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Oak Wilt Transmission is Happening Now

While you have heard lots of reports regarding Emerald Ash Borer lately, it’s important to not forget another major threat to our urban trees – Oak Wilt Disease.

Oak Wilt is a vascular wilt disease caused by the fungus Bretziella fagacearum. It disrupts the flow of water and nutrients by plugging the vessels in the vascular system of the tree. Once infected, Red Oaks (the extremely susceptible species) can die as quickly as 6 weeks after infection. Live Oaks are also susceptible, but the decline occurs much slower.

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Spread in the Springtime by Beetles

Oak Wilt transmission can easily occur in the springtime, when the disease produces fungal spore mats on Red Oak. These fungal mats smell sweet & attract the Nitidulid Beetle – a sap-feeding insect. The beetle then carries the spores to a nearby tree and infects it through open wounds. Since fresh, open wounds are needed for the disease to spread, it’s often advised to avoid pruning oak trees from mid-February through mid-June when beetle activity & disease transmission is at its peak.

If an oak tree must be pruned during this time period due to structural issues or storm damage, we have special measures we take to protect your oaks from infection. Our Certified Oak Wilt Specialists can put together the right pruning and protection plan for your oak trees.

Other Ways Oak Wilt Spreads

Oak Wilt is also spread through root-to-root contact. Live Oaks are known for their ability to form root grafts which quickly spread the disease an average of 75 feet per year. This type of transmission seems to occur most frequently in central Texas in established stands of Live Oaks.

Oak Wilt Prevention Treatments

You should consider having your oaks treated with preventative measures if they are pruned in spring and you live in an area with confirmed Oak Wilt. If a neighbor has a tree with Oak Wilt, preventative treatments in your oaks are highly recommended.


Signs and Symptoms

Red and Live Oak exhibit Oak Wilt differently. You should contact your arborist if you notice any of the following:

In Red Oak

  • leaves turning pale green or bronze from the tips inward
  • branches dying one at a time
  • fungal mats on dying trees that smell like fermenting fruit

In Live Oak

  • veinal necrosis of leaves, meaning the leaf veins yellow and then brown
  • fallen leaves with brown veins
  • rapid defoliation

How You Can Stop the Spread

In order to slow the movement of Oak Wilt, follow the steps below:

  • Avoid pruning and wounding oaks February through June unless you are working with a Certified Oak Wilt Specialist.
  • Remove and dispose of diseased trees and wood immediately. The diseased wood should be chipped, burned or buried.
  • If a tree is showing symptoms already, trenches can be dug, at least 4 feet deep and 100 feet from the center of the diseased tree.
  • Preventative treatment with the fungicide Propiconazole has shown to be effective when used in conjunction with trenching.
  • Plant a variety of trees in your landscape or plant Oaks that show greater resistance, such as Monterrey or White Oaks. As always, avoid planting monocultures.

Now that trees are leafing out, it’s important to pay attention to any signs and symptoms of Oak Wilt. If you have any questions or suspect an issue, call in a professional immediately.

Entry Info

Tags: Oak, Oak wilt
Posted: April 24, 2019