Japanese maples are small to medium-size ornamental trees. Dwarf varieties are as small as 4 feet tall and wide, while larger varieties grow up to 25 feet tall and wide. The shapes vary from upright to spreading and weeping. Some varieties of Japanese maples have gold, pink, purple or red foliage, especially in the spring and fall. Japanese maples grow best in slightly acid organic soil in dappled shade. The soil should be evenly moist but well drained. The trees need to be protected from late spring frosts and high winds.
Phylolosticta and septoria fungi cause tan leaf spots on Japanese maples. Leaf spots usually occur during wet springs and cause minimal damage.
Tar spots are raised areas of a tar-like substance on the upper surface of Japanese maple leaves. They are caused by a fungus and result in little damage.
Fungicides that have been approved for the treatment of phyllosticta or septoria leaf spots on Japanese maples can be used according to the manufacturer's directions to control the diseases.
Bacterial leaf scorch on Japanese maples commonly occurs in late summer to early fall after a prolonged period or drought. The margin of the leaves develop chlorosis and the center of the leaves turn dull green or brown. There is no chemical treatment for bacterial leaf scorch.
Anthracnose is a fungal disease that sporadically attacks Japanese maples during cool wet weather. Symptoms include leaf spots, dead leaf tissues, twig dieback and cankers on small branches. Anthracnose is usually not a major disease on Japanese maples. Use a fungicide approved for anthracnose on Japanese maples according to the manufacturer's directions to prevent and control the disease.
There is no treatment for verticillium wilt, a soil-borne fungus that attacks Japanese maples. The foliage on all or a section of the tree can show systems, such as curling or wilting, yellowing and premature dropping. Severe cases result in branch dieback and discoloration of the wood under the bark.