In recent years there has been an increase of reports from clients that oaks are suddenly dying. Whether it is in their woods or landscapes, the calls are increasing. Is this because people are paying more attention or is there a real increase in oak fatalities? It remains to be determined. The NC Forest Service has a great publication on the topic of Oak Decline.

Plant Health

Oak decline is a complex of heat and drought stress weakening trees and leading to  disease and wood boring insect infestations. Our weather has warmed over the last decades with winters not as cold and more frequent dry hot spells. Early springs and late frosts seem to be annual occurrences. All of these weather changes may be stressing trees.

Also most of our forests in the southeast are in mid succession. This is the stage of forest growth when trees begin to compete with one another for space, light, nutrients and water. You may have noticed the density of trees in a mature forest is less than in a young forest. Forests start out dense with growth and over time trees compete and the weaker trees will be outcompeted in this system.

Causal Agents

Stressed trees are more susceptible to diseases and insects. Fungi and bacteria can overcome the defenses of weak trees. Insects can smell chemicals emitted by stressed trees and are drawn in.

Frequently the armillaria  fungus kills stressed oaks. Other fungi can attack trees as well such as ganoderma. These fungi are pathogens and actively kill their tree hosts.

Insects such as the two lined chestnut borer attack stressed oaks. Ambrosia beetles also are attracted to stressed trees. These insects eventually kill their tree hosts as well.

What Type of Oaks?

We see oak decline mostly on red oaks such as red, scarlet, pin and black oaks and white oaks such as white oak and chestnut oaks. It appears that red oaks are the most susceptible however.

What Can You Do?

The only thing we can do for our trees is to try and keep them as healthy as possible. If we can access them, we should water during drought and fertilize twice annually. Learn how to care for trees here. If a tree is obviously declining, get in touch with a arborist to inspect your tree and recommend a course of action. If you need a list, get in touch with our office and we will send you a copy via email.