Description: Cabbage looper larvae move like inchworms, in a looping motion, because they lack legs in the middle portion of their bodies. Older caterpillars are light green, usually with a white stripe down each side. Younger larvae tend to be paler. Adult moths are grayish brown, but can be recognized by a distinct silvery mark on each forewing shaped like a figure eight. Cabbage looper eggs are very pale green to white, and found on the upper surfaces of leaves.
Life cycle: Adult cabbage looper moths migrate to northern areas in spring or summer. Moths deposit eggs on host plants, usually singly. The eggs hatch in 2-10 days, dependent on temperature. Early instar larvae feed on the lower surfaces of leaves, while larger caterpillars do more conspicuous damage. Mature larvae pupate on the undersides of foliage or in the soil. The adult emerges in 1-2 weeks. Multiple generations occur during the growing season.
Crops damaged: Mainly brassicas: cabbage, cauliflower, broccoli, kale, turnips, mustard, and others. Sometimes damages other crops, including tomatoes, peppers, eggplant, potatoes, watermelons, cucumbers, melons, squash, cantaloupe, peas, beans, and others.
Signs and symptoms: Ragged holes in leaves, mainly between the veins. Dark green frass. When looper numbers are high, damage may be enough to stunt plant growth or prevent head formation in cabbage and similar crops.
- Keep the garden free of weeds, especially those preferred by cabbage loopers – wild mustard, peppergrass, and wild cabbage.
- Monitor susceptible plants for cabbage looper eggs and crush them before they hatch.
- Check the undersides of leaves for young looper larvae. Hand pick and destroy them by dropping the caterpillars in soapy water.
- Use floating row covers as a barrier to moths. Be sure to anchor all sides of the row covers.
- Collect diseased caterpillars and make your own cabbage looper remedy. Cabbage looper larvae are susceptible to a virus that kills them. Infected caterpillars will look yellow or white, and swollen. Blend these sick caterpillars with water and spray it on plants to infect other larvae.
- Apply Bacillus thuringensis when larvae are young.