Birch trees usually grow to small or medium height. They are easily recognizable due to their paper park marked with the characteristic, dark horizontal lines known as lenticels. There are a number of diseases common to birch trees, but if treated in time, an infected tree can be saved.
Leaf blight can affect all types of birch tree, although River Birch is more susceptible because this disease thrives in damp conditions. Blight causes black spots to appear, first on the young leaves and gradually spreading to more mature leaves, eventually causing the tree to lose almost half of its leaves throughout the summer. Gather all infected leaves as soon as they fall, and burn them to prevent the blight from returning next season.
Birches may become infected with canker caused by a species of the Cytospora family. The disease causes dark brown spots on leaves and black ulcerations on limbs and bark that may eat through to the inner layers if left untreated. Often a young or already weakened tree falls prey to this disease, so it is important to soak the tree regularly to prevent water or oxygen starvation. If a birch has canker, be sure to remove all of the infected limbs and leaves. You can use a commercial tree fungicide to cover any ulcerations in the bark, which should prevent the disease from spreading and help the tree heal.
All types of birch are vulnerable to rust. The disease begins with tiny yellow or red bubble-like blisters on the underside of leaves, often near the stem. It occurs during late summer and can cause leaves to turn yellow and fall prematurely. All leaves should be burned as they fall to prevent the disease from retuning next season. New spring buds should be sprayed with liquid copper two to three times, in three-week intervals.
Birch dieback can affect all types of birch tree. It causes death of branches or sections of branches and can affect the whole tree or just one half. Birch trees have shallow roots and need regular watering. Fallen leaves (if they are not diseased) or mulch should be allowed to protect the roots from heat damage. You also may prevent dieback by planting the tree in semi-shade and adding organic mulch to ensure that the soil surrounding the roots has good drainage.