Bumps on roots
Clubroot is a soil-borne fungal disease that causes the yellowing, stunting, and wilting of cruciferous plants, especially cabbage. The clubroot diagnosis is confirmed by the presence of club-like galls (swellings) on infected plant roots. (resistant vs. susceptible) The disease is worse in acidic soils.
Remove weeds from the garden area and borders, rotate crops, clean up and discard all plant debris at the end of the season and incorporate 3.5 lbs. of hydrated lime per 100 sq. ft. of garden area prior to planting to maintain a soil pH of 7.2-7.4.