An estimated 80 percent of new outbreaks of oak wilt result from wounding during construction activity, according to Iowa State University Extension in Ames.

Special care should be taken before and during site clearance and construction to protect high-value oaks from wounding and to apply wound dressings where these trees are damaged.

Once a tree is infected, it can infect nearby trees through its roots.

Sometimes homeowners can stop the spread in their yards by removing diseased trees and then digging a trench to a depth of 3 1/2 to 5 feet between where the infected tree was and the non-infected trees, thereby severing any root grafts underground.

FOR MORE INFORMATION

"Oak Wilt Identification and Management," www.extension.iastate.edu/Publications/SUL15.pdf

"How to Identify, Prevent and Control Oak Wilt," www.na.fs.fed.us/spfo/pubs/howtos/ht_oakwilt/toc.htm

To obtain a free CD, "Oak Wilt: People and Trees," from the U.S. Forest Service, St. Paul, Minn., call (651) 649-5000.