Insects and Diseases of Sycamore Trees

Anthracnose blight commonly affects sycamore trees in the United States. Caused by the Apiognomonia venata fungus, blight affects sycamores in four stages: twig blight, bud blight, shoot blight and leaf blight. Blight results in blackened and wilted leaves and blackened twigs, as well as dead buds and shoots. Clemson University horticulturalists Marjan Kluepfel and J. McLeod Scott recommend regular fertilization for trees as a preventative measure. Removing afflicted portions of a tree with sheers rubbed in a 10 percent alcohol helps prevent the spread of blight. Applying sprays such as chlorothalonil, thiophanate-methyl or copper fungicides helps small trees, though this proves ineffectual on large trees.

Powdery mildew sometimes forms across the leaves and the new growth of sycamore trees. This disease proves particularly prevalent in humid, shady areas. Bacterial leaf scorch, another disease affecting shade-dwelling trees, causes the sides and veins of leaves to scorch, or turn brown and die, though the leaves don't fall from the tree. Other diseases affecting sycamore species include root and crown rot, canker stain and wood decay. No effective management for bacterial leaf scorch exists, though powdery mildew may be cured by fungicides. The most effective method of disease management is maintaining optimal tree culture and fertilization. Optimal culture includes regular watering, ideal soil conditions, extensive sun exposure and good air circulation. Use a complete fertilizer at a rate of 2 to 4 pounds of nitrogen per 1000 square feet. The label of a fertilizer indicates the nitrogen content.

The sycamore lace bug feeds exclusively on sycamore leaves, piercing the outer layer with their mouthpieces and sucking the sap out. Nymphs, or baby lace bugs, leave distinctive yellow dots when feeding on sycamore leaves. The undersides of leaves on trees affected by lace bugs bear black spots from bug waste and shed skin material. Kluepfel and Scott recommend managing mild infestations by spraying insect populations with a hose and encouraging the presence of predators such as assassin bugs, lacewings, pirate bugs and spiders. Encouraging the presence of these insects entails tolerating their presence. According to Kluepfel and Scott, major infestations prove impractical to manage by chemical means but don't seriously affect the health of the tree, and thus should be tolerated.

Japanese beetles destroy countless plants throughout the United States each year. These insects eat a number of common plants throughout North America, including sycamore trees. The United States Department of Agriculture reports that Japanese beetle populations prove too extensive to eradicate, though they can be managed through pesticides such as acephate, carbaryl, diazinon and bendiocarb. Always consult labels, local laws and plant or insect experts before applying a chemical control. Introducing Bt, a natural soil bacteria poisonous to Japanese beetles, to the soil around sycamore roots may help manage populations, as do natural predators such as predatory wasps and certain nematodes. Finally, planting beetle-resistant plants such as garlic, begonias, poppies, hickory, red maple, pine and ash in and around the garden may prevent infestation.

Other pests that could affect sycamore trees include spider mites, caterpillars, flatheaded borers, aphids, scale bugs, whiteflies and non-sycamore-specific scales. Chemical control of these pests should be undertaken with caution. Encouraging the presence of natural predators of these pests, such as ladybugs, spiders, predatory wasps and various species of songbirds, helps prevent excessive damage. Encourage songbirds by placing bird feeders in the garden, or purchase ladybugs through a supplier such as garden store or online retailer. As with sycamore diseases, the most effective method of pest management is maintaining a healthy tree.