Moth Damage Declines

Virus, Intense Spraying Take Bite Out Of Gypsies

September 16, 1991|By Robert Lee | Robert Lee,Staff writer

More spraying, stronger bug juice and a nasty caterpillar virus combined to substantially reduce the defoliation of gypsy moths in the county this summer.

State surveyors reported last week that 2,163 acres of hardwoods were defoliated by gypsy moth caterpillars this summer, down from 7,440 last year and 3,684 in 1989, the first year the county had any substantial defoliation.

The bad news was that almost all of the defoliation was heavy, meaning more than half a tree's leaves were destroyed -- enough to killa tree in a drought season, said Robert Tichenor, chief of forest pest management for the state Department of Agriculture.

Most of thedamage was done along Millersville's Severn Run Natural Environmental Area. About 1,200 acres of the state-owned property was heavily defoliated between Dicus Mill Road and Benfield Boulevard, said Richard Olsen, head of the county's gypsy moth control program.

Though thenew figures are encouraging, state and county and local gypsy moth experts say it's too early to celebrate.

"There're a lot of naturalfactors at work. I'd hesitate to say we're over the peak yet," Tichenor said.

Olsen said property owners and community leaders should wait for their egg mass counts this winter before deciding whether tospray next year.

Approximately 35,000 acres of the county were sprayed in a myriad of private, county, state, and Army programs, up 50percent from last year, Olsen said.

Only 1 percent of the 10,000 acres sprayed in the county-subsidized program were visibly damaged, Olsen said. The county doubled the concentration of the pesticide Bt in its spray compound this year and had ideally warm and dry weather during the late April/early May spraying season.

Another, perhaps more significant factor was a viral plague in the gypsy moth population.

Olsen noticed the virus in June and July when he discovered hundreds of caterpillar corpses swinging under leaves in a "very characteristic upside-down J."

The gypsy moth-specific virus kills about95 percent of its hosts. Many experts believe the virus is responsible for the streaks and crashes in gypsy moth populations documented every three years in New England and Pennsylvania, where the moth has been present for decades, Olsen said.

The hairy brown European caterpillars have blighted American oaks and other hardwoods since 1869,when some escaped from a French naturalist who was experimenting in Medford, Mass. Since then they have spread across the country to the Pacific.

The pests were first discovered in the county in the late1970s. The state began spraying in 1983, in hopes of eradicating them. But now state and local officials agree that they are here to stay. The main issue now, they say, is controlling the damage to trees inthe most cost-effective way.

Tichenor said Maryland's complete figures for this year are not ready yet, but Anne Arundel's improvementis part of a general trend across Central Maryland.

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.