University of Maryland Extension

Cutworm - Vegetables

cutworm

UGA5361045: Black cutworm larva (Agrotis ipsilon) and damage it caused to a young corn plant. W.M. Hantsbarger, Bugwood.org

 Back to Common Problems - Vegetables

Back to leaves/stems chewed - vegetable seedlings and transplants

Appearance

Eggs: Tiny, white-brown spheres (black cutworm) or half-spheres (variegated cutworm), with ribs radiating from center, laid on foliage in clusters of up to several hundred.  
Larvae: Stout caterpillars with rough skin, almost 2” long when full grown (there are usually 6 instars). Black cutworm: uniformly gray/brown to nearly black, somewhat greasy sheen. Variegated cutworm: brownish/gray to grayish/black with yellow-white spots on its back and a dark “W” mark on 8th abdominal segment of last instar.
Pupae:  Dark brown/mahogany colored case, ¾ - 1” long, in a chamber near soil surface.

Adults: Moths with up to 2" wingspan. Black cutworm: wings uniformly dark brown with black “dash” marking on forewing. Variegated cutworm:  wings grayish/brown with darker bean-shaped spot and smaller round spot usually visible on each wing

Life Cycle/HabitsCutworms are important early-season pests of vegetable crops in Maryland. They typically overwinter as pupae, with additional adult moths migrating in from the south in spring. Adult moths feed on nectar from flowers and lay eggs on foliage. Early instar larvae may feed during the day, but larger larvae feed at night and seek shelter during the day in soil or elsewhere. Young larvae begin feeding on foliage in early May. Older larvae feed near the soil surface, cutting off young plants at or below ground surface and sometimes pulling them underground to consume. Larvae are also defoliators, and may feed on fruits, roots, and tubers as well. Variegated cutworms readily climb trees to feed on buds, foliage and even tree fruit. Cutworms curl up when disturbed. There are several generations a year.
Host PlantsExtremely wide host plant range. Primarily tomato and corn, but also feed on asparagus, beans, beet, brassicas, broccoli, cantaloupe, carrot, celery, collards, cucumber, eggplant, lettuce, okra, onion, peas, pepper, potato, radish, rhubarb, spinach, squash, sweet potato, turnip and watermelon, plus tree fruits and small fruits.
Signs/SymptomsSeedlings or even transplants are cut off at the soil line or disappear entirely at night (dragged underground into cutworm burrows).  Feeding damage appears on foliage, fruit, or buds, often without any pest visible during the day. Variegated cutworms may tunnel into tomatoes or cabbage and cauliflower heads.  Cutworms may feed on storage roots or tubers, making smooth cavities.
MonitoringWatch for seedlings cut off at the soil line or disappearing altogether at night. The first generation of mature cutworm larvae does the most damage.
Prevention/Control
  1. Most feeding injury is superficial and can be ignored.
  2. In spring or fall, till soil to disrupt possible overwintering sites, exposing pests to predators and freezing temperatures.
  3. Larger transplants better withstand damage. Pre-sprouting seeds is also helpful.
  4. Floating row cover prevents egg-laying and excludes larvae.
  5. Protect seedlings with a 3" cardboard, foil or plastic collar pushed into soil around plant stems.
  6. Discourage cutworms with coarse materials such as crushed oyster shell, sand, or diatomaceous earth, placed around plant stems.
  7. Handpick larvae, and either crush them or drop them into a container of soapy water.
  8. Bacillus thuringiensis (Bt), an “organic” pesticide, will kill young larvae.

Photo Gallery:

black cutworm larvae
Black cutworm
photo credit 
G. Dively

black cutworm moth
Black cutworm adult moth
Photo credit: Ian Kimber, Bugwood.org

cutworm climbing up stem
Climbing cutworm

two yellow cutworms
Yellow Cutworm

cutworm pupa in soil
Black cutworm pupa
Photo credit: Merle Shepard, Gerald R.Carner, and P.A.C Ooi, Insects and their Natural Enemies Associated with Vegetables and Soybean in Southeast Asia, Bugwood.org

 

 

 

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