More In-Depth Information

Imported Cabbageworm

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Imported Cabbageworm Life StagesImported Cabbageworm Life Stages
Imported Cabbageworm with Feeding Damage and FrassImported Cabbageworm and Frass
Imported Cabbageworms with Feeding Damage and Frass on Brussel SproutsBrussels sprout plant with cabbageworm feeding damage and frass.
Severe Imported Cabbageworm Larvae Feeding DamageSevere Larvae Feeding Damage

HOSTS

  • Cauliflower
  • Brussels Sprouts
  • Broccoli
  • Cabbage
  • Kale
  • Collards
  • Kohlrabi
  • Leafy Greens

DESCRIPTION

Imported cabbageworm (Pieris rapae) larvae are green with a fuzzy/velvety appearance due to dense short hairs, and they are about 1.2 inches long. Adult butterflies are white with dark spots. Their wingspan is 2 inches.

BIOLOGY

Egg | Larva | Pupa | Adult
Imported cabbageworms overwinter as pupa (naked chrysalis) on plant foliage or debris. They are primarily active in the day. Larvae develop through 5 instars. They can have 3 to 4 generations a year in Utah.

SYMPTOMS

The larvae chew round holes in leaves, and may occasionally cause serious defoliation. As caterpillars mature, their feeding intensifies, and they often move into the developing heads. Larvae may also leave frass (fecal material) that can stain broccoli and cauliflower heads.

SCOUTING

  • Scout weekly for imported cabbageworms starting when broccoli and cauliflower are at the button stage.

GENERAL MANAGEMENT

  • Hand remove caterpillars.
  • Plant cabbage early in the season in order to harvest before cabbageworm populations are at damaging levels.
  • Use floating row covers to exclude cabbageworm butterflies from laying eggs on crops.
  • Plant tolerant crop varieties, including ‘Mammoth’, ‘Red Rock’, ‘Chieftan Savoy’, and ‘Savoy Perfection Drumhead.'
  • Clean growing site of plant debris after harvest.
  • Manage weeds to remove overwintering sites for pupae. 

INSECTICIDES

Insecticides containing Bacillus thuringiensis var. kurstaki (Bt) and spinosad are effective in suppressing imported cabbageworm.

 

 

Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.