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Region begins fight against beetle targeting its many ash trees

In this article with The Baltimore Sun, Kevin Mullinary, district manager of Davey's Baltimore office, talks about the presence of EAB in area trees.

Posted: June 2, 2015

By Tim Wheeler  

With the arrival of an invasive green Asian beetle in Baltimore, local governments and property owners are confronting tough — and potentially costly — choices about whether to try to save ash trees at risk of infestation or cut them down.

The culprit is the emerald ash borer, which could attack any of the 5 million to 6 million ash trees across the Baltimore metropolitan area. With the infestation already underway, City Hall is seeking a contractor to inject as many as 820 curbside ash trees with insecticide.

"We are taking the initial steps to deal with what's going to be a tragic situation," said Erik Dihle, the city's arborist.

Ash borers, which have shredded the urban forest canopy in communities across North America, have been found in 12 Maryland counties. They've killed millions of trees in 25 states, threatening the popular ash with the kind of devastation wrought decades ago by Dutch elm disease on another once-common urban tree.

"You're in for some bad times, probably," said Deborah McCullough, an entomologist at Michigan State University who began researching ash borers shortly after they turned up in the United States in 2002 near Detroit and in Ontario, Canada.

The adult borers, metallic green beetles, munch on ash leaves in spring, causing no major damage. It's their offspring, tiny immature larvae, that bore into the trees and, unseen from the outside, devour their inner bark, cutting off the flow of water and nutrients. By the time the dieback is apparent, the tree often is seriously weakened. It gradually starves to death, typically within a few years.

With emerald ash borers claiming their first victims in Baltimore — including a pair of large trees cut down in Franklin Square Park — the city is moving to protect some of its largest street trees.

City Hall took bids last week for treating hundreds of curbside ash trees by injecting an insecticide into the trunk. Inoculations could start by late June or early July.

McCullough and other experts urge homeowners and other landowners with ash trees to consult arborists for expert advice on treatment or removal. There's hope of saving many ash trees, if prompt action is taken to treat them.

Treatment costs depend on a tree's size, but injecting pesticide into the trunk can cost as little as $50 to a few hundred dollars for a big, old shade tree. The injections have to be repeated every two years or so. But the costs of removal and replacement, especially of a mature tree, is many times higher.

The insects have been in Maryland since 2003 — brought in on trees from Michigan delivered to a Prince George's County nursery. Despite a pre-emptive effort to isolate that incursion by cutting down 42,000 ash trees, the borers spread across Central and Western Maryland. They were found last year in the city, in traps placed in Druid Hill Park and near Fort McHenry, and in Carroll County.

Only the Eastern Shore and Baltimore and Harford counties have yet to have a confirmed sighting. But experts caution that doesn't mean they aren't already there. To keep an eye out for them, the Maryland Department of Agriculture hung 15 purple traps in ash trees this spring in Baltimore and Harford counties, and it plans to distribute another 105 traps across the Shore, according to spokeswoman Julie Oberg.

Meanwhile, officials urge people not to transport logs or untreated firewood from one area to another, which may unwittingly spread the borers. The state also imposed a quarantine barring the shipment of potentially infested wood from areas where the beetles are established.

More than shade is at stake. With 5 million to 6 million ash trees estimated in the Baltimore area alone, the U.S. Department of Agriculture figures their cumulative loss from ash borer infestation could exceed $227 million.

Kevin Mullinary with Davey Tree Service said many homeowners in leafy city neighborhoods like Roland Park and Homeland are contacting him with questions about what to do.

"They're definitely here," said Mullinary, reporting that one of his arborists spotted the telltale D-shaped holes borer larvae make in an ash by Union Memorial Hospital. "This year, we're going to see some decline [in foliage] as summer progresses. These insects are feeding inside the trees as we speak. Next year, you're going to see a lot of the trees in bad shape."

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