Plant Diagnostic Database

Cabbage Loopers (Trichoplusia ni)












Cabbage family plants (cabbage, cauliflower, brussels sprouts, broccoli, kohlrabi, kale), beans(pods), celery, lettuce, radish, tomatoes.

Larvae are light green, 1/2 inch long, with a white stripe along each side of the body. They hump their middle sections when they move.
Life Cycle:
Larvae feed at the base of developing cabbage heads inside the leaves, excreting a greenish, jellylike substance as they go.

Traps are available to catch male cabbage looper moths.

Spray Bt if you find 1 worm per 2 plants. Bacillus thuringiensis (Bt) must be ingested by worms before it has any effect. Good coverage of upper and lower leaf surfaces is important. Use lots of water and insecticidal soap as a sticker (1-1/2 oz/gal) when spraying Bt. Using a feeding attractant, such as molasses (½ - 1 oz/gal), may improve control. Bt breaks down rapidly in sunlight (usually within 24 hours). It is best to apply it in the evening. Bt is washed off leaves by rainfall of 1/2 to 1 inch and thus must be reapplied if rain occurs within a few hours of application. Bt is most effective if sprayed when temperatures are above 45° F. Use Bt within 2 years of purchase - it does not store well. 

Flies and wasps parasitize these worms. Eggs and larvae are both fed upon by other beneficial insects and birds.

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