Oak wilt is a disease that affects all oak trees, however red oaks (with pointed leaf tips) are the most susceptible. The disease is caused by a fungus that develops in the water-carrying cells of the trees and block the flow of water and nutrients from the roots to the crown. This blockage usually causes the leaves to wilt and fall off, killing the tree.

Once a red oak tree develops the fungus it usually dies within a few weeks to 6 months, and the disease spreads quickly from tree to tree. White oaks, however, can take years to die from the disease, and usually do not spread from tree to tree.

Oak Tree with Oak Wilt

The origin of the fungus is still unknown, but it was first discovered in 1944 in Wisconsin. It has spread throughout the Midwest and Texas, and in 2008 was discovered in NY, it was quickly dealt with, but resurfaced in 2013 and then again in 2016.

It spreads from tree to tree either above ground by beetles or below ground through tree roots.

Above Ground: When the fungal spores form just under the bark of a red oak tree during the summer months they emit a sweet odor which attract sap-feeding beetles and bark beetles. They then pick up the fungal spores, and can transfer the fungus to healthy trees, sometimes miles away.

Below Ground: Roots can graft (fuse together) to one another and create a connection where nutrients and the disease can move through. These things are much more common in red oaks, and are more rare in white oaks, hence the number of affected trees.

How do you know if your tree is affected?

If you have a red oak tree on your property look for the following signs:

  • Brown coloration from the outer edge progressing inward toward the mid-vein
  • Branch dieback at the top of the tree’s canopy
  • Leaves suddenly wilt in the Spring and Summer
  • Leaves fall while there is still green on them
  • Fungal spore mats develop under the bark

Signs of Oak Wilt

What can you do?

Avoid pruning or wounding oak trees in the spring and summer when beetles are the most active, and adhere to firewood regulations, limiting the movement of firewood in order to help prevent the spread if any is infected.

If you think you have a tree that may be infected, or you would like us to take a look at the Oak Trees on your property give us a call at (908) 204-9918.