Most often when we hear about dangerous contagious diseases, we think of the flu, colds, strep throat and other warm blooded afflictions. What many of us don’t often consider is that disease is not limited to the animal kingdom. Some of the most dangerous diseases in the world specifically attack organisms that aren’t warm or cold blooded but rather plants.
Oak wilt, first identified in 1944, is threatening only to trees (particularly different types of oak). This disease also indirectly affects humans and other animals as much of our ecosystem and agricultural economy depends on these beautiful, deciduous trees remaining healthy.
What causes oak wilt?
Oak wilt is caused by the fungus ceratocystis fagacearum. This fungi can grow on the outside of an oak and form a parasitic relationship with it.
Quickly the host (infected tree) will detect the parasite and react by developing tyloses (growths) which restrict the flow of water and nutrients to the affected area in an attempt to wall-off pathogens and prevent infections from spreading. Unfortunately this defense is self-destructive and ends up causing the tree to wilt and die.
How does oak wilt spread?
Oak wilt fungus can spread via one of two ways:
fungus spores of an affected tree can be transported by wind or insects
connected roots between an infected tree and a healthy one
Most disease is spread by interconnected roots – trees within as much as a 50 foot radius of a diseased tree can be infected. The disease is most active in moderate temperatures and trees are more susceptible when new wood is forming in the spring according to the University of Georgia. Red oaks are more susceptible than white oaks which are moderately resistant to the disease.
How to tell if my trees have oak wilt?
Since there are many different types of oak, and symptoms can vary, it’s most conclusive to get a diagnosis of your tree’s tissue through a laboratory. With a few samples, professionals can identify under a microscope whether or not your tree is infected. Common symptoms include:
leaf discoloration (starting at the top of the tree)
death – oak wilt is a rapid and devastating disease, often killing infected trees in a single season
Where is oak wilt an issue?
Oak wilt is currently found only in the United States and is most commonly an issue in the eastern, central, and midwestern states including: Iowa, Minnesota, Wisconsin, Illinois, Missouri, Michigan, Indiana, Ohio, Pennsylvania, West Virginia, Kentucky, and Texas. Though rare, it has been found in Georgia and South Carolina among other states in the region as well.
How can you treat or prevent oak wIlt?
Sadly, no viable options exist to treat a tree once it has been infected with oak wilt fungus, the only option is to get rid of the infected tree to prevent the spreading of the disease.
The success of prevention is primarily driven by keeping the healthy and infected trees and roots separated. This can be done mechanically or chemically; a trencher can separate roots a couple feet down, while soil fumigants can kill connecting roots. Trees which succomb to oak wilt should be quickly and properly disposed of: debarked, split or chipped and then burned or covered with plastic sheeting. Infected logs, even in the form of firewood, should never be transported to unaffected areas.
On a more positive note, check out this checklist to ensure your lawn will be primed and ready for summer.