Bacterial Leaf Spot or Xanthomonas causes small brown angular to circular spots with yellow halos. In some plants these bacteria can cause dead spots in foliage and or fruit and sometimes cankers in stems. As with most bacterial diseases, the pathogen, Xanthomonas campestris pv. vitians, is highly dependent on wet, cool conditions for infection and disease development. Symptoms develop only if rain or sprinkler irrigation is present. Splashing water from these sources moves the bacteria from plant to plant. The pathogen is seedborne. In the case of seedlings grown as transplants, the pathogen may become established on plants during the greenhouse phase of growth. The bacterium can also survive on undecomposed plant residue and be spread to subsequent crops.