Little Green Men

The emerald ash borer is proving to be a serious threat to the U.S. supply of ash trees.

By Jo-Ann Kaiser

It's little, it's green and it's causing a whole lot of trouble for domestic ash trees. It's the emerald ash borer, and if you have not heard of it yet, you probably will soon because U.S. entomologists and forestry experts say this unwanted visitor is threatening America's abundant supply of ash trees.

"The emerald ash borer has the potential to do harm on a scale of the Dutch elm disease," said entomologist Phil Pellitteri, distinguished faculty assistant at University of Wisconsin, Madison.

Pellitteri said the insect, a native of China, was first discovered in southeastern Michigan in 2002, but experts believe the emerald ash borer, also known as EAB, first arrived a decade earlier.

Family Name

Fraxinus americana, Fraxinus pennsylvanica and Fraxinus nigra of the Family Oleaceae

Common Names

White ash, green ash, American ash, red ash, black ash, brown ash, Canadian ash


Tree grows from 80 to 120 feet with 2- to 5-foot diameters. White, red and green ash weigh approximately 41 pounds per cubic foot, while black ash averages 35 pounds per cubic foot.


  • One of the best woods for steam bending.
  • Glues, stains and polishes well.
  • Wood has good strength, elasticity, toughness, stiffness and hardness qualities compared to its relative light weight.

"We suspect the emerald ash borer came to the United States via the port of Detroit on dunnage or on solid wood packing materials," said Pellitteri. "Entomologists didn't suspect a problem initially because the damage to the trees was similar to that caused by other pests." The EAB was first detected after it had infested and killed thousands of ash trees in southern Michigan.

When experts realized they were dealing with a new and potentially deadlier problem, they immediately mobilized. "EAB is 100 percent fatal to an ash tree and the best science to date is that there is little that can be done to save ash trees once they have been infected," according to the Michigan Department of Agriculture.

To date, 20 counties and outlying areas have been quarantined due to evidence of EAB infestation. As many as 15 million ash trees have already been affected by the EAB. The adult beetles nibble on ash leaves and cause little damage, but the larvae feed on the inner bark. This is what kills the tree by harming its ability to transport water and nutrients. The EAB has also been found in Windsor, ON, Ohio and northern Indiana. The hardest hit area, however, remains southeastern Michigan.

The EAB seems to be targeting ash trees exclusively in North America, and what is surprising, said Pellitteri, is that they target healthy, as well as diseased trees. "The EAB does not do similar damage to ash trees in China or Russia."

The fight against EAB has been aggressive. Experts have joined forces to publicize the problem. Several states have enforced quarantines to prevent infested ash firewood, logs or nursery trees from being transported and starting new infestations.

Eradication efforts by state and federal agencies in Michigan, Ohio, Indiana and Canada are underway to prevent small infestations from growing into large problems. On March 22, the Wisconsin Department of Natural Resources issued an emergency rule banning out-of-state firewood in state parks and other DNR properties.

"EAB is on the move and it's moving around on firewood," said Jane Cummings Carlson, forest health coordinator of the Wisconsin DNR. Carlson said that the most recent infestations and spread of EAB was likely due to emerald ash borers who "hitchhiked in on firewood. Firewood is the Typhoid Mary of the emerald ash borer in the Great Lakes," said Cummings Carlson.

Worries about firewood have come forward because ash is a popular firewood that doesn't require curing time before it can be used. Also, both fresh and aged ash firewood burns easily and produces good heat.

In addition to eradication and quarantine programs, there's been a concerted effort by a long list of agencies and universities to educate the public about the EAB threat. Research is being conducted at universities to try and understand the life cycle of the beetle and find ways to detect new infestations, as well as control EAB adults and larvae, and contain the infestation.

"Ash logs infested with EAB can still be useful if they are properly debarked," according to experts from Michigan State University and the USDA Forest Service. Mobark Manufacturing Inc., in Winn, MI, and Bedrock Express, Ltd., Ortonville, MI, cooperated with researchers from MSU and the Forest Service in a study to see if standard debarking equipment would be an option for using large ash trees that have value for lumber, said Deborah McCullough, MSU forest entomologist and lead EAB researcher at MSU.

If enough bark and wood can be removed to eliminate EAB infestations, the logs can be transported safely to other areas and provide additional opportunities to use the wood. The study was done to find more economical options to treat trees infested by EAB - beyond simply grinding and burning the trees. Al Steele of the USDA Forest Service, and Andy Sabula of the Ohio Department of Natural Resources believe that using a portable version of sawmill debarking equipment offers a safe and productive option compared to chipping the trees and burning them.

McCullough and USDA Forest Service entomologist Theresa Poland sampled 41 ash logs that were donated to the study. The logs ranged from 9 to 21 inches in diameter and most were heavily infested with EAB. A professional grader determined that 26 of the 41 logs were "high quality saw logs."

"There was a total of 7,750 EAB larvae in the saw logs," said McCullough. "Of the 7,750 larvae that went into the debarker in the saw logs, none came out."

On the reject logs, which were crooked or had other defects making them unusable as saw logs, McCullough said 3,211 EAB larvae went into the debarker and 14 came out. McCullough said that because EAB do not burrow far into the wood, nearly the entire debarked log from their test samples was useable. "The bigger the log, the thicker the bark," said McCullough.

All About Ash

Ash is used for cabinet work and interior joinery, plywood, oars, cues and the handles of striking tools and hoes, spades and forks. Some ash is sliced into decorative veneer for furniture and paneling, and it also is prized for its wood-bending properties. Greg Shadko, owner of Wood Craft of Michigan in Eaton Rapids, MI, uses ash along with a variety of other woods.

"I like ash because it is a cheaper alternative to hard maple," Shadko said. "We have been doing some new product testing but I'm not sure if I will use ash in new designs because I'm not sure that the supplies will be there or if the price is going to go up."

Shadko already has seen a slight rise in the price of ash. He is encouraged that researchers are looking for ways to use salvaged wood, but said if the trees are too small or have worm holes, they are not useable for the higher end products he makes. Shadko said his supplier had been looking to northern Minnesota and the Upper Peninsula of Michigan for reliable sources of ash. Now that the EAB has been found in the UP, Shadko wonders what the impact will be on supplies.

"There is a big question mark for us when it comes to ash and our future plans," Shadko said. He hopes the supplies remain available and reasonably priced.


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