I recently visited a small Chatham County blueberry farm and found some of the bushes were infected with Exobasidium, a fungus that causes leaf and fruit spots. Infected fruit have spots that don't ripen normally.

The disease is not common on large commercial blueberry farms where growers spray preventive fungicides. According to NC State University Specialist Bill Cline, Exobasidium can be severe one year but almost totally absent the next, so small growers may want to adopt a "wait and see" approach to spraying. Low levels of the disease don't require intervention...but if the problem becomes severe then a grower can initiate a spray program the following season.

When the disease is present, it tends to be worse in areas where the bushes are densely planted, so pruning to increase air flow and sunlight penetration can help reduce the severity.

Read the article on Exobasidium Leaf and Fruit Spot by NC State University Blueberry Specialist Bill Cline. The article discusses control measures.