Occasionally reddish spots may be observed on the petioles and fruit. This disease is readily distinguished from drought injury by the presence of the tiny black spore producing bodies within the infected tissues. The fungus survives in infected leaf tissues throughout the winter. Where nursery stock is in close proximity it allows for the easy and rapid spread of the disease during wet weather. Once the leaves have been infected there is no cure.
Control depends on prevention.
Because dense foliage retards drying of the leaves, nursery stock should not be planted close together. Pruning of trees to obtain a more open growth habit will help decrease drying times. At the time of bud break during wet springs, fungicides may be applied to protect developing foliage. Repeat at 7-10 day intervals depending on the weather. If the foliage has been successfully protected against the spring ascospores, no conidia will be produced to continue the infection process and further sprays may be unnecessary.