Oak Wilt in Texas

Ceratocystis fagacearum

Oak wilt is a vascular wilt disease caused by the fungus Ceratocystis fagacearum. This fungus grows in the water conducting vessels of oak trees, which kills the tree. Oak trees outside of the Texas area may be subject to Northern oak wilt.

Download Oak Wilt in Texas Fact Sheet

Treatment Strategy

The treatment strategy for oak wilt in Texas involves two phases. Protection with Alamo® fungicide and root graft disruption.

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Oak Wilt in Texas Treatment Option 1

Alamo® Application 

Alamo® is most effective (95%) when used to protect healthy trees that are near diseased trees. Treatment involves injecting the fungicide directly into the root flares of your oak using the Low Volume Macro-Infusion Pump equipment. Alamo® protects trees from root graft infections and lasts for two years, so two cycles of injections are recommended to get a current infection under control.

Alamo® treatment is recommended for healthy live oaks. Infected live oaks can sometimes be saved if the defoliation is less than 20%. Do not treat infected Spanish oaks. For complete instructions see the Low Volume Macro-Infusion Application Guide or view the application video.

Find out more about quick tips on oak wilt treatments.

Option 1

Application Type -Low Volume Macro-Infusion

DIY Product/Equipment Needed:

• Alamo®

• Low Volume Macro-Infusion Kit

• Stiff bristled hand brush

• Drill

• Shovel

• Gloves

Oak Wilt in Texas Treatment Option 2

Root Graft Disruption

Root graft disruption is an important means of controlling oak wilt in Texas. This is a difficult process and cannot be used in all situations. In Texas, a very large piece of equipment that can cut through soil and rock is needed to achieve the depth necessary to sever the root grafts and stop the disease spread. A rock saw is most often the tool of choice.

Root graft disruption is usually done by a professional. Contact your county seat or city forester for help with this.

Application Type -Root Grafting

Equipment Needed:

• Contact your city forester

Oak Wilt in Texas Treatment Option 3

Removal of Diseased Spanish Oaks

Spanish oaks with oak wilt symptoms should be removed only after all adjacent healthy Spanish oaks have been treated with Alamo and after root-graft barriers have been established. Wilted oaks in the red oak family can produce fungal spore mats between the bark and the wood. The purpose of removing trees is to protect against spore mat production.

Application Type -Tree Removal

Equipment Needed:

• Contact a certified arborist for information about tree removal.

Oak Wilt in Texas DIY Kit

Option 1

Application Type -Low Volume Macro-Infusion

DIY Product/Equipment Needed:

• Alamo®

• Low Volume Macro-Infusion Kit

• Stiff bristled hand brush

• Drill

• Shovel

• Gloves

Option 2

Application Type -Root Grafting

Equipment Needed:

• Contact your city forester

Option 3

Application Type -Tree Removal

Equipment Needed:

• Contact a certified arborist for information about tree removal.

How Is It Spread?

There are two ways oak wilt spreads in Texas:

1 New infection centers are created by sap-feeding insects called Nitidulidae (aka the picnic beetle). These insects feed near oak wilt spore mats that grow on Spanish (red) oaks that died the season before. Afterwards they fly to and feed on sap that flows from a fresh tree wound, spreading the fungus to a new area. For this reason, oaks should only be pruned during the dormant season when spore mats are not active. All initial infections on live oaks must come from a red oak spore mat.

2. Root graft transmissions. Once a new infection is created the disease grows down into the roots and spreads to neighboring trees via root grafts. Root graft transmissions are responsible for most oak wilt infections, and create and expanding ring of dead and dying trees that can grow for miles. Root grafting is the natural underground growing together or joining of the roots of nearby plants of the same species.

Susceptible Trees

Spanish and Live oaks are most often affected with the oak wilt fungus in Texas.

Symptoms

Spanish oaks and Live oaks exhibit different symptoms.

Texas Oak Wilt Symptoms in Spanish Oaks

Spanish oaks die within 4-6 weeks after symptoms appear:

• Leaves wilt and turn brown starting at the top of the tree, this progresses quickly to the rest of the tree.

• The leaves will fall off the tree and be half green and half brown in color. Typically, in other oak issues, the leaves will stay attached to the tree and be a light brown.

• Visible staining is present in the wood underneath the bark of affected branches.

• Infected Spanish oaks produce spore mats the following spring.

Texas Oak Wilt Symptoms in Live Oaks

Live Oaks: Can die within 30 -60 days after symptoms appear:

• The leaves appear bronze and fall off the tree. Necrosis along the main vein is common.

• Wood staining is often present, but is sometimes difficult to see.

• Live oaks do not produce spore mats.

Lookalikes

Other problems mistaken for Texas oak wilt include:

Anthracnose: Anthracnose-effected leaves curl at the location of the brown tissue, whereas oak wilt effected leaves remain flat.

Herbicide damage: Herbicide damage often causes the leaves to curl and grow in abnormal patterns, especially on newly formed leaves and shoots.

Spider mite: Spider mites attack small, random pockets in the tree, unlike the more top-down oak wilt symptoms.

There are several disorders of oak that can be mis-identified as Texas oak wilt, however very few cause leaf drop as oak wilt does.

Related/Similar Problems

Two-lined chestnut borer (TLCB)

Timing

Year Round

Urgency

High

Risk of Spreading

HIgh

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