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Northern Research Station
11 Campus Blvd., Suite 200
Newtown Square, PA 19073
(610) 557-4017
(610) 557-4132 TTY/TDD

Emerald Ash Borer

Regulatory Treatment of Firewood

[photo:] Emerald ash borer trapped emerged from firewood are trapped inside a plastic bagResearch Issue

Since its discovery in Detroit, Michigan in 2002, the emerald ash borer (EAB) has caused extensive mortality of ash as it has spread across southeast Michigan, Ohio and Ontario. In addition to this core infested area, numerous outlier populations have been found throughout Michigan’s Lower Peninsula, Ohio, Indiana, and Ontario, as well as isolated infestations in the Upper Peninsula of Michigan, Maryland, Illinois, Pennsylvania and West Virginia.  Spread of EAB is a result of natural dispersal and human-assisted movement of infested materials including ash nursery stock, logs and firewood.  EAB can survive and emerge from logs cut from infested trees; therefore, movement of ash logs from infested to uninfested counties is regulated by a federal quarantine.  In the case of firewood, all hardwood species are regulated because inspectors cannot easily identify the species of tree that was cut.  Nevertheless, EAB has continued to spread and new outlier infestations, many of which resulted from human-assisted movement of infested material prior to enactment of the quarantine, have been detected each year.  Movement of firewood is extremely difficult to regulate and enforce.  Unlike nursery trees and wood products that are produced and moved by licensed businesses, firewood is often moved by the general public.  Despite extensive outreach efforts many individuals are unaware of regulations prohibiting movement of firewood from infested areas. It is estimated that of outlying infestations in Michigan with known origins, approximately 80% originated in campgrounds, state parks, lakes and recreational areas, or cottage communities, suggesting they were the result of firewood movement.  In order to prevent the spread of EAB through movement of firewood, state regulatory and natural resource agencies are enforcing quarantine regulations by conducting inspections for firewood at campgrounds, rest areas and key transportation gateways.  Guidelines for treating and certifying wood to allow safe movement and for storage and handling of confiscated firewood are urgently needed to prevent new establishments of EAB.

 Our Research

We evaluated two regulatory treatments for infested logs:  1) bagging firewood to prevent emergence and escape of EAB, and 2) vacuum treatment to kill EAB inside infested wood and logs.

Bagging Firewood

Logs were placed individually inside two plastic bags and then placed inside rearing containers.  In a second experiment, double bagged logs were held in the open on a bench in the laboratory.  In a third experiment, pairs of logs were placed inside single plastic bags that were sealed tightly-pressed against the logs.  Plastic bags were clear, 24 ´ 48 inches, 4-ml-thick poly bags. In all experiments, emergence and mortality of EAB inside the bags was compared to emergence of EAB from unbagged control logs placed in rearing containers.  The bagged logs were examined by carefully inspecting the bag for holes and looking through the transparent bag to note any beetles inside.  Once beetle emergence was complete (i.e., no new beetles were collected for 6 days) the experiments were ended.  Logs were removed from their rearing containers and/or bags.  All dead adults found inside the rearing containers and bags were tallied.  The number of new emergence holes on each log was also tallied.  A subset of logs were dissected to determine the number of dead adults and larvae that remained.

Vacuum Treatment of Firewood: 

We evaluated vacuum treatment for efficacy in killing EAB larvae either exposed or inserted into wood.  Exposed larvae were placed individually in open petri dishes inside the vacuum oven.  Ten larvae were treated in the oven at a time and all larvae were weighed before and after treatment.  Larvae were subjected to different temperatures and pressures to determine desiccation rates and lethal percentage weight loss.  Larvae were inserted into blocks of wood (10 cm wide by 10 cm long by 2.5 cm thick) made from 5.1 cm ´ 10.2 cm (2” ´ 4”) Douglas fir lumber with a moisture content of 16.6%.  The blocks of wood with larvae inside were subjected to vacuum treatment at different temperatures and pressures.  We also evaluated vacuum treatment of naturally-infested logs with > 30% moisture content.  Infested logs were placed inside a vacuum treatment bag at 20 mmHg and 20 °C and held for 10 days.  Logs were partially dissected at periodic intervals to determine EAB mortality.  All logs were completely dissected after 10 days to determine the total number of live and dead larvae remaining. 

