Common Kohlrabi Pests and Diseases and Natural Controls

Kohlrabi is a hardy, cool-season vegetable, but like all brassicas, it can fall victim to pests and diseases. With over 30 years of growing kohlrabi in California’s Central Valley and Sonoma Valley, I’ve learned that early detection and natural management strategies are the keys to healthy, productive plants. In this guide, I’ll share the most common threats and proven organic methods to control them.

Table of Contents

Common Kohlrabi Pests

1. Aphids

Symptoms: Curling or distorted leaves, sticky honeydew, clusters of small green, yellow, or black insects.
Natural Control: Spray with a strong stream of water, encourage ladybugs or lacewings, use insecticidal soap.
Experience Tip: Morning treatments are most effective, and repeated checks prevent outbreaks.

2. Cabbage Worms (Cabbage Loopers & Imported Cabbageworms)

Symptoms: Small holes in leaves, green droppings, visible caterpillars.
Natural Control: Handpick caterpillars, cover plants with row covers, or apply Bacillus thuringiensis (Bt) if infestations are severe.
Experience Tip: Covering seedlings immediately after transplanting drastically reduces egg-laying.

3. Flea Beetles

Symptoms: Tiny shot-hole damage on leaves, stunted seedlings.
Natural Control: Use row covers, sprinkle diatomaceous earth, and maintain healthy, well-amended soil.
Experience Tip: Flea beetle pressure is worst in early spring; planting transplants slightly later reduces damage.

4. Slugs and Snails

Symptoms: Irregular holes, slime trails on leaves, especially near soil level.
Natural Control: Handpick at night, use beer traps, or scatter crushed eggshells around plants.

Common Kohlrabi Diseases

1. Clubroot

Symptoms: Swollen, deformed roots, wilting, and stunted growth.
Natural Control: Rotate crops yearly, raise soil pH to 6.5–7 using lime, and plant resistant varieties.

2. Downy Mildew

Symptoms: Yellow spots on upper leaves, grayish mold on the underside.
Natural Control: Improve air circulation, avoid overhead watering, and space plants properly.

3. Black Rot

Symptoms: Yellow V-shaped lesions from leaf edges, black veins, stunted plants.
Natural Control: Remove infected leaves, rotate crops, and water at the soil level to keep leaves dry.

Preventive Care Tips

Start with healthy seedlings free of pests.
Keep plants spaced for good airflow.
Mulch to retain soil moisture and reduce weeds.
Inspect plants regularly—early detection makes natural control much easier.

My Experience

Even with decades of experience growing kohlrabi, pests and diseases are inevitable—but manageable. By combining observation, preventive care, and natural control methods, gardeners can maintain strong, healthy plants and enjoy crisp, flavorful kohlrabi bulbs throughout the season.

Kohlrabi Pests & Diseases Quick Reference

Pest / Disease	Symptoms	Natural Control	Experience Tip
Aphids	Curling leaves, sticky honeydew, clusters of small insects	Spray with water, introduce ladybugs or lacewings, use insecticidal soap	Morning treatments work best; check plants regularly to prevent outbreaks
Cabbage Worms (Loopers & Imported Cabbageworms)	Holes in leaves, green droppings, visible caterpillars	Handpick, row covers, Bacillus thuringiensis (Bt)	Cover seedlings immediately after transplanting to reduce egg-laying
Flea Beetles	Tiny shot-hole damage, stunted seedlings	Row covers, diatomaceous earth, maintain healthy soil	Plant slightly later or use transplants to reduce spring damage
Slugs & Snails	Irregular holes, slime trails on leaves	Handpick at night, beer traps, crushed eggshells	Elevated containers with barriers minimize damage
Clubroot	Swollen, deformed roots, wilting, stunted growth	Rotate crops, raise soil pH to 6.5–7, plant resistant varieties	Neutral/alkaline soil greatly reduces incidence
Downy Mildew	Yellow spots on top, gray fuzzy growth underneath	Improve air circulation, avoid overhead watering, space plants properly	Proper spacing prevents fungal buildup
Black Rot	Yellow V-shaped lesions, black veins, stunted plants	Remove infected leaves, rotate crops, water at soil level	Early removal of infected leaves prevents spread

💡 My Tip from Experience:
Frequent observation, preventive care, and early intervention are key to managing kohlrabi pests and diseases naturally.

Kohlrabi Growing Hub

Start here: The Ultimate Guide to Growing Kohlrabi: From Seed to Harvest

🌱 Planning & Varieties

Best Kohlrabi Varieties to Grow in Your Garden – Compare early, late, and specialty varieties for flavor, color, and growth speed.
When to Plant Kohlrabi: Seasonal Planting Guide – Spring, summer, and fall planting windows for cool, crisp bulbs.
Kohlrabi Companion Planting: Best and Worst Neighbors – Plants that boost growth or deter pests naturally.
Growing Kohlrabi in Containers and Small Spaces – Pot size, soil mix, and care for urban gardens.

🌿 Seed Starting & Transplanting

From seed to sturdy seedlings.

Kohlrabi Seed Starting Tips – Germination tips, soil temperature, and timing for successful strong plants.
How to Transplant Kohlrabi Seedlings Successfully – Hardening off, spacing, and planting depth for seedlings.
Kohlrabi Spacing and Layout for Maximum Yield – Row vs. raised bed spacing, companion planting considerations.

🌾 Care & Maintenance

Tips for strong growth and pest-free plants.