Buxus: Volutella Canker and Blight

Problem
In the spring before new growth appears, leaves on the tips of affected branches turn pale green, then red, tan, and finally yellow. The bark loosens and peels off at the base of infected stems and branches, revealing areas of darkened, discolored wood; the entire twig or stem eventually dies. Cream pink pustules appear on the undersides of infected leaves that have survived the winter. Later in the season, new growth may turn yellow and develop pustules, especially if the weather is wet.

Analysis
This plant disease is caused by a fungus (Volutella buxi) that attacks both American and English boxwood. Plants are more susceptible to the disease if they have been weakened by winter injury, poor growing conditions, or insect infestation. The fungus survives the winter on infected stems, leaves, and plant debris. Wind and splashing water spread the spores to healthy leaves and twigs. In the early spring, cankers form in twigs and branches, resulting in dieback. The fungus can continue to blight new growth throughout the growing season as long as conditions remain moist.

Solution
Remove shrubs that are dying. Prune out and destroy infected twigs and branches. Clean up accumulated plant debris. Spray with a fungicide containing basic copper sulfate or ferbam, just before growth begins in the spring, or whenever the disease is first noticed. Repeat the spray 3 more times at intervals of 10 days. Maintain plants in good health. For cultural information, see Buxus.