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Symptoms: The leaf symptoms of anthracnose are dead areas of the leaf that develop along main veins, often in a V-shape from the margin of the leaf. If infection occurs before and during bud break, anthracnose can cause buds and young expanding leaves to turn brown and die.
Cause: Several trees -- including sycamore, maple, white oak, ash and dogwood -- are very susceptible to anthracnose. When the disease becomes severe, it deforms the plants, making each one an unsightly addition to a landscape. Susceptible plants are distorted by the death of shoots and buds, which causes the plants to grow asymmetrically. Affected branches may look crooked and angular. Often clusters of shoots -- "witches'-brooms" -- grow from one area of a branch. When the fungus grows through the bud or down the leaf petiole into the wood, it kills the branch. In the wood, the fungus grows as a canker. Each year's new buds, shoots and leaves may become infected by spores produced on the cankered wood in early spring. The disease is most severe when springs are cool (average temperatures less than 60 degrees F) and wet.
Control: The most effective control is to replant using resistant trees as substitutes. For anthracnose, planetree is a good resistant substitute for sycamore and most oaks are less severely affected than white oak. Otherwise, revitalize the root system as described under General decline and dieback.
Visuals associated with this text.
|Visual title - Visual size||Visual title - Visual size|
|Oak anthracnose - 49K||Sycamore anthracnose - 42K|
|Ash anthracnose - 42K||Maple anthracnose - 48K|
|Sycamore anthracnose - 59K||Sycamore anthracnose, twig cankers - 24K|
|Sycamore anthracnose, withces broom - 47K|