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Past Articles Library | Organic Pest Control | Imported Cabbageworm


(Pieris rapae)

The imported cabbageworm (ICW), is commonly known as the cabbage butterfly. This butterfly was imported from Europe to Canada in the mid-1800s and has since spread to all parts of North America.



Adult: wingspan about 2 inches (5.1 cm) (male slightly smaller), with a black area near the tip of the forewing and a small black spot on the front edge of each hind wing. Female has two black spots on each forewing; male has only one.
Larvae: velvet-like green, with a faint yellow stripe down their back, a row of faint yellow spots on each side, and five pairs of prolegs. Up to 1.4 inches long (3.5 cm).



Pupae spend the winter in garden debris. Adults emerge in early spring and lay eggs on the undersides of leaves. Larvae feed for 2-3 weeks, then pupate in garden trash on soil surface. The adults emerge in 1-2 weeks. 3 to 5 overlapping generations per year. All ages of larvae may be present all season.




Larvae of this insect feed widely on plants in the family Cruciferae, but occasionally on a few other plant families that contain mustard oils. Commonly attacked are vegetable crops such as broccoli, Brussels sprouts, cabbage, cauliflower, turnip, collard, rasish, mustard, lettuce, horseradish, kale, and kohlrabi. Also sometimes attacked are flowers such as nasturtium, sunflower, and sweet alyssum, and weeds in the family Cruciferae. Adults sip nectar from flowers, and are commonly seen feeding at a number of plants.




Larvae feed on the first formed outer leaves of their host plants, which often appear riddled with irregularly shaped holes. When large larvae are feeding, you will find wet masses of dark green excrement dropped on the surfaces of leaves below. It is common for high larval populations in July and August to damage plants so severely that they die or become unmarketable. The larvae eat large holes in the leaves. As they feed, they frequently move toward the center of the plant in order to feed directly on cabbage heads and on leaves shading cauliflowers from the sun. They are also often found inside broccoli heads when they are cooked.



Floating row covers


  • With light infestations, handpick larvae and eggs.
  • Place yellow sticky traps among host plants to catch female butterflies
  • Sprinkle damp leaves with corn meal or rye flour. Cabbageworms that eat this coating will bloat and die.
  • The imported cabbageworm has many insect natural enemies, including several parasitic wasps and predators of eggs and young larvae. Trichogramma spp., egg parasitoids introduced from Europe, offers the best potential for control of the ICW. Since Trichogramma develops in the egg of the ICW, feeding damage is dramatically reduced. Timely mass releases of Trichogramma, during peak flight, could be an effective control agent.
  • To control larvae, spray with Bacillus thuringiensis at 1-2 week intervals.


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When to Water

If you can, it is always best to water early in the morning. This allows the plant's leaves and flowers to dry off as the day warms up.

If you water at night, the plant stays wet for hours in the cool, which are prime conditions for fungi and other problems to set in.

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