Anthracnose in sycamore trees is a fungus that spreads from infected to healthy trees from spores carried by the wind or rain. This fungus spreads from the leaves and causes cankers on the 1- to 2-year-old twigs. These cankers serve as a source of inoculum and cause repeated annual infections of young twigs, which result in abnormal branching, loss of vigor, dieback, and increased susceptibility to secondary diseases and insects. Sycamore anthracnose is not a fatal disease by itself, but often weakens the tree giving other problems the opportunity to kill the tree.
Signs and symptoms
- Necrotic patches along veins on leaves beginning in late spring.
- Defoliation beginning in early summer.
- Sunken cankers on 1- to 2-year-old twigs.
- Witches’ brooms forming at the canker sites.
- Combine leaf spots, defoliation, and presence of cankers and witches’ broom all needed for correct diagnoses.