The state Department of Environmental Conservation reported on Sept. 24, that oak wilt was detected in Middlesex. This is the first location in Yates County where oak wilt has been confirmed.

DEC management efforts to contain the oak wilt fungus include removal of the infected trees, as well as any nearby oaks that could become infected. A quarantine district will be established by DEC, which will prohibit movement of oak material out of the immediate area to prevent spreading of the fungus. DEC will also conduct aerial and ground surveys for additional trees that may be infected. During the fall and winter months, DEC will remove infected trees.

Oak wilt was first detected in New York state in 2008, in Schenectady County. Other counties with confirmed cases of oak wilt are Ontario, Kings, Suffolk, and Schenectady counties. It was first detected in the Finger Lakes region, in Ontario County, during 2016. In 2018, there was another finding of oak wilt in Ontario County.

What is oak wilt?

Oak wilt is a disease that affects trees in the oak genus (Quercus) and is caused by a fungus (Ceratocystis fagacearum) that grows in the xylem, or water-carrying cells, of oak trees. The fungus prevents the flow of water and nutrients through infected trees, clogging the xylem cells and causing the leaves to wilt. Wilting usually starts at the outer portions of branches, located at the top of the tree crown, and progresses downward. Leaves begin to turn reddish-brown along the tip and edges, spreading toward the midrib and base of the leaf. This process occurs rapidly in trees in the red oak group, causing them to drop their leaves in the spring and summer months, which is not typical.

What trees are most susceptible?

The genus of oak trees is divided into two groups: red and white. Red oaks (including red, scarlet, pin, and black oak, etc.) are most severely affected by oak wilt, the disease being fatal to these trees, dying within a few weeks to six months. White oaks (including white, chestnut oak and bur oak, etc.) are less vulnerable, often able to survive years with the disease, and it is much less likely to spread to nearby trees in the white oak group.

How does oak wilt spread?

Oak wilt is spread primarily through root-to-root connections between oak trees, which occurs more often among red oaks than white oaks. Oak roots that are in close proximity commonly graft together, which is beneficial for sharing nutrients, but unfortunately creates a pathway for spread of oak wilt disease. Spread of the disease is assisted by sap feeding beetles and bark beetles. Sap feeding beetles are attracted to freshly wounded trees, to feed on the sap. The oak wilt fungus creates fungal spore mats under the bark of infected oak trees, and in the last stages of disease, the bark splits open to reveal these mats. The mats emit a sweet odor that attracts sap beetles to feed, and as they feed, fungal spores attach to them. The beetles transport spores to uninfected areas (a fresh wound is required by the fungus in order to invade) and once infected, the disease can then spread underground through root grafts.

What can I do?

The best way to deal with oak wilt is prevention. Learn to recognize the symptoms of oak wilt and be on the lookout. Avoiding pruning, wounding or cutting down oak trees in the spring and summer when spore mats are present and beetles are the most active. Prune only during November through March. Be careful with the lawnmower and weed-whacker. If possible, put off construction activities around oaks until late summer. If an oak becomes wounded, it should be sealed immediately with wound dressing. The beetles can potentially find fresh wounds in less than a half-hour. The disease can also be transported in logs and firewood. Adhere to the NYS firewood regulation which limits firewood movement to no more than 50 miles.

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, to the Forest Health Information Line toll-free at 1-866-640-0652. For more information about oak wilt, visit or call or stop by the Cornell Cooperative Extension of Yates County office for oak wilt fact sheets or to talk with an Extension Educator. The office is in the Yates County Building at 417 Liberty St., Suite 1024, Penn Yan or call (315) 536-5123.

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