Sycamore Anthracnose

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.

Treatment Strategy

The fungus that causes Sycamore Anthracnose causes cankers on the 1-2 year old twigs. These cankers serve as a source of inoculum (conidia) 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.

Other Treatment Practices

  • Pruning out infected twigs will remove the fungal inoculum, but may not be a practical solution for many arborists.
  • Foliar Spray Fungicide

Macro-Infusion Using Arbotect 20-S

Foliar Spray Using Propiconazole 1.3ME T&O

Expected Results

  • Applications 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.
  • 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.

Signs of Damage

  • Necrotic patches along veins on 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)
  • No signs (as opposed to symptoms) are visible without magnification

Robert L. Anderson
USDA Forest Service, Bugwood.org

Joseph O’Brien
USDA Forest Service, Bugwood.org

Joseph O’Brien
USDA Forest Service, Bugwood.org

Trees At Risk

  • American sycamore* (P. occidentalis)
  • California sycamore* (P. racemosa)
  • London plane tree (P. x acerifolia)
  • Oriental plane tree (P. orientalis)

*denotes those most susceptible

A Treatment 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 of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments by forestryimages.org

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