Valued as a shade tree across much of the United States, the sycamore tree can reach up to 100 feet tall. These trees feature characteristic mottled bark of white, tan and brown colors, and large, hand-shaped leaves. Several diseases affect sycamores, some of which may result in the eventual death of the tree. Use of chemical treatments and practicing preventative methods will help fight diseases and keep sycamore trees healthy.
The most serious disease affecting sycamores, the fungal disease anthracnose, typically occurs during periods of cool, wet weather. The likelihood of an outbreak of this disease increases when average temperatures hover below 55 degrees F after the emergence of buds in the spring. The symptoms of anthracnose are often mistaken for frost damage. During the first stage of the disease, the tips of young sycamore twigs die before new leaves emerge. In mid spring, buds die, followed by the death of new shoots. In the final stage, leaves crinkle and turn brown and eventually fall from the tree. Sycamore trees may lose all of their leaves several times during the growing season. If left untreated, the tree may die from repeated defoliation.
Dispose of fallen foliage to prevent the spread of the disease and prune back any diseased branches. Disinfect your pruning shears between each cut with rubbing alcohol. Once buds appear, spray young trees with fungicides containing chlorothalonil, thiophanate-methyl or copper every seven to 14 days to prevent outbreaks of the disease. If a new set of leaves appears after the first set has dropped, apply fungicides again, especially if conditions remain wet and cool. Consider growing more disease-resistant sycamores, such as the London plane varieties.
If grown in shady, wet areas, powdery mildew may affect new growth on sycamore trees. The spores of this fungus appear as a white or gray powder on leaves and twigs. If untreated, small patches of the fungus will grow and merge to form a layer that covers the leaves. Small black spots that allow the disease to over-winter may appear in the late summer. Purchase products labeled to treat powdery mildew and apply according to the label instructions.
Bacterial Leaf Scorch
Insects such as leafhoppers transmit bacterial leaf scorch to sycamore trees after feeding on the xylem fluid of host plants. Sycamore trees affected by bacterial leaf scorch display brown leaves that often curl upward but do not fall from the tree. The disease first affects older leaves on a branch, before moving to newer leaves and eventually killing the entire branch. This disease cannot be prevented, but removal of infected limbs will extend the life of the tree.
Prune back diseased branches with sharp, sterilized pruning tools. Once a significant number of branches have succumbed to the disease, remove the tree and replace it with a tree not susceptible to bacterial leaf scorch. Antibiotic injections will suppress the symptoms of the disease if applied once a year, but will not cure it. The wounds caused from injecting the tree with antibiotics may allow the entry of other diseases or pests.