Cercospora Twig Blight of Juniper

Disease Information

Cercospora Twig Blight

 Symptoms and damage

This disease is caused by the fungus Cercosporasequoiae var. juniperi. It begins by infecting the oldest needles that are located on the lower branches, inside of the plant. As disease development progresses, the needle browning spreads upward and outward. Branch tips usually remain healthy and green. Needles of spur branches turn brown and die usually in the late summer, leaving a plant with an inner crown devoid of foliage. This disease is sometimes confused with mite damage.

Management

 Each of these diseases requires similar methods of control. First, closely inspect the entire plant, since symptoms of tip blight and twig blight can be caused by other problems, such as drought, overwatering or root injury.

Purchase disease-resistant varieties that are healthy with no evidence of dead or dying twigs. Do not stress junipers by planting them in shaded or poorly drained locations. Plant junipers in areas with good air circulation to promote rapid drying of the needles. Do not crowd plants, and avoid using sprinkler irrigation. Promptly prune and remove any diseased or browning branches as they occur. Except on highly susceptible cultivars, pruning will usually control these diseases.

If chemical control is necessary, fungicides are available to provide protection, but they must be applied before infection occurs. Select a fungicide labeled for use on junipers containing one of the following: mancozeb, thiophanate-methyl or copper salts of fatty acids.

 



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