Coastal live oaks are fast growing, shade-tolerant trees. The tree is found along the coastal plains from southeast Virginia to southern Florida, to southern and central Texas. The tree is the dominant species in maritime forests because of its tolerance to salt spray. Diseases of the coastal live oak include oak wilt, leaf blister and slime flux.
Oak wilt is caused by the fungus Ceratocystis fagacearum, according to the U.S. Department of Agriculture. The fungus is nearly always fatal because it bores into the tree and invades the vascular system, cutting off the tree's water supply. The fungus kills leaves, branches and finally the trunk. The symptoms first appear in the spring on young trees as wilted and discolored leaves on the upper branches. The rest of the leaves wilt and die quickly thereafter. Branch death follows leaf wilt. By summer's end, the trunks of the young trees are affected and the trees die. Mature trees will show wilt leaf symptoms late in the summer. Mature trees often survive the winter, but will die in the spring. There is no cure for oak wilt, only preventive measures. Prune coastal live oaks in the coldest part of the winter. Remove any damaged limbs and destroy them. Isolate an infected tree by digging a trench around the tree and cutting the roots of the live oak.
Oak Leaf Blister
Oak leaf blister is another fungal disease that affects coastal live oaks. Oak leaf blister is an infectious disease that spreads during cool, moist conditions during the early spring and summer when new leaves are forming. Oak leaf blister appears as circular bulges on the tops of leaves, according to the University of Arkansas. On the bottom of leaves, the circles create depressions. The spots are yellow-green at first, then turn white or translucent, and then gray or brown. Blisters often merge together on a leaf, creating one large spot. The disease is largely aesthetic, affecting only the appearance of the leaves, although the coastal live oak may drop its leaves prematurely. Fungicidal treatment is effective only before the leaves emerge in the spring. Prevent the disease by removing and destroying twigs and leaves of affected trees, and fertilizing and watering the tree.
Slime flux, or wet wood, is caused by a bacterial infection that affects coastal live oak trees. The disease presents itself as a foul-smelling wet bark on the tree. Fermented bacteria causes carbon dioxide pressure to build up in the wood, pushing the tree's sap out through the bark near the base of the coastal live oak, close to the grass. The sap seeps from holes caused by injury or directly through the bark, according to North Carolina State University. The sap attracts insects that feed on the liquid. The disease generally does not kill the trees, and treatment is unnecessary beyond removing the affected bark around the seepage. Prevent slime flux by pruning correctly and keeping damage to the bark at a minimum.