Problems of Japanese Maple

Tree Grows Poorly
Girdling Roots -Many trees, including sugar and silver maples are weakened and even killed by the tendency of some of their roots to grow closely pressed to the main trunk and around their large lateral roots, choking off water and nutrients. When a lateral root is severely girdled, the branches that depend on it for nutrients are weakened and eventually die. Trees with girdling roots become progressively weaker over 5 to 10 years even with good care. Girdling roots are more of a problem with street trees and in older trees. Carefully cut through any roots that are visibly wrapped around or over large ones with a clean, sharp pruning saw. Do not take the trouble to remove them from the soil, as long as they are severed they are no longer harmful. Do not paint or cover the saw wound.

Surface Roots Or Suckers
Compacted Soil - Tree roots need air, which they normally get from the soil. When the soil where tree roots are growing is compacted, so compressed that most air is squeezed from the soil pores, then roots tend to gravitate to the surface for air. Some trees also generate suckers, extra vertical roots that grow out of the soil as modified stems that access air. Simply pruning off the suckers and covering the surface roots with a layer of soil does not solve the problem. It is a temporary cosmetic measure.

Tree Is Stunted
Too Near Black Walnut Tree - Maple trees can suffer stunting, wilting, or even death when they come in contact with black walnut roots, which give off a substance poisonous to many other plants. This toxic substance affects plants within a radius of 1-1/2 times the distance from the walnut tree's trunk to its outermost branches (the dripline). Move the maple tree outside that area to restore it to health and solve this problem.

Leaves Wrinkled, Stunted, Defoliation
Aphids - Aphids are soft-bodied and pear-shaped, about the size of a pinhead. They may be green, brown, or pink. They retard or distort tree growth, especially on young trees. Maple leaves may turn yellow or brown, wilt under bright sunlight, or curl and pucker. They may actually drop off the tree. Aphids suck plant sap from the leaves and excrete drops of honeydew. With heavy infestations it can be quite messy, although studies have shown that these abundant sugar secretions, soaking into the root zone, actually benefit the tree.

Branches Girdled, Leaves Fall Early, Trunk Scarred
Borers - Borers are the larvae of various sawflies, beetles or moths that tunnel into maple twigs and cause premature leaf fall. Often their entrance holes are visible, a little deposit of sawdust in the area. Borers girdle branches or even the entire tree as they tunnel. New growth over wounds forms a series of scars and ridges on the trunk. Prevent borer attacks on young or newly transplanted trees by wrapping the trunks in plastic, paper tree wraps or even aluminum foil.

Small Bumps On Leaves and Branches
Scale Insects - Several kinds of scale insects infest maples. Sap-sucking insects that feed beneath whitish, gray or brown blister-like protective shells, scale appear as 1/8 to 1/4 inch bumps on tree twigs and as cottony patches on leaves. Affected leaves may turn yellow. Scale insects often secret a sticky sweet honeydew as they feed which coats leaves and invites sooty mold. Do not attempt to treat this problem in large trees that require you to climb a ladder. A certified arborist can do it more safely. It is more of a problem on young trees, anyway.

Sunken Spots On Leaves
Anthracnose - This fungus disease causes distinct lesions on maple leaves, which appear as moist, sunken spots with fruiting bodies in the center. The leaf spots may run together, causing a blotch or blight. The dead areas follow the veins or are bounded by larger veins. Sometimes the ends of young shoots blight down to several inches. Pustules containing pinkish spores appear. Dieback and loss of foliage may occur in severe cases.

Gather and destroy diseased leaves when they fall to prevent the spread of the fungus. Replace existing mulch with fresh that does not have fungal spores on it. Prune away diseased branches, then disinfect your pruning saw or loppers by dipping them into a solution of hot water and household bleach. Maintain tree vigor by feeding and watering it well, especially during droughts. Mature trees can usually handle this disease and regenerate new leaves.

Swollen, Bleeding Lesions Appear on Stems and Trunk
Canker - A canker disease caused by a fungus attacks maples. Sap oozes from fissures overlying cankers in the bark. Leaves wilt, branches die back. Mildly infected trees may recover without any special care. A similar disease infects the base of the trunk. Once the tree is heavily infected, it cannot be cured. Remove and destroy severely diseased trees. Avoid mechanical injuries to the bark on the trunk, and feed, water and mulch trees as needed to maintain good vigor.

Mushrooms Sprout At Base of Tree
Shoestring Root Rot - A root rot disease caused by a fungus causes gradual or sudden dieback of tree crowns. Affected trees show a decline in vigor of all or part of their top growth. Foliage becomes thinned, withers, turns yellow and drops prematurely. Large white "fans" of fungal mycelium appear between the bark and the hardwood of the larger roots. Often, small, dark brown shoestring-like strands cover the outside of the bark of infected roots. Mushrooms appear at the base of the tree in late fall or early winter.

Once this fungus becomes established, it is difficult or impossible to control. Because the fungus cannot exist under dry conditions, expose roots of infected trees to air. Improve soil drainage in the area by aerating and adding organic matter to the surrounding soil. Avoid overwatering. Dig out and destroy seriously infected trees and discard the surrounding soil. Avoid bark injuries and keep trees in vigorous health by watering, fertilizing and mulching young trees to get them off to a good start.

Foliage Turns Yellow Or Brown & Collapses
Verticillium Wilt - A wilt disease caused by a soil-dwelling fungus sometimes attacks maples. Infected leaves appear pale and wilted, and may fall prematurely. One or more branches wilt suddenly and die, often on only one side of the tree. Infected trees may die slowly (over a period of several years) or suddenly (within a few weeks). Sapwood is discolored. Heavy feeding with a high-nitrogen fertilizer sometimes enables trees to put a new ring of sapwood outside the infected area and the trees may then recover. Prune out dead branches. Remove badly infected trees, together with as many roots as possible. Do not replant with wilt-susceptible shrubs or trees in the same location.