Common Kale Pests and Diseases and Their Natural Controls

Kale is a hardy, nutrient-rich leafy green, but it’s not immune to pests and diseases. Even in the best conditions, insects and fungal problems can threaten your harvest. Fortunately, most issues can be managed with natural methods that keep your garden—and your food—safe and chemical-free. Below, you’ll find the most common kale pests and diseases, along with organic treatments and prevention tips.

Table of Contents

Common Kale Pests

Kale belongs to the brassica family, making it a favorite target of insects like cabbage worms, aphids, and flea beetles. These pests can damage leaves, stunt growth, and reduce yields.

1. Aphids

Symptoms: Clusters of tiny green, black, or gray insects on leaf undersides; leaves may curl or yellow.
Treatment: Spray with a strong jet of water to dislodge aphids. Apply insecticidal soap or neem oil if infestation persists. Encourage natural predators such as ladybugs.

2. Cabbage Worms & Loopers

Symptoms: Ragged holes in leaves; small green caterpillars or white cabbage moths nearby.
Treatment: Handpick caterpillars daily. Use floating row covers to block moths. Apply Bacillus thuringiensis (Bt), an organic biological control.

3. Flea Beetles

Symptoms: Tiny round holes in young leaves; plants may look “peppered” with damage.
Treatment: Cover seedlings with floating row covers. Dust with food-grade diatomaceous earth. Mulch heavily to deter adults.

4. Harlequin Bugs

Symptoms: Orange-and-black shield-shaped insects sucking plant sap; leaves may wilt or turn brown.
Treatment: Handpick and destroy bugs. Use neem oil or insecticidal soap for larger infestations.

5. Cutworms

Symptoms: Seedlings cut off at soil level.
Treatment: Place collars (cardboard or plastic) around plant bases. Keep beds free of weeds and debris where cutworms hide.

Common Kale Diseases

Diseases often occur when kale is stressed by poor airflow, wet foliage, or contaminated soil.

1. Downy Mildew

Symptoms: Yellow patches on upper leaf surfaces; fuzzy gray mold underneath.
Treatment: Space plants for airflow. Remove affected leaves. Spray with a natural fungicide such as copper or potassium bicarbonate.

2. Black Rot

Symptoms: Yellow V-shaped lesions starting at leaf edges; darkened veins.
Treatment: Remove infected plants immediately. Practice crop rotation. Use certified disease-free seed.

3. Clubroot

Symptoms: Stunted growth, wilted leaves, swollen or deformed roots.
Treatment: Remove and destroy infected plants. Raise soil pH above 7.0 with lime to deter the fungus.

4. Powdery Mildew

Symptoms: White powdery coating on leaves.
Treatment: Improve airflow and reduce overhead watering. Spray with a homemade solution of 1 tablespoon baking soda, 1 teaspoon mild soap, and 1 quart water.

Quick Reference Chart: Kale Pests & Diseases

Problem	Key Symptoms	Natural Treatments	Prevention Tips
Aphids	Leaf curling, sticky honeydew	Water spray, neem oil, insecticidal soap	Encourage ladybugs, avoid excess nitrogen
Cabbage Worms	Ragged leaf holes, green caterpillars	Handpick, Bt spray, row covers	Cover plants early, rotate crops
Flea Beetles	Tiny round holes in leaves	Row covers, diatomaceous earth, mulch	Remove weeds, keep soil moist
Harlequin Bugs	Orange-black bugs, wilting leaves	Handpick, neem oil, insecticidal soap	Remove plant debris, rotate crops
Cutworms	Seedlings cut at soil line	Plant collars, clear debris	Till soil before planting
Downy Mildew	Yellow spots, fuzzy gray underside	Remove leaves, copper spray	Space plants, water at soil level
Black Rot	V-shaped yellow lesions, dark veins	Remove infected plants	Use clean seed, rotate crops
Clubroot	Swollen roots, stunted growth	Remove plants, lime soil to pH 7+	Rotate crops, avoid infected soil
Powdery Mildew	White powdery leaf coating	Baking soda spray, improve airflow	Water early, avoid overhead watering

Natural Prevention Tips

Crop Rotation: Avoid planting kale or other brassicas in the same bed for at least three years.
Healthy Soil: Add compost to promote strong plants that resist pests and disease.
Companion Planting: Grow kale near aromatic herbs like dill, mint, or rosemary to deter insects.
Regular Inspection: Check plants daily and treat problems early before they spread.

Final Thoughts

Growing kale organically requires vigilance, but natural solutions are effective and safe for your garden ecosystem. By maintaining healthy soil, practicing crop rotation, and using preventive measures, you can enjoy a steady harvest of clean, crisp kale leaves.