Diseases of cole crops (
Black rot
Black rot is caused by the bacterium, Xanthomonas campestris. The bacterium is systemic in the plant and is seed borne. It attacks only crucifers, and although it is a major pathogen in wet, humid climates, it occurs in Arizona only when introduced on seed or transplants. Once introduced, the pathogen spreads rapidly and disease can be severe under conditions created by abnormally high rainfall or overhead irrigation (photo 1). The bacterium survives in infested root and stem tissue.
The disease is named for the vascular discoloration in stem, root and leaf tissue. Heads of cauliflower and cabbage become discolored. Wedged shaped marginal leaf yellowing is usually the first symptom (photo 2), but plants also may be stunted and wilted.
Disease can be controlled by using clean seed and transplants
that are certified to be disease free by the grower or supplier.
Infested fields should be plowed well, rotated to crops other than crucifers
for at least two years and kept free of cruciferous weeds.
1 
2 
February 10, 2003