Birch trees are desirable for their beautiful, mottled bark, graceful branches and slender form. Unfortunately, these trees are also quite fragile and are known to succumb easily to both insect pests and tree diseases. Birch tree diseases can range from the slightly disfiguring to the severely damaging. In some cases, they can be fatal to the tree. Preventative control programs and good culture are musts for keeping birch trees disease-free.
Birch wood is very soft and is quite susceptible to decay. There are many fungi that can infect the wood of the tree and cause it to rot. These fungi usually enter the tree on the bodies of boring insects or through wounds caused by gardening tools. For this reason, severe pruning of birch trees is not recommended. Symptoms of heart rot include the development of cankers (sunken, dark, cracked areas of bark) and oozing sap.
Anthracnose is a disease caused by a fungus. The spores of the fungus are spread on water and usually infect trees during cold and very wet spring weather. The disease causes premature leaf drop and can defoliate an entire birch tree. Anthracnose becomes progressively worse each year the tree is infected, and can kill parts of the tree, particularly new shoots and twigs.
Leaf Spots and Rust
Leaf spot is caused by several different fungi. Depending on the fungus, the symptoms can be relatively mild, such as tiny orange spots on the leaves (rust diseases) or more serious. In severely infected leaves, the spots will be large, brown or black, and greasy, growing until they merge and causing the leaves to curl up or drop off the tree prematurely.
The spores of these fungi are transported on water--usually rain--during very wet spring weather. Once the spores land on a leaf, they start to multiply, causing the spots to appear. Many of these fungi can overwinter in the ground on the dropped leaves, rising again in the spring.