Common Oak Tree Diseases Caused by Insects and Other Trees

Last week, we focused on common oak tree diseases of the leaves and twigs. We hope that you found the information interesting. Did you know that there are other oak tree diseases? These are caused by insects and other trees. In this article, we’ll be focusing on those diseases so you can recognize the signs and symptoms before they do real damage to your oak trees.

Bacterial Leaf Scorch

Carried by leafhoppers and spittlebugs, bacterial leaf scorch can also be transferred through contact with other oak roots. The symptoms of this disease mimic plant stress due to a lack of water as in a drought. The oak leaves will turn brown along the edges in response to any drought. What separates plant stress from disease is a reddish brown or yellow border between the brown leaf margin and the green portion of the leaf. Once bacterial leaf scorch is diagnosed, you need to remove the effected tree. Oaks do not discover from this disease. Even if the scorching is minor, it will continue to spread throughout the tree.

Oak Wilt

We have a whole article on this oak tree disease here. Basically, oak wilt starts at the top of the tree and appears as brown or bronzing of the leaves along the margins. The discoloration continues toward the center of a leaf until the leaf dies prematurely. This dieback of the leaves will go along until the tree is dead. This can occur as quickly as four weeks to several years. This disease is spread through root grafts and oak bark beetles. It can live in leaf litter but only until the environment gets up to 90 degrees. Then, oak wilt is killed. To control the disease, you need to cut the tree down. Trenching is also suggested so that root grafting cannot occur.

Fusiform Rust

This oak tree disease is not exactly caused by insects but rather other trees. The offending trees are the loblolly and stash pines. The symptoms on an oak are orange to yellow pustules on the lower branches during the summer and fall. Fusiform rust can cause premature leaf drop and an unsightly appearance, but it will NOT kill the tree. The process of this disease starts in the spring when pine galls open up and release spores.  The spores are carried by the wind to the oak tree. Pustules on the underside of the leaf open up in the late spring and release spores that are carried to pines. Once in the pines, they attack new growth. The only way to make sure that your oak does not catch this disease it to ensure that there are no pines in the area.

Are there other oak tree diseases? Yes, but the ones we have mentioned are the most common. If you have any questions about your oaks or any other tree on your property, feel free to give us a call at 512-341-8888. We look forward to helping you with all of your tree needs.


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