Sycamore Anthracnose

Gnomonia leptostyla

Sycamore anthracnoseGnomonia leptostyla, is a fungal disease that affects sycamores throughout the United States. While rarely deadly, it can make the trees unsightly and cause large areas of the tree to die back. The fungus attacks the buds and twigs, so infected trees often have “witches brooms” (many twigs originating from a common point) on the ends of their branches, which consist mostly of dead twigs.

Download Sycamore Anthracnose Fact Sheet

Treatment Strategy

Macro-Infusion with the systemic fungicide Arbotect® has proven effective 90-95% in controlling the symptoms and reducing the injury from sycamore anthracnose.

Readily moving into new growth, Arbotect® lasts for three years in your tree. The best time to inject is in July, after the affected leaves have regrown, through fall color change.

What Can I Expect After Treating with Arbotect®?

• First season: In the first season post treatment, the tree will still exhibit sycamore anthracnose leaf infection symptoms, which can include blotched leaves and even some defoliation. Twigs will stop becoming infected.

• Second season: Arbotect® prevents new twig cankers from forming, so, there will be a significant reduction in leaf blotching.

• Third season: In the third season following treatment, the tree will have further significant reduction in leaf blotching and defoliation. By re-treatment of the tree every 3 years, protection from sycamore anthracnose will be maintained.

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Sycamore Anthracnose Treatment Option 1

Root flare injections with Arbotect® are about the only way to protect new branch growth from sycamore anthracnose.

The purpose of treatment is to protect the 1-2 year old twigs from becoming infected and to keep the fungus out of new woody tissue. It takes two seasons after treatment for the tree to look much better because systemic fungicide injections do not protect leaves from spore infection and cannot cure already infected tissue.

Application TypeHigh Volume Macro-Infusion

DIY Product/Equipment Needed:

• Arbotect®

•  115v High Volume Macro-Infusion Kit (plugs into an outlet) or 12v High Volume Macro-Infusion Kit (clips to a marine battery)

• Drill

• Shovel and hand trowel

• Stiff bristled hand brush

Sycamore Anthracnose DIY Kit

Option 1

Application Type – High Volume Macro-Infusion

DIY Product/Equipment Needed:

• Arbotect®

115v High Volume Macro-Infusion Kit (plugs into an outlet) or 12v High Volume Macro-Infusion Kit (clips to a marine battery)

• Drill

• Shovel and hand trowel

• Stiff bristled hand brush

How Is It Spread?

There are four stages of the disease that occur every year. The sycamore anthracnose disease cycle begins with leaf infection. In the spring, leaves become infected from spores that are emitted from the twigs. The fungus grows down the leaf and back into the new twig where it will live – usually for 2 years. When environmental conditions are cool, the fungus often grows throughout the twig and infects buds and newly forming leaves from the inside.

Susceptible Trees

Sycamore anthracnose most commonly infects American sycamore. London planetree, exhibits varying degrees of resistance and Oriental planetree is completely unaffected.


• Witches brooming, and a twisted gnarled growth pattern

• Cankers on twigs

• Curling of new shoots

• Twig dieback

• Black to brown lesions on the leaves


Late spring through summer (after second flush of leaves have appeared)



Risk of Spreading


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