Symptoms
Roots swell into large, knobbly club- or spindle-shaped galls, crippling water and nutrient uptake. Above ground, plants are stunted, wilt in the midday sun and recover at night, then yellow and fail to head. (A soil-borne protist, managed like a soil fungus.)
Prevention
Raise soil pH to about 7.2 with lime, which strongly suppresses the disease, and ensure good drainage. Rotate brassicas out for at least four years and never move infested soil on tools or transplants.
Treatment
Organic
Lime the soil well before planting and raise seedlings in clean, pathogen-free media. Remove and destroy galled roots — do not compost them.
Chemical (last resort)
There is no reliable curative fungicide; fluazinam soil treatment gives only partial suppression. Liming, long rotation and sanitation are the real controls — observe PHI if any product is used.
Affects 1 crop
Sources
MARDI Brassica Production Guide; DOA IPM Manual