You might think that because white oaks are tall, strong hardwood trees that they would be immune to diseases. In reality, diseases in white oak trees are fairly common and can topple one of these giant trees if they are allowed to go unchecked. Knowing the signs and symptoms of white oak diseases will help you keep your tree "happy" and healthy for decades.
Anthracnose is a disease that is caused by fungal infections that splash onto white oaks during heavy rains. It affects white oaks by causing the leaves to turn brown around the edges, giving them a scorched look. The veins may also become pale and develop light splotches. To control anthracnose, rake up all debris lying under the oak tree and use sterile pruning to remove affected leaves. Thin the crown of the tree to encourage more circulation among the leaves and branches. If you wish to use a fungicide, use one containing mancozeb for the best results.
If your white oak has oak tatters disease, new leaves will emerge looking lacy or tattered. This particular disease has only been on record since the 1980s and appears mostly in the midwestern United States. The tattered leaves do not usually survive, requiring the oak to produce a new "flush" of leaves later in the season, which weakens the tree and leaves it susceptible to other infections. There is not much that can be done for oak tatters other than watching out for and treating secondary infections, which are what kill the tree.
White oaks can develop powdery mildew infections if their environment is wet and humid. Powdery mildew can be black, gray, white or pink and looks like a coating of thick chalk dust. It is largely an aesthetic problem, although if it is allowed to grow unchecked it can weaken the tree over time. Make sure your white oak has plenty of room in which to grow to allow for air circulation and if you water, do so using a drip hose early in the morning. Use sterile pruning to remove affected leaves and small branches, disposing of the debris in a garbage bag rather than simply dropping it on the ground.
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