Pest: Major Pests
Periodic widespread oak decline has been recorded over the past 100 years. Oak decline is described as the gradual weakening of oak trees over several years, ultimately followed by death. No one single cause is responsible. Several factors such as tree age, site, location, soils, weather, insects and disease attacks all work together to cause widespread oak decline.
According to the 2010 Tennessee Resource Assessment and Strategy, oak decline is currently the most pervasive problem within the forests of Tennessee. The Western Highland Rim and the Cumberland Plateau have the highest risk although oak decline is an issue in any oak forest. As Tennessee’s forest mature, the risk of oak decline will greatly increase.
Although no formal oak decline survey is conducted annually throughout Tennessee, several agencies including the TN Division of Forestry, the University of Tennessee, Tennessee Wildlife Resources Agency, TN Department of Environment and Conservation, Tennessee Forestry Association, TVA, and the US Forest Service work together to monitor the health of Tennessee’s oak forests.
The first symptom of oak decline is progressive die-back of the upper crown leaves beginning at the tips of the branches. The leaves may develop spots on their surface or become dwarfed or sparse. The leaves may also turn brown prematurely yet remain on the tree. Epicormic sprouts may develop on the trunk or larger branches. Most often, trees in the red oak family such as black oak, scarlet oak or southern red oak are affected. Oak decline can however occur in hickories and in trees in the white oak family such as chestnut oak, post oak, white oak, or chinkapin oak.
Once oaks show signs of stress and begin to decline, they become highly susceptible to insects or diseases. Some common insects that invade declining oaks are the two-lined chestnut borer and the red oak borer. Common diseases that infect declining oaks are armillaria root rot and hypoxylon cankers.
Maintaining forest health is the best way to prevent oak decline. Harvesting over mature oak trees, encourage growth of oak seedling or saplings by removing undesirable mid story trees, conduct ½ acre patch cuts to let in more sunlight to your forest, or use prescribed fire to encourage oak seedling growth are excellent management options.
What Can You Do?
Contact your local forester, extension agent or Division of Forestry personnel for advice on healthy oak forest management. Monitor your forest for signs of decline especially in times of drought or after events such as wildfire or early/late frosts. Check oak trees frequently for signs of insect or disease activity and be proactive if signs of oak decline are present.