Botrytis Blight (fungus – Botrytis cinerea): Under high humidity and mild temperatures this fungus can attack blooms and tender growth. Blossoms may shrivel prematurely as if injured by frost. The fungus grows profusely, producing a gray to brownish fuzzy material on infected parts. Rarely is Botrytis a serious problem, but when it occurs, heavy losses can result. Botrytis can also cause post harvest fruit rot. [See fungicide chart below]

Leaf Spot (fungus – Gloeocercospora inconspicua, Septoria albopunctata): Leaf spot diseases develop on occasion but are considered minor problems in production plantings. Fungicide treatments are not generally recommended.

Mummy Berry (fungus – Monilinia vaccinii – corymbosi): The fungus infects when growth begins in spring, causing a leaf and flower blight (See Photo). It might be confused with Botrytis blight at this stage. Blighted leaves and blossoms quickly develop a light brown fungal growth on external surfaces as they dieback (See Photo). Some infected blossoms continue development without noticeable symptoms. As these fruit approach maturity, they turn a pink to white color instead of blue (See Photo). By this time the fungus has colonized the fruit, forming hard, black, survival structures inside that remain dormant until the following spring (See Photo). Mummy berry disease is not common, but when it occurs, there can be heavy losses, especially during bloom. Preventive fungicide treatments are recommended for control [See fungicide chart below].

Stem Blight (fungus – Botryosphaeria dothidea): Leaves yellow and infected branches die. Rarely is the entire plant lost. Prune out diseased wood. Fungicides have not proven beneficial.

Stem Canker (fungus – Botryosphaeria corticis): Although susceptible, most rabbiteye varieties have some degree of resistance to stem canker. Like stem blight, stem canker eventually causes branch dieback. Prune out affected wood. Fungicides are not effective.

Other diseases: Other diseases that may occur on blueberry are Phytophthora root rot, powdery mildew, crown gall and ripe rot (fruit rot near maturity).