Clubroot
Plasmodiophora brassicae
Overview
A soil-borne disease of brassica crops caused by a protist, producing dramatic swelling and distortion of roots that interfere with water and nutrient uptake. Resting spores can persist in soil for 20+ years.
Symptoms
Swollen, distorted, club-shaped roots. Wilting during hot days despite adequate soil moisture. Yellowing and stunting of above-ground growth. Premature bolting. Plants may collapse in severe cases.
Environmental Conditions
Humid
Prevention
Lime soil to raise pH above 7.2. Rotate brassicas on a 7+ year cycle. Use resistant varieties. Ensure good drainage. Use clean transplants. Avoid moving infested soil.
Management
No effective chemical cure. Raise soil pH with lime. Remove and destroy infected plants. Improve drainage. Long crop rotation. Some biological controls (Bacillus) show promise.