Cabbage Worms on Kale: Damage Signs and IPM Control Guide
By Paul Smith, pemdasgarden.com
Kale is picked leaf by leaf over a long season, so caterpillar damage shows up right where you harvest. If your kale leaves have ragged holes, chewed edges, and small dark green pellets tucked in the folds, this looks most like cabbageworm feeding, but cabbage looper, diamondback moth larva, or flea beetle damage is also possible, so check the worm itself before you choose a control step. This guide covers kale only: why kale is hit hard, what damage looks like on curly and flat types, how to inspect a plant in five minutes, and how to respond in IPM order.
Why kale is hit harder than heading brassicas
Cabbage forms a head that wraps and partly shields its inner leaves, while kale keeps its leaves open to egg-laying butterflies all season. Every new leaf is exposed, and because gardeners harvest kale repeatedly rather than cutting one head, a small caterpillar population can spoil pickings week after week. The butterflies that lay the eggs fly during the day and place tiny pale yellow eggs singly on leaf undersides, so a bed that looked clean on Monday can carry fresh eggs by the weekend (UC IPM, University of Maryland Extension).
Kale also stays in the ground for months in many gardens, which gives several caterpillar generations time to build. In mild-winter areas, cabbageworm activity can run through much of the year, while in colder climates it typically runs from spring into early autumn, so scouting dates shift with local conditions (UC IPM, University of Illinois Extension). Planting and harvest times vary by climate region, so set your row-cover and inspection calendar by what you see in your own bed and by your county extension office, not by a single national date.
What cabbage worm damage looks like on kale
Start with the leaf blade. Feeding begins as small smooth holes that grow into large ragged, irregular holes, and heavy feeding can strip a leaf down to its veins. On kale, that damage matters more than on a heading crop because there is no wrapper leaf to peel away: the holed leaf is the leaf you planned to eat. Check the leaf ribs and midribs next. Imported cabbageworm larvae often rest sluggishly along midribs, where their green color blends in, and you may find dark green frass pellets sitting on the blade or caught in the folds below the feeding site (UC IPM).
Then check the center of the plant. Young leaves at the growing point are tender and heavily fed on, and damage there slows regrowth after picking. A plant that keeps losing its newest leaves will look stunted even if the older outer leaves still look passable. If whole young plants are cut at the soil line overnight instead of showing leaf holes, that pattern points away from cabbageworms and toward cutworms; our cabbage worm identification and control guide explains the broader caterpillar set, and our holes in cabbage leaves guide shows how hole shape narrows the suspect list.
Kale types: where worms hide and how hard they are to check
Not all kale hides caterpillars equally well. The table below is an original checking guide compiled for this article from the leaf shapes gardeners actually inspect, ranked by how easy it is to miss a small green larva. Use it to decide where to spend your five minutes.
| Kale type | Leaf shape | Where worms hide | Checking difficulty |
|---|---|---|---|
| Curly kale | Tightly ruffled, curled edges | Inside the ruffles and along folded midribs | Hardest: unfold each ruffle and check the underside |
| Lacinato (dinosaur) kale | Long, narrow, puckered and blistered surface | In the puckered creases and near the central rib | Hard: run a finger along each crease |
| Red Russian kale | Flatter, oak-leaf shaped, frilled edges | On the underside near veins and stem joints | Moderate: underside scan usually finds them |
| Flat-leaf kale types | Broad, fairly smooth blades | On the underside and along the midrib | Easiest: holes and frass show plainly |
When you choose what to grow next, leaf shape is a practical factor alongside flavor and yield. If checking curly types has cost you harvests, a flatter type is easier to scout, and re-sowing a mix lets you compare them in your own bed. Browse our kale seeds collection when you plan that next sowing, and keep a row cover ready for the new plants from day one.
The 5-minute kale inspection walkthrough
Walk the row once a week, and more often when you see white butterflies around the bed. Work plant by plant, oldest leaves first, and carry a small container for anything you pick off.
- Scan from above. Look for fresh ragged holes, chewed leaf edges, and dark green pellets. Mark the worst plant and start there.
- Flip the worst leaves. Turn each damaged leaf over and look for tiny pale yellow eggs standing singly on the underside. Remove any you find before they hatch (University of Maryland Extension).
- Unfold the curls. On curly kale, gently open each ruffle and check the folds. On lacinato types, check the puckered creases along the rib. Most missed worms are found in this step.
- Check the ribs and center. Look along the midribs for sluggish, smooth green larvae, then check the young leaves at the growing point for fresh feeding.
