Disease Threatens Missouri’s Black Walnuts

Oct 28, 2013

Missouri is the leading black walnut producer in the country, and they make an impressive amount of money producing nutmeat and lumber. But this leading title may soon disappear, as a vector-borne pathogen called Thousand Cankers Disease threatens to breach the state lines. The disease is difficult to track and has the potential to nearly wipe out the Show Me State’s walnut industry.

Thousand Cankers Disease could be disastrous for a place like Martin Tree Farm, a naturally beautiful grove of never-ending walnut trees just a short drive outside Cape Girardeau. It’s owned by Dr. Richard Martin and his family.

Mike Edmunds manages this 288 acre walnut farm and sell the nuts across the region at farmer’s markets.

“When he bought this ground in 1988 and ‘89, at first they looked at this as the city dump but then they changed which was good because then we’d bought the land the city dump was going to be next to it. But this was all plowed ground,” Edmunds said.

The farm itself has a deep connection to the community, Edmunds said, and has a very high sentimental and monetary value.

“Most of the trees out there that have any value is walnuts, not only for the nut production, but you’re talking $3,00 to $4,000 from lumber companies,” Edmunds said. “You can cut down, so if you have 20,000 of those and you lose them all, you know obviously the impact of that can be pretty devastating.”

The Martin Tree Farm is one of the many walnut tree farms across Missouri which have helped the state become a black walnut powerhouse. But despite this success, the entire state is now under the threat of Thousand Cankers Disease. 

This disease only affects walnut trees and has been spotted all across the western United States. Simeon Wright, a forest pathologist with the Missouri Department of Conservation, said the disease is carried by an insect called the walnut twig beetle.

“The insect that spreads Thousand Cankers Disease is very tiny, about the size of a flea, and its very hard to see,” Wright said. “What you’re going to see when you look at an infected tree is going to be dieback, usually in the upper crown of the tree.”

Not only is the insect hard to find, but the disease-causing fungus it carries, Geosmithia morbida, takes a few years to physically manifest within the bark of the infected tree. Should this disease cross state lines, not only will its impact on the environment be noticed, but its economic impact on the state will be just as devastating, according to Wright.

“We estimate that over twenty years, this disease could cause more than $851 million in damages and perhaps 700 jobs lost. So it is something we’re quite concerned about,” Wright said.

For now, Thousand Cankers Disease hasn’t been found in Missouri. But nearby states like Tennessee, Kentucky and Indiana aren’t so lucky.

Infected states have quarantined the movement of walnut wood to within their own state, such as Colorado where the terrible effects of Thousand Cankers Disease was first observed.  The mortality rate within their population of black walnut trees was just below 100% with similar rates in other infected states.

It’s not all gloom and doom here. There is a speck of hope. Ned Tisserat, a Professor and Plant Pathologist from Colorado State University, has noticed that some of the trees survived attacks from the beetles.

“We are hoping that those trees are resistant to either the insect or the fungus,” Tisserat said. “There’s some hope that there are trees out there, walnut trees that have some resistance.”

But Tisserat cautioned the chance of natural resistance is very slim, and each state’s walnut trees will react differently.

In the end, Thousand Cankers Disease remains a looming threat to people like Mike Edmunds back at the Martin Tree Farm and all he can hope for is the quarantines to hold.

“Watch out, be careful, prevent it, because if it comes, you’re done,” Edmunds said. “If it hits a walnut tree it’s gone.”

If the quarantines fail, places like the Martin Tree Farm may cease to be in a few years, and this beautiful forest may return to the nondescript plowed lands it once was.