Firewood hitchhikers threaten Maryland's trees

Authorities warn about spread of invasive beetle

  • Dick Bean of Maryland Department of Agriculture prepares to hang a pair of traps designed to attract emerald ash borers so officials can detect their spread.
Dick Bean of Maryland Department of Agriculture prepares to… (Maryland Department of…)
May 22, 2012|Tim Wheeler

With Memorial Day about to kick off the unofficial start of summer, agriculture officials are warning the public not to take firewood with them if they go on camping or cookout trips - those logs could harbor some unseen, tree-destroying hitchhikers.

The U.S. Department of Agriculture has declared this Emerald Ash Borer Awareness Week, in hopes it will slow the spread of this destructive beetle from Asia, which officials say has killed tens of millions of ash trees so far.

Probably brought in on some imported packing material, the borer was first spotted in Michigan in 2002, but has spread to 14 other states since, including Maryland. It showed up first in Prince Georges and then Charles counties, but now has been seen in Anne Arundel, Howard, Washington and Allegany counties. They're a big threat to the extensive stands of ash trees in the state - it's the most common tree in Baltimore, for instance, with estimates approaching 300,000.  Officials are saying emerald ash borers could rival gypsy moths and chestnunt blight for their destructiveness.

The state has quarantined 14 counties in all, barring commercial transport of nursery stock, mulch and firewood. But there's still a threat from individuals unwittingly carrying infested wood products to new places the beetles haven't reached yet. So people are urged not to move firewood under any circumstances, and to buy only local, kiln-dried firewood wherever they go.

State agriculture officials have hung 500 colorful traps in trees around Maryland to track the beetles' spread, though the monitoring network has shrunk considerably because of funding cuts. The state had put out 2,600 purple traps last year, but federal funding for the effort has been reduced 51 percent this year, according to Dick Bean, program manager for the Maryland Department of Agriculture.

The state has been experimenting with some sting-less wasps, also not native to Maryland, to see if they can control the borer population.

"Unfortunately, right now the beetles are winning, but time will tell," Bean said recently.  "A lot of these biocontrol efforts take a while for things to get established and things to reach an equilibrium."

Meanwhile, for worried ash tree owners, the beetles and their larvae are hard to spot.  Experts suggest watching for signs of dieback in the canopy, bark splitting, and lots of woodpecker holes, among other things. Any suspected sightings should be reported to the state's plant health director at

State officials say there are several insecticides that can be used to treat infested trees, though most require multi-year injections into the bark or soil, a long-term and costly process. For more on those, go here.

For more on ash borers generally, go here and here.

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