Tree in county forest may help fight disease
Foresters looking for butternut trees resistant to a disease known as butternut canker need look no farther than Pierce County's stewardship demonstration forest on Ellsworth's northwest side.
A crew from the state's USDA Forest Service took a sample from an apparently healthy tree there Tuesday. County Forester Gary Zielske had specially marked for their purposes the straight and tall specimen, which he estimated stands over 90 feet high.
"Others here have the disease, but we're hoping this one's resistant to it," Zielske said about efforts to save the threatened species.
The two-member crew used a rifle-like device to shoot a 100-foot-long string, weighted at its opposite end, over a branch to collect the sample. Carrie Sweeney said the service has been directed to approximately 40 healthy butternuts throughout the state since actively seeking them, beginning in 2005. They've most recently worked in the Chequamegon National Forest in Northern Wisconsin and the largest concentration so far has been found to the northeast.
"This is the nicest butternut I've ever seen," said Sweeney's associate, Paul Berrang, as he prepared the string-shooting device.
The pair was successful in collecting a branch providing about 10 twigs suitable for grafting, Zielske said. Their goal is to establish a seed orchard serving as the foundation of a breeding program to develop disease-resistant butternut, and provide a source of butternut seed for restoration projects.
The disease was originally identified in this country during the late 1960s, first observed in Southwest Wisconsin 29 years ago, he said. It's killing large numbers of butternut trees, according to information from Sweeney. Many of the surviving trees are infected and the future of butternut looks grim. Healthy butternut trees are rare, but it's thought some of them have natural resistance to the disease.
"At this time, we are searching for the healthiest butternut trees and propagating them at an agricultural site in Northern Wisconsin," she says in the information.
The grafting process used to propagate them involves removing twigs from the crowns of healthy butternut and attaching them to the root systems of seedlings, the information states. Those aware of healthy butternut trees or interested in knowing more about the program are asked to contact Sweeney at (715) 276-7400 or .
To date, butternut canker has infected over 90 percent of butternut trees throughout their native range from New Brunswick, Canada, to Georgia to Minnesota. It's never been found outside North America. Unlike elms and chestnuts, butternuts are little-known and have always been sparsely distributed. But their wood is highly valued by woodcarvers, and people and wildlife seek out their tasty nuts.
For butternut lovers who want to give the trees a boost, Dr. Dale Bergdahl, a retired University of Vermont forestry professor, suggests planting nuts in open areas, covered by a screen to keep squirrels away.
The Forest Service otherwise advises:
--Retain butternut trees with more than 70 percent live crown and with less than 20 percent of the combined circumference of the stem and root flares affected by cankers.
--Harvest dead or declining trees to salvage the quality and value of the wood, or maintain the trees in the forest for their wildlife value.
--Retain trees free of cankers with at least 50 percent live crown and growing among diseased trees. These trees may be resistant and have value for propagation by grafting or for future breeding.
Last summer, Sweeney's crew determined the butternut tree in the county demonstration forest met the criteria they were looking for, Zielske said. The Pierce County Agriculture and Extension Committee, whose members are Chair Richard Purdy, Vice Chair Mel Pittman, and Bill Gilles, Jerry Kosin and Don Rohl, is responsible for managing this "county woodlot." The committee wished to support the efforts to save the butternut species and approved the request from the Forest Service to collect the sample last week. Rohl was on-site to observe and assist in the collection.