Oak Wilt

Asked August 3, 2017, 8:36 AM EDT

Our neighbors have lost several trees and has an oak tree within 20 feet of our healthy pin oak that has its leaves turning brown and dropping. We are concerned about our tree which seems to be healthy and have been told the neighbors tree has oak wilt. The first tree service recommends injecting our tree as prevention from oak wilt. Another tree service states the tree needs to be injected in the spring. And the third tree service doubts it is even oak wilt and states there is nothing we can do for our tree. We are confused and need to know where to find an honest and reliable answer. Any suggestions on where to turn for answers? I have attached three pictures. The first shows the neighbors tree. The second shows the close proximity to our tree and the third is a close up of the leaves on the neighbors tree..

Allegheny County Pennsylvania

1 Response

Hello caller,

My apologies for slow response.

You may want to take a twig sample having symptomatic, and also healthy foliage to your Penn State Extension office to send to the Plant Disease Clinic.

The office is located at Penn State Center, 1435 Bedford Avenue, Suite A
Pittsburgh, PA 15219 phone (412) 482-3455 Ask for Sandy Feather or Brian Wolyniak,

Results will probably take about 3 weeks, and will be accompanied by a prescription.

Also, Bartlett Tree Experts have a definitive test for oak wilt, also requiring a sample, and I expect will also have a waiting period for results.

Spread

  1. Sap-feeding and bark beetles feed on the fungal mat that erupts through the bark in the spring and pick up sticky spores. They spread the spores as they move short distances to adjacent oaks to feed on fresh, bleeding wounds. A fresh wound is required by the fungus in order to invade. It is thought that beetles are not responsible for spreading the fungus for long distances.
  2. The fungus remains viable under firmly attached bark. Transport of infected logs is one way the fungus can be moved long distances.
  3. The most important means of spread in a local area is through roots naturally grafted to the infected tree.

Management: First, obtain a positive diagnosis that oak wilt is the cause of the wilting and defoliation.

Break root grafts to nearby oaks before removing an infected tree. This can be done by trenching or fumigating midway between oaks that are within 50 feet of the infected oak, to a depth of 3 feet. Fumigation is best done when the soil temperature is at least 50°F.

After root grafts are disrupted, remove infected trees. Bury, burn, or debark the logs and stump. Do not stack or transport any wood from the tree if it has bark firmly attached because insects in it may leave and carry the fungus to other oaks.

Do not prune oaks in the late spring or summer because this creates fresh wounds that are attractive to insects that may be carrying the fungus. Prune only during November through mid-April.

The disease in trees with less than 30% of the crown affected can be put into temporary remission by injecting a fungicide. The fungicide does not kill the fungus that is already in the tree's roots. Therefore, root grafts between this tree and neighboring oaks must be disrupted even if the tree is injected with fungicide. It is reported that oaks in high risk areas, but that are not yet infected, can be protected by injecting a fungicide once every 2 years.

Fungicidal injections suppress oak wilt pathogen (Ceratocystis fagacearum) advance but will not kill it. Treatments will need repeated every year or two. Recommended fungicide is propiconizole.

Recommendations for trees exhibiting extensive ( more than 30% foliage wilt) symptoms are to cut them down immediately and remove the wood from the site.