Symptoms do not become obvious until typical knotted swellings form on the roots. The first above ground symptom of disease is usually wilting, particularly during hot dry weather. Severely diseased plants are generally stunted and the foliage may be different in colour from healthy plants. Crop losses are most severe for crops planted between October and April. The disease rarely affects winter sown crops in southern Australia.
Infected roots contain millions of fungal spores.
After the roots decay, these spores are released into the soil where they can remain alive but resting for up to twenty years. The fungus can be spread on or in anything that may carry contaminated soil from place to place. Farm machinery, boots, animals, infected transplants, contaminated irrigation water and surface flood water are all important means of spread. If growing on transplantsIsolate seedbed, maintain free of cruciferous weeds and avoid contaminating the area with diseased soil or water. In the field Rotate cruciferous Asian vegetables with non cruciferous crops as often as practical.