Loopers
By Leslie E. Stevens UCCE Master Gardener
Looper caterpillars get their name from their distinctive locomotion – arching their middle section by drawing up their back legs and inching along leaves and stems of plants. Unfortunately, this engaging trait belongs to some of the garden's more destructive pest families. Long before you spot one of these slinky critters, they'll have chewed the leaves of your prized plants into tatters overnight.
Cabbage Loopers
Cabbage loopers (Trichoplusia ni) are among the most common looper caterpillars. They're members of the noctuid moth family and cutworms and army worms. These green 1-1/2-inch-long larvae chomp their way through cabbage, broccoli, Brussels sprouts, cauliflower, kale and collards. They also have a taste for lettuce, spinach, beans, peas, celery, parsley, radishes, potatoes and tomatoes.
The adult cabbage looper – a brown, nocturnal moth – lays its tiny, domed-shaped eggs singly on the undersides of mature leaves. The pupa is enclosed in a thin cocoon attached to leaves in the plant's crown or in debris on the ground. The looper's lifecycle lasts between 23 to 95 days as long as temperatures stay above 50°F and below 90°F. The higher the temperature, the shorter the lifecycle. In our mild coastal climate, five or more generations may occur annually.
Geometridae Family
A host of other caterpillars share the cabbage loopers peculiar gait and voracious eating habits, but are otherwise unrelated. Commonly known as inchworms, geometrid relatives number in the thousands. They're about an inch long, many are green or brown with vivid markings. They feed on fruits, vegetables and ornamental plants, such as apple, avocado, oak and bougainvillea.
Prevention & Control
Despite the different lineage, management is similar for caterpillars of both families. As weather warms in the spring, watch for moths. Use row covers to protect your susceptible crops and prevent moths from laying eggs among your plants.
At the first sight of damage, inspect the undersides of leaves early in the morning for larvae and physically destroy them. Squish them or flick them into a container of soapy water. Avoid broad-spectrum and long-acting pesticides since they also kill beneficial predators such as spiders and wasps that help manage looper populations. If physical removal of loopers is insufficient, try applications of less toxic Bacillus thuringiensis.