Shot hole of Tree nuts
Wilsonomyces carpophilus, Xanthomonas pruni, Blumeriella gaapi, Cercospora spp.
The shot hole fungus is notoriously more prevalent in wet years. This fungus requires water for all its activities, so periods of extended rainfall create a situation that favors shot hole disease epidemics.
The fungus can cause lesions on leaves and fruit, but most of the time it infects the leaves as they emerge from the leaf bud. Leaf infections lead to defoliation, which usually occurs in early spring. Shot hole infection of young fruit, shortly after they emerge from the jacket, can cause the fruit to drop. As fruits enlarge, shot hole infection results in a lesion, but the fruit no longer fall.