Worms on a Cauliflower

Cabbage Worm

• As an adult, the cabbage worm is a white moth with black tips on the top wings and one small black spot on both the top and bottom wings. Larvae are bright, velvet green with pale yellow lines running up the sides and back of the 1-inch-long worm. Adult moths appear in May and lay eggs all summer on the underside of cauliflower or cabbage leaves that hatch in just seven days. Three generations or more are generated during one summer. The worms eat ragged holes in the leaves and move inward, toward the center of the plant. The cauliflower heads are discolored yellow by their fecal matter.

Cabbage Looper

• Moths of the cabbage looper are dark brown with silvery figure-eight spots on the top wings. They fly only at night and lay eggs in clusters on the undersides and tops of cauliflower leaves. The larvae are 1-inch green worms with white strips running along the body. The worm has three pairs of thin legs in the front and three pairs of larger legs in the back with none in the middle, causing it to arch its back upward, like an inch worm, when it moves. Loopers do not live through cold weather as the cabbage worm does, but they migrate to warm areas and return in spring. Loopers manifest themselves by small holes in leaves that do not go all the way through to the top.

Diamondback Moth

• Diamondback moths are identified by three diamond shapes at the top of the wing when at rest. The moths are brown with slender bodies and long antennae. The larvae are one-third-inch to 1-inch green worms that move quickly. They curl and fall off the leaves when touched, but they usually connect themselves to the leaf by a silk thread that they can climb. The larvae stage goes from 10 days to a month, so they do a great deal of damage to crops by chewing holes in the leaves. Older larvae eat holes in the heads of cauliflower.

Management

• Check the undersides of leaves for egg clusters or for worms and pick them off, dropping them into a bucket of soapy water. Use insecticides on worms while they are young. BT, or Bacillus thuringiensis, is a biological pesticide that does not harm birds, bees and other beneficial insects. Remove spent plants in the fall to prevent those pests that tolerate cold from hiding and breeding. All three worms are controlled by parasitic wasps that lay eggs in the larvae, which eats its host. Other insecticides that work against these pests are carbaryl and malathron, but they also kill beneficial insects.