Diseases of the Ornamental Maple

Fungal diseases

Most maple trees are susceptible to verticillium wilt, a serious fungal infection that creates symptoms of yellowing leaves, slowed growth and death of stems and branches. Leaves may wilt or curl. If the infection is serious enough, the health of the entire plant could diminish immediately and severely. Verticillium fungi enter through the tree's roots and emit toxins throughout the plant. Infected trees cannot be cured with fungicides. To counter symptoms and strengthen the tree, fertilize and water regularly and remove dead and weakened branches.

Infection by Gloeosporium apocryptum fungi causes a disease called Anthracnose, where leaves, buds, twigs and branches turn brown and die. The Phyllosticta minima fungus creates spots with yellow centers and purple cedges, called Phyllosticta Leaf Spot. As this disease progresses, the fungus develops fruiting bodies on the spots and can cause leaf loss. Spraying plants with copper-based fungicide, chlorothalonil, mancozeb or thiophanate methyl will control these diseases. Some red maple varieties including "Gerling" and "Autumn Flame" are resistant to Phyllosticta.

The bacterium Xyella fastidiosa can cause symptoms of fading leaves, loss of tree vigor, and dying branches, called Bacterial Leaf Scorch. The symptoms may be a result of water stress and are often noticed after periods of drought. To combat this infection, encourage root development and soil aeration by adding organic matter to the soil. Provide plenty of water during periods of drought.

Leaf scorch incorporates a common set of symptoms, rather than a disease, and could be indicative of one of a number of problems. Leaf regions between veins turn brown or tan and margins may turn yellow. It may be caused by hot, dry weather, which causes leaves to dry out. Soil contaminants such as high levels of salts, phosphates or fluorides could also create these symptoms. Certain infections, either fungal or bacterial, can create leaf scorch symptoms as well.

Ornamental maples are subjected to certain environmental stresses that naturally-growing maples do not experience. High levels of salts can cause leaf scorch. Girdling roots occurs when a maple's roots wrap around the base of another tree, cutting off water and nutrient uptake. Girdled roots is common among Norway maples and may harm the tree's vigor. If this is the case, remove the portion of root and cover the wound with root paint before planting. Soil compaction is common in urban environments and can cause browning of leaf margins, shrinking and yellowing leaves and twig die-back. Keeping a tree healthy with appropriate fertilizer, irrigation practices and soil conditions will help combat effects of infections and environmental stresses.