Got dead oaks? Could be oak wilt; please report it

oak leaf with wilt
Oak leaf with wilt. Photo courtesy New York State Department of Environmental Conservation

Oak wilt, a serious disease that affects oak trees, has been detected for a second time in Ontario County, southeast of Rochester, according to the New York State Department of Environmental Conservation (DEC).

If you know of an oak tree that died over a short period of time, especially if it occurred between July and August, please report it to the Forest Health Information Line toll-free at 1-866-640-0652.

Symptoms of oak wilt infection are often very noticeable in red oak species, but aren’t easily seen in white oaks.

  • Brown coloration develops on leaves starting at the outer edge and progressing inward toward the mid-vein of the leaf.
  • Branch dieback starts at the top of the tree’s canopy and progresses downward.
  • Leaves suddenly wilt in the spring and summer and may fall while there is still some green on them.
  • Fungal spore mats may develop under the bark of infected trees.

Oak wilt, caused by the fungus Bretziella fagacearum, kills 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.

See more information about oak wilt here.

The disease was confirmed recently in South Bristol and in 2016 in Canandaigua, both in Ontario County.

A concerned landowner in South Bristol contacted DEC after several oak trees on their property began showing signs of oak wilt, including dropping discolored leaves in July and then dying rapidly. 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.

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.

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, DEC will conduct aerial and ground surveys over the next few weeks to identify additional trees that may be infected. 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, DEC will remove infected trees. Surveys will resume in the spring, when dead trees and signs of the fungus may be more apparent.

Ontario County is one of four counties in the state that have confirmed oak wilt infections. Other counties are Kings, Suffolk and Schenectady.

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