Drive out to Fredericksburg and Kerrville and you’ll pass miles and miles of haunted oak tree stands. What once were majestic trees are now ghostly skeletons of their former beauty.
The cause is oak wilt, which is spreading fast in areas where Austin continues to sprawl. If you’re lucky enough to have a home in a neighborhood with some trees, then you should know the hazards of this deadly disease, and what you can do to contain it in your neighborhood and yard.
An infected tree can die quickly, in as little as a few months, or it can struggle on for years, losing some of its canopy bit by bit. The cause of oak wilt, how to prevent it, and even how to get help from the City of Austin to control it was the subject of a talk at the Ladybird Wildflower Center last weekend.
Arborist Chris Dolan explained the oak wilt problem at the Tree Talk Winter Walk event on Saturday. While we can’t eradicate oak wilt, working together, observing patterns in our local trees, and sharing information; we can control it.
The best way to battle this disease is to be aware of the signs, and act immediately. Keep your eye on the red oaks and live oaks in your area, because these trees are the most susceptible. The first telltale signs of infection are usually yellowing leaves that start in the veins. Don’t confuse oak wilt with a tree in draught, which has leaves that turn brown. The oak wilt infested tree’s leaves are much more colorful. If you’re unsure, call an expert. They’ll come check it out, and help you decide your next steps.
How is a tree infected and how does oak wilt spread?
A tree is first infected by a tiny nitidulid beetle, which feeds on fungal mats of diseased oaks (usually red oaks). Then they transfer the fungus to other oaks, where it attacks the water conducting system in healthy trees. The spread if oak wilt through the root systems of live oaks accounts for the epidemic, but it’s the beetle — attracted to fungal mats in diseased trees and the smell of fresh wounds in healthy trees — that starts the chain reaction.
To prevent oak wilt’s spread:
Don’t cut live oaks and red oaks unless temps are over 90 degrees or less than 50 degrees Fahrenheit. After a brief discussion about the various “safe months,” Chris made it clear it’s the temperature you should be aware of, not the month per se. The bugs that spread it just are not active during extreme temperatures and the fungus isn’t likely to grow.
When you do cut or prune trees, be sure to clean your saws with Lysol as you move from tree to tree just in case there’s an infected tree you’re not aware of. Also, immediately seal the wound with spray paint or brush on a less toxic latex paint.
Here’s a tip you don’t often hear: Store only dried out or cured firewood, especially if you’re storing cut wood near other healthy oak trees. Fresh cut, diseased wood accounts for the spread of oak wilt as much just as a contaminated saw. Make sure it’s cured and stored away from healthy oaks.
Another precaution: When a red oak is in the process of dying, let it die naturally before removing it. Once the tree is dead, the oak wilt is mostly gone. So let nature take its course and THEN remove the dead tree ASAP.
The expense of treating oak wilt in Austin
A 5000-ft trench cut around Travis Heights in 2004 cost about $150,000. The good news is the trench held the oak wilt at bay except for two small spots. Dolan considers this massive trench a success. Austin’s citizens, the City, and oak wilt specialists worked together to keep the oak wilt to a minimum so the community could enjoy their gorgeous oaks for years to come.
Because Austin’s trees are a source of pride and pleasure, the City of Austin will pay a homeowner or neighborhood association up to 40% of the cost to remove a diseased tree. The same goes for the cost of digging a trench around a stand of sick trees to prevent spread via roots. A private homeowner can get up to $10,000 to help prevent the spread of oak wilt in central Texas.
Oak wilt control can indeed be expensive. A four foot trench dug a minimum of 100 feet from the nearest infected tree is the mimnimum preventative safety zone. In the city where there are cables and underground utilities to worry about, the cost can escalate to around $60 per linear foot. In the country, the cost of a trench is far less ($2 per foot) so be sure and get help as soon as possible after you discover a sick tree.
Besides isolating by trenching, you can try staving off oak wilt by treating a tree with injections of a “medicine” called Alamo™ around the roots of the tree. If a tree is already infected, you might hold off the spread of the disease inside the tree. If it’s healthy you can prevent oak wilt altogether, as long as you continue to treat the tree every few years.
The caveat: the Propiconazole must be applied by a trained and licensed arborist, and by the way, don’t bother treating a tree that’s a full block away. The most effective application is when the nearest oak wilt is 150 feet from the healthy tree, since the injections only last 18 months and oak wilt spreads between 75 and 150 ft. per year. (Do the math!)
Which trees will replace oaks in the future?
If oak will moves in to your neighborhood, you can do some wonderful preventative maintenance, too. That is, plant some resistant trees on your property. Some trees to consider as you replace lost trees are any of the white oak species: Burr Oak or Chinquipin. Beech and Cedar Elm are also good options.
Chances are, oaks are on their way out. The best thing tree lovers in central Texas can do is plant a wide variety of trees. Diversity is the answer, and we can start now. Drive to the outskirts of town toward all the new neighborhoods where developers are clear cutting entire hillsides to construct homes. These communities have an opportunity to create a gorgeous tree-filled community if they look to the future.
“You don’t plant trees for yourself. You plant them for your grandchildren.”
As Chris Dolan points out, “Oak wilt can never be eradicated. But it can be managed.” Share this article with your neighbors and visit texasoakwilt.org for tons of great information.