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Updated: Thursday, 31 Mar 2011, 7:01 PM CDT
Published : Thursday, 31 Mar 2011, 7:01 PM CDT
AUSTIN (KXAN) - it's spring. Birds are singing: flowers are blooming; gardens are growing. Also, beetles are flying. Several varieties of Nitidulid beetles are flying hither and thither, landing on wounded oak trees and handing those trees an oak wilt death sentence.
"A beetle can fly," said Texas Forest Service forester Eric Beckers. "They've been documented to fly in West Virginia, through radio-isotope tracking, from one mountain top to another a mile away. So in Texas, we have pretty big hills around here and with these good winds we have, I don't doubt a beetle can fly a mile."
So here's what happens: A red oak tree in an oak wilt-infected live oak area gets the disease by root transfer. Sometimes, not always, but sometimes, that now diseased red oak will produce a mat of fungus under the tree's bark. The sweet smell of the fungal mat attracts the sap eating beetles. They walk on the mat; the spores from the fungus get all over the beetle, which then flies away. If it lands on an open wound on a live oak tree for a meal, the spores invade the live oak and voila: A new oak wilt infestation is born.
"We need to destroy more diseased red oaks," said Beckers. "March, April: A good time of the year to drive neighborhoods where you know there's oak wilt and look for those red oaks that are not budding out."
At this point, it's probably time for a little refresher course.
"In the colder winter, remember: We can prune because the beetle activity is low," said Beckers.
"The dangerous season is spring: Remember, we're not supposed to be injuring our oaks from February through June. That's a great time to avoid injuries on oaks, because that's when the spores are most often available. They can be available as early as November through June, but typically, February, March, April are the top months for spore mats to form and insects to feed. When it warms up, the insects get more involved.
"They're going to be off flying about the neighborhood looking for their next meal. That could be sap on a hedge that you've pruned or the maple or elm tree that you've pruned, the lawn mower damage to your hackberry tree. They'll feed there.
"But if it's a wound on an oak, the spores that they picked up on a red oak fungal mat can be carried to the new wound. They'll germinate and grow into the new tree. Then it's off to the races in the new neighborhood, tree to tree, root to root, throughout the neighborhood.
"So a diseased red oak needs to be burned, buried or chipped. It needs to be eliminated. In the urban, suburban setting, an arborist, a tree-care company can be hired and a tree can be removed completely and taken to a sanitary landfill and be buried that day."
In rural areas, diseased trees can be burned. However, with area burn bans in place because of drought, that is not an option at the moment. An alternative is submerging the tree remains in a pond or stock tank.
Now, not every dead red oak is a problem, though. All across central Texas, trees in the red oak family, like Spanish oaks, blackjack oaks and shumard oaks, die all the time. Sometimes it's because of boring insect damage or severe wounding by humans. Sometimes they just die of old age.
However, if a red oak dies suddenly in an existing oak wilt infested area, alarm bells should go off.
"That's when people need to call a certified arborist or a forester and say, 'Hey, what's wrong with my red oak.'" Beckers said.
Okay, but what about using dead oak trees for firewood?
"It is dangerous to use unseasoned firewood," Beckers warned. "What will happen is someone will lose a Spanish Oak and say, 'Well, I'll make good use of it by turning it into firewood.' But that diseased tree, if it died near a live oak disease center, that diseased Spanish oak or blackjack oak, any of the red oaks, is harboring the disease.
"You could move that cut log 200 miles and there it could go into its life cycle and produce fungal mats. And in every neighborhood, there are these sap feeding beetles and they will be attracted to this fermenty, fruit, sweet-smelling aroma of the fungal mat. They will pick up the spores and in that far, far away neighborhood where the firewood was taken, spores will be distributed into a new community."
Live oaks, on the other hand, do not develop the fungal mats that produce the dangerous spores. Still, live oak wood can present its own issues.
"If you are dismantling a dead, diseased live oak, we encourage you to store it for a year before you distribute it to healthy neighborhoods of trees," Beckers said. "When you are buying firewood, make sure it's well-seasoned. If it's quartered and halved, that would be great. If the bark is falling off and the wood is cracking on the ends, that's well-seasoned fire wood. A fresh cut log wouldn't burn so well anyway; you want dry wood. So if it's well-seasoned and dry, the oak wilt has perished in that log."
Meanwhile, of course, it's still important to consider trenching around oak wilt areas to cut the root connections
that cause gradual movement of the disease from tree to tree. If wilt does hit your neighborhood, fungicide treatments can help save vulnerable trees. And it's crucial to use a spray disinfectant to sterilize tools you use to trim trees.
Admittedly, it's a big and somewhat complicated problem. But Beckers attacks it with gusto.
"Management of oak wilt is very difficult," he said. "I call it a beast or a bear. Once it's out and moving, it's hard to stop and hard to manage. It's a very effective fungus at killing live oaks and red oaks. It's the number one pathogen of oaks in North American, in 23 states.
"So I would much rather spread the message of prevention. We can avoid injuries in the spring months, February through June. We can paint wounds on oaks year-round. Then the part we're missing is this: We need to destroy more diseased red oaks."
Here's the good news: We're not alone in the fight. Using federal funds, the Texas Forest Service picks up the tab for 40 per cent of the cost of getting rid of those red oaks. Also, the agency is actively recruiting volunteers for a Red Oak Monitoring Network. Beckers calls it his "Red Oak Posse."
"I'm equipping organized groups with maps of their communities, if they have oak wilt especially," Beckers said. "I'm showing them the outline of the disease and which red oaks they need to be monitoring closely over the coming seasons.
"As long as the red oaks leaf out in the spring and are beautiful trees, they don't need to be worried about them. But as soon as one dies in September or October, or doesn't leaf out in the March, April time frame, that's the key time to get in there and take a closer look."
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