The cabbage looper (Trichoplusia ni), also commonly known as the inchworm, is an insect known for destroying cabbage and cole crops. In their youth larval stage, cabbage loopers consume more than half of their body weight a day in plants.
This destructive worm can be recognized by their movement when they double (loop) their body as they move along. This unique way of moving is due to the looper's lack of legs at the segments in their body.
Their larvae can grow as long as 1-½ inches. They are a caterpillar with a pale lime green body and white stripes that run along each side and several lines down the back.
Their adult parents are night-fliers that are gray moths with a 1-½ inch wingspan and metallic silver V-shaped marking in the center of each forewing.
The moths emerge during the spring, mate, and lay their pale green eggs on the cabbage plants in your garden. The eggs hatch into Larvae in a matter of days, wreaking havoc on the plants for weeks until they are ready to pupate and start the lifecycle all over again.
The damage left by the loopers isn't just to cabbage crops, however. These destructive inch worms will also attack broccoli, cauliflower, kale lettuce, spinach, celery, cucumbers, and tomatoes in your garden.
Keep a continuous watchful eye on your cabbage plants, both under the leaves where they tend to borrow and on the outside. You can pick off the larvae and brush eggs into a container of warm soapy water for easy disposal.
There are numerous predators of the cabbage looper that gardeners can benefit from such as birds and other insects that are attracted to herbs in your garden. Dill, coriander, fennel, and parsley are just a few of the herbs that beneficial insects are attracted to. One of the biggest enemies to the cabbage looper's larvae is the trichogramma wasp that when released will destroy their eggs.
For cole crops, after harvesting at the end of the season, bury any spent crops to destroy the larval cocoons before they have a chance to emerge into adults the following spring.
While rotating your cabbage heads to another part of the garden might seem like an effective idea, once the cabbage looper becomes an adult, the moths only need to fly around to find where your cabbages are growing. Using floating row covers in your garden can prevent the moths from landing on your plants to lay their eggs.