Cole crops are susceptible to imported cabbageworm.
Imported cabbageworm adults are white or yellowish-white butterflies with black spots on the wings. Larvae/caterpillars are velvety green, up to one inch long, with a faint yellow stripe running down their back.
Damage Caused by Imported Cabbageworms
Cabbageworms attack the heads of cabbages, flowers of broccoli, and curds of cauliflowers. Caterpillars feed on the upper surface of the leaf, creating large, irregular holes. As caterpillars grow, they may move toward the center of the plant leaving only the midribs intact. Defoliation can be severe enough to cause crops to be unsaleable or fit for consumption.
Life Cycle of the Imported Cabbageworm
They first appear in mid-April and they continue to be a problem until mid-September. Adults fly during the day and lay eggs singly on the leaves of cole crops. After feeding, caterpillars will pupate. The bright green pupa is attached to the lower surface of the leaf by a silky thread. Cabbageworms overwinter as pupae in crop debris. The life cycle is about 5 weeks, and 3 to 6 generations can occur in a year.
Management of Imported Cabbageworms
- Removing plant debris and tilling can help manage overwintering cabbageworms.
- Using floating row covers can protect plants and prevent egg laying. Since cole crops don’t need to be pollinated, row covers can be left on plants until harvest.
- Pesticides, such as Bacillus thuringiensis var Kurstaki or Aisawai, can also be used to manage these pests; make sure to read and follow all label directions.
- Younger, smaller caterpillars are easier to manage than older, larger individuals.
Contact your county Extension office for current pesticide controls.