Caterpillars on kale are usually imported cabbageworms, cabbage loopers or diamondback moth larvae. Hand-pick them every 2 to 3 days and crush the eggs under the leaves. Add Bt only if counts stay above 2 or 3 per plant, while larvae are under 1/2 inch, then cover the next planting with fine mesh.
Kale is supposed to be the easy crop. Then one week the leaves look like lace and there are green pellets in every fold.
Caterpillars on kale are predictable, which is good news. They hatch from eggs laid on the leaves, they leave clear signs, and a few quick checks tell you whether to pick, use a targeted spray or simply cover the next planting.
Before treating anything, note what the caterpillar looks like, how long it is, where the holes are and whether there are eggs. The 11 clues that follow turn each of those into a decision.
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11 clues that explain caterpillars on kale
1. Remove only confirmed damage
Kale can lose a fair share of its leaf area and still keep producing, as long as the center bud is intact. Pick the caterpillars, then remove only leaves that are mostly skeleton or soiled with droppings.
Leaves with a few holes are still food. Rinse them well and use them. Stripping every holed leaf weakens the plant more than the caterpillars did, especially on a young plant with fewer than 8 leaves.
2. Check every treatment label
The two common targeted options are Bt (Bacillus thuringiensis var. kurstaki) and spinosad. Bt only affects caterpillars that eat it and works best on small larvae under about 1/2 inch. It breaks down in sunlight within a few days, so labels usually call for repeats every 5 to 7 days while caterpillars are active.
Spinosad is toxic to bees until the spray dries, so apply it in the evening when flowering plants nearby are not being visited. Check the label for kale or leafy brassicas and its pre-harvest interval.
No leafy greens on the label? Then it doesn’t go on your kale.
3. Escalate a worsening case
If you find more than 2 or 3 caterpillars per plant after 2 rounds of hand-picking a week apart, hand-picking alone is losing. Add Bt at that point, timed for when eggs are hatching and larvae are still small.
If the growing center of young plants is being eaten out, act within a day or two. Kale that loses its bud stops making new leaves, and no treatment brings that back.
4. Prevent kale caterpillars from returning
Nothing prevents them as reliably as a physical barrier. Floating row cover or fine insect mesh laid over hoops right at planting keeps the white butterflies and moths from laying eggs. Kale does not need pollinators to produce leaves, so it can stay covered all season.
Seal the edges with soil, boards or bags of sand. A cover put on after eggs are laid traps caterpillars inside, so check plants carefully first, and leave enough slack to lift one side for harvest every week.
5. Confirm the kale caterpillar pattern
The four common species are easy enough to tell apart. Imported cabbageworms are velvety green, up to about 1 1/4 inches, with a faint yellow stripe, and chew large ragged holes. Cabbage loopers are pale green with white side lines, move by arching their back, and reach about 1 1/2 inches.
Diamondback moth larvae are tiny, about 1/3 inch, wiggle hard when touched and drop on a silk thread. They often scrape the leaf, leaving clear “windowpanes” of thin tissue rather than full holes. Cross-striped cabbageworms, bluish gray with black bands, feed in groups and show up mostly in southern states.
6. Compare new and old growth
Cabbageworms and loopers tend to work through the larger outer leaves and the center, while diamondback larvae often favor the young inner leaves and growing tip. If the holes are mostly in the newest leaves of a small plant, move faster.
Old lower leaves that are yellow but not chewed are not a caterpillar problem. That is usually age or hungry soil, much like cucumber leaves turning yellow from the bottom up, and the fix is feeding, not spraying.
7. Inspect leaves, stems and soil
Turn over 10 leaves per plant. Imported cabbageworm eggs are single, pale yellow and bullet-shaped, about 1/16 inch tall. Looper eggs are single, whitish and dome-shaped. A 10x hand lens makes both easy to spot.
Dark green pellets (frass) in the leaf axils and on the soil below mean caterpillars are feeding above, even if you cannot see them. Fresh, moist frass means they are still there; dry, faded frass may be days old.
8. Check moisture before treating
Kale wants about 1 to 1 1/2 inches of water a week. The RHS kale growing guide covers watering and feeding through the season. Push a moisture meter or finger 2 inches into the soil before spraying. A wilting, dry plant scorches more easily from sprays, so water first and treat the next evening.
Water also decides how fast kale bounces back. A well-watered plant replaces lost leaves within 1 to 2 weeks in mild weather; a drought-stressed one sits still, and the caterpillar damage looks worse than it is.
9. Review the last care change
Outbreaks often line up with a change made a few weeks earlier: removing the row cover once plants looked big enough, adding new transplants from a garden center, or feeding heavily with nitrogen, which produces soft, lush leaves caterpillars favor.
Rich, unfinished compost can push that same soft growth, and common compost problems explain how to tell when compost is ready. If nothing changed, look to the season instead.
10. Match the caterpillars to recent weather
Cabbage white butterflies fly on warm, sunny days from spring through fall, and numbers usually build through mid to late summer as generations overlap. A sunny week with white butterflies circling the bed is your warning that eggs are coming.
Pressure drops in cool fall weather and stops after a few hard frosts, which is one reason fall kale is often cleaner. Heavy rain can knock small larvae off leaves, so recheck 1 to 2 days after a storm before deciding to spray.
11. Separate pest evidence from plant stress
Not every hole is a caterpillar.
Tiny round pinholes less than 1/8 inch across, especially on young plants in spring, are flea beetles. Ragged holes with slime trails and no frass are slugs. Curled, sticky leaves with no holes at all are aphids.
Seedlings started indoors sometimes show weak growth from soggy trays rather than any chewing pest; a yellow sticky card catches adult gnats within 2 to 3 days, and fungus gnats on seedlings explains what that means for young brassicas.
Which caterpillar is eating your kale?
The larva’s color, size and the way it moves tell you which caterpillar is eating your kale. Give it 7 days of looking before you spray: check the same 5 plants every other morning and write down what you find. The University of Minnesota Extension notes on cole crop caterpillars describe how to tell the main species apart and why scouting comes before spraying.
| What you find | What it points to |
|---|---|
| Single yellow eggs, velvety green larvae | Imported cabbageworm: pick, then Bt if numbers climb |
| Larvae that loop as they move | Cabbage looper: Bt works best while they are small |
| Tiny wiggling larvae, windowpane damage | Diamondback moth: check the growing tip daily |
| Groups of striped larvae on one leaf | Cross-striped cabbageworm: remove the whole leaf |
| Holes but no larvae, eggs or frass | Look at slugs or flea beetles instead |
Count caterpillars per plant and note their length. Larvae under 1/2 inch respond well to Bt; those over 1 inch are close to finishing and are better picked by hand.
Quick rule: keep hand-picking until you find more than 2 or 3 caterpillars per plant after 2 rounds a week apart. Then add Bt, which works best on larvae under 1/2 inch.
Is it caterpillars or heat stress?
If the holes are few but the plant is slow and bitter, heat is often the bigger problem. Heat stress makes kale tough, bitter and slow, and caterpillar damage on a slow plant looks dramatic because nothing replaces the lost leaves. Kale grows best in cool weather, roughly 60 to 70°F, so midsummer damage in zones 7 and warmer often comes with heat stress on top.
Yellow, V-shaped patches spreading in from the leaf edge with dark veins point to black rot, a bacterial disease, not caterpillars. Pull and bag those plants, and do not grow brassicas in that spot for 2 to 3 years.
How do you get rid of caterpillars on kale?
Get rid of caterpillars on kale by hand-picking first and adding Bt only if numbers hold. Start with hand-picking every 2 to 3 days for 1 week, and crush eggs on the leaf undersides as you go. If counts drop below 1 caterpillar per plant, keep going and add nothing.
If counts hold or climb, add Bt on a dry evening, covering the leaf undersides, and repeat per the label. Keep picking alongside it and keep the notes, so you can see whether new holes slow within 3 to 5 days.
Leave paper wasps alone and look for small cocoons or parasitized, swollen caterpillars. Those natural enemies kill a lot of cabbage caterpillars for free, and broad-spectrum insecticides kill them too. A short list of beneficial garden insects helps you recognize which ones to spare.
When to ask your county Extension office
Ask a county extension office or Master Gardener help desk if caterpillars keep surviving correctly timed Bt treatments, if you find a species that does not match the common four, or if leaves show spreading yellow or black patches. Bring a few larvae in a sealed jar, a damaged leaf and your 7-day notes.
Key takeaways
- Most caterpillars on kale are imported cabbageworms, cabbage loopers or diamondback larvae, and each looks different at 1/3 to 1 1/2 inches long.
- Check the growing center first, since a plant that loses its bud stops making leaves.
- Hand-pick every 2 to 3 days for a week and crush the yellow eggs under 10 leaves per plant.
- Use Bt only if counts stay above 2 or 3 per plant, and repeat it every 5 to 7 days per the label.
- Row cover or fine mesh laid at planting keeps butterflies from laying eggs all season.
FAQ
What usually causes caterpillars on kale?
White cabbage butterflies and small moths lay eggs on the leaves, and the hatching larvae feed for about 2 to 3 weeks. Uncovered plants on sunny summer days get the most eggs. Turn over 10 leaves per plant to see how many eggs are waiting.
How do I tell which caterpillars are on my kale?
Look at the larva and how it moves. Velvety green and slow is a cabbageworm; arching its back is a looper; tiny and wriggling is a diamondback larva. Measure one against a ruler, since size decides whether Bt will still work.
What should I check first when I notice caterpillars on kale?
Check the growing center of each plant first, because losing it ends leaf production. Then count caterpillars on 5 plants and look for green frass. If centers are intact and counts are low, hand-picking is enough to start.
Will caterpillars on kale go away on their own?
Partly. Wasps, birds and parasites take many caterpillars, and pressure drops after a few hard frosts in fall. In midsummer, with butterflies laying daily, numbers usually keep rising unless you pick or cover the plants.
How do I keep caterpillars off kale for good?
Cover kale with row cover or fine mesh on hoops right at planting and seal the edges. Check new transplants for eggs before they go in. Planting for fall harvest, timed so plants mature around your first frost, also avoids the heaviest summer pressure.
Should I pull a kale plant eaten by caterpillars?
Replace a plant if its growing center has been eaten out, or if it shows signs of black rot. A plant with holed outer leaves but a healthy center will regrow. If there are fewer than 6 to 8 weeks before your first fall frost, resow a fast baby kale instead of full-size plants.
Final thoughts
Caterpillars on kale come down to timing. Find them while they are small, pick what you can and save Bt for when numbers climb.
This evening, turn over 10 leaves on 5 plants and write down the egg and caterpillar counts. Then plan the next sowing under cover with this walkthrough of insect mesh for a vegetable garden, so the butterflies never land.
Last update on 2026-10-01 / Affiliate links / Images from Amazon Product Advertising API