Expected Outcomes

Treatment recommendations are required for regulatory agencies and natural resource agencies for handling firewood that may be infested with EAB.  Based on our research we recommend that firewood should be double bagged in “contractor-grade” 4 mil plastic bags.  Bags should fit loosely around the logs and sealed tightly at the end.  Logs should be held in bags until all EAB have emerged and died or until logs can be burned or destroyed.  At least 10 days of vacuum treatment would be required to kill EAB in infested logs.  Regulatory treatment guidelines will help slow the spread and prevent new establishments of EAB by eliminating emergence from infested firewood.

Research Results

Bagging Firewood:  

Several new emergence holes were found and many live EAB adults emerged from the unbagged logs in rearing containers; however, no adults escaped from the double-bagged logs.  All of the EAB that emerged from the unbagged control logs were collected live in the rearing container; whereas, all of the EAB that emerged from the double-bagged logs held in rearing containers or in the open on laboratory benches were found dead in the bags by the end of the experiment.  There was no evidence of beetles attempting to chew through the inner or outer bag.  For the pairs of logs that were held in single bags pressed tightly against the logs, many EAB were found dead inside the bag; however, 1 EAB chewed through the bag and escaped. 

Vacuum Treatment of Firewood 

Some EAB larvae died at 26% weight loss and all were dead at approximately 40% which required at least 15 hours of vacuum treatment at 20 mmHg and 20 °C.  The desiccation rate of EAB larvae under vacuum at 20 mmHg and 20°C was 2.395 % weight loss per hour.  Temperature, pressure, and relative humidity affected desiccation rate.  Larvae desiccated slower at cold temperatures; no larvae had died after 36 hours of vacuum treatment at -10 °C and 20 mmHg and weight loss was approximately 5%.  Desiccation and mortality were also lower for larvae when inserted into blocks of wood.  After 28 hours of vacuum treatment at 20 mmHg and 20 °C, mortality of larvae inside wooden blocks was only 13% and weight loss was only 26%.  After 10 days of vacuum treatment mortality of EAB larvae inside the logs was >98%. The final moisture content of logs following treatment was 18.7%. 

Publications

Chen, Zhangjing; White, Marshall S.; Keena, Melody A.; Poland, Therese M.; Clark, Erin L. 2008. Evaluation of vacuum technology to kill larvae of the Asian longhorned beetle, Anoplophora glabripennis (Coleoptera: Cerambycidae), and the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), in wood. Forest Products Journal. 58(11): 87-93.

Poland, Therese M.; Ciaramitaro, Tina M.; Pureswaran, Deepa S.; Diss-Torrance, Andrea. 2008. Evaluating the use of plastic bags to prevent escape of the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) from firewood. The Great Lakes Entomologist. 41(1&2): 40-48.

McCullough, Deborah G.; Poland, Therese M.; Cappaert, David; Clark, Erin L.; Fraser, Ivich; Mastro, Victor; Smith, Sarah; Pell, Christopher. 2007. Effects of chipping, grinding, and heat on survival of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), in chips. Journal of Economic Entomology. 100(4): 1304-1315.

Research Participants

Principal Investigators

  • Therese Poland, USDA Forest Service - Northern Research Station Research Entomologist
  • Andrea Diss-Torrance, Wisconsin DNR
  • Chen Zhangjing, Virginia Tech
  • Tina Kuhn, Michigan State University

Last Modified: 12/07/2017

About this Research Area
About Emerald Ash Borer
Selected Studies