Bacterial Spot
(bacterium - Xanthomonas campestris pv. pruni): Symptoms on leaves
are observed first as small, circular, or irregularly shaped, pale green lesions.
During early development, lesions almost always are concentrated near the leaf
tip. In advanced stages, the inner portion of the lesion falls out, giving the
leaf a "ragged" or "shot hole" appearance. Leaves heavily infected with bacterial
spot turn yellow and fall. Repeated infection can occur throughout the growing
season as long as the environment is favorable. Symptoms first appear on fruit
as small, olive brown, circular spots. Spots become slightly darker and depressed
as the bacteria develops. Lesions are scattered over the fruit surface and tiny
cracks develop in the center of the spots. Sometimes symptoms
resemble peach scab. Leaf infection is more common than fruit infections.
Apparently, more specific climatic conditions are necessary for fruit to become
infected. Chemical control during the season is difficult. Dormant sprays have
been somewhat effective if the spray is timed to protect stems during the fall
infection period. Copper containing fungicides should be applied just as the leaves
begin to shed. Resistant varieties are available. See fungicides.
