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Oak Wilt

What is oak wilt?

a graphic comparing the oak wilt symptoms of white oak and red oak
Symptoms of oak wilt in
A. white oak and
B. red oak.

Oak wilt is a disease that affects oak trees. It is caused by Ceratocystis fagacearum, a fungus that develops in the xylem, the water carrying cells of trees. All oaks are susceptible to the fungus, but the red oak group (with pointed leaf tips) often die much faster than white oaks (rounded leaf tips). Red oaks can take from a few weeks to six months to die and they spread the disease quickly. White oaks can take years to die and have a lower risk of spreading the disease.

Why is oak wilt a problem?

The oak wilt fungus blocks the flow of water and nutrients from the roots to the crown of the tree. This causes the leaves to wilt, and kills the tree.

Where is it found?

In 1944, oak wilt was discovered in Wisconsin. Since then, oak wilt has spread throughout the Midwest and Texas.
Oak wilt is currently present in the Towns of Islip, Riverhead, and Southold in Suffolk County; in the borough of Brooklyn, Kings County; in the Town of Glenville, in Schenectady County; and the Town of Canandaigua, in Ontario County. View the emergency orders that establish Protective Zones around the infections and prohibit the movement of oak and firewood out of the infected areas:

How does it spread?

Oak wilt can spread below ground through tree roots and above ground by beetles. The roots of nearby oak trees can graft (fuse together), creating a connection through which nutrients and some diseases can move. Red oaks are much more likely to form root grafts, so the disease is more likely to spread from and between red oaks. Locally, most of the spread (about 90%) occurs through roots directly from one tree to the next.

The majority of new infestations are started from sap feeding beetles and bark beetles (including Pseudopityophthorus minutissimus and P. pruinosus). Fungal spore mats form just under the bark of diseased and dead red and burr oaks. In the spring and summer, these fungal spore mats emit a sweet odor that attracts beetles. The beetles then crawl on the mats where fungal spores attach to their bodies. Beetles can spread the spores from infected trees to open wounds on uninfected trees, which they are highly attracted to. Wounds can occur from storm damage, pruning, tree climbing spikes, and lawn and garden equipment. Oak wilt can spread several miles by beetles. Transported wood, including firewood, poses a threat to oaks because it can harbor the fungus and/or beetles that can then pass it to other uninfected trees, and increases the distance and speed of oak wilt spread.

Symptoms

Symptoms of oak wilt infection are often very noticeable in red oak species, but can be relatively nondescript in white oaks.

  • Branch dieback starts at the top of the canopy and progresses downward.
  • Brown coloration develops on leaves starting at the outer edge and progressing inward toward the mid-vein of the leaf.
  • Leaves suddenly wilt.
  • Leaf loss during spring and summer. Leaves may fall when green or brown.
  • Fungal spore mats may develop under the bark, forming pressure pads that can raise and split the bark.

What is being done?

DEC will conduct aerial and ground surveys in and around the oak wilt Protective Zones to identify any additional diseased trees. In addition, DEC will be increasing its sampling efforts statewide. All infected oaks will be removed to prevent the spread of the disease.

What can I do?

  • Learn to recognize the symptoms of oak wilt including leaf discoloration, branch dieback, and fungal spore mats. If you think your tree is infected with oak wilt, contact DEC Forest Health.
  • Avoid pruning or wounding oak trees in the spring and summer, when spore mats are present and beetles are the most active. If a wound occurs, it should be dressed immediately with latex paint. This will slow wound recovery but also deter beetles from landing on those areas.
  • Use tree care professionals. Read more about how to select an arborist or tree service.
  • If you prune, learn how to do it properly (PDF, 380 KB).
  • Seal any oak tree wounds during spring and summer immediately with would dressing.
  • To report oak wilt, email the DEC Forest Health office or call 1-866-640-0652. To help verify the symptoms of oak wilt, include photos of the symptoms in your email.

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