Alternaria Leaf Spot of Blueberry

Alternaria Leaf Spot (Alternaria tenuissima) occurs primarily in the spring during prolonged periods of cool wet weather, when spores are produced in abundance. In most cases only lower leaves are affected; however, instances do occur when severe infection completely defoliates the plant. Because of its importance as a postharvest fruit decay organism, an increase of the fungus on blueberry leaves in May can result in considerable damage to fruit after harvest. Leaf symptoms appear as circular to irregular-shaped brown to gray lesions surrounded by a red border. Prolonged periods of high humidity favor disease development.