- Do the movement test. Touch the suspect larva. A slow, smooth green caterpillar that stays put points toward imported cabbageworm; one that arches its back into a loop as it moves points toward cabbage looper; a small larva that thrashes or drops on a silk thread points toward diamondback moth larva (University of Connecticut IPM).
- Decide on the spot. A few larvae on a few plants: pick them off now and recheck in a few days. Eggs and larvae across the row: put row covers on new sowings at once and move to the IPM steps below.
The hand lens in the photo above is the tool that turns a guess into a check: at 10x magnification the smooth skin of an imported cabbageworm, the looping movement of a looper, and the small size of a diamondback moth larva are all much easier to separate. A lens, a bucket, and row cover fabric are the core of the gardening tools kit for this job. If you are unsure after the movement test, treat the ID as open and recheck in two days rather than acting on a single sighting.
Cabbageworm vs. cabbage looper on kale: comparison
These two are the pair most often confused on kale, because both are green, both chew ragged holes, and both leave similar-looking damage. Compare the larva, not just the holes.
| Trait | Imported cabbageworm | Cabbage looper |
|---|---|---|
| Larva appearance | Smooth, velvety green, no stripes, up to about 1 inch | Pale green, up to about 1.5 inches, with faint stripes |
| Movement | Sluggish; rests along midribs | Arches its back into a loop as it walks |
| Adult | Small white daytime butterfly with dark wingtips | Brownish-grey night-flying moth |
| Eggs | Tiny pale yellow eggs laid singly on leaf undersides | Small pale eggs laid singly, often on leaf undersides |
| Kale damage pattern | Large ragged holes plus dark green frass pellets | Ragged holes, often with more edge feeding |
Verdict: choose imported cabbageworm if the larva is smooth, uniformly green, and sluggish and you also see white butterflies by day. Choose cabbage looper if the larva loops as it moves and you rarely see a daytime butterfly. If the holes are tiny windowpanes where only a thin leaf membrane remains, choose diamondback moth larva instead, and if the damage is many tiny shot-holes rather than ragged chewing, suspect flea beetles. Our green caterpillars on vegetables guide walks through the wider look-alike set when the larva does not match either row here.
IPM step 1: prevention first
Prevention is the first and cheapest step, and on kale it works better than on any heading brassica because there is no head to clean up later. Put lightweight floating row covers over transplants at planting time, before butterflies appear, and keep the edges sealed so butterflies cannot slip underneath (Utah State University Extension, University of Maryland Extension). Covers stay on all season for kale, since kale does not need insect pollination to produce leaves.
Rotate brassicas to a new bed each year and clear plant debris at season's end, since the pest overwinters as pupae in debris (University of Illinois Extension). Plant early where your climate allows, or pick fast-maturing types, so harvest comes before populations peak. When you start the next round, sow from seed so you control the timing: our kale seeds collection covers curly, lacinato, and flat types, and the same rotation bed can carry broccoli seeds or cauliflower seeds in a later slot.
IPM step 2: cultural and mechanical control
Handpicking is the most reliable immediate control for a home kale patch (UC IPM). Pick larvae off by hand, crush eggs on leaf undersides, and drop what you find into soapy water. A strong jet of water dislodges larvae as well, and heavy rain knocks populations down naturally (University of Connecticut IPM). Check leaf undersides weekly, and check curly types fold by fold, since a quick glance from above misses most larvae on ruffled leaves.
Succession sowing is a cultural control that fits kale well: start a fresh small batch every few weeks under row cover, and pull a badly hit older plant rather than fighting a heavy population on it for the rest of the season. Healthy, well-watered plants regrow after picking better than stressed ones, so keep watering even while you treat.
IPM step 3: biological control
Biological controls target caterpillars without broad-spectrum chemistry. The bacterium Bacillus thuringiensis var. kurstaki (Bt) is listed by UC IPM and Utah State University Extension as very effective against imported cabbageworm, especially on young caterpillars, and it must be eaten by actively feeding larvae to work. Apply in the evening, cover leaf undersides as well as tops, and follow label directions exactly.
Free help also arrives on its own: parasitic wasps such as Cotesia and tachinid flies attack the larvae and pupae, and generalist predators including ground beetles, spiders, lacewing larvae, lady beetles, and birds reduce larval numbers (University of Connecticut IPM, Utah State University Extension). Protecting those allies is one reason IPM puts broad-spectrum sprays last: a spray that clears the worms and their predators together often leaves the next generation unchecked.
