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Northern Research Station
One Gifford Pinchot Drive
Madison, WI 53726
(608) 231-9318
(608) 231-9544 TTY/TDD

Emerald Ash Borer

Debarking High-Value Logs

Research Issue

[photo:] Debarking as a means of eab controlRemoval of trees infested with the emerald ash borer (eab) from the core infested area and eradication cuts at outlier sites are important components of the eab management program.  Several 100,000s of trees have been removed as part of eradication and containment efforts in Michigan.  Currently, almost all of the cut trees are chipped and burned at a cogeneration plant.  Recently, efforts have been initiated to pursue utilization of ash for lumber, railroad ties, tool handles, pulp, chips for paper, composite lumber, landscaping, and metalurgical or industrial uses.
Utilization of ash for value-added products would be greatly facilitated if ash material could be safely moved to existing sawmills and manufacturing plants, most of which are outside of the quarantined area.  eab excavates galleries just under the bark and pupates in the bark or outer sapwood (approximately 1 cm deep).  The location and depth of pupation depends on the thickness of the bark. Thus if all bark and outer sapwood to a depth of approximately 1 cm is removed, logs should be free of eab and safe to move. 

 Our Research

We evaluated the use of a debarker to remove bark and destroy eab in large infested ash logs.  We selected 41 ash logs with varying degrees of eab infestation.  Logs were donated by the Hudson Mills Park Association from the Huron Clinton Metroparks in Michigan. Twenty six of the logs were considered saw logs (logs meeting minimum regional standards of diameter, length, and defect) and the rest were reject logs. Logs were measured and bark windows were removed to determine eab larval density and the depth of eab galleries and pupal cells. We used a Morbark model 640 debarker to debark the logs.  After debarking we measured the logs to determine the amount of bark removed and checked them for any residual bark and eab infestation.

Expected Outcomes

These results demonstrate that debarking can be an effective treatment in removing and destroying eab in high value logs.  If debarked sawlogs are free of eab they should be safe to move to sawmills and manufacturing plants outside of the quarantined area.

Research Results

We estimated that a total of 10,961 eab larvae were present in the 41 logs prior to debarking.  Of the 7,750 larvae that went into the debarker in the 26 saw logs, none came out. On the reject logs, 3,211 eab larvae went into the debarker in the logs, and 14 came out – 11 on one log, 1 on another log, and 2 on another log.  These eab larvae were found under small patches of bark that remained in curved areas of the logs.  The debarker removed a total of 99.8 percent of the bark, and 99.9 percent of the eab larvae from the all of logs, including both sawlogs and reject logs.  Regardless of log size, the debarker removed wood to a depth of at least 1.4 inches, even with crooked (reject) logs. The eab prepupal larvae were an average of 0.65 inches deep into the wood. They do not burrow far into ash wood, making much of the tree useable.  The larger the logs, the more eab were found in the bark rather than in the sapwood.  All the eab prepupae were in the bark of logs that were larger than 12 inches in diameter when the bark was at least 1/2 –inch thick.


Research Participants

Principal Investigators

  • Deborah McCullough, Michigan State University
  • Therese Poland, USDA Forest Service - Northern Research Station Research Entomologist
  • Al Steele, USDA Forest Service, S&PF Morgantown

Last Modified: 12/07/2017

About this Research Area
About Emerald Ash Borer
Selected Studies