Wednesday, December 13, 2006

On site debarking of logs infested with emerald ash borer: A means for utilization

Robert J. McDonald,, Michigan State University, Entomology, 243 Natural Science Building, East Lansing, MI, Deborah G. McCullough,, Michigan State University, Entomology, Forestry, 243 Natural Science Building, East Lansing, MI, Therese M. Poland,, USDA Forest Service, North Central Research Station, 1407 S. Harrison Rd, East Lansing, MI, and Al Steele,, USDA Forest Service, Morgantown Field Office, 180 Canfield Street, Morgantown, WV.

Since its discovery in 2002, the emerald ash borer (EAB) (Agrilus planipennis) has killed millions of ash trees in urban, rural and forested areas. Quarantines were imposed in affected states including Michigan, Ohio, Indiana and Illinois, to limit inadvertent transport of EAB life stages in ash logs, firewood or nursery trees. Roughly 800 million ash trees in Michigan alone are threatened by this pest and more than one billion ash trees occur in Ohio.

We conducted a study to test the ability of a Morbark log debarker to remove EAB life stages, which could enable ash logs to be transported to mills for processing. The study occurred in December, a high risk period when most EAB are prepupae and less vulnerable to exposure or injury than other life stages. Bark and phloem thickness were measured on 26 sawlogs and 15 logs classified as “rejects” because of crook, forks or other defects. Bark was removed from four windows per log to determine EAB density and depth of prepupal cells. After logs were processed, we quantified the volume of wood removed and determined if EAB life stages remained. Virtually all of the estimated 7750 EAB on the 26 sawlogs were removed by debarking. Only 7 of an estimated 3211 EAB remained on three of the 15 reject logs. On-site debarking could be widely employed to enhance utilization of large, valuable ash trees and reduce overall EAB density.

Species 1: Coleoptera Buprestidae Agrilus planipennis (emerald ash borer)