Bot Rot (fungus - Botryosphaeria ribis): The fungus infects woody tissues and fruits. Wounded apple wood is very susceptible. On limbs and twigs, infection is visible in July. It appears as a blister on the infected limbs. At maturity the blister ruptures and a liquid spreads over the limbs. The wet area then becomes sunken with a dark colored appearance. The spot spreads into the cambium where it enlarges in concentric rings until fall. Lesions stop enlarging in the fall and cracks appear along the edge of the spot. It may or may not begin growth next spring.

Fruit infection is observed as small reddish-brown spots. These eventually coalesce, causing a soft rot to occur. As the decay develops, the lesion turns light brown to dark brown and is covered with beads of exudate on the surface of the decayed fruit.

The fungus overwinters in live and dead limbs. In the spring, an ooze is formed which is spread over the tree. Mature and ripened fruit are very susceptible. The disease develops at temperatures of 75 degrees F or above. Botryosphaeria infection is encouraged by any condition which reduces tree vigor such as drought, winter injury, and low nutrition. Jagged pruning wounds and grafting sites are sometimes invaded. Pruning out the decayed areas and a thorough spray program will significantly reduce losses to this disease.

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