Cabbage looper

Trichoplusia ni Trichoplusia ni (Hübner, [1803])

falso medidor de la col · Spanish, Mexico and Latin America
fausse-arpenteuse du chou · French, Canada and France
粉纹夜蛾 (fěnwén yè'é) · Chinese, East Asia

The cabbage looper is the caterpillar of a grey-brown moth. It moves by arching its back into a loop, because it has fewer pairs of legs on its abdomen than most caterpillars. It chews large holes in the leaves of cabbage, broccoli, lettuce, spinach, tomato, cotton, soybean and many other crops, and contaminates leafy vegetables with its body and droppings. It migrates long distances each year and is also a serious pest in greenhouses.

Cabbage looper caterpillar (Trichoplusia ni), pale green with thin white side lines, arching as it moves. Photo: Alton N. Sparks, Jr., University of Georgia, United States, CC BY 3.0 US, via Wikimedia Commons.

Type: Insect · Insect (moth; the caterpillars chew leaves)
Classification: Animalia › Insecta › Lepidoptera › Noctuidae
Main crops: Cabbage, Cauliflower & broccoli, Kale, Lettuce, Spinach, Celery, Tomato, Cucumber, Cotton, Soybean, Common bean
Found in: Americas, Africa and the Middle East, Europe, Asia
Chemical groups: IRAC 11A, IRAC 5, IRAC 18, IRAC 28 (mode-of-action groups, not products)
Last reviewed: 2026-10-20

Cabbage looper scientific name, order and family

The scientific name of cabbage looper is Trichoplusia ni Trichoplusia ni (Hübner, [1803]), in the order Lepidoptera, family Noctuidae.

Where it occurs

Found throughout the Americas, Africa, southern Europe, the Middle East and much of Asia. In North America it cannot survive cold winters and migrates north from southern areas each year; it also persists year-round in greenhouses.

Region	Status
Americas	Widespread; seasonal migrant in cold regions
Africa and the Middle East	Widespread
Europe	Mainly southern Europe; migrant further north
Asia	Widespread

Symptoms and identification of cabbage looper

Adult cabbage looper moth (Trichoplusia ni), grey-brown with a silvery mark on the forewing. Photo: xpda, CC BY-SA 4.0, via Wikimedia Commons.

The organism

Moths are grey-brown with a wingspan of about 3-4 cm and a small silvery-white mark shaped like a figure 8 or a U on each forewing; they fly at night. Eggs are round, ridged and pale, laid singly on leaf undersides. Caterpillars are pale green with thin white lines along the sides, grow to about 3-4 cm, and have only two pairs of prolegs in the middle of the body plus a pair at the end, which gives the looping walk.

Signs in the crop, stage by stage

Crop stage	What you see
Young caterpillars	Small, irregular feeding patches on leaf undersides, leaving the upper surface as a thin window.
Older caterpillars	Large ragged holes in leaves; feeding in the heads of lettuce and cabbage; droppings between leaves.
Fruiting crops	Occasional shallow feeding on tomato fruit; heavy defoliation of cotton and soybean in outbreaks.

Life cycle of cabbage looper

Life cycle of Cabbage looper — diagram drawn by Laisha from the stages below. Durations depend on temperature.

Females lay several hundred eggs singly on the leaves of host plants. Caterpillars feed for two to four weeks through five or more instars and then spin a thin, loose silk cocoon on the underside of a leaf, where they pupate. Moths emerge after about one to two weeks, mate and lay eggs within days.

Stage	Duration	Notes
Egg	About 3-5 days	Laid singly on leaf undersides.
Caterpillar (usually 5 instars)	About 2-4 weeks	Older caterpillars cause most damage.
Pupa (in loose cocoon on leaves)	About 1-2 weeks	Not in the soil.
Adult moth	About 1-3 weeks	Night-flying; migrates.

Temperature

Egg to adult takes about 3-4 weeks in warm weather; it does not survive cold winters outdoors and does best around 25-30 °C.

Generations

Two to three generations in northern areas after migrants arrive, and up to seven or more in warm areas and greenhouses.

Conditions that favour it

Warm weather, large areas of host crops, migrant moth flights, greenhouses with year-round crops, and loss of natural enemies after broad-spectrum sprays.

Economic threshold level (ETL)

There is no single international threshold. Extension services set action levels by crop and stage, such as the percentage of plants infested in heading brassicas and lettuce, which are lower near harvest for fresh-market crops; check with your local extension service.

Thresholds are local. They depend on crop price, control cost, variety and natural-enemy activity, so use the figure your local extension service publishes where one exists.

