FOR IMMEDIATE RELEASE
February 4, 2025
Prevent the spread of oak wilt in Texas
COLLEGE STATION, Texas— Oak wilt is
one of the deadliest tree diseases in the United States, killing millions of
trees across 76 Texas counties. Texans can help prevent it from spreading by avoiding
pruning or wounding oak trees from February through June.
“Prevention is key to stopping the
spread of oak wilt,” said Demian Gomez, Texas A&M Forest Service Regional
Forest Health Coordinator. “Any new wound on an oak tree can be an entry point
for infection including those produced by pruning, construction activities,
livestock, land or cedar clearing, lawnmower, string trimmers and storms.”
Small insects, called sap beetles,
move spores of oak wilt fungus to new trees and are very active in late winter
and early spring. Because of this, pruning or wounding trees should be avoided
from February through June and no matter the time of year, all oak tree wounds
should be painted immediately.
Oak wilt is caused by the fungus Bretziella
fagacearum. The fungus invades the xylem, the water-conducting vessels of
the trees, and the tree responds by plugging the tissues, resulting in a lack
of water to the leaves, slowly killing the infected tree.
All oaks are susceptible to oak
wilt. Red oaks are the most susceptible and can die in as little as one month
after being infected. Live oaks show intermediate susceptibility, whereas white
oaks are the least susceptible, but they are not immune to infection.
Oak wilt can spread two ways –
above ground by sap-feeding beetles or underground through connected roots.
The disease spreads above ground by
sap beetles more rapidly in late winter and spring because of high fungal mat
production and high insect populations. During this time, red oaks that died of
the disease last year may produce spore mats under the bark. With a fruity
smell, these mats attract small, sap-feeding beetles that can later fly to a
fresh wound of any oak tree and infect it, starting a new oak wilt center.
The second way oak wilt can spread
is underground by traveling through interconnected root systems from tree to
tree. Oak wilt spreads an average of 75 feet per year by the root system. This
occurs primarily in live oaks and is responsible for the majority of spread and
tree deaths in Central Texas.
Oak wilt is often recognized in
live oaks by yellow and brown veins showing in leaves of infected trees, known
as veinal necrosis. This time of year, it may be difficult to diagnose oak wilt
due to seasonal transitioning of oak leaves in the spring – when evergreen oak
trees shed their old leaves while simultaneously growing new leaves. The signs
of oak wilt can be seen on a majority of leaves when a tree is fully infected.
Landowners should contact a certified arborist if they are unsure if their tree
is infected.
“For red oaks particularly, one of
the first symptoms of oak wilt is leaves turning red or brown,” said Gomez.
“While red oaks play a key role in the establishment of new disease centers all
oaks can move oak wilt through root grafts, particularly live oaks.”
To stop the spread of oak wilt
through the root system, trenches can be placed around a group of trees, at
least 100 feet away from the dripline of infected trees and at least four feet
deep, or deeper, to sever all root connections. Another common management
method for oak wilt is through fungicide injection. The injections only protect individual trees
that have been injected. The best candidates for this treatment are healthy,
non-symptomatic oaks adjacent to and up to 75 to 100 feet away from symptomatic
trees.
Other ways to help prevent oak wilt
include planting other tree species to create diversity in the area; avoiding
moving firewood; and talking with neighbors about creating a community
prevention plan for oak wilt. Infected red oaks that died should be cut down
and burned, buried or chipped soon after discovery to prevent fungal mats that
may form.
Not only is saving oak trees
important for our ecosystem and health, but also for property values and
community aesthetics. Loss of trees due to oak wilt can reduce property values
by 15 to 20 percent.
Some cities and municipalities,
including Austin, the City of Lakeway, Dallas, Houston, San Antonio and Round
Rock, have oak wilt programs in place with municipal foresters dedicated to
managing the disease. Texans can also contact their local Texas A&M Forest
Service representative with any questions about this devastating
disease.
For more information on oak wilt
identification and management, visit https://texasoakwilt.org/ or the Texas A&M Forest Service website at
https://tfsweb.tamu.edu/.
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Photos: https://agrilife.photoshelter.com/galleries/C00004ctr0uNLkTQ/G00006o6TrfnxovU/Oak-Wilt-2025
Texas A&M Forest Service Contacts:
Demian Gomez, Regional Forest Health
Coordinator, demian.gomez@tfs.tamu.edu, 512-317-8166
Communications Office, newsmedia@tfs.tamu.edu, 979-458-6606