Quick Facts

  • Main symptom is progressive dieback of the crown, which is an expression of an impaired root system
  • Can kill susceptible oaks within 3-5 years of the onset of crown symptoms
  • Moist, dark stains may be present on the trunk of trees affected by oak decline.

Species Facts:

Oak decline, Phytophthora quercina, is a slow-acting disease complex that can kill physiologically mature trees in the upper canopy. Decline results from interactions of multiple stresses, such as prolonged drought and spring defoliation by late frost or insects, opportunistic root disease fungi such as Armillaria mellea, and inner-bark-boring insects such as the two-line chestnut borer and red oak borer. Oak decline occurs throughout the range of eastern hardwood forests, but is particularly common in the Southern Appalachian Mountains in North Carolina, Tennessee, and Virginia, as well as the Ozark Mountains in Arkansas and Missouri.

Oak decline shows evidence that dieback has occurred over several years from the top down and outside inward. Newly killed branches with twigs attached are usually found in the same crown as those in a more advanced state of deterioration killed years before. Dieback associated with sudden oak death occurs over a growing season or two. The inner bark beneath the dark stain associated with stem-boring-insect attacks has a discrete margin with no zone lines or evidence of canker development beyond the attack site.

Portions of this article courtesy of: U.S. Department of Agriculture Forest Service, Pest Alert
A tree suffering from Oak Decline (Photo from www.bugwood.org Credit to: Joseph O'Brien)