Bacterial Spot symptoms on Plum
Bacterial Spot (bacterium
- Xanthomonas campestris pv. pruni): Symptoms are observed first as small,
irregularly shaped lesions. The spots are pale green in contrast to the dark green
surrounding tissue. In advanced stages, angular lesions are formed, surrounded
by a halo of lighter colored tissue. The inner portion of the lesion turns black
and drops out. This gives the leaf a "ragged" or "shot hole" appearance. Leaves
heavily infected with bacterial spot turn yellow and fall. Leaf spots are concentrated
toward the distal end of the leaf. Fruit infection is not as common as foliage
infection. When it occurs, small spots develop and gum may flow from these spots.
Highly susceptible varieties like Methley and Santa Rosa are more likely to have
fruit infections than Morris, Bruce or Ozark Premier. The bacterium overwinters
on infected twigs. Chemical control has not been highly
effective. Early and late dormant copper sprays will aid in control. Optimum nutrition
is also important.
January, 1995
