Japanese maple trees and shrubs (Acer palmatum) may not provide the brilliant warm autumn colour expected in your home garden if fungus problems occur. Home gardeners should provide consistent care to their Japanese maple plants as a means of avoiding a variety of fungal infections. Anthracnose, for example, results in spots of dead plant tissue on foliage, leaf drop and malformation while verticillium wilt leads to curled, wilted, discoloured leaves that drop early, branch dieback and plant death. Remove fungus from your Japanese maples to maintain vigorous trees.
Provide consistent care for vigorous trees as fungus is often more attracted to stressed or weakened trees. Grow Japanese maple trees in locations that provide partial shade and moist, well-drained soil conditions.
Look for cankers, or areas of dying plant tissue, lesions on leaves, malformed leaves that appear wilted or curled, discolouration on plant parts, leaf drop or branch dieback.
Prune and destroy affected plant parts while collecting and destroying any fallen debris to prevent further spread of infection. Sterilise pruning tools between each cut and when moving from one plant to the next to avoid disease transfer.
Avoid creating wounds through which fungi invade, particularly when pruning, gardening or mowing near trees.
Contact a licensed professional or your local county extension agent for assistance with determining the particular fungal infection attacking your Japanese maple tree.
Apply a fungicide for diseases which respond well to chemical treatment like anthracnose. Employ fungicidal treatment according to the fungus in question. For example, apply a fungicide like Bordeaux mixture at bud break for anthracnose control and reapply every two weeks as leaves develop, according to the University of Illinois Extension HortAnswers.
Always wear gardening gloves when using sharp tools to prevent injury.