Tips for Blueberries With Black Leaves

Causes

• Red leaf disease is one problem that causes the leaves of a blueberry plant to turn black late in its life cycle; earlier symptoms include reddish leaves with white fungal spots on the undersides, according to the Michigan State University Extension website. Stem blight is another disease affecting the leaves of blueberries, turning them black as it spreads through the blueberry's vascular tissue, according to the North Carolina State University Plant Pathology Extension.

Effects

• Exobasidium vaccinii, or red leaf disease, is a fatal fungal disease that causes serious problems for commercial growers of blueberries, especially in Michigan, according to the Michigan State University Extension website. The red leaf disease spreads systematically during the summer and will travel from one bush to another. Stem blight causes rapid wilt and the discoloration of branches and frequently enters the blueberry bush through an injury, whether man-made or natural. Stem blight that affects the base of the bush will kill it quickly.

Red Leaf Control

• No fungicidal treatment is available for red leaf disease. The disease spreads rapidly through an individual bush and will affect other bushes. Treating red leaf disease requires the removal and destruction of any infected bushes; the Michigan State University recommends burning it. Pick up any remaining leaves or twigs from the bush, as these may still have fungal spores that can attack remaining bushes.

Stem Blight Control

• The North Carolina State University Plant Pathology Extension recommends strict cultural control for stem blight, as there are no available fungicides that control it. Prune infected stems on plants to control the spread of the disease; remove the stems and branches from the garden and destroy them. Avoid using fertilizer after mid-summer, as it encourages the growth of shoots injured by cold weather in the spring; these shoots are a primary point of entry for the stem blight. Plant resistant cultivars in well-drained soil to avoid stem blight problems.