Sycamore Fungus

Sycamores are stately, large landscape trees.

Sycamore trees (Platanus occidentalis) are a large and important part of the home landscape, providing year-around beauty and cooling summer shade. The tree's complex, intertwining root system makes it an excellent choice for controlling erosion. Sycamores can grow to 100 feet tall or more and large, palmate or hand-shaped leaves. Sycamore trees generally withstand fungal infections, but may require treatment to ensure survival.

Canker Stain

Caused by Ceratocystis fimbriata f. sp. platani, a fungus, canker stain disease can be fatal. This fungus enters the tree through wounds and causes twig dieback, thinning foliage and reduced leaf size. Elongated cankers on the trunk and large branches are usually sunken and may be hidden underneath the bark. Wood beneath the cankers is darker than surrounding areas. Use care with gardening tools, especially lawnmowers that can nick upper roots. Sterilize gardening tools between uses to avoid spreading infection. No chemical controls are available. To prevent a dead tree from falling on your house or spreading infection to healthy trees, have infected sycamores removed.

Anthracnose

Anthracnose is a complicated fungal disease, but usually does not kill sycamores. Anthracnose is caused by Apiognomonia venata and appears in stages. In early spring, anthracnose causes twig blight, discoloring and killing the tips of year-old twigs. In mid-spring, buds begin to die from cankers that girdle the branches. New shoots and young leaves may die suddenly. Leaves turn crinkly and brown, and may fall prematurely. In early spring, apply a protective fungicide, especially if the weather is unusually rainy and humid. In early summer, when the plant is preparing to produce more new growth, apply protective fungicide. Follow all label instructions. To help prevent anthracnose, prune away infected parts of the sycamore and clean up all plant debris and weeds from around the plant. Destroy the detritus away from the plant. Avoid over-watering and over-fertilizing. Sanitize gardening equipment.

Powdery Mildew

If the sycamore is growing in a humid climate, it may develop powdery mildew, caused by Microsphaera. Irregular, white patches appear on the leaves. If numerous enough, the spots look like talcum powder sprinkled on the foliage. The spots often merge, spreading as larger patches and stunting or distorting new growth. Leaves may fall off the tree prematurely. Small black spots that develop atop the fungal patches are fruiting bodies that produce new spores next year. If the tree is young and small, use a fungicide formulated to control powdery mildew. Follow package directions. Avoid overhead watering and improve drainage around the tree, if necessary to avoid standing water. Sanitize gardening utensils and remove and destroy plant debris from around the tree.

Other Fungal Infections

Phomopsis and botrytis fungal infections are nearly identical. Both cause cankers, though phomopsis is easier to spot when the tree is wet. Cankers are generally narrow, but long. Entire branches or limbs may die. Chemical treatment is not practical, and the disease may not kill the tree unless the cankers grow large enough to cause serious damage. Practice good gardening techniques to prevent infection. Keep the trees healthy to avoid stress and avoid injuring the tree.

References

• Virginia Tech: American Sycamore
• Pennsylvania State University; Canker Stain in Sycamore and London Plane Tree; Gary W. Moorman
• Colorado State University; Sycamore Anthracnose; C. E. Swift; March 2008
• Pennsylvania State University; Sycamore Diseases; Gary W. Moorman
• Clemson University; Sycamore Diseases & Insect Pests; Marjan Kluepfel, et al.; May 2009
• USDA Forest Service; Sycamore Diseases; F.I. McCracken

Resources

• Virginia Tech Forest and Range: American Sycamore
• USDA Plant Guide; American Sycamore; Guy Nesom; June 2008