Pests
Symptoms You'll see ragged holes eaten in the leaves, green caterpillars on the plant, and little dark droppings. Some caterpillars loop up in the middle as they crawl.Ragged holes chewed through the leaves, with green caterpillars and dark frass on the foliage. Imported cabbageworms are velvety green; cabbage loopers move in a looping arch; diamondback larvae are small and wriggle when disturbed. Cause These are caterpillars that hatch from eggs laid by white butterflies and small moths. They love cabbage-family plants like kale and chew the leaves, which are the part you eat.The larvae of the imported cabbageworm, cabbage looper, and diamondback moth feed on brassica foliage; the adults are white or brownish butterflies and moths that lay eggs on the leaves. Because kale is harvested as leaves, even modest feeding damages the crop. Organic treatment Spray a product called Bt, which is safe and targets only caterpillars, or pick the caterpillars and eggs off by hand from under the leaves. Spray again after rain, since it washes off.Spray Bt (Bacillus thuringiensis) or spinosad, which target caterpillars, and hand-pick larvae and eggs from leaf undersides. Repeat after rain, since Bt breaks down. Prevention Cover plants with a light fabric row cover right after planting to keep the butterflies and moths from laying eggs. Clear away old cabbage-family plants, and watch for the first white butterflies as your signal to act.Use floating row cover from transplanting to exclude the egg-laying adults, clean up brassica debris that shelters pupae, and scout for the first white butterflies as a spray cue.
Symptoms You'll see clusters of tiny soft insects on the new growth and tucked into the curled leaves, often a waxy gray-green kind. Leaves curl and pucker, and there may be a sticky coating.Clusters of small soft-bodied insects on growing tips and leaf undersides; the waxy gray-green cabbage aphid is especially troublesome because it lodges in the crinkles and curls of kale leaves and is very hard to wash out at harvest. Cause Aphids are tiny insects that suck juice from the plant. They breed fast and hide deep in kale's crinkled leaves, where they are hard to wash out.Several aphid species, notably the cabbage aphid, suck sap from kale; they multiply quickly and their feeding distorts growth and contaminates the harvested leaves. Organic treatment Blast them off with a strong spray of water, or use insecticidal soap or neem oil, making sure to hit under the leaves and into the crinkles where they hide. Repeat every few days.Knock colonies off with a strong jet of water, or spray insecticidal soap or neem, covering leaf undersides and the leaf crinkles; repeat every few days. Curly-leaf varieties are hardest to clear, so catch infestations early. Prevention Welcome helpful bugs like ladybugs and lacewings that eat aphids, don't overdo the nitrogen fertilizer (lush growth attracts them), and check the new growth often.Encourage natural enemies like ladybugs and lacewings, avoid overfeeding nitrogen (which spurs the soft growth aphids favor), and inspect growing tips early so colonies do not lodge in the leaves.
Symptoms Lots of tiny round holes in the leaves of young plants, made by small dark beetles that jump away like fleas when you get close. Bad damage can stunt seedlings.Tiny round shot-hole pits chewed in the leaves of young plants; the small dark beetles jump like fleas when disturbed. Heavy feeding stunts or kills seedlings and scars the leaves of a leaf crop. Cause Flea beetles are small jumping beetles that chew on young cabbage-family leaves. They hurt seedlings most, because a tiny plant can't grow fast enough to recover.Flea beetles chew the foliage of young brassicas and are most damaging at the seedling stage; on kale they also leave cosmetic shot-holes in the harvested leaves. Organic treatment Cover young plants with a row cover, and if there are a lot of beetles, use a spray such as spinosad or a kaolin clay coating. The main goal is to get the seedlings big enough to handle it.Protect seedlings with row cover, and spray spinosad or apply kaolin clay if pressure is high; the goal is getting plants past the vulnerable seedling stage. Prevention Cover seedlings with row cover from the start, keep them strong with steady water and food so they grow past the damage, and pull nearby weeds in the cabbage family.Use row cover from sowing or transplanting, keep seedlings vigorous with even water and feeding so they grow through the damage, and clean up weedy brassica relatives nearby.
