Cabbage Looper (Trichoplusia ni) Control and Identification (Pictures)

If you think you may be suffering from a cabbage looper infestation, the first step is to confirm that cabbage loopers are present. Below we will help you identify cabbage loopers and if it is indeed what is invading your garden, help you control and eliminate the unwanted pests.

Identifying Cabbage Loopers

Trichoplusia ni, otherwise known as the cabbage looper – larvae [Worms] are a light green color with faint stripes down their backs. They reach approximately 1.5 inches long and have three pairs of slender legs near the head and three pairs of larger legs at the rear end. The middle section is legless and is looped when the insect is moving. (Inch-worm style).

Cabbage Looper Identification

The adults are a gray moth with a silver spot in the center of each forewing. Their eggs, like the worm, are light green, dome-shaped, and can be found on undersides of leaves. They range from southern Canada to Mexico and everywhere in between.

A picture of a cabbage looper crawling up a leaf.

What Plants are Affected by Cabbage Loopers?

Larvae are the damaging stage of this insect. Worms feed on the undersides of leaves between the veins and leave ragged holes. They feed on cabbage, cauliflower, broccoli heads, cabbage family plants, and many other vegetables.

Cabbage Looper Life Cycle

They can be present from early spring to late fall. They gnaw holes in the leaves and can generally be found on the bottom side of the foliage. Their green color tends to camouflage them somewhat.

Moths emerge from the overwintering pupae in mid-spring and lay eggs on leaves, which hatch quickly. The larvae will feast for up to a month, then pupate for about 10 days in cocoons attached to branches and leaves. There are up to four generations per season.

Cabbage Looper Control

1. Handpick Worms and Eggs

Search and destroy eggs on the undersides of leaves. Handpicking of worms and adults is feasible and should be done several times weekly if their presence is detected.

2. Use Insecticidal Soaps

Insecticidal soaps will also help keep their populations under control, but must be applied on a regular basis in heavier infestations. Neem Oil and Neem based products are also effective .

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3. Bacillius Thuringiensis to Control Cabbage Loopers

Bt Bacillius thuringiensis has proven effective against almost all species of Moth and worm, it is a bacterium/organic pesticide that is readily available to home gardeners. It’s harmless to people and pets.

Apply it at either bloom or petal fall, or both. Bt It is a stomach poison and must be ingested. It is more effective when applied during warm, dry weather while the larvae are actively feeding. Bt breaks down quickly in nature so multiple treatments per season are necessary.

Bt should be applied at either bloom or petal fall, or both. Bt is not generally harmful to beneficial insects. It is a stomach poison and must be ingested by the caterpillar and is effective when applied during warm, dry weather while the larvae are actively feeding. Requires more than 1 treatment.

4. Companion Planting for Cabbage Looper Control

Diverse gardens that include a symbiotic mingling of flowers and vegetables are a poor environment for insect pests, but also attract many natural predators. Encourage natural predators such as predatory wasps by mingling varying plants and flowers blooming at different intervals throughout the season. Native parasitic wasps are known to be advantageous in controlling cabbage looper populations.

5. Use Floating Row Covers

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Floating row covers in the spring are helpful but need to be removed by mid-May. The row covers create a barrier that keeps insects out but allows for moisture, light, and air circulation. In keeping insects out, it also bars pollinators.

6. Bio Pesticides

Bio Pesticides such as Neem derived products and Spinosad, another biopesticide, harmless to humans are advisable. Spinosad will interfere with pollinators as well as pests – evening/night time use is advisable. Broad-spectrum insecticides, such as pyrethrin or malathion only as a last resort.

Sprays/Pesticides must be applied in the pre-bloom stage to prevent injury. Pesticides such as pyrethroids that are more effective in cool than warm weather will work more efficiently against worms earlier in the season and is the recommended early season chemical treatment for most worms and caterpillars.

7. Free Your Garden from Diseased and Damaged Plant Materials

Proper sanitary practices are vital to the health of your garden. Proper sanitation can help to ensure disease-free pest-free and productive gardens. Try to keep the garden free of any diseased dead or damaged plant materials.

Remove cuttings from pruning and trimming and either destroy them – if diseased or send them to the compost pile. Leaving rotting fruits and vegetables in the garden is like a written invitation to unwanted pests and diseases.

If a diseased or dead plant part has to be cut, the microorganism that caused the problem is probably on the tool you just used. Like a surgeon, sterilize all tools by washing in soap and water – rubbing alcohol wouldn’t hurt either.

If you pinch off diseased plant parts, wash hands before handling any other plants. Keep Weeds under control. Till the soil in the spring before planting to expose and kill larvae that wintered over in the soil.

8. Dizainon

Diazinon can be applied at petal fall, but is not as eco-friendly as the bio-pesticides listed above as it is toxic to beneficial insects and pollinators. Other Broad-spectrum insecticides, such as pyrethrin or malathion only as a last resort, generally used commercially and not really advisable for smaller plantings or home gardeners.

Sprays/Pesticides must be applied in the pre-bloom stage to prevent injury. Pesticides such as pyrethroids that are more effective in cool than warm weather will work more efficiently against Cabbage Looper earlier in the season, and is the recommended early season chemical treatment for most worms.