Fungus destroying butternut trees in Iowa

CEDAR RAPIDS - Part way down a wooded slope above a tiny, unnamed stream, a bleak tale is playing out nearly without notice.

Here, at this spot on the property of the Indian Creek Nature Center, a scattering of butternut trees has been coming down, one by one, in the onward march of a killing fungus known as butternut canker.

Rich Patterson, the center's longtime director, wrote a piece 18 years ago for American Forests magazine called “Butternut Blues,” in which he documented the already-apparent start of the demise of the butternut tree in Iowa and elsewhere in a habitat that stretches from Iowa to the Atlantic Ocean and to the start of the Deep South.

Twenty years ago, the Nature Center's 300 acres, about half forested, featured about 100 butternuts, estimates Patterson. Today the number is down to 25, and falling.

The story is as grim statewide, where a tree survey in the last few years has left the Iowa Department of Natural Resources to conclude that Iowa has lost 90 to 94 percent of its butternut trees since 1990. The recent survey concluded that 80,000 butternuts, plus or minus 40,000 trees, are still here, down from 1.5 million in 1990, reports Aron Flickinger, a DNR special projects forester and the agency's butternut specialist.

Butternut trees are so decimated in Iowa that Flickinger doesn't bother walking into a woods in hopes of finding one. Instead, in his current effort to identify and study the remaining butternuts, he sent an inquiry to entities like the Indian Creek Nature Center, asking them to steer him to butternuts that they know about.

His resulting examination of about 100 trees did not turn up one without the canker fungus, he reports. Even so, he says a few trees appeared to have the capacity to heal, and it is those trees to which he is looking to take material to graft into the start of new trees.

Evidence of the butternut canker's telltale wounds in the trunks of some of the Indian Creek Nature Center's butternuts was on full display last week. There is little chance of saving a tree from the fungus if and once the fungus has spread and created numerous cankers that then essentially strangle the tree's trunk, the center's Patterson says.

The approach to saving the butternut is to keep in place seemingly healthy trees and even those with some evidence of the fungus in hopes that some resistant or resilient trees might survive. In fact, Canada has declared the butternut an endangered species and has adopted regulations to keep butternuts in place until it is clear they are dying.

As part of Iowa's butternut project, Flickinger says the scattering of about 20 butternuts in one timbered piece of Nature Center property is the largest cluster of large butternuts he has found in the state.

“That's not saying much,” Patterson says.

He also has studied a couple of butternuts along railroad tracks near Carver-Hawkeye Arena at the University of Iowa in Iowa City and some in Delaware County.

According to the U.S. Forest Service, the butternut canker fungus, first identified in 1967 in southwestern Wisconsin, initially infects trees through buds, the scars left on stems once leaves fall and possibly openings in a tree's bark. The fungus is then carried down the tree's trunk, forming cankers or localized dead areas that eventually surround a trunk, killing it.

“You get enough of these sores and it blocks the plumbing of the tree and kills it,” says Patterson. “It prevents the tree from sending nutrients and moisture and all up and down it.”

At the ready in his Nature Center office is a profile of the butternut in the book, “A Natural History of North American Trees” by Donald C. Peattie, a favorite of Patterson's.

In his profile, Peattie notes that the butternut, often called the white walnut, has walnut-like nuts of oblong shape that leave a stain on the hand that only vanishes over time. He also notes that many Confederate soldiers in the Civil War wore uniforms colored a golden brown from the dye of the butternut, and so were referred to as “Butternuts.”

As Peattie says, “So the very name of the tree has become a synonym for tattered glory.”

Patterson says the passing of the butternut has gone largely unnoticed because the butternut is a rural tree, not a city tree. Farms kids know the butternut, city kids don't, he says.

The DNR's Flickinger agrees and says the passing of the butternut is “one of those quiet stories that goes untold.”

The eulogy, though, has not been written. Among current research efforts, the Iowa DNR is using a federal grant to work with state agencies in Indiana, Pennsylvania, Connecticut and Vermont and scientists at three universities to try to harvest the genetic material from the best native butternuts and to reproduce it in the hopes of creating a butternut that is resistant to the canker fungus.

In these efforts to date, Flickinger says he has planted 300 butternuts from seed in the Loess Hills in western Iowa and about 100 in the Yellow River State Forest in northeast Iowa. Plans call for planting new trees from grafts in the near future.

In the bigger picture, the Nature Center's Patterson points to Dutch elm disease that has killed elms and the borer of Chinese origin that has killed and is killing millions of ashes and has the state of Iowa on high alert. Then there's chestnut blight, oak wilt and more.

“What are we going to be left with, Siberian elms and just junk trees?” asks Patterson. “It's almost like, what do you plant anymore, everything's got a disease?”

Even so, he says the forest has a great ability to “buffer” itself.

“You got, who knows, 30 species of trees,” he says. “If one gets wiped out, others will kind of take its place. But to have so many diseases and insects of foreign origin in a relatively short period of time is pretty rough on the forest.”