Symptoms New transplants wilt and grow badly or fall over. If you pull one up, you'll find small white maggots eating the roots. It's worst in cool, wet spring soil.Transplants wilt, grow poorly, and may collapse; pulling a plant reveals small white maggots tunneling in the roots and lower stem. Damage is worst in cool, wet spring soil. Cause A small fly lays eggs at the base of the plant, and the maggots that hatch burrow down and eat the roots. The fly is most active in cool spring weather.The larvae of the cabbage root fly tunnel into brassica roots; the adult lays eggs at the stem base, and the maggots feed on the roots below, sometimes killing young plants. Organic treatment Once the maggots are in the roots you can't save that plant, so pull and throw away the badly damaged ones. Put your effort into protecting the rest from new eggs.There is no effective rescue once maggots are in the roots; remove and destroy badly affected plants and protect the rest from further egg-laying. Prevention Put a small collar or disk around the base of each transplant to stop the fly from laying eggs there, or use a row cover. Don't plant into cold, soggy soil, and avoid spots where you grew cabbage-family plants last year.Place a collar or disk around the stem base at transplanting to block egg-laying, or use row cover; avoid planting into cold, wet soil and rotate away from where brassicas grew.
Symptoms Shield-shaped black-and-orange (or black-and-red) bugs on the leaves, which develop white or yellow spots, then brown and look tattered. It's mostly a warm-region problem and loves kale.Shield-shaped bugs up to about 3/8 inch, brightly black-and-yellow or black-and-red, feeding with piercing-sucking mouthparts that leave white stipples; affected leaves brown and look tattered, and heavy feeding wilts and deforms plants. A warm-region pest that prefers kale, mustard, and collards over other cole crops. Cause The harlequin bug is a colorful stink-bug relative that pierces the leaves and sucks the juices, leaving pale blotches. It strongly prefers cabbage-family plants like kale, mustard, and collards, especially in the South.The harlequin bug (Murgantia histrionica) is a brassica-specialist stink bug, most damaging in the southern United States, where it completes two to four generations a year and overwinters as an adult in debris and weeds. Organic treatment Search out and crush the bugs, their eggs (little barrel-shaped eggs in rows), and young ones by hand. Use a row cover to keep them off, pull out badly infested plants, and clear away weeds and old plants where they hide over winter.Hand-pick and crush adults, nymphs, and the barrel-shaped egg rows; exclude with floating row cover; remove heavily infested plants. Pyrethrins are permitted in organic production if pressure is severe. Prevention Clean up garden debris and cabbage-family weeds where the adults overwinter, use row cover, and consider a trap crop of mustard or an early kale planting to lure them away from the main crop, then destroy it.Eliminate overwintering sites by removing crop debris and crucifer weeds, use row cover, and deploy an early trap crop of mustard, kale, or rapeseed to divert overwintering adults, then destroy it before the main crop is set out.
Diseases
Symptoms Plants wilt in the afternoon, stay small and yellowish, and don't bounce back. If you dig one up, the roots are swollen into lumpy, club-shaped knobs.Plants wilt in the heat of the day, grow stunted and yellowed, and recover poorly; roots are swollen into distorted clubs and galls instead of normal fine roots. Cause A germ that lives in the soil infects the roots of cabbage-family plants and makes them swell, which stops the plant from taking up water and food. It stays in the soil for years.A soilborne organism (Plasmodiophora brassicae) infects brassica roots and causes the galls, which block water and nutrient uptake. It persists in soil for many years and spreads in contaminated soil and water. Organic treatment There's no cure once a plant has it, so pull and destroy infected plants. Adding lime to make the soil less acidic (closer to neutral) helps hold it back, and growing cabbage-family plants only rarely in that spot starves the germ out.There is no cure once plants are infected; remove and destroy them. Raising soil pH toward 7.0 or above with lime can suppress the disease, and long rotations starve it out over time. Prevention Don't grow kale or its cabbage-family relatives in the same spot more than once every 3 years, or longer if you've had clubroot. Keep the soil from being too acidic, improve drainage, and clean soil off your tools.Rotate brassicas on a cycle of at least 3 years, and longer where clubroot is known; keep soil pH up, improve drainage, and avoid moving infested soil on tools and boots.
