Sycamore Anthracnose Diagnostic Guide
Sycamore anthracnose is a disfiguring disease of sycamore and plane trees (Platanus sp.) caused by the fungus Apiognomonia veneta. Believed to be native to the United States, it is found throughout the range of sycamores. The fungus spreads from infected to healthy trees as spores carried by the wind or rain. Although not a fatal disease by itself, sycamore anthracnose often weakens a tree making it more susceptible to other pests and issues.
Trees at Risk
American sycamore and London plane tree.
London Plane Tree
Signs of Damage
- Dead patches along veins of leaves beginning in late spring (leaf blight)
- Defoliation beginning in early summer (leaf blight)
- Sunken cankers on 1 – 2 year old twigs (twig blight)
- Witches brooms forming at the canker sites on 1-2 year old branches (caused by cankers that girdle twigs and buds)
- American Sycamores are much more susceptible than London planes
The fungus that causes sycamore anthracnose causes cankers on the 1-2 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 of branches, and increased susceptibility to secondary diseases and insects. Unlike foliar sprays, macro-infusion with Arbotect™ reduces the amount of inoculum in twigs over time. Foliar spray fungicide treatments are effective only for managing the leaf infection stage of this disease. Macro-infusion treatment with Arbotect™ can be made any time after mid-summer re-foliation until early fall. Do not treat until infected trees have re-foliated from the current season’s infection, and avoid treatment after significant fall color is evident. Protection begins the year after application and lasts for up to three growing seasons.
Tree Injection using Arbotect 20-S
Dosage: Apply 8 fl oz of Arbotect/5 in DBH (1.6 fl oz/inch DBH) in a single application. For trees >30 in DBH consider applying 12 fl oz/5 in DBH (2.4 fl oz/inch DBH). Dilute each 1 fl oz of Arbotect in 1 qt of water. Timing: Begin in mid-late summer up to significant fall color (May - Oct). Do not treat trees with a thin, partial canopy early in season. Re-Treatment: Every 2-3 years depending on pressure
- Applications with Arbotect™ will begin to reduce the overwintering inoculum in cankers near buds on the 1-2 year old twigs the season following application.
- Efficacy may increase during the second and third cycle of treatments on trees larger than 30 inches.
- Arbotect™ does not directly reduce leaf infection symptoms, however, suppression of leaf infections may occur over time as inoculum levels decline in an individual tree. To ensure protection from leaf infection, treat with foliar sprays of ProCon-Z™.
- Spores from the sycamore anthracnose pathogen can be spread by wind and or rain from infected trees and increase the amount of leaf infection that occurs even in treated trees during wet, cool springs.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org