Two common bacterial leaf diseases in brassicas are bacterial leaf spot (Pseudomonas syringae pv. maculicola) and black rot (Xanthomonas campestris pv. campestris). Both affect a range of brassica crops. Pseudomonas syringae is primarily a leaf pathogen whereas Xanthomonas campestris systemically infects the plant.

 

Identification

Pseudomonas syringae pv. maculicola is typically seen as light brown-black spots with narrow to wide yellow halos. Xanthomonas campestris pv. campestris causes V-shaped lesions on the leaf edge where the veins turn black. Black internal stem staining also occurs. Infected leaves become yellow and die prematurely

 

 

Importance

Damage to leaves can be severe and result in reduced feed quality and quantity.

 

Spread

Both these bacterial pathogens can survive on crop debris in the soil and can be seed-borne. In addition, Pseudomonas syringae pv. maculicola can also survive on weeds. Warm, wet, windy conditions help disperse spores, which enter the host tissue through wounds or natural openings.

 

Prevention and management

Sow machine cleaned and certified seed to minimise infection, and allow at least a 3-year rotation following an outbreak using non-host crops like ryegrass.