Fungal infections that attack Chinese elm and Chinese dogwood trees, as well as hundreds of others, can lead to the disease known as leaf blight, twig blight or shoot blight. This fungus can spread rapidly throughout a tree, damaging both new and old branches. If left untreated it can lead to plant death.
There are many types of fungi that will attack trees of a Chinese origin and lead to anthracnose, or leaf blight, in the plant. A few of these, Discula faxinea, Colletotrichum gloeosporioides and Stegophora ulmea, thrive in wet soils, spreading spores during rain fall. These fungi will not damage trees during dry conditions.
Many fungi that cause anthracnose are able to survive winter by clinging to fallen twigs and branches or hiding within the soil. As spring returns and rains start to fall, the fungi will begin to grow again. Rain will help spread spores between tree organs and hosts and lead to further destruction of the plant.
Anthracnose causes a variety of symptoms to appear on Chinese trees. Often brown or black spots will begin to form on the tree leave as they lose color and become deformed. Cankers will also develop on the branches, cracking the wood and allowing for other pathogens to invade the tree. Premature leaf drop and crooked branches are more severe symptoms that are signs of the disease's progression throughout the plant.
Damaged leaves and branches should be removed from the tree through pruning. Shears should be sterilized after every cut to help avoid further spread of the infection. This will allow for new growth to replace the damaged areas. Also, fungicides can be used as chemical controls and are available for retail purchase. Be sure to follow all manufacturer guidelines when using chemicals since they can be highly toxic to humans.
The most common method of preventing the infection of fungal diseases is to plant resistant varieties. Kousa and Drake Chinese Elm trees are far more resistant than other varieties. Also, by placing host plants farther apart from one another, you can limit the spread of spores between them. Lastly, avoid overwatering the tree and plant all trees in full sun. This will help keep the plant dry and limit the growth of fungi.