To many, live oak trees call to mind the landscapes of the southern United States. This is because the tree primarily grows between USDA hardiness zones 7 through 10 and will not grow well in the northeastern or midwestern U.S. Live oaks have a wide spreading habit. A mature tree may grow as wide as 80 feet in diameter and is typically green year-round. The trees are also susceptible to a number of diseases.
Leaf blister is a form of fungal infection that creates galls in the leaves. Galled leaves have a bumpy appearance. These blister bumps may be up to 1 inch in size. They will be yellowish-white in contrast to the bright green of the rest of the tree. The leaf blister will disfigure live oak leaves but will not harm the tree. Oak leaf blister typically appears on trees after a wet spring creates conditions right for the fungus. Almost all species of oaks, not just live oaks, can suffer from leaf blister. To control leaf blister, treat a live oak in winter with a fungicide before the wet conditions of spring can breed the fungus.
Oak wilt is a deadly fungal infection that can kill an oak tree in just a few years. It is primarily active in the midwest, but it can affect live oaks in Texas and Louisiana. According to Clemson State University, even live oaks in South Carolina can contract oak wilt. Once a live oak contracts oak wilt, it is impossible to rid the tree of the disease--but prevention of oak wilt is possible. The disease travels through the interconnected roots of live oak trees. Once you notice live oaks in your neighborhood with oak wilt, create trenches around the root zone of your live oak to physically separate it from neighboring trees and prevent the spread of the disease.
Root rot is caused by a fungal disease that infects a live oak at the root line and below the soil. Symptoms of the disease include smaller, yellowish leaves, a thinner canopy, twig dieback in the canopy, and plate fungus or black, shoestring-like fungus below the bark at the roots and around the trunk. As with oak wilt, it is easier to prevent root rot than to treat it. Root rot often begins when a tree is weakened by freezing, drought, and damage to the bark, a damaged canopy or other environmental conditions. To prevent root rot, water trees during drought periods and avoid injuring the bark of the tree.