Brown Spots on a Blueberry Plant

Anthracnose

• Anthracnose is a fungal disease caused by the Gloeosporium minus fungus that infects the foliage and stems. Symptoms of infection consist of small red leaf spots with a brown boarder, defoliation, stem spots and stem death. Defoliation and stem death reduce crop yield and plant vigor. Severe infections can result in bush dieback, making it one of the most serious diseases of blueberry plants. Preventive fungicides applied before harvest and once every two week during harvest can help prevent infections. Planting disease-resistant blueberry cultivars can reduce the severity of anthracnose infections.

Septoria Leaf Spot

• Septoria leaf spot is a serious fungal disease with symptoms similar to anthracnose infections. The disease produces small brown spots on leaf surfaces, stem spots and premature defoliation. The fungus favors water on leaf surfaces and splashing water. Septoria leaf spot fungi overwinter on fallen infected tissue, which causes perennial infection. Apply preventive fungicides before symptoms occur and avoid overhead irrigation to prevent infection.

Alternaria Leaf Spot

• Alternaria fungal infections are a minor to moderate disease of blueberries that occurs during cool, wet and humid weather. Symptoms consist of gray or brown leaf and stem spots with a red border and premature defoliation. The disease can overwinter on infected tissue, which can cause perennial infections. Apply preventive fungicides during the early growing season and avoid freestanding water on leaf surfaces to prevent infection. The fungus can also cause post-harvest fruit rot, which can reduce crop yield after harvest.

Blueberry Rust

• Blueberry rust is a fungal disease of blueberries and several other related species, such as cranberries and huckleberries. The fungus infects immature leaves during the early spring and summer months, producing small yellow spots. As the disease progresses, the spots enlarge and turn red to brown. Leaf curl and premature defoliation occur with severe infections. Plant disease-resistant blueberry cultivars and apply preventive fungicides on a regular basis during the growing season to prevent infection. Avoid planting when weather conditions favor disease development and remove diseased plants to avoid the fungus from spreading to healthy plants.