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The last stand last chance?

Sometime around 1885, near Hoyer Coulee just outside West Salem, Wisconsin, a farmer named Martin Hicks planted nine American chestnuts. Hicks had come to Wisconsin from the East, possibly Pennsylvania, and apparently appreciated the tree's value (see The Perfect Tree sidebar).

Farmer Hicks' nine trees thrived, growing in unglaciated, well drained soils like those of their native range. That woodlot, dominated by American chestnuts, today stretches across 60 acres and two property lines. According to Mary Craig, a University of Wisconsin-LaCrosse student who studied the woodlot in 1987, American chestnut accounted for 59 percent of all trees in the stand and 53 percent of the stand's basal area.

Other important tree species associated with the West Salem stand are shagbark hickory (Carya ovata), paper birch (Betula payrifera), red oak (Quercus rubrum) and white oak (Quercus alba). All are typical species for the area.

The Wisconsin Department of Natural Resources recently surveyed the entire 60 acres and identified 2,434 American chestnuts that were more than two inches in diameter. While more than half of those were less than five inches, the three largest were 36, 40 and 49 in diameter. They are thought to have been among the original nine planted by Hicks.

The organism that causes chestnut blight, Cryphonectria (Endothia) parasitica, was first found in the West Salem stand in 1987. Four trees had been infected, and one, a 60-foot tall triple-stemmed giant, was already dead. It was infested with multiple cankers that contained asexually reproducing fruiting bodies. The other three trees were still alive, but two of those also displayed fruiting cankers. No sexually reproducing fungus was found, therefore it was likely the spores had no yet been spread by the wind.

Why did the blight finally arrive in West Salem? No one knows for sure. The first report of it in Wisconsin was in 1986, at a site more than 80 miles away. There are thousands of vectors for the disease spores, but the stand may have been a victim of its own fame. As the only remaining uninfected stand of its kind in the world, it attracted lots of attention--and visitors--during the mid 1980s. One of those visitors may have carried fungus spores on his or her clothing or shoes.

From the initial discovery of the infection until the end of 1991, 23 infected trees were identified. No sexual reproduction (spores capable of transmission by wind) of the fungus had been noted.

The most likely reason why the West Salem stand went uninfected for so long was its remoteness from other chestnuts, and from the tree's native range. If the infection was a fluke, an improbable event that might occur once every 50 or 100 years, then quick action to isolate and destroy the infected trees might save the stand. A crew from the Wisconsin Department of Natural Resources counterattacked with an ingenious battle plan.

Since cutting down the trees could spread the spores, and hauling them could spread the spores even further, the crew first covered the infected trees with fire fighting foam, then cut them. The thick, white foam smothered any fungal fruiting bodies and prevented the release of spores. Before a tree was cut, a bulldozer was used to cut a four-foot-deep trench. Then, the tree, dressed in its white shroud, was dropped into the waiting grave by a skilled sawyer. The dozer finished its work by covering the tree with soil.

When four more infected trees were discovered in the spring of 1988, the procedure was repeated. To further reduce the chances that the infection would spread to the rest of the stand, additional precautions were taken. The stumps were covered with soil to prevent sprouting. The bulldozer was washed down before leaving the woods. The workers' shoes were cleaned and disinfected with ethyl alcohol.

But two more infected trees were found that fall and three more the following spring. Allen Pray, supervisor of forest pest management for the Wisconsin DNR said, "I thought we had the problem under control, but when we continued finding infected trees, we had to abandon the labor-intensive type of eradication we had been practicing." The use of foam and burial trenches was halted; infected trees were simply cut and burned. Stumps were still covered, using a mixture of soil and manure.

While the experts haven't given up, they have changed tactics. Scientists have felt there is hope for the tree since discovering infected, but still alive, American chestnuts in Michigan and several other states in the late 1970s (see Infecting an Infection sidebar). The fungus that infects these trees is not as virulent as the one that killed billions of trees throughout the chestnut's native range.

Wisconsin Department of Natural Resources decided to introduce some of the weaker fungus into the stand of trees in West Salem and have been working with experts such as Dennis Fulbright of Michigan State University and Bill MacDonald of West Virginia University. The idea is to inoculate all infected trees with the less virulent, non-lethal fungus, thereby infecting the virulent native fungus and tipping the odds in favor of the trees.

But implementation is not easy: According to Jane Cummings Carson, the DNR forest pathologist in charge of the West Salem project, "Introducing hypovirulence requires a permit for the U.S. Department of Agriculture, funding for the cooperators in the project, much planning and at least two visits to the stand per year for the next three years."

Another difficulty is the hypovirulent fungus itself. Before it could be introduced, fungus from the stand in West Salem had to be combined in the laboratory, via tissue culture, with hypovirulent fungus obtained from trees infected with it in Michigan. The task was accomplished in the fall of 1991.

"This form of disease management is still experimental and has had a history of successes and failures," Cummings Carson said. "The small number of infected trees in the West Salem stand provide an excellent starting point for the introduction."

The inoculation finally took place in June. A 10-person team, including Cummings Carson, Pray, and the landowner, spent two days painstakingly inoculating 55 individual cankers on 23 different trees. "The crew used knives and hatchets to rip off bark around cankers to find the canker margin, then used a leather punch to put holes in around the margin, "Cummings Carson said once this had been accomplished, the team placed a slurry of hypovirulent virus and agar into each hole.

By October, Cummings Carson said, callose tissue should have formed around some canker margins if the introduced hypovirulent strain is reproducing. She is "optimistic, probably foolishly. I am excited and anxious. This is such a wonderful site, with large trees and many acres of land involved. We are doing some great research, very worthwhile, and exciting. "We did the best thing we could do for those trees."
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Title Annotation:American chestnut stand in West Salem, Wisconsin
Author:McGrath, Chad
Publication:American Forests
Date:Nov 1, 1992
Previous Article:Tree in a coma.
Next Article:The species you save may be your own.

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