The state Department of Environmental Conservation announced last week that oak wilt — a disease that kills oak trees — has been detected in South Bristol, which borders Yates County west of Canandaigua Lake.

A concerned landowner contacted the DEC after several oak trees on the landowner’s property in South Bristol began showing signs of oak wilt, including dropping discolored leaves in July and then dying rapidly, according to the DEC. Samples from one of the trees were sent to the Cornell Plant Disease Diagnostic Clinic, where they tested positive for the fungus that causes the disease.

Oak wilt, caused by the fungus Bretziella fagacearum, is a serious tree disease in the eastern United States, killing thousands of oaks each year in forests, woodlots and home landscapes. As the tree attempts to defend itself, it produces gummy plugs to restrict the movement of the fungus. These plugs, together with the growing fungus, prevent the water transport in the tree. As water movement within the tree is slowed, the leaves wilt and drop off, and eventually the tree dies.

Oak Wilt is not new in the Southern End of Canandaigua. It was identified last year by Natural Resource Educator Emily Staychock of the Yates County Cooperative Extension.

This is the second location in Ontario County where oak wilt has been confirmed. The disease was confirmed in the town of Canandaigua in 2016. Ontario County is one of four counties in the state that have confirmed oak wilt infections, according to the DEC. Other counties with confirmed cases of oak wilt are Kings, Suffolk, and Schenectady.

The current treatment method to contain and kill the oak wilt fungus is to remove the infected trees, as well as any nearby oaks that could become infected.The DEC will issue an order establishing a quarantine district prohibiting the movement of oak material out of the immediate area to prevent the fungus from spreading. In addition, the DEC will conduct aerial and ground surveys over the next few weeks to identify additional trees that may be infected.

The N.Y. Invasive Species Information is an education and dissemination clearing house on the researched best practices for identification and management of invasive species. http://nyis.info/invasive_species/oak-wilt/

According to NYISI, the oak wilt fungus is spread to an oak tree via root grafts or oak bark beetles feeding on sap at open wounds or on the leaves of healthy trees. Once inside the tree, the oak wilt fungus begins to replicate within the sapwood of the tree.

Symptoms first appear near the top of the canopy. The outside of the leaves turn bronze, brown, or dull green, usually starting at the top of the leaf, while the base of the leaf remains green. Some leaves curl, droop and wilt. Leaves begin to drop soon after symptoms first develop. Root grafted oak trees usually die 1-6 years after the first oak is infected, and disease centers can move up to 50 feet per year. Oak wilt can also be spread long distances through the movement of infested firewood.

Arlene Wilson, Executive Director of Yates County Cornell Cooperative Extension emphasizes:

1. The importance of the seasonal timeline for addressing/treating trees while the beetles that carry it are active;

2. The importance of having a licensed professional assess/administer any pesticides, if a decision or recommendation is made to go in that direction;

3. The importance of not transporting any part of an infected tree outside of the property, as it may spread the disease.

Impacted property owners will be contacted with information about oak wilt and to provide them with information about how to help protect remaining oak trees. During the winter months, the DEC will remove infected trees. Surveys will resume in the spring, when dead trees and signs of the fungus may be more apparent.

The DEC asks the public to report any occurrences where an oak tree died over a short period of time, especially if it occurred between July and August. Call the Forest Health Information Line toll-free at 1-866-640-0652.

For more information about oak wilt, visit DEC’s website.

Includes reporting by John Christensen