by rainwater to tree stems. Stem cankers develop 1 to 3 years after branches die. Tree tops killed by stem-girdling cankers do not resprout. Diseased trees usually die within several years. Completely free-standing trees seem better able to withstand the fungus than those growing in dense stands or forest. In some areas, 90% of the butternut trees have been killed. The disease is reported to be spreading rapidly in Wisconsin. By contrast, black walnut seems to be resistant to the disease. Hybrid resistance Butternut hybridizes readily with Japanese walnut. The hybrid between butternut and the Japanese walnut is commonly known as the 'buartnut' and inherits Japanese walnut's resistance to the disease. Researchers are back-crossing butternut to buartnut, creating 'butter-buarts" which should have more butternut traits than buartnuts. They are selecting for resistance to the disease. Most butternuts found as landscaping trees are buartnuts rather than the pure species. Other pests Bunch disease also attacks butternut. Currently, the causal agent is thought to be a mycoplasma-like organism. Symptoms include a yellow witches' broom resulting from sprouting and growth of auxiliary buds that would normally remain dormant. Infected branches fail to become dormant in the fall and are killed by frost; highly susceptible trees may eventually be killed. Butternut seems to be more susceptible to this disease than black walnut. The common grackle has been reported to destroy immature fruit and may be considered a butternut pest when populations are high. Butternut is very susceptible to fire damage, and although the species is generally wind firm, it is subject to frequent storm damage. Conservation The species is not listed as threatened federally in the US, but is listed as "Special Concern" in Kentucky, "Exploitably Vulnerable" in New York State, and "Threatened" in Tennessee. The Committee on the Status of Endangered Wildlife in Canada placed the butternut on the endangered species list in Canada in 2005. Approximately 60 grafted butternut trees were planted in a seed orchard in Huntingburg, Indiana, in 2012 as part of a larger effort by the USDA Forest Service to conserve the species and to breed resistance to butternut canker disease. Forest Service staff from the Hoosier National Forest, the Eastern Region National Forest genetics program, the Northern Research Station, and the Hardwood Tree Improvement and Regeneration Center at Purdue University are involved in the project. Famous specimens The American Forest National Champion is located in Oneida, New York.