A new study shows that while we're winning isolated battles, we couldwell lose the war to prevent the devastating spread of the emerald ashborer in eastern Canada and the United States. It's a failure thatwould cost billions of dollars in lost timber and ornamental trees, anddramatically change the forest and neighbourhood landscape in easternNorth America -- with even more impact than Dutch elm disease.
The soon-to-be published study is the first to document the invasivebeetle's rate and distribution of spread from its epicentre in theWindsor-Detroit area.
"In the Great Lakes region this beetle invasion is mushroomingout like an atomic bomb going off," says the study's co-author Dr. HughMacIsaac, an expert in invasive species at the University of Windsor'sGreat Lakes Institute for Environmental Research.
The small, metallic green beetle -- adults are about thelength of a thumbnail -- was first detected following an unusualdieback of ash trees in southeastern Michigan and southwestern Ontarioin the summer of 2002. A native of southeast Asia, the insect iscapable of rapidly spreading with a little human help. Adult beetleslay eggs under tree bark and the feeding larvae kill trees bydisrupting the flow of nutrients in the soft tissues under the bark.
The new study funded by the Natural Sciences and EngineeringResearch Council of Canada (NSERC) reveals that unprecedented actionstaken to stop the borer's spread have so far failed to halt its outwardmarch. At risk are nine billion ash trees in the United States andOntario, with an estimated value of more than $300 billion in theUnited States alone.
"Its distribution continued to spread during 2005 in the GreatLakes region despite extensive containment, quarantine and eradicationmeasures," write the authors, including Ken Marchant, a lead emeraldash borer expert at the Canadian Food Inspection Agency (CFIA).
Since 2002, all areas in Michigan and Ontario known to beinfected with the borer are under quarantine. Prominent signs alonghighways advise the public of the total ban on the transport out of thearea of ash trees, saplings and firewood. During the winter of2003-2004, the CFIA took the dramatic step of creating a borer"firewall" in Ontario's Essex County. That involved removing all theash trees in a ten kilometre wide swath between lakes Erie and St.Clair, beyond the eastern boundary of the borer's current range.
Regardless, the report notes, "the borers distribution expandeddramatically in 2004" primarily through natural dispersal, but in somecases through human transport. In Ontario, the borer infected 23 newsites to the east, all beyond the firewall. The study suggests that thenew infestations most likely came from infected firewood or saw logsmoved there prior to the creation of the firewall -- but MacIsaacdoesn't rule out the possibility that beetles jumped the ash-free zone.The study notes that scientists still need to determine the maximumflight potential of adult borers.
In Michigan, the borer was reported at 29 new sites in 2004. New infestations were also reported in Ohio and Indiana.
The one bright spot in the study is the apparently successfuleradication of a borer population that was introduced into Marylandand, subsequently, into Virginia in a shipment of infected nurserysaplings from Michigan. Officials destroyed the saplings as well as allash trees within a kilometre of each infected site.
"The success in Maryland shows that if you get them early andbefore they build up large populations you can probably extinguishcolonizing groups," says Dr. MacIsaac, whose research is primarily onfreshwater and marine invasive species. Scientists believe the borerprobably entered North America in ash shipping materials, and waspresent for as much as a decade prior to being identified.
The challenge in the Great Lakes region, he says, is thecurrent extent of the infestation. The infected zone now covers all ofOntario's Essex County and extends to include the entire lowerpeninsula in Michigan and much of northern Indiana and Ohio.
"It's not just an Ontario or Canadian problem. Even if we'reable to contain it here, it could come across at Sarnia or at SaultSte. Marie. It's a case where we need, and are getting, internationalcooperation," says MacIsaac, noting that the American and Canadiangovernments are making extraordinary efforts together.
The 2005 federal Canadian budget contained the first line itemever to target invasive species directly -- $85 million, much of whichis earmarked for battling the borer and another forest pest, the Asianlonghorn beetle, which has infected hardwood trees in areas aroundToronto, New York and Chicago.
If containment isn't effective, MacIsaac knows well what thefuture will look like. He arrived at his Windsor-area home one day inthe summer of 2003 to see a neighbour cutting down 25 ash trees, amongthe borer's first victims. In Michigan's Wayne County, the first areainfected, 60 per cent of the ash trees are already dead.
"In my opinion, the prognosis does not look good in the GreatLakes region," says Dr. MacIsaac. "If containment doesn't work, we aregoing to see a repeat of Dutch elm disease, which wiped-out a dominantforest tree species from eastern North America."
Dr. MacIsaac's paper on the beetle will be published in a forthcoming issue of Diversity and Distributions.
Materials provided by Natural Sciences and Engineering Research Council. Note: Content may be edited for style and length.
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