Cabbage Looper Insect Pests of Vegetable Crops

Cabbage Looper Quick Guide

Affected Plants: Beans, broccoli, cabbage, cauliflower, other brassica crops, lettuce, parsley, spinach, and tomato.
Primary Insect Pests: Cabbage looper (Trichoplusia ni).
Primary Damage Symptoms: Jagged holes in plant leaves caused by caterpillar feeding.
Most Important Prevention Strategy: Reduce the use of harmful broad-spectrum insecticides to preserve naturally occurring parasitic wasps, predators, and other beneficial insects.
Biological Controls: Bacillus thuringiensis subsp. Kurstaki (Bt), Trichogramma wasps, and naturally occurring predators and parasites.
Chemical Control: Use insecticidal soaps and oils on small caterpillars first; other options include pyrethrin, azadirachtin, neem oil, and spinosad. Reserve malathion for heavily infested plants.

Related HGIC Resources for Cabbage Loopers

• Insecticidal Soaps for Garden Pest Control (HGIC 2771)

Cabbage looper (Trichoplusia ni) is a common vegetable garden pest that feeds on many crops. Affected crops include:

• Beans
• Broccoli
• Cabbage
• Cauliflower
• Lettuce
• Other brassica crops
• Parsley
• Spinach
• Tomato

Cabbage Loopers on Vegetable Crops

Cabbage loopers are caterpillar pests that feed on vegetable crops and are recognized by their distinctive body features and looping movement.

Identification

Cabbage loopers are about 1 to 1½ inches long. They start life with a dusky white color, and as they eat, they turn pale green. Cabbage loopers have a distinct white stripe down both sides and have a lighter green head.

Key identification features include:

• Two pairs of abdominal prolegs
• A body that is wider at the tail end than at the head
• A tendency to rear up like a cobra when disturbed
• An arched, looping movement when crawling

Female moths lay small hemispherical eggs in clusters of seven or eight on plant leaves. The eggs hatch in one to ten days, depending on the temperature.

Cabbage looper damage looks like jagged holes in leaves.
Photo Courtesy of: David Riley, University of Georgia, Bugwood.org

Cabbage looper feeding on a leaf.
Photo Courtesy of: R.J. Reynolds Tobacco Company Slide Set, R.J. Reynolds Tobacco Company, Bugwood.org

Cabbage Looper Damage on Vegetable Crops

Cabbage looper feeding causes jagged holes in the leaves of vegetable crops.

Cabbage Looper Damage and Symptoms

• Jagged holes in plant leaves

Cabbage Looper Prevention and Treatment on Vegetable Crops

Integrated pest management for cabbage loopers should prioritize biological controls and practices that protect pollinators and natural enemies before using broad-spectrum insecticides.

Prevention and Treatment

Cultural Controls

• Reduce the use of harmful broad-spectrum insecticides to preserve naturally occurring parasitic wasps, predators, and other beneficial insects.
• Plant a variety of flowering plants to provide pollen and nectar for naturally occurring predators and parasites.

Biological Control

Bacillus thuringiensis subsp. Kurstaki (Bt)

• Bt is the primary biological control for cabbage loopers.
• The caterpillar ingests Bt during feeding.
• Releases toxins in the caterpillar’s digestive system, causing it to stop feeding and die.
• Applied as a liquid spray.

Parasitic Wasps

• Tiny (1mm or less)
• Includes Trichogramma spp. wasps
• Endoparasitoids – parasites that live and reproduce inside another animal, ultimately killing it
• Parasitizes the eggs of over 200 species of moths and butterflies
• The most widely released biological control agent in North America
• Reduce broad-spectrum insecticide use to protect naturally occurring wasps in gardens and landscapes

Chemical Control

Use chemical insecticides only when biological control measures have failed to keep cabbage looper populations under control. Select insecticides with minimal impact on pollinators and natural enemies.

Before purchasing and using an insecticide, be sure to read and follow all label directions. The label is the law; therefore, the product label is the final authority on which crops or areas the product can be applied to and at what rate.

• Insecticidal soaps and oils: Most effective on small caterpillars. They work by coating the caterpillar and clogging its respiratory system, causing suffocation. Insecticidal soaps and oils have no residual activity. Therefore, they are less harmful to beneficial insects and pollinators after the spray solution has dried.
  • Application precautions: Do not apply soaps or oils to drought-stressed plants or when temperatures are 90°F or higher. Apply during cooler temperatures, such as the mid- to late evening, to avoid any potential plant damage. For more information on using insecticidal soaps, visit Insecticidal Soaps for Garden Pest Control (HGIC 2771).
• Pyrethrin: A botanically derived compound that provides relatively quick knockdown of caterpillars. It can harm natural enemies and pollinators directly exposed to the spray.
• Azadirachtin and neem oil: These botanically-derived chemicals have relatively short residual activity. Azadirachtin is a natural growth regulator that affects insect growth, feeding, mating, and egg laying. Neem oil clogs the spiracles of small-bodied insects, causing suffocation.
• Spinosad: Provides good control and is less hazardous to pollinators and other beneficial insects, though it is not completely harmless. It is derived from the Actinomycete bacterium, Saccharopolyspora spinosa. Caterpillars stop feeding within minutes of being exposed to or ingesting spinosad and usually die within 48 hours. Repeat applications may be necessary as additional eggs hatch.
• Malathion: A broad-spectrum contact insecticide that should be reserved for heavily infested plants due to its toxicity to pollinators and natural enemies.

Always spray late in the day for best results and to better protect beneficial insects.

Pesticide Products for Cabbage Loopers on Vegetable Crops

The following products contain active ingredients used to manage cabbage loopers; always follow the current product label before application.

Abbreviations:

• RTS = Ready to Spray
• RTU = Ready to Use

Pesticides are updated annually. The last updates were made on 9/26 by N. Jordan Franklin.

Originally published 01/19