Cabbage Looper - Vegetables

Trichoplusia ni

 Cabbage Looper Larva
(larva): David Cappaert, Michigan State University, Bugwood.org

Back to Common Problems - Vegetables

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.
Life Cycle/Habits Moths overwinter in 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.
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 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.

 

Photo Gallery:

Cabbage looper on collards

Cabbage looper egg. UGA1455107 (egg):
Whitney Cranshaw, Colorado State University
Bugwood.org

Adult cabbage looper moth. UGA5140052
(adult moth):Keith Naylor
Bugwood.org

Cabbage looper pupa in cocoon. 5369941
(pupa in cocoon): Whitney Cranshaw,
Colorado State University, Bugwood.org
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