Live Oak Tree Diseases

Updated April 17, 2017

Several diseases affect live oak trees. Many of these diseases are caused by fungi, but insects and parasites can also damage trees. Any part of the tree may be harmed, including leaves, branches, roots and trunks. Knowing the symptoms of diseases can help determine what is wrong with a tree and the proper treatment.

Oak Wilt

Oak wilt is a fungal infection affecting all types of oak trees. As there is no cure for this disease, the best way to deal with it is to isolate and destroy affected trees. The disease is caused by a fungus that clogs the tree's vascular system and stops the flow of nutrients and water. The earliest sign of oak wilt is leaf damage; they begin to lose colour, turning brown or yellow. Leaves might appear to be wilting. Live oaks with the disease can live as long as six months. If a tree is infected, it should be cut down the wood burnt and covered in plastic. To stop the spread, sever any root connections between healthy and infected trees. It's also spread by insects.

Diplodia Canker

Diplodia canker is a small branch and twig disease that causes trees to look shabby because of leaves falling off and turning brown. This type of canker rarely affects branches that are more than an inch in diameter; it tends to target shaded or weak branches. The Diplodia canker thrives on trees that are stressed such as transplanted trees, trees that are poorly maintained and trees under compaction stress.

Oak Root Rot

Root rot consists of two diseases that are caused by fungi and water moulds, and parasitic algae. Irrigation can lead to root rot. Some trees are predisposed to the disease and certain pathogens also make a tree more likely to develop root rot. Two pathogens that are common for root rot are Armillaria mellea and Pytophthora spp., both of which thrive in moist soil.


Anthracnose is a leaf disease that also affects young shoots. It's caused by a fungus and spread by rainfall. Symptoms will follow the infected leaves' veins; the infection begins in the lower branches and spreads upward. Some sprays have been used to combat the disease, but weather has the biggest effect. Anthracnose occurs when it's wet and warm; when it is dry, the disease clears up.


Mistletoe is a parasite that takes food from the host tree. If it is left to grow on a tree, it will weaken its host. Birds eat mistletoe berries and seeds end up dropped on nearby trees so if left unchecked, mistletoe can be tough to control. Pulling it from the branch is a temporary solution. To get rid of the plant permanently, remove parts of branches where the mistletoe is growing.

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About the Author

T.L Chancellor has more than 12 years of newspaper reporting and editing experience. She has written extensively about education, business and city government. She has also worked at a public relations firm, focusing on environmental issues with clients.