White Oak Tree Fungi

Fungi

• Fungi cause a variety of plant problems. Fungi are microscopic plants that do not contain chlorophyll. These plants gain their nourishment by infesting green plants. Fungi are the most common cause of disease on plants, cites the North Dakota State University Extension. Serious fungal diseases of white oak include oak wilt and hypoxylon canker.

Causal Agents

• Hypoxylon canker is one the main white oak diseases. Biscogniauxia atropunctata var. atropunctata causes it. Other hosts include the Southern red oak, water oak and post oak. The wood rooting disease is common in poorly growing trees that are already under stress. Oak wilt affects a wide range of oak varieties, causing the most significant damage in the Eastern regions of the United States. Ceratocystis fagacearum causes the disease.

Damage

• Early sign of hypoxylon canker is crown dieback. The bark starts rotting and falls. Infection sites occur on limbs and trunk and range anywhere between a few inches to several feet long. Brown-colored fungal spores develop within the rotting areas. Infected white oaks slowly die from the disease with damage progressing from limb to limb. Foliage is discolored starting from margins and going to the base.

Control

• Hypoxylon canker is a lethal disease. There is no cure. Although branches may be pruned and burned at the initial signs of disease, other affected areas gradually keep appearing. The best way to avoid the disease is ensuring that the tree is in vigorous health with adequate water and fertilizer. Beetles frequently transport the oak wilt fungus during spring and early summer. Avoid tree injuries or pruning especially during the susceptible periods when pests are in flight. Fungicides are only effective as a preventative measure when injected into healthy trees.