IPM step 4: least-toxic options last
Only after prevention, cultural, mechanical, and biological steps should other sprays enter the picture, and then the least-toxic options first. Spinosad, the active ingredient, is listed by UC IPM and Utah State University Extension as very effective against imported cabbageworm larvae. Use it as a spot treatment when young larvae are present, apply in the evening to reduce contact with daytime pollinators, and follow the product label directions exactly. No spray works every time, and timing plus coverage matter more than the product choice. Avoid broad-spectrum insecticides that kill the beneficial wasps, beetles, and pollinators doing free pest control for you (University of Maryland Extension).
Harvesting and washing kale after damage
Do not write off a whole plant for a few holed leaves. Pick the cleanest outer leaves first, discard leaves that are heavily tunneled or soiled with frass, and leave the growing point intact so the plant can regrow. At the sink, rinse each leaf under running water, open the curls, and rub the folds where pellets and small larvae hide. A short soak in a bowl of cool water, followed by a second rinse, dislodges most of what a first rinse misses. Inspect the washed leaves once more before cooking or eating them raw, and discard any leaf you cannot clean to your satisfaction.
If damage keeps returning to the same plants, the fix is usually timing, not a stronger spray: covers that went on late, a missed egg check, or a neighboring brassica bed feeding the next generation. Fix the cover seal, restart the weekly check, and consider a fresh sowing under cover while the old plants recover.
Frequently asked questions
Can I still eat kale with cabbage worm holes?
Yes, if the leaf itself is sound. Discard heavily tunneled or frass-soiled leaves, wash the rest fold by fold under running water, and inspect again after washing. Leaves you cannot clean well should be composted, not eaten.
Why is my curly kale hit worse than my flat kale?
Curly ruffles hide larvae and eggs from a quick glance, so populations build unnoticed, while flat leaves show holes and frass plainly. That is a checking problem as much as a preference problem: unfold the ruffles on every inspection and the gap narrows.
Do row covers work on kale?
They are the single most recommended prevention in the extension sources behind this article, but only if the cover goes on at transplant time, before butterflies lay eggs. A cover placed after eggs are already on the leaves protects the larvae inside. Seal the edges and leave the cover on, since kale leaves need no insect pollination.
How do I tell a cabbageworm from a cabbage looper on kale?
Use the movement test in the inspection walkthrough above: smooth, sluggish, and green points toward imported cabbageworm, while arching into a loop as it moves points toward cabbage looper. The comparison table gives the full verdict for each case.
Will Bt harm bees on my kale?
Bt var. kurstaki affects caterpillars that eat treated foliage and is not a broad-spectrum insecticide (UC IPM). Still, apply in the evening, keep spray off blooming flowers and non-target plants, and never spray while pollinators are actively foraging.
When should I give up on a kale plant?
Pull a plant when its growing point is repeatedly stripped, regrowth has stalled, and most leaves are tunneled or soiled despite weekly checks. Replace it with a fresh sowing under row cover rather than continuing to treat a plant that can no longer produce clean leaves.
Sources
- UC IPM — Imported cabbageworm (identification, life cycle, damage, solutions): ipm.ucanr.edu/home-and-landscape/imported-cabbageworm/
- University of Minnesota Extension — Cabbageworms: extension.umn.edu/yard-and-garden-insects/cabbageworms
- Utah State University Extension — Imported cabbageworm (management, row covers, Bt, spinosad): extension.usu.edu/vegetableguide/leafy-greens/imported-cabbageworm
- University of Maryland Extension — Imported cabbageworm on vegetables (monitoring, prevention, control): extension.umd.edu/resource/imported-cabbageworm-vegetables
- University of Connecticut IPM — Caterpillar pests of cole crops (natural enemies, cultural controls): ipm.cahnr.uconn.edu/cole-crop-worms-caterpillar-pests/
- University of Illinois Extension — Imported cabbageworm (life cycle, generations, management): web.extension.illinois.edu/hortanswers/detailProblem.cfm
- University of Massachusetts Extension — Imported cabbageworm fact sheet: ag.umass.edu/vegetable/fact-sheets/imported-cabbageworm
- Michigan State University Extension — Cabbageworm: canr.msu.edu/resources/cabbageworm
Ready to re-sow kale with a plan? Start from seed, cover from day one, and check fold by fold each week: shop our kale seeds collection, plus broccoli seeds and cauliflower seeds for the rotation bed.
