Beetle Destruction Could Chew $1 Billion Out of Forest Oaks

More than $1 billion worth of red oak trees in the Ozark Mountains could be destroyed if researchers don’t find a way to squash a one-inch-long beetle.

Since 1999, red oak borer beetles have killed 50 million oak trees along some of the most scenic highways in the Arkansas Ozarks, including state Highway 7 near Pelsor and Highway 23, also known as the “Pig Trail,” in north Franklin County.

The borers have destroyed half the oak trees on 300,000 acres within the Ozark National Forest in Arkansas, said Howard Freerksen, U.S. Forest Service forester for the Ozarks.

“This is the worst anybody has seen it in recorded history,” said Freerksen, who is stationed in Russellville. “I have yet to look at a stand [of trees] that wasn’t infested.”

Fred Stephen, a professor of entomology at the University of Arkansas in Fayetteville, said red oak borers can be found in forests throughout the eastern United States, but they’re only at epidemic levels in the Ozark highlands of Arkansas, Missouri and eastern Oklahoma. And there’s no easy, affordable way to kill them.

The Ozark National Forest in Arkansas encompasses 1.1 million acres of the 15-million-acre Ozark highlands plateau, which stretches from the Arkansas River Valley north into central Missouri. But 78 percent of the Ozark highlands is private land, and it’s difficult to gauge the extent of the red-oak borer damage there.

The National Forest Service estimates the damage at $1.1 billion based on the cost of lumber and 33 percent of the red oaks in the Ozark highlands being damaged by the borers. But some experts think that’s a conservative estimate. Freerksen said there may already be $500 million worth of borer damage to the red oaks in the Ozark highlands. The borers also attack white oak trees but not as severely as red oaks.

The beetle larvae bore holes through the inside of the oaks, making the wood useless for lumber. If the infestation is high, the logs can’t even be run through a chipper because the borers gum up the machinery.

“When we had high infestation before, it didn’t kill trees or devalue timber,” Freerksen said.

Boring Boomers

Freerksen said the borers have left many dead oak trees standing throughout the Ozarks.

But the borer epidemic shouldn’t affect tourism, he said, because most people who visit the Ozarks won’t notice the difference. Even though oaks made up about 60 percent of the trees in the region, other trees have sprouted leaves to fill in part of the canopy.

Partially gutted oaks could fall at any time, posing a threat to hunters, hikers and campers.

“It does create a dangerous situation,” Stephen said. “Both limbs and trees could fall. It’s a frightening place to be. You don’t know when something is going to break, and those limbs are hugely heavy.”

Freerksen said the borer epidemic appears to be waning, but that’s largely because so many trees have already been killed.

The flying insects are native to Arkansas, but historically the state’s oak trees have been able to fight off borer infestation.

One of the major problems is old age.

Before European settlers reached the Ozarks, Native Americans regularly burned the forests to create more grasslands, which in turn lured more elk and buffalo.

As a result, the Ozarks had fewer trees, but the trees that remained were larger. Stephen estimates the area had about 10 trees per acre then, compared to about 100 now.

The Ozarks were heavily logged from the early 1800s through the 1920s.

“It was oaks from the Ozarks that moved the railroads west,” Stephen said, referring to railroad ties. Oak is also used for flooring, furniture and pallets.

“At one time, this was one of the heaviest concentrations of logging in the country,” Freerksen said of the Ozarks.

During the 1930s, the logging industry slowed and “we started heavy fire-suppression activities,” Freerksen said.

Because of those factors, many of the oaks throughout the region are about the same age, although some stands of oaks in the region are about 120 years old and there’s an occasional 300-year-old oak or pine tree left standing.

Oaks are considered mature when they’re between 60 and 80 years old. That means the oaks of the Ozarks are, like the baby boomers, entering that age where they’re not as able to fight off disease and the bugs of life.

Other factors, such as too many trees and a drought a few years ago, have exacerbated the problem.

But a rainy summer in 2002 helped the oaks fight back. The water allowed a fungus to grow that acts as a parasite and kills some of the borer larvae in the trees.

Meet the Beetles

Red oak borers lay eggs in bark crevices and under lichens on oak trees. When the eggs hatch, the larvae bore into the phloem, under the bark, and feed off that nutrient-rich part of the tree for two years.

“They essentially girdle the tree,” Freerksen said. “They make so many holes in it that the tree can’t transmit nutrients to the upper part of the tree, so it basically suffocates.”

Adult beetles emerge from the trees every other year, only taking flight in odd numbered years in the Ozarks, Stephen said.

The adults are active for a six-week period, from mid-June to early-August. During that time, the females are laying eggs over a 200-acre territory.

Finding one or two red oak borer beetles or larvae per tree is normal, Freerksen said. Before 1999, finding four or five borers per tree was considered an epidemic. Since then, many trees were found to be infested with 400 to 500 borers. Stephen said he has found more than 4,000 borers in one of the 32 trees that was cut down and brought back to his lab for analysis.

But since the summer of 2002, Freerksen said he’s usually finding five to six borers per tree. That’s still considered an epidemic, but he said it’s not likely to kill the trees.

“I think the mortality rate has significantly tapered off,” he said.

Freerksen said a healthy oak might be able to tolerate 30 to 40 borers.

“Our efforts right now suggest there are a lot of trees still dying, and the population of red oak borers is still high,” Stephen said. “We don’t know if we’ve seen the worst of it.”

Stephen said he and his researchers have been studying the natural enemies of the red oak borers to try to battle the beetles. Possible solutions include woodpeckers, fungal pathogens, nematodes (roundworms) and whatever it is in the chemistry of young oak trees that enables them to fend off the borers.

“Trees are normally resistant to these things,” Stephen said. “Whether through chemistry of the bark or what, they normally wouldn’t let the larvae live in there.”

The UA has received two $35,000 grants from the U.S. Department of Agriculture to study the problem. Stephen said his researchers in the entomology department are working with other parts of the UA to battle the borers. The UA’s Center for Advanced Spatial Technologies, for example, has been providing geographic information systems technology to map the Ozarks and see where borer damage has occurred.