Damage and yield loss from cabbage looper

Defoliation reduces yield in brassicas, lettuce and soybean, and contaminated or damaged heads are rejected by fresh markets; in greenhouses it damages vegetables and flowers.

Monitoring

Use pheromone traps to detect moth flights, then check plants for eggs and young caterpillars.
Inspect leaf undersides and heads weekly, counting caterpillars on a set number of plants.
Look for caterpillars that are sluggish, discoloured or hanging limp, which may be infected by virus, and for parasitised caterpillars.

How to control cabbage looper (integrated management)

Control works best as a sequence: prevent, monitor, then act only when a threshold or a risk forecast says so, using the least disruptive option that works.

Cultural control

Remove crop residues and weeds that host caterpillars after harvest; avoid planting new crops next to infested older ones.
Transplant healthy seedlings and keep a break between successive brassica or lettuce plantings in the same area, so that each new crop does not receive caterpillars from the last.

Mechanical and physical control

Insect netting on greenhouse vents and row covers in the field prevent egg laying.

Biological control

Natural enemies include egg parasitoids (Trichogramma), the polyembryonic wasp Copidosoma floridanum, tachinid flies and predators; a naturally occurring nucleopolyhedrovirus often causes outbreaks to collapse. Bacillus thuringiensis and virus products are used, although greenhouse populations resistant to Bt have been reported.

Host resistance

Some cabbage and collard varieties suffer less damage; resistance is partial.

Chemical control of cabbage looper — by mode-of-action group only

Laisha names chemical options only by their resistance-committee mode-of-action group (IRAC for insects, mites and nematodes, FRAC for fungi, oomycetes and bacteria, HRAC for weeds), never by active ingredient or product. What is registered differs by country and changes over time; the label and your local plant-protection authority decide what may be used, on which crop, at what rate and with what pre-harvest interval.

Sprays work best against young caterpillars; older caterpillars are harder to kill. Resistance to several groups is known. What is registered differs by country and changes over time; follow the label and your local plant-protection authority.

Scheme	Group	Mode of action	Notes
IRAC	11A	Microbial disruptors of insect midgut membranes (Bacillus thuringiensis)	Selective; rotate strains and groups.
IRAC	5	Nicotinic acetylcholine receptor allosteric modulators, site I (spinosyns)	Selective.
IRAC	18	Ecdysone receptor agonists (diacylhydrazines)	Selective; acts on caterpillars.
IRAC	28	Ryanodine receptor modulators (diamides)	Rotate with other groups.

Resistance management

Rotate groups between generations, avoid repeated use of Bt alone in greenhouses, and protect natural enemies.

Look-alikes and how to tell them apart

Cabbage white butterflies — Velvety green caterpillars that walk normally, with day-flying white butterflies.
Diamondback moth — Much smaller caterpillars that wriggle backward and drop on silk.
Beet armyworm — Caterpillars that walk normally, with a broad pale stripe along each side and egg masses covered in hairs.

Host range

More than 160 plants in many families, especially crucifers, lettuce, spinach, celery, tomato, potato, cucurbits, beans, soybean, cotton and greenhouse vegetables and flowers.

What is still uncertain

Migration patterns outside North America are less well documented.
The extent of Bt resistance in field populations is not well known.

Grow guides for its host crops

How to grow the crop well is the first line of defence. Laisha's free grow guides cover each crop from sowing to harvest:

How to grow Cabbage How to grow Cauliflower & broccoli How to grow Kale How to grow Lettuce How to grow Spinach How to grow Celery How to grow Tomato How to grow Cucumber How to grow Cotton How to grow Soybean How to grow Common bean

Not sure this is what you are seeing?Ask Laisha: describe the symptoms or send a photo, and get a reasoned first read with what to check next — for your crop, your stage and your region.Ask Laisha

Sources

Trichoplusia ni (cabbage looper) datasheet — CABI Compendium. https://doi.org/10.1079/cabicompendium.54832
Trichoplusia ni (TRIPNI) — EPPO Global Database. https://gd.eppo.int/taxon/TRIPNI
Cabbage looper, Trichoplusia ni (Hübner) (Insecta: Lepidoptera: Noctuidae) — UF/IFAS EDIS. https://doi.org/10.32473/edis-in273-1999
Cabbage looper: Cole Crops Pest Management Guidelines — UC IPM. https://ipm.ucanr.edu/agriculture/cole-crops/cabbage-looper

Written by Laisha from the sources above, in its own words. This page is general reference, not a prescription: confirm identification locally and follow the label and your plant-protection authority.