Grit Blogs > A Lakeside View

A Deadly Hitchhiker: The Emerald Ash Borer

By Cindy Murphy


Tags: trees, insects, pests,

Cindy MurphyI just read a pest update article in The Michigan Landscape, a horticultural trade magazine, which states that the Michigan Department of Agriculture (MDA) revised its Emerald Ash Borer quarantine to consolidate all 68 counties of the Lower Peninsula into one quarantine level effective immediately. The article is just another reminder of a nearly decade long battle we’ve been fighting in this state – a battle which we’ve seemingly lost.

If you think this might be a localized issue restricted only to Michigan, or have never heard of Emerald Ash Borer, I urge you to please read further.

Emerald Ash Borer AdultEmerald Ash Borer (EAB) is an insect native to Asia which was first discovered in the United States in the Detroit area in 2002. It’s thought this exotic pest gained entry into the country by hitching a ride on wood packing crates loaded on cargo ships and planes. Despite strict regulations and quarantines, the pest has spread to Ohio, Indiana, Illinois, Maryland, Pennsylvania, West Virginia, the Canadian provinces of Ontario and Quebec, and most recently was discovered last summer in Wisconsin, Missouri, and Virginia.

States affected by the Emerald Ash Borer infestation

The death toll this pest has dealt our native ash species is staggering, (please note that mountain ash is not affected; it is a completely different genus). Since its discovery here less than ten years ago, EAB has killed or infested approximately 35 million ash trees in Michigan’s Lower Peninsula alone, and caused the death of 25 million more in the Upper Peninsula of Michigan, and other affected states. The effects of it spreading further will be an unfathomable amount of lost trees and money. Emerald Ash Borer has already cost government agencies, municipalities, property owners, nursery operators, and forest industries tens of millions of dollars.

Larval tunnelling in a tree affected by the Emerald Ash BorerThe fatal damage is caused by the larva, which feeds under the bark of the ash trees, effectively girdling the tree, making it unable to take up water and nutrients. The trees die in three to four years. Because the larva feed unseen, damage usually remains undetected until the tree starts showing signs of stress, occurring first in the crown of the tree as it becomes deprived of nutrients.

Scientists at Michigan State University determined through tree core analysis that EAB may have been present in southeast Michigan over half a decade before it was found. It’s possible its range increased undetected for years. But this is not a fast moving insect – the natural dispersal range of EAB is only ½ to 2 miles annually. Because federal quarantine prohibited the sale or movement of nursery stock from infested areas since its discovery, it’s thought unlikely that Emerald Ash Borer will spread so quickly, nor will it spread further through the nursery trade.

So how did EAB continue to spread to nine states, and two Canadian provinces? Its range is greatly increased, and its spread accelerated when it catches a free ride from humans … and firewood is one of its favored modes of transportation.

Consider the following scenario: You help your cousin across state fall trees on his property; as a gesture of thanks, he offers you a cord of wood for your fireplace which you take home to your property. Meanwhile, hoping to make a little extra money, he places a sign out by the road, offering firewood for sale. A family from out-of-state camping in the area, purchases some, and not burning it all ‘round the campfire, takes the remainder home with them for use in their own fireplace. A new pest has just been introduced into previously non-infested areas. Sound like an alarmist’s far-fetched nightmare? Not so.

Ken Rausher, MDA’s Pesticide and Plant Pest Management Division Director confirms the transportation of firewood as a major issue in the spread of the Emerald Ash Borer, stating, “Hardwood firewood is (still) prohibited from leaving the Lower Peninsula as it is the leading cause of spreading EAB and other invasives.”

Parks and Recreation Chief for the Michigan DNR, Ron Olson says, “Campers and hunters are reminded to purchase firewood locally when visiting state parks, recreation areas and state forest campgrounds. Bringing ash firewood into state forests, state parks, recreation areas and state forest campgrounds violates state land use rules.”

Interstate and intrastate ash product movement, to include firewood, has been prohibited for years in Michigan; violators face fines of up to $250, 000 and jail sentences up to five years. All other states infected with EAB have instituted similar restrictions prohibiting the movement of all hardwood firewood, ash nursery stock, green lumber, and other material living, dead, cut, or fallen, including logs, stumps, roots, branches, and composted and uncomposted chips of the genus Fraxinus (all ash species). The quarantines include all hardwood species of firewood because when dried, it’s difficult to identify the tree species.

Millions of dead ash trees and the threat posed to millions more, as the Wisconsin Department of Natural Resources’ website states, “serve as a stark reminder of how firewood can harbor many different kinds of invasive pests and diseases ... both in forest and urban settings. Gypsy moth, oak wilt, and the emerald ash borer are just a few examples of pests and diseases that hitch hike on firewood, making their way easily into previously unaffected, healthy areas.”

To learn more about firewood restrictions and EAB in your state, or what to do if you suspect EAB in your area, visit www.emeraldashborer.info – a site maintained in a multi-state effort by Michigan, Illinois, Indiana, Maryland, Ohio, Pennsylvania, and Wisconsin, dedicated to providing the most up-to-date information about Emerald Ash Borer.

(photos 1 and 2 courtesy of www.emeraldashborer.info; photo 3 courtesy of the Wisconsin Department of Natural Resources)