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Experts: Gypsy moth populations have dwindled

April 27, 2003|by ANDREW SCHOTZ

andrews@herald-mail.com

This year, trees have a fighting chance.

Armies of gypsy moths continue to gnaw leaves, but their numbers have dwindled, which means less defoliation, agriculture experts say.

West Virginia will spray a little more than 4,000 acres with insecticide this year, a steep drop from the 75,000 acres sprayed last year.

Maryland's insecticide spraying program will be cut in half this year.

Pennsylvania's gypsy moth population has dropped off so much the state won't spray insecticide this year.

Gypsy moth caterpillars usually hatch around the end of April. They are pervasive pests that kill trees through their leaf chewing.

They prefer oaks, which make up about 77 percent of West Virginia's woodland, according to a state Department of Agriculture Web site.

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"Spruce, pine and hemlocks die after one heavy defoliation," the site says. "Hardwood tree mortality, after two successive years of defoliation, can reach as high as 80 percent."

A 90,000-acre state forest in Pennsylvania lost $40 million worth of timber to gypsy moth infestation in four years, the Web site says.

In Maryland, gypsy moths