University of Maryland Extension

Cabbage Looper - Vegetables

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Ragged holes in the leaves of cole crops, broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, turnips, etc.

 Cabbage Looper Larva
Larva of cabbage looper (Trichoplusia ni)
Photo: David Cappaert, Michigan State University, Bugwood.org

Appearance 

  • Eggs: Tiny yellowish-white to greenish half-spheres, laid singly on leaves, often in small clusters of 6-7.
  • Larvae: Caterpillars initially hatch off-white and become pale green with distinct white stripes down each side and 4 light stripes down the back. 5-7 instars, reaching 1½” at maturity.
  • Typical “measuring” worm that arches its body up into a loop as it crawls. 
  • Pupae: About 3/4" long, initially green, turning dark brown/black, contained within a white, thin, fragile silky cocoon formed on underside of foliage, in plant debris, or in loose soil.
  • Adults: Moderate size (up to 1½” wingspan) mottled gray-brown moth with silvery white mark near center of each forewing.

cabbage looper moth
Adult cabbage looper moth
Photo: Keith Naylor, Bugwood.org

tiny cabbage looper egg
Cabbage looper egg
Photo: Whitney Cranshaw, Colorado State
University, Bugwood.org 
 

Life Cycle/Habits

  • Moths overwinter in the south and come north on storm fronts; a few may overwinter here as pupae.
  • Moths are semi-nocturnal, being most active around dusk, overnight, and sometimes on cloudy days.
  • Larvae population doesn't build up until May, and there are two or more overlapping generations a year.
  • Early instar larvae feed voraciously, usually on leaf undersides; late stage larvae feed more generally and may bore into heads of vegetables.

Host Plants

  • Cole crops (a.k.a. crucifers or brassicas), including broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, turnips, etc. May also damage potato, tomato, pea, lettuce, and spinach, as well as some flower and field crops, and a wide range of broadleaf weeds.

collards infested with cabbage looper
Cabbage looper on collards

Signs/Symptoms

  • Only larval feeding causes damage; adult moths feed on nectar.
  • Early larval instars feed on leaf undersides, creating windowpane patterns on thick-leaved plants like cabbage.
  • Later instars chew ragged holes in leaf centers and may bore into cabbage and broccoli heads, causing stunting or failure to form a head.
  • Serious defoliation and damage can occur.
  • Larvae excrete many moist, brown droppings.

Monitoring

  • Check leaf undersides early in season for feeding damage. Later, monitor for large larvae and droppings.

Prevention/Control

  • Inspect transplants carefully. Camouflaged larvae are hard to spot.
  • Use floating row cover, if this is a yearly pest.
  • Hand pick and destroy larvae.
  • Bacillus thuringiensis (Bt), an organic pesticide, can be used if loopers become established. Neem is also effective.
  • Early maturing plants are less damaged by this warmth-loving pest.
  • Plant resistant varieties.

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