Symptoms Yellow patches shaped like the letter V appear at the leaf edges, pointing inward, with black veins inside them. It can spread through the plant and rot the leaves you want to eat.Yellow, V-shaped lesions spread inward from the leaf margins, with the veins inside the V turning black; the disease moves through the vascular system and can blacken and rot the harvested leaves. Cause A bacteria that often comes in on infected seeds or transplants. It gets into the leaves and travels through the plant's veins, spreading fastest in warm, wet weather.A seedborne bacterium (Xanthomonas campestris) that enters through leaf pores and wounds and moves through the plant's veins; it spreads in warm, wet conditions and on infected seed or transplants. Organic treatment There's no real cure, so remove and destroy infected plants to keep it from spreading. Don't handle or brush against the plants while they're wet, because that spreads the bacteria.There is no effective cure; remove and destroy infected plants. Avoid working among plants when foliage is wet, since that moves the bacteria. Prevention Begin with clean, certified seed and healthy transplants, don't plant where cabbage-family crops grew recently, space plants for good airflow, and avoid overhead watering.Start with clean, certified seed and healthy transplants, rotate away from brassicas, give plants room for airflow, and avoid overhead watering and handling wet foliage.
Symptoms Pale yellow blotches on top of the leaves, with fuzzy grayish growth on the underside, mostly in cool, damp weather. Bad cases discolor the leaves.Pale yellow patches form on the upper leaf surface with a fuzzy gray-white growth underneath, mainly in cool, damp weather; severe infection discolors and downgrades the leaves. Cause A mold-like disease that loves cool, wet, humid weather and spreads through the air and water. Wet leaves and crowded plants make it worse.A fungus-like organism that thrives in cool, wet, humid conditions and spreads by spores in water and air; long leaf wetness and crowded plantings favor it. Kale's cool-season window overlaps the weather it likes. Organic treatment Open up the airflow so leaves can dry, remove the worst leaves, and use a copper spray if it's spreading. It's hard to stop once the weather stays damp.Improve airflow and let foliage dry, remove badly affected leaves, and apply a copper-based fungicide if pressure is high; the disease is hard to stop once humidity stays high. Prevention Space plants so air moves between them, water at the soil instead of from above, and pick resistant varieties if downy mildew is common where you live.Space plants for good air movement, water at the soil line rather than overhead, and choose resistant varieties where downy mildew is common.
Symptoms Small dark spots on the leaves that grow into round patches with concentric rings, like a tiny target. Bad cases make the leaves yellow and unusable.Small dark lesions enlarge into circular spots with characteristic concentric rings (a target-spot look) and a yellow halo; because the leaves are the crop, even moderate spotting reduces the harvest. Favored by warm, wet conditions. Cause A fungus that spreads in warm, wet weather and infects the leaves, leaving target-like spots. It's worse on stressed plants and in crowded, damp plantings.Fungi in the genus Alternaria (with Cercospora causing a similar leaf spot) infect brassica foliage, spreading by spores in wind and splashing water; infected seed, crop debris, and long leaf wetness drive it. Organic treatment Remove and destroy badly spotted leaves, improve airflow so leaves dry quickly, and use a copper spray if it spreads. Avoid wetting the leaves when you water.Remove and destroy spotted leaves and debris, improve airflow, avoid overhead watering, and apply a copper-based fungicide if pressure is high. Prevention Start with clean seed, rotate away from brassicas, space plants for airflow, water at the soil line, and keep plants healthy so they resist infection.Use clean, disease-free seed, rotate away from brassicas, space for airflow, water at the soil line, and clear crop debris that harbors spores.
