Anthracnose – A Common Tree Disease On Thick, Water Storing Leaves

Anthracnose is very common in California. In most cases anthracnose does not cause permanent damage to established trees. However, trees stressed by root restrictions, drought, and heavy insect infestation are much less tolerant of this fungus and may show decreased vigor because of infestation.

Symptoms of anthracnose arise in spring on thick, fleshy, water-storing leaves. The infected patches of the leaf are greenish brown to dark brown. Many leaves become curled and distorted due to the infection. Round to irregular blotches appear along margins and midribs of leaflets. Severely infected and dead leaves are shed. Symptoms are more severe in the lower crown of the tree.

A severe case of anthracnose may cause defoliation in the spring, but the tree usually recovers and produces a second crop of leaves later in the season. Severe defoliation year after year, however, may weaken the tree and increase its susceptibility to insects, other diseases, and stressful environmental conditions. In addition, branch structure may be affected by the disease.

On sycamore and oaks, repeated twig dieback promotes the development of side shoots, resulting in bushy growth and angular branching. On trees used mainly for ornamental purposes, even a moderate level of anthracnose may cause unacceptable aesthetic damage.

The Anthracnose Wellness Program includes commonly affected species such as: Sycamore, Ash, Dogwood, Chinese Elm. To control anthracnose and greatly improve the tree’s appearance, the program includes fall trunk injections of trunks and early spring applications to the tree’s leaf buds.

Please call or email City Arborist Tree Care to discuss your tree’s disease and pest control needs.