Gary W. Moorman, Professor of Plant Pathology
|Anthracnose||Dead twigs and branches have sunken cankers. Bud death followed by new bud formation and more bud death results in witches’ broom-like proliferation of branch ends as well as very crooked branching patterns. Black fungal fruiting structures are visible on the bark covering newly killed twigs early in the spring. Young shoots are killed. Leaves, especially on lower and inner branches, are blighted and fall early in the season only to be replaced by new leaves in mid-season. Tan, dead areas expand along leaf veins. Large, irregularly shaped areas are killed along the leaf margins and between the veins. Fungal fruiting structures can be found with a magnifying glass along the veins.||Apiognomonia||Prune and destroy dead twigs and branches during dormancy, cutting 3 to 4 inches below the canker. Plant resistant cultivars that have been vegetatively propagated from Bloodgood, Columbia, or Liberty clones of London plane trees. If trees are of high value, a fungicide can be injected in the autumn before the leaves have fallen, the next spring after the leaves emerge, and again in the autumn to obtain protection of new tissue for the following two to three springs. Or spray a fungicide in the spring at bud break and repeatedly until the weather dries and daily temperatures average above 65°F.|
|Bacterial leaf scorch||Oldest leaves brown along their margins and eventually between the veins beginning in mid to late summer on one branch or a few branches on inner and lower portions of the tree. A brown band sometimes develops between the brown and green tissue of the leaf. The browning of leaves progresses to include more leaves toward the ends of branches. Infected trees have delayed bud break in the spring and produce smaller-than-normal leaves.||Xylella fastidiosa||Leafhoppers and spittle bugs carry the bacteria from tree to tree. See the information on this disease in the “Common Plant Diseases” section. Promote plant vigor by protecting the tree from stresses. X. fastidiosa from elm does not infect sycamore or vice versa.|
|Canker stain||London plane and sycamore trees have sparse foliage, small leaves, and elongated sunken cankers on the trunk and larger branches. Beneath the cankers, the wood is stained bluish black or reddish brown. Viewed in cross section, the discolored wood is wedge shaped with the point of the wedge extending toward the center of the trunk or branch.||Ceratocystis fimbriata f. sp. platani||Since the fungus enters only through wounds, pruning tools, ropes, ladders, and other equipment must be disinfested immediately after use on a tree before proceeding to another tree. Do not use wound paints since brushes efficiently move spores from tree to tree. Sap-feeding beetles can also transmit the fungus.|
|Powdery mildew||Heavy white fungal growth develops on the upper surface of leaves in late summer and in the autumn. Leaf shape is very distorted.||Microsphaera||Little damage occurs to the tree itself other than deforming the leaf appearance. No control is recommended unless the tree is of very high value. a fungicide can be applied in late summer to protect leaves. fungicide injection (described under anthracnose) gives some powdery mildew control.|
Anthracnose on leaves and twig.
Powdery mildew symptoms and signs.
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