I Have Brown Leaves Falling Off My Blueberries

Stem Blight

• Stem blight is a severe fungal disease caused by the Botryosphaeria dothidea fungus. Symptoms of infection consist of premature leaf browning, rapid plant wilt, leaf drop and plant death. Initial infections cause stem death and leaf browning. Leaf drop occurs a few weeks after infection occurs and stems turn black. The fungus requires wounds in the stem and base for infection, which occur from mechanical, insect and weather damage. Plant resistant blueberry cultivars, avoid fertilization after mid-summer and avoid wounds to prevent infection. Prune and destroy infected stems to control the disease. This removes diseased tissue and prevents new infections by reducing the number of fungal spores.

Fusicoccum Canker

• Fusicoccum canker is a serious fungal disease that infects the stems of blueberry plants. The fungus favors moisture on leaf surfaces and temperatures between 50 to 72 F. The disease produces red to brown lesions on leaf surfaces that enlarge as the disease progresses. As the disease progresses, infected tissue dies and premature defoliation occur. The cankers cause stem girdling, which results in rapid stem wilt and death during dry weather conditions. Remove infected stems and apply fungicides to reduce the spread of the disease.

Alternaria Leaf Spot

• Alternaria leaf spot is a fungal fruit rot disease of blueberry that produces symptoms on the plants leaves. The disease produces red to brown leaf spots that kills the infected tissue. Severe infections cause premature defoliation. The disease can also spread to the berries, causing sunken lesions on the fruit and reduced crop yield. The disease survives overwinter on infected fruit and stems, causing yearly infection. The fungus favors wet weather conditions and temperatures around 68 F. Apply fungicidal sprays and prune infected stems to reduce the severity of the disease.

Soil pH

• Blueberry plants require slightly acidic soil for optimal growth. Soil with a high pH, or alkaline-based soil, causes poor foliage growth, foliage that turns yellow to brown and premature defoliation. Once blueberry plants start deteriorating due to high soil pH, there is no cure. Reduce soil pH by applying sulfur to soil during moist and warm weather conditions. According to Oregon State University, blueberry plants require a soil pH of 4.2 to 5.5, depending on the cultivar.