Content provided in partnership with
Butternut blues - US butternut tree, endangered species - Forest Health - Cover Story
American Forests, July-August, 1993 by Rich Patterson
More threatened than even the American chestnut, the "white walnut" may be headed for the Endangered Species list.
One morning last fall, a middle-aged woman entered my office at Iowa's Indian Creek Nature center.
"When I was a young girl," she said, "my father took me out to gather butternuts. We'd crack them at home by the woodstove. They were wonderful, and I want take my own kids out to gather some. We went back to the family farm, but I couldn't find any. Do you know where we might gather a few?"
As the Center's director, I try to help people solve their nature problems, and I knew we had some large butternuts up near our north property line. I told her I'd gladly abandon paperwork for a while and walk up there to inspect the nut crop.
- Most Popular Articles in News
- The Ten Best Laptop bags
- Tata plans cheapest-ever car for Indian market
- GLOBALIZATION AND THE DEVELOPMENT OF UNDERDEVELOPMENT OF THE THIRD WORLD
- Corn is good for you; Corn is not only a tasty treat, but also a cereal that ...
- THE 50 BEST STYLISH HANDBAGS TO CARRY
- More »
A half hour later, we stood at the base of a wide-spreading butternut nestled amid white oaks overlooking the Red Cedar River. Although squirrels had made off with most of the crop, we gathered enough for her to make a couple of plates of cookies for her kids.
As we walked back to her car, we passed other, scattered butternut trees, and gloom descended on us. Although the husky tree that yielded our nuts appeared healthy, all the others we passed were loaded with a disease called butternut canker. Many were dead, standing or toppled; others were obviously fighting a losing battle.
"That's why you're not finding butternuts," I said. "The healthy tree where we found the nuts is the only one I know of around here."
Tragedy has befallen the butternut. "It is more threatened than even the American chestnut," said Mike Ostry, a U.S. Forest Service research plant pathologist. "In fact, it may be the first tree I'm aware of that's being considered for addition to the Endangered Species List."
Butternut has declined so steeply that Minnesota has banned cutting it on state lands. At least two-thirds of Wisconsin's butternuts have visible cankers, and death awaits them.
As the accompanying articles clearly show, tree epidemics aren't unprecedented. Unfortunately, butternut canker (actually a fungus) appears to be doing a more thorough job of eliminating its host than even the chestnut and elm diseases.
"There's an awful lot we don't know about butternut canker," said Ned Tisserat, a Kansas plant pathologist. Tisserat studied the disease for his PhD dissertation at the University of Wisconsin.
A major problem in studying the butternut canker disease is the nature of the tree itself. The butternut, Juglans cinerea, is not and never has been very common. It tends to be solitary and rarely forms groves. Butternuts are scattered all over their range, which takes in a huge swath of the continent, from New England southward to northern Alabama and westward into Iowa. They are probably most common in Wisconsin.
As a general rule, the butternut tolerates colder climates and rockier soil than its close relative, the black walnut. In fact, many people call butternut the white walnut, a reference to its wood of light weight and color that has excellent working qualities, beautiful grain, and a natural sheen.
The tree produces a nut similar to the black walnut, but it's oblong instead of round and is even tastier and oilier. Also like the walnuts, the nut husk and bark contain a powerful dye that stains the hands and can be used to color clothing. Generally, the tree is better known for its nuts than its wood.
Unlike black walnuts, butternut trees are short-lived and medium to small in stature. An old specimen may span three-quarters of a century. Rarely do they reach over 60 feet high, and most are under two feet in diameter. Like walnuts, butternuts love sunlight and usually die if shaded by faster-growing trees.
Butternut's habit of living in isolation makes the spread of the canker disease baffling. "Usually epidemics are fueled by high densities of a species," said Ostry. That makes it easy for disease to rapidly spread from tree to tree, as with the Dutch elm, chestnut, and dogwood diseases.
"You would think that scattered butternut trees would be protected by their isolation, but they are catching the canker disease everywhere," Ostry said.
Butternut canker, Sirococcus clavigignenti-juglandacearum, first identified in 1967, is now found throughout the tree's range. It is not known if the canker was introduced from overseas or if it's an old disease that mutated into a virulent form.
Ostry believes the canker spread to the Midwest from the East. Tisserat's research indicated it may have moved into Wisconsin and Minnesota from an outbreak near Dubuque, Iowa. At any rate, too little is known about the disease, how it moves so effectively across vast distances, and how to protect healthy trees.
Butternut canker produces spores that enter healthy trees through a leaf scar or bark injury. Infected trees form cankers, usually starting on lower branches. These spread to the trunk, where large cankers form. Unlike many other pathogens, the fungus doesn't produce a toxin that kills the tree. Rather, trees produce so many cankers that they girdle themselves and choke to death. Death may occur within a few years after the tree is first infected.
