Kale attracts a predictable lineup of insect pests, mostly caterpillars, aphids, and flea beetles. If you’re finding holes in your kale leaves, sticky residue, or tiny jumping insects, one of these culprits is almost certainly responsible. The good news is that all of them can be managed organically with a combination of physical barriers, natural sprays, and smart planting choices.
Cabbage Worms and Cabbage Loopers
These are the most common kale pests and the ones most likely behind those ragged holes in your leaves. Both are small green caterpillars that grow to about an inch long, and they look so similar that gardeners often confuse them. The easiest way to tell them apart is to watch how they move: cabbage loopers lack middle legs, so they arch their bodies into a loop as they crawl. Cabbage worms tend to be a darker green with faint yellow stripes and yellow heads.
Younger loopers feed from the undersides of leaves, while older ones chew large, irregular holes right through the foliage. You’ll also notice dark green droppings (frass) scattered on and around your plants. The damage is almost always concentrated on brassicas like kale, broccoli, cabbage, and cauliflower, so if your tomatoes next door are untouched, caterpillars are a strong bet.
Start by removing all damaged leaves and clearing debris from around the base of the plant. Check stems and leaf undersides carefully, pick off any caterpillars you find, and drop them into a bowl of soapy water. For larger infestations, a spray containing Bt (Bacillus thuringiensis) targets caterpillars specifically without harming beneficial insects. It works against cabbage worms, cabbage loopers, and diamondback moths, with a residual effectiveness of about five to seven days per application. Follow the label directions for your specific product, as dilution rates vary by brand.
Cabbage Aphids
Cabbage aphids are small, grey-green, soft-bodied insects covered in a white waxy coating. They cluster in dense colonies on the undersides of leaves and in the curled centers of kale plants, and once established, they’re difficult to wash off. A large enough colony can stunt your kale’s growth or kill the plant entirely.
For small infestations, a strong blast of water from a hose can knock aphids loose and is often enough to keep them in check. If they return, several organic sprays are effective: insecticidal soap, neem oil, horticultural oil, and capsaicin-based sprays are all approved for organic use. Insecticidal soap often requires several applications to fully control an outbreak. Kaolin clay, applied as a foliar spray, acts as a physical repellent that discourages aphids from landing in the first place.
One biological ally worth cultivating is the ladybug. Adult ladybugs eat up to 50 aphids per day, and their larvae are even more voracious, consuming over 300 aphids during development. Planting sweet alyssum near your kale draws ladybugs, lacewings, hoverflies, and parasitic wasps into your garden, all of which prey on aphids.
Flea Beetles
If your kale leaves are peppered with tiny round holes that look like someone went at them with a hole punch, you’re dealing with flea beetles. The crucifer flea beetle is the species that targets brassicas. Adults are tiny (roughly the size of a pinhead), shiny metallic blue-black, and jump when disturbed, thanks to enlarged hind legs. Their larvae live underground and feed on roots and root hairs, which can weaken plants from below while the adults chew the foliage above.
Flea beetles are especially dangerous to seedlings. A heavy infestation on young plants can kill them outright, and even moderate feeding on established kale causes stunting and stress. One cultural trick is timing your planting: putting brassica transplants out in mid to late July avoids the peak spring activity of adult flea beetles. Mustard planted nearby can serve as a trap crop, luring beetles away from your kale. Mulching around plants and keeping beds clean of debris also reduces flea beetle pressure.
Floating Row Covers: The Best Prevention
If you want to stop pest problems before they start, floating row covers are the single most effective organic tool for kale. A few yards of lightweight garden mesh or tulle draped over hoops creates a physical barrier that keeps caterpillar moths, aphid colonies, and flea beetles from ever reaching your plants.
Timing is critical. Install covers immediately when you seed or transplant your kale, before any pests are active in the area. If you wait until you see damage, eggs and larvae may already be present. Before transplanting, inspect seedlings carefully to make sure no insects are hiding in the soil or on the leaves. Rotate your crops by plant family each year so you’re not laying covers over soil where pest eggs were deposited the previous season.
To build them, install PVC, metal, or wire hoops along your bed, drape the cover over the frame, and secure it with binder clips. The edges need to be sealed completely: shovel soil or place heavy rocks every three feet along each side so nothing can crawl underneath and wind can’t lift the fabric. Allow extra room inside for the plants to grow upward. One thing to watch for with kale specifically is heat buildup. You may need to remove covers by mid-June in hot climates, as trapped heat can promote disease. Covers can also become unwieldy once kale gets tall.
Neem Oil and Insecticidal Soap
For active infestations where row covers aren’t an option, neem oil is a versatile organic spray that works against aphids, flea beetles, and soft-bodied insects. A standard recipe is one to two tablespoons of neem oil per gallon of water, mixed with about one tablespoon of pure castile soap (or one teaspoon of other liquid soaps) as an emulsifier. Start with the lower concentration and increase only if needed.
Always test spray first. Apply to a few leaves and wait 48 hours before treating the whole plant. Soap type and quantity are the most common causes of leaf burn, and results vary based on temperature, elevation, and plant variety. Neem oil breaks down on leaf surfaces after about five days, so plan to reapply every seven to fourteen days depending on pest pressure. Spray in early morning or late evening to avoid direct sunlight (which accelerates breakdown) and to minimize contact with pollinators.
Companion Plants That Deter Kale Pests
Strategic planting around your kale beds can reduce pest pressure significantly. Lemongrass has a citrusy aroma that masks the scent kale pests use to locate the crop, keeping aphids and flea beetles away. Hot peppers planted nearby serve a similar purpose, with a strong odor that repels insects and browsing animals, and they don’t compete with kale for nutrients.
Sweet alyssum is one of the most useful companion plants for any brassica garden. Its flowers attract lacewings, parasitic wasps, hoverflies, and ladybugs, all of which feed on the caterpillars and aphids that plague kale. It’s low-growing, so it won’t shade your kale, and it blooms continuously through the growing season. Tuck it along bed edges or between rows for the best effect.