Oak wilt is caused by the fungus Certocystis fagacearum. This disease is an important one for all oaks. For example, members of the white oak group tend to die very slowly after the infection occurs and can carry the fungus in the vascular system without showing any symptoms at all. Red oaks, on the hand, die rapidly after infection. Symptoms show up on red oaks in early May as a bronzing of the leaves.
Now, on live oaks, the leaf symptoms are variable. The most common symptom is brown necrosis of the leaf veins. The remainder of the leaf might stay green or it can turn slightly yellow. Severe leaf drop occurs while the leaves are still green. If you cut through the wood, you may see a discoloration in the last annual ring. Symptoms develop usually on one limb or branch and, in time, spread rapidly to the remainder of the tree.
What makes oak wilt so problematic is that the fungus may be carried from tree to tree by various insects and through root grafts. Sap beetles can be important in the short range spread of oak wilt. Red oaks suffering from oak wilt have problems in the later summer or early fall. They develop spore mats under their bark that show up during the spring. As the mats develop, the bark begins to slough off or ruptures. This exposes the fungus. Insects are attracted to the mats. If they move from the mats to healthy trees which have open wounds, oak wilt can then enter the healthy tree and move into water inside the tree, affecting its tissue.
Oak wilt can be difficult to stop or control. You can destroy the diseased trees and remove or burn the stumps. The only secret to protect your trees from getting infected is to properly prune them and seal off the cuts to eliminate sap flow. Neglected trees are more susceptible to oak wilt. Let us help you keep your trees healthy.
Oak trees, as a rule, should not be pruned during the spring particularly the months of March, April, May and June. Please give us a call at 512-341-8888 for more information or visit our website at http://www.keepaustingreen.com.