter hind wings. Females lay hundreds of white eggs, either singly or in clusters, depending on species, on leaves or stems close to the ground. After hatching, young larvae may feed on leaf surfaces for a while, but older larvae drop to the ground, tunnel into the soil, and emerge at night to feed.

DAMAGE

Seedlings or young plants are cut off at or just below ground level; often several plants in a row will be wilted or cut off. Losses can be especially severe in fields seeded to a stand or recently thinned. Occasionally cutworms will bore into cabbage heads, but this is not common. Damage often recurs in the same fields and same parts of fields from year to year; damage is worst where large numbers of cutworms are present before planting.

MANAGEMENT

Cutworms migrate into newly planted crops from surrounding weeds or infested crops. Check for cutworms in weeds around the edges of the field before you plant. Remove weeds from field margins and plow fields at least 10 days before planting to destroy larvae, food sources, and egg-laying sites. Cutworms have numerous natural enemies, but none can be relied on to bring a damaging population down below economic levels.

Organically Acceptable Methods
Cultural practices such as removal of adjacent weeds are an essential part of an organic management program.

Monitoring and Treatment Decisions
After the crop is up, check for a row of four or more wilted plants with completely or partially severed stems. If you find damaged plants, look for cutworms by digging around the base of plants and sifting the soil for caterpillars. If you find substantial numbers of cutworms, you can use bait to control most species, except the glassy cutworm, which occurs in the southern San Joaquin Valley. Baits are more effective when food is limited, so get it out before the crop emerges. If unexpected damage occurs after crop emergence, treat as soon as you find several severed plants in the same row.

PUBLICATION

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Insects
W. E. Chaney, UC Cooperative Extension, Monterey Co.
E. T. Natwick, UC Cooperative Extension, Imperial Co.
Acknowledgments for contributions to the insects section:
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
N. C. Toscano, Entomology, UC Riverside

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