Field Guide     Pest Management     Cabbage Looper

Cabbage Looper

CROPS IMPACTED: Cabbage, Chinese cabbage, beets, broccoli, cantaloupe, cauliflower, celery, collards, cucumbers, kale, lettuce, lima beans, mustard, parsnips, peas, peppers, radishes, rutabaga, snap beans, spinach, squash, sweet potatoes, tomatoes, potatoes, turnip, watercress, watermelon

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Family: Noctuidae

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About Cabbage Looper

Reproduction and Life Cycle

Due to their low tolerance to cold weather, cabbage loopers will reinvade the colder States and Canada annually. This means that cabbage loopers are not active during the winter except for in continual warm states. Depending on your geographical location will dictate how many generation a year cabbage loopers will produce. It is about 2 to 3 in Canada and 5 to 7 throughout the United States. The development from eggs to adult takes about 18 to 25 days when weather conditions are between 21 to 32˚C, meaning that there is generational overlapping. After about 10 days with the temperature at approximately 15°C, the eggs will hatch. The larva/ caterpillar will go through 4 to 7 instar stages which takes between 2 to 4 weeks to fully complete. After the instar stages, the larva will go into a pupa stage also known as a cocoon for about 4 to 6 weeks, depending on the temperature; a moth will then be produced.

Cabbage Looper Identification and Habitat

Identification

The eggs that adult cabbage looper moths produce are round with one flat side that is attached to foliage. The eggs are greenish or whitish-yellow in colour with a bare longitudinal ridge and measures 0.6 in diameter. These eggs are deposited on both the lower and upper surfaces of leafs, although clusters with 6 to 7 eggs can be quite common. The larvae when they first hatch are a dusty white to pale green as they mature and feed on foliage. Some mature larvae are completely green, but typically cabbage loopers are marked with several faint, narrow, white strips that are cluttered into 2 broad bands. The larvae initially have some hair, but as they age the amount of hair decreases. They also have 3 pairs of pro lags that can be either pale green or brown. Their bodies are narrower, measuring from 3 to 4 cm long at maturity. Their most prominent feature is the small, nipple-like structures, or in other words, vestigial prolegs that are located on their third or fourth segment of their abdomen. To protect themselves, cabbage loopers curl into loops. When the cabbage looper reaches the pupation stage, they can be found in a thin, white, fragile cocoon that is about 2 cm long. These cocoons can be found on the bottom side of foliage among clods of soil or in plant debris. When the larvae enter the pupa stage, they are green but quickly turn into a dark brown or black. Finally, adult cabbage loopers are moths that are molted gray-brown in colour. Their back wings are light brown at the bottom, with the distal portions being dark brown. Their forewings have silvery white spots sitting in the middle of the wing with a u-shaped mark, along with a circle or dot that is usually connected. An Adult cabbage loopers wingspan ranges for 33 to 38mm and flies from March to October.

Habitat

Cabbage loopers feed on a wide range of weeds and cultivated plants. As its name implies, it feeds on crucifers vegetables including cabbage, cauliflower, broccoli, rutabaga, collards, watercress, radishes, turnip, Chinese cabbage, mustard, and kale. That being said, they have been known to injure other vegetable crops including beets, squash, parsnips, peas, lima beans, cucumbers, celery, snap beans, watermelon, spinach, sweet potatoes, lettuce, cantaloupe, peppers, tomatoes and potatoes.

Cabbage Looper Management and Control Methods

Management

It is important that you check for caterpillars soon after planting. It is best to scout your crops once a week or more as the growing season progresses. Look for the damage that they are creating, along with checking both sides of leaves for caterpillars. The older and bigger they get the more they feed and the bigger the damage is.

Cultural Control

The best way to eliminate cabbage loopers is to make sure there are no weeds from the Brassicaceae family such as peppergrass, wild mustard and shepherd’s purse in or around infested areas. Handpicking caterpillars in a small infested area can be effective form of control. Once picked, drop them into soapy water to kill them. Another cultural control option is floating row covers that will help prevent cabbage looper moths from laying eggs on desired plants. A floating row cover can be made out of an all-purpose, lightweight garden fabric draped over the plants themselves, or a wooden frame or over metal hoops for support. Put the row covers over plants that can be potentially infested and can be removed upon harvest. The cabbage looper has many natural enemies that can keep them under control including wasps, bees and flies.

Chemical Control

If you are looking to take chemical action to control cabbage loopers, the best time to do so is while the caterpillars are still small and before they cause too much damage. Also, the application of insecticide on older caterpillars will not be as effective in killing them. If possible pick an insecticide that has low impact and is less toxic to cabbage loopers natural enemies like wasps, bees and flies. There are a several low impact insecticides that work well. Neem is a plant based insecticides and acts as an anti-feedant. This particular kind of insecticide does not kill cabbage looopers fast; however, it does cause them to stop eating which will lead to their death. Spinosad is another insecticide that is from naturally occurring soil-dwelling microorganism which provides great control and will not harm their natural enemies. Broad-spectrum or convention insecticides typically last longer but will kill a variety of insects, including the cabbage loopers natural enemies. Some popular broad spectrum insecticides include bifenthrin, carbaryl, lambda-cyhalothrin and permethrin.

Latin / Alternative Cabbage Looper Names

  • - Trichoplusia ni

Sources

http://www.ipm.ucdavis.edu/PMG/r108301011.html

http://www.extension.umn.edu/garden/insects/find/caterpillar-pests-of-cole-crops-in-home-gardens/