Latest pest has an insatiable appetite for an array of trees

ON THE FARM

June 24, 2007|By Ted Shelsby

Once again, Maryland trees are under attack by creepy crawlers.

Unlike the voracious emerald ash borer that is blamed for the destruction of 25,000 ash trees in Prince George's County this year, the new invader has an appetite for an array of trees -- oak, apple, American beech, birch, sweet gum, willow and hawthorn.

This time it is the gypsy moth doing the damage, unleashing the worst infestation in Maryland in 12 years, state agriculture officials say. The damage spans 12 counties, all of the counties of the Baltimore metropolitan area and running from Cecil to Garrett.

"We have sprayed over 50,000 acres, and we know the damage is well beyond this," said Robert H. Tichenor, chief of the department's office of forest pest management.

Garrett County and regions between Frederick and Hagerstown are hot spots, he said.

Tens of thousands of gypsy moths in their caterpillar stage attack a tree, eating the leaves and robbing the tree of the nutrients. Many trees die, while others in a weakened state are done in by other insect predators, including the two-lined chestnut borer. As many as 15 percent of the infested trees die, Tichenor said.

In Harford County, most of the damage has been in the Pylesville area, Tichenor said. And in Baltimore County, where outbreaks have not been seen since the 1980s, the Freeland area and Prettyboy Reservoir have been hit, he said.

Tree damage is also in the Pasadena area of Anne Arundel County, where the state sprayed about 4,000 acres. Damage in Howard County begins near Ellicott City and runs west to the border with Carroll County, where the effect of the pest is scattered.

"We are on the edge of an outbreak that spreads from eastern West Virginia, through Pennsylvania and into New Jersey," Tichenor said.

Gypsy moth damage is more noticeable in thick forests where it is easy to see acres of trees that have lost leaves. But shade trees in homeowners' yards are more at risk.

"It's that old, spreading oak tree in the front lawn that is most likely to be killed," Tichenor said. "It's old, it's out in the open and it is not protected by other trees."

Barbara Lambert didn't know what was happening when the leaves began disappearing from the 40-foot-tall oaks in the yard of her home in the Upperco section of Baltimore County.

"My father came by last weekend and said, `You have a gypsy moth problem,'" she said.

She said the caterpillars made their way to her deck, on the side of the house, and a storage shed in the backyard.

The caterpillars are only about an eighth of an inch long when they begin feeding on trees, and eventually grow to about 2 1/2 inches long.

Caterpillars were several inches deep under trees last week at a home in the Pylesville area visited by Bob Tatman, an entomologist with the University of Maryland extension office in Forest Hill.

"People first notice when their yards get sunnier and sunnier," he said, as the leaves from their shade trees disappear. "It sounds like rain when the caterpillars' excrement drop through the leaves to the ground."

This year's outbreak does not appear to be shaping up as bad as in 1995, when the state sprayed 64,000 acres of trees and an additional 93,000 acres were defoliated. A solid estimate of the damage won't be available until a gypsy moth egg mass survey is completed in the fall.

The state contracted to have trees sprayed between May 5 and May 28, when the caterpillars were eating leaves and vulnerable to the insecticides.

Even Mother Nature seemed to conspire this year: Dry weather favors the pest, and May was the driest month on record in Maryland, Tichenor said. And the cool conditions impeded the development of a fungus -- Entomophaga maimaiga -- that usually takes a heavy toll on the young gypsy moth caterpillar.

State officials warned that trees that have lost more than 60 percent of their leaves are at the greatest risk of dying. The trees might begin to grow new leaves in coming weeks and would benefit from daily watering. Water should be administered in a slow trickle over several hours.

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