A little native beetle is taking advantage of forests weakened by oak decline to decimate large tracts of red oaks in Arkansas and neighboring states.
The red oak borer lays its eggs almost exclusively on red oak trees, though they've been known to attack white oaks in some areas, said Fred Stephen, forest entomologist for the Arkansas Agricultural Experiment Station and interim head of the University of Arkansas Division of Agriculture's department of entomology. When hatched, the larvae bore into the trees, emerging two years later as adult beetles.
Although the red oak borer has always been found in Arkansas, it was not considered a serious pest until a few years ago, when sudden population growth turned it into a threat to the region's hardwood forestry industry.
“Red oak borer populations are a hundred times higher than at any other time on record,” Stephen said.
A survey of 1,000 red oaks in the early 1970s found up to 71 red oak borer attack holes in a single tree, said UA post-doctoral entomologist Damon Crook. “Now we're finding up to 4,200 attack holes in a tree.”
This population explosion is part of a chain of events in a general oak decline that stretches across the hardwood forest belt from the Atlantic Coast to Arkansas, said Forrest Oliveria, entomologist for the U.S. Forest Service Forest Health Protection, Southern Region. As oak populations decline, other species take over.
“We're witnessing an ecosystem-changing event,” Oliveria says. “Oaks won't disappear, but the composition of species will change and other trees may become dominant in many areas.
The red oak borer is an opportunistic pest that probably got a boost during a severe drought in the late 1990s. Healthy trees kill boring insects by suffocating them or pushing them out with sap. “Drought stress reduces sap the trees use to defend themselves,” Oliveria said.
Red oak borers are already having an impact on Arkansas' timber industry, said Matthew Pelkki, economist for the Division of Agriculture's Forest Resources Center at Monticello, Ark.
“There are 13.8 billion board feet of standing red oak in Arkansas, Missouri and Oklahoma — about $1 billion in standing timber,” Pelkki said. “Thirty percent of this volume is at risk from red oak borer.
“Severe red oak borer damage could lead to a $250 million drop in Arkansas' total annual timber industry output of about $8 billion in this state,” he said. “Labor income could drop as much as $60 million and the state could lose about $5 million in taxes.”
He said economic losses could be greater in Missouri, where the timber industry is more dependent on production of hardwood lumber.
“Landowners need to inform themselves about the value of their timberland and always get the help of a professional, registered forester when selling their timber,” said Tamara Walkingstick, Arkansas Extension forestry specialist. “The best thing a landowner can do to minimize potential damage is to actively manage forest land.”
How much damage the red oak borer will do is unknown and no strategy has been developed to stop its onslaught. Stephen believes controlling the beetle with traditional means may be impossible.
UA graduate students are conducting research on genetic traits that govern the red oak borer's life cycle or habits; using geographic information systems to identify infested areas and track and predict their spread; and other projects to help shed light on how to understand and control this pest.
It's possible that nature will solve the problem. “One of the things we're looking at is how many borers actually survive to emerge as adults this year, compared to those that emerged in 2001, to see if the population is increasing, declining or maintaining,” Stephen said.
Fred Miller is science editor for the Arkansas Agricultural Experiment Station. e-mail: firstname.lastname@example.org.