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Emerald ash borer found in Howard County

Steve Parker

It's official: The emerald ash borer —the ash tree's deadliest pest— has arrived in Howard County, threatening to kill tens of thousands of trees here.

The insect has been spotted in Glenwood, Jessup and in Columbia's Owen Brown village. Beginning next week, county, state and federal officials will begin a complete assessment in Howard, after which they will come up with a plan for eliminating the pest.

The invasive, emerald-colored Asian beetle first appeared in Maryland in 2003, when a Michigan nurseryman broke a quarantine and shipped infected wood to Prince George's County. Though officials from the Maryland Department of Agriculture tried to eradicate the infestation through a strict quarantine, the insect was detected again in 2006 in Prince George's County, which then chopped down all of its ash trees within a five mile radius of the infected area.

Despite that effort, the emerald ash borer was discovered in 2008 in Charles County and now in Howard. All three infected counties are prohibited from moving ash wood out of their jurisdictions.

"The genie is clearly out of the bottle," said University of Maryland entomologist Mike Raupp, who has taken to calling the beetle the "green menace."

"This infestation is older than we suspected and is fairly widespread, which is not good news because it means that this is going to be very difficult to manage," Raupp said of the Howard County discoveries.

The county maintains approximately 230,000 trees planted along its streets and parks, between 27,600 and 32,200 of which are ash trees, said Steve Parker, a certified arborist and supervisor of the Howard County Department of Public Work's tree maintenance division. Those trees, plus ash trees on private properties and large, wooded areas, are now at risk.

"There's some neighborhoods in the county where ash trees are all that's planted up and down the streets," Parker said. "If this little bug make its way in there, it will be completely bare."

'Time has … run out'

Carol Holko, MDA program manager for plant protection and weed management, said the quick spread of the emerald ash borer is likely due to the transportation of infected wood and tree branches, not from the insect's natural migration.

According to Raupp, the emerald ash borer has a natural spread of one mile per year.

"We're now in an exponential phase," Raupp said. "Time has basically run out."

Holko, who predicted 2011 "is going to be a breakout year for the emerald ash borer," said the insect is 100 percent fatal to Ash trees.

"It's devastating," she said. "Te ns of millions of trees are dead in 15 states because of this beetle.

But Holko said that the blame doesn't lie entirely with the emerald ash borer.

"It's persistent," she said of the beetle, "and unfortunately we as humans can assist its movements on firewood and ash wood and tree debris that gets moved around."

Raupp said that while the insect is deadly to all strains of ash, domestic strains are particularly at risk.

MDA field supervisor Dick Bean said many of the ash trees in Howard County, and in Columbia in particular, are already weakened by drought, age and other conditions.

"The trees have not been looking very good lately," Bean said. "These ash trees have been easy picking because they are stressed. And stressed trees have reduced resistance, so basically the larva just have a field day."

Bean said that the infestations discovered so far in Howard County are two to three years old. He said that the discovery of emerald ash borer in Owen Brown "is very problematic because Columbia has thousands of ash trees throughout its neighborhoods."

But there is a silver lining, Raupp said. While Columbia has thousands of ash trees, it also has a fairly diverse tree population — unlike Baltimore City, where ash trees dominate the street landscape. Additionally, the county government stopped planting ash trees when the emerald ash borer resurfaced in Prince George's County in 2006.

Saving the trees

Unlike Prince George's County in 2006, Parker said Howard County plans to eliminate as few ash trees as possible. He said infected trees will be cut down, while at-risk trees will be given injection treatments.

Additionally, federal and state authorities have begun releasing predatory wasps in hopes of eliminating some of Maryland's emerald ash borer population, which has no local natural predators.

However, experts say eradication can be difficult. For the first 11 months of their lives, the beetles live underneath the bark of a tree as larvae.

Raupp said that while eliminating trees is the "cheapest approach" to eradicating infestations, it can be devastating to urban eco-systems. Ash trees help significantly cool urban areas, intercept rainwater and help mitigate pollution. Plus, the "aesthetic benefits of ash trees are enormous," he said.

"We'll battle and we'll fight with every ounce of breath that we have to try and save all the ash tees we can," Parker said.

For information on how to detect an infestation, go to http://www.dnr.state.md.us/forests/forester/eab.asp.

Copyright © 2014, The Baltimore Sun
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