A fungal infection caused by Bretziella fagacearum that infects oaks within their water-conducting vessels (xylem). The tree responds by plugging these tissues, resulting in a lack of water to the leaves. This causes canopy loss and death in most circumstances.
Yes, oak wilt can be confused with other tree problems such as severe drought, heat, lightning strikes, herbicide damage, excessive salt and fertilizer, and other diseases that can cause a response in oaks that resembles oak wilt. When in doubt, seek professional assistance or send samples to the Texas Plant Disease Diagnostic Lab.
No, oak wilt is caused by a fungus, Bretziella fagacearum. Oak decline is caused by a combination of factors (environmental, tree care practices, insects/pathogens) that lead to the decline of a tree’s health over time. Unfortunately, oak wilt in Texas was first misdiagnosed as oak decline and the name and confusion have persisted.
A red oak that was recently killed by oak wilt should be cut down and destroyed immediately to reduce the risk of fungal mat formation. Live oaks that are dying/dead from oak wilt can remain standing as they do not pose a risk to disease spread. If a tree becomes a risk to property or person, it should be removed for safety concerns.
Avoiding any pruning or wounding of oak trees from February through June. Immediately paint any wounds to oak trees year-round. Destroy infected red oaks by burning, burying or chipping. Practice caution with firewood by moving and storing only thoroughly dried wood, burning all wood before spring, never storing wood near healthy oaks, and covering firewood with clear plastic and burying the edges.
Once an area is infected with oak wilt, the disease will be present until the host tree(s) die. The disease has been observed several years after initial infection in some trees. If there are viable root connections, the disease can still spread further.
No. Oak wilt is a primary pathogen meaning it can infect any oak regardless of health. It is the tree’s response to infection (the closure of water-conducting vessels) that actually kills the tree. It has been observed that healthy trees are the most affected because they have a stronger response to the fungus compared to stressed trees.
Sap-feeding beetles are not maliciously infecting trees. They are opportunistic feeders and are just taking advantage of the resources available to them; fungal mats and tree sap. These beetles also find food in other plants like cacti. Prevention is easily accomplished by immediately painting wounds to oaks and not pruning oaks during the spring.
Pruning & Painting
Any paint will suffice. The purpose of the paint is to prevent spore-carrying sap beetles from visiting the wound. Any method will work as long as the paint is applied immediately upon making the wound. Oak wilt only affects oaks; therefore, only oaks need to be painted.
In Texas, fungal mats are produced when sap beetles are most active, making oaks more vulnerable to infection in spring. Therefore, it is recommended to avoid pruning oaks from February through June and to always immediately paint any pruning cut. Generally, the best time to prune trees is when trees are dormant and when fewer insects and diseases are present (Nov – Jan).
As a best practice, all wounds – no matter the size – should be painted. However, very small wounds from twigs and suckers that are less than the size of your little finger have a very low probability of attracting beetles.
Probably not since oak wilt can only survive within living oak trees and is killed at temperatures above 95°. However, sterilizing tools is a good idea when moving from tree to tree to avoid spreading other tree diseases. Spray disinfectants, rubbing alcohol, or 10% bleach solutions will suffice. Caution: do not spray rubbing alcohol on hot or running chainsaws!
Management (Trenching and Injections)
Since the inception of the Oak Wilt Suppression Program in 1988, the Texas A&M Forest Service has assisted landowners in installing over 4 million feet of trenches, following program protocols, with a success rate of approximately 74%. Protocols include placing trenches at least 100 feet beyond symptomatic trees, excavated to a minimum depth of 4 feet, and having at least 1 non-symptomatic tree between the infection and the trench. When trenches fail to contain the disease, they were either not placed far enough from the infection or were not cut deep enough, resulting in remaining root connections that are still linking the diseased side to the protected side.
Properly injected trees, which do not currently show any oak wilt symptoms, but are in the vicinity of the disease, will have the highest success rate – reaching 80-90% – using the approved fungicides and the macro-infusion method. The success rate decreases drastically depending on the severity of the crown loss in the tree and the amount of visibly-symptomatic leaves. Approximately 10-20% of live oaks survive oak wilt with no treatment. Note: surviving trees (both treated and untreated) may show significant canopy loss, but remain alive.
No. Most of the fungicide moves up into the tree, rather than into the roots. There is not enough fungicide in the roots to provide a sufficient barrier to disease movement; therefore, the fungus still has the opportunity to travel in the unprotected root system to adjacent trees.
We don’t know. Current treatment recommendations are based on years of research from USDA Forest Service, universities, other state agencies and years of experience managing this disease. We can provide a landowner with realistic expectation of results using current treatment protocols. We can only recommend products that are legal to use; labelled and registered for oak wilt. We can only recommend delivery methods based on research results. If hiring vendors to treat trees, those vendors must be licensed through Texas Department of Agriculture. One must have a thorough understanding of the fungus, the trees, and how they interact and any treatment must increase the survival rate compared to what occurs in the natural population (10-20% survival). Unless these criteria are met, we do not know the success of alternatives.
Although uncommon, oaks can form root grafts between differing species and it is possible for red or white oaks to contract the disease from the other through these connections. Depending on the value of the tree and proximity to the disease, injecting red or white oaks may be warranted. Note: it is more common to inject live oaks (which are white oaks) due to the fact their root systems are frequently grafted together.
It depends on the progression of the disease in that area. For best results, trees should be evaluated every 18-24 months for new oak wilt symptoms and re-treated if necessary. In most cases, trees are initially treated then re-injected two years later.
No. Live oaks have vast, interconnected root systems that stretch for hundreds of feet in all directions. Pushing or cutting trees causes very little if any root disruption, and the fungus can still live in the roots without the tree present. This method was tried at the onset of the discovery of the disease and proven ineffective.
Yes. The fungicide is not a restricted-use pesticide. A pesticide applicators license is not required to purchase the fungicide to you treat your own trees; however, you cannot treat trees for money, goods or services for others. Learn how to treat trees by watching this video. If you are not confident with the treatment process, there are arborists who have specific training and experience with oak wilt injections.
Many arborists and vendors sell the fungicide and equipment. Some rent equipment. You can find results on the Vendor page or by doing a quick internet search using keywords like “oak wilt injection kits” and “oak wilt fungicide.”
Yes. The fungus that causes oak wilt is a living organism and burning will kill it. Plus there is no danger of spreading the disease through burning or smoke.
Possibly. The fungus that causes oak wilt cannot survive temperatures above 95°F nor moisture content below 20%. Thoroughly dried, seasoned wood poses no risk to spreading. Green, infected red oak wood poses a risk as fungal mats can form on logs and become a source of fungal spores. These spores are picked up by sap-feeding beetles that could infect healthy oak trees in the immediate area. Never move or store infected and unseasoned red oak wood. Only move, purchase and store thoroughly dried firewood and cover with clear plastic to heat and dry the wood and to keep insects from escaping. Thoroughly dried wood will have loose bark, cracks in the wood, and will be lighter in weight than green firewood.
Yes. Chipping the wood will facilitate heating and drying. The fungus cannot survive these conditions.
Yes with precautions. It is recommended to wait a few years before reintroducing oaks as there is potential for roots to graft with existing root systems, creating a pathway for infection. Non-oak species can be planted at any time.
No. All oaks are susceptible to infection from oak wilt; however, some species are more tolerant of the disease than others. Red oaks (blackjack, Shumard, Texas red, water) are extremely intolerant of the disease and will die if infected. White oaks (bur, chinquapin, Lacey, Mexican white, post, white shin) are more tolerant of the disease; however, they can become infected and suffer canopy loss, and, in some cases, die from the disease. Live oaks (live, Texas live) are intermediate in tolerance, with approximately 20% of infected trees surviving the disease in various states of decline.
Texas is a very large state with 12 distinctive ecoregions that support a variety of trees. Trees adapted to some parts of the state may not grow in others. View our Recommended Trees and check out the Texas Tree Selector for help with choosing appropriate trees for your property. In Texas, fall is the most appropriate time to plant trees. This gives trees a chance to establish in the landscape before the heat of summer. Texas celebrates its Arbor Day the first Friday in November. Texas A&M Forest Service (TFS) offers seedlings through the Central Texas Restoration and Recovery Program. Seedlings are grown from seed collected throughout central Texas and are available through the Texas A&M Forest Service – West Texas Nursery.
No. Some municipalities, homeowner associations, and property owner associations have ordinances concerning oak wilt. These ordinances vary from community to community.
No. TFS is not a regulatory agency. If your community has an ordinance concerning oak wilt, you can follow the protocols stated in that ordinance. If not, informational and educational resources are located on the Community Tools tab of this site.
No. Texas A&M Forest Service personnel can only come onto a property at the request of the owner. There are private vendors that do offer this service.
Yes. If you know oak wilt is present on the property and you fail to disclose that information, you could be in violation of the Deceptive Trade Practices-Consumer Protection Act.
Inform, educate, and monitor! Form a committee or task force to inform the community of the problem, educate the community about oak wilt management, and monitor the disease progression in the community.
Limited cost shares are available (through TFS) to reimburse a percentage of approved treatment costs. Ask your TFS Forester for more details.