General
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.
Contact local TFS personnel, a local
AgriLife Extension agent, an
ISA Oak Wilt Qualified Arborist, or take samples and send to the Texas Plant Disease Diagnostic Lab.
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.”
As a government agency, the Texas A&M Forest Service cannot make vendor
recommendations. Learn how to hire an arborist to make sure you are making
the right choice, then find local oak wilt vendors in your area.
Firewood
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.
Planting
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 can be infected by the fungus that causes oak wilt; however, some species are more susceptible to the disease than others. Red oaks (blackjack, Shumard, Texas red, water) are extremely susceptible to the disease and will die if infected. White oaks carry some resistance to the disease, with variations among the group depending on species. Post oak, bur oak and Mexican white oak are very resistant to the disease. These species may exhibit some canopy loss, but rarely die when infected. White shin oak, chinquapin oak and Lacey oak can grow in stands with interconnected root systems, enabling the fungus to infect adjacent trees. These species carry more resistance to the disease than red or live oaks and usually survive infection with moderate to severe canopy loss; but they can die in large numbers from the disease. Live oaks (live, Texas live) are intermediate in susceptibility, with approximately 20% or less 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.
Community Assistance
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.