The Missouri walnut industry is looking at a potential no-win battle against a beetle with an insatiable lust for walnut trees.
The walnut twig beetle, an insect sweeping east from its native Arizona, carries thousand cankers disease, a fungus that kills every black walnut tree it touches.
The beetle has already been found in nine states in the West and five in the East since 2008, including nearby Tennessee. When it comes in contact with a black walnut grove, it’s nothing short of a slow-action mass murder. A 100 percent fatality rate.
Missouri has a lot to lose. A U.S. Department of Agriculture inventory shows the nation’s biggest population of black walnut trees at 112 million. The Missouri Department of Conservation estimates the beetle would do almost $1 billion in damage over 20 years to the Missouri walnut industry.
So it would be good to kill the beetle. One problem, though, is that it’s virtually undetectable. The beetle is the size of a grain of rice, and once it has infected a tree, the symptoms aren’t evident for about five years. By the time it’s recognized in an area, it probably has moved on to others, and the tree showing symptoms will be dead within a few years.
“It’s like trying to hold back an ocean,” said Hank Stelzer, the head of the Forestry Department at the University of Missouri.
Another problem is that uninfected trees can’t be protected — and infected ones can’t be saved. There’s no effective preventative, no insecticide that will either kill bugs on a walnut tree or keep them from getting on it.
To make matters worse, people are to blame for spreading the disease by transporting the beetles. It’s not a fast-spreading beetle by any means. On its own, it moves only a couple miles a year in the forest, said Ned Tisserat, professor of plant pathology at Colorado State University and the leading expert on thousand cankers disease.
But people in effect give the beetle wings by transporting infected firewood and shipping untreated hobby wood. The only real defense is to raise awareness to discourage the long-distance shipping of untreated wood.
All of that, from the lack of detection of the beetle to its spread by careless transport of wood, sets off alarms for anyone who cares about walnuts: arborists, foresters, walnut growers, sawmills, even plant nurseries.
In April 2010, Missouri enacted what’s called an external quarantine, meaning no hardwood from states known to have thousand cankers could come into Missouri.
But what happens if the disease is ever found inside the state?
“All bets are off,” said Tisserat.
Bucky Pescaglia is the president of Missouri-Pacific Lumber in Fayette, and his sawmill can produce 16,000 board feet of lumber daily and ship it out nationally and internationally. Depending on the year, 90-99 percent of his production is walnut wood.
If the Missouri Department of Conservation ever found the disease in the state and responded with an internal quarantine — barring or restricting shipments from Missouri to other states or countries — he can only speculate what that would mean for his business, as well as any other business reliant on walnut.
“We’re already competing with (other businesses) with all of our labor laws and environmental policy,” he said. “Now we’d be having the issue of the twig beetle.”
An outright ban on exporting walnut out of the state would be devastating — for growers and sawmill operators. Or standards for treating the wood before shipment might be developed that weren’t too onerous, at least for the mills.
Ash wood is similarly endangered by the emerald ash borer, but it can be shipped within the U.S. To do that, a company like Pescaglia’s just has to show that the wood reached a high enough core temperature in its kilns. Then again, there hasn’t been any research on what level of heat would be required to kill the walnut twig beetle.
And shipping internationally can be even tougher. Pescaglia remembers an order for ash wood last year from the United Kingdom, whose standards are more stringent. So Pescaglia and his son, Tony, and his cousin and business partner, Ryan Pescaglia, spent two days hand scraping 5,000 feet of lumber of any shred of bark to meet shipping requirements.
Since the walnut twig beetle is native to the southwest, the USDA doesn’t consider it a foreign invasive pest, and states are left to fend for themselves. Missouri’s Departments of Agriculture and Conservation are in the drafting stages of a plan for when thousand cankers is discovered in the state, said conservation entomologist Rob Lawrence, but they do not yet have a clear indication of what quarantines would look like.
A quarantine on shipping wood out of the state mainly would hit the growers, said Harlan Palm, former national president of the Walnut Council, a trade and research group, and a walnut grower himself.
Missouri-Pacific, however, ships internationally to Europe, east and Southeast Asia, and Mexico. Thousand cankers was discovered last month in Italy, and Stelzer is all but certain it came from wood shipped from the U.S. There’s no telling how foreign countries might react. They could set strict quarantines of their own, like the one Pescaglia confronted with his ash shipment to the U.K. Or foreign businesses could simply cut themselves off from thousand-canker-infected America and use walnut wood grown on other soils.
“In many cases, the companies that purchase walnut logs … will export a portion of their inventory on a regular basis,” said Brian Brookshire, executive director the Missouri Forest Products Association. “The quality of walnut leads the country as well. We have a lot at stake when it comes to walnut, the manufacturing of that species, and the jobs that it represents in the state.”