Arborvitae Tip Blight

Disease Cause

• Juniper tip blight is the tip blight disease likely to affect arborvitaes. The fungal disease results from an infection from one of three fungi -- Kabatina juniperi, Phomopsis juniperovora or Sclerophoma pythiophila. This tip blight disease is also called phomopsis tip blight and kabatina tip blight.

Symptoms

• The disease is characterized by the appearance of gray colored lesions or spots on 4 to 6 inches of the tip of new foliage during early spring. As disease progresses, the affected branches turn dull gray and brown. The lesions enlarge and assume an ash-gray color, encircling or girdling the entire tip area and killing it. Small, black fruiting bodies of the fungus or pycnidia are visible on the dead branches. In cases of severe infection, the entire tree may die.

Favorable Conditions

• Juniper tip blight causes the worst damage to young shrubs and tree. Plants that are over 5 years old are less seriously affected. The fungus produces spores all through the growing season, and these spores spread within the tree and to other plants through the air and splashing water. High humidity and moisture are especially favorable for fungal growth. Fertilizing and watering trees and shrubs excessively also makes the emerging burst of new growth more prone to the infection.

Management

• Prune and remove all affected areas immediately during dry weather. Make the cut 4 to 6 inches below the site of infections and disinfect the pruning tool after every cut. Use resistant tree varieties and make sure that the tree or shrub is growing in a well-drained and adequately ventilated site. Avoid overpruning because the overproduction of new growth is prone to infection. Do not use overhead sprinklers to water plants, as the moisture tends to linger on the foliage, inviting the fungal infection. Chemical control options include the use of copper-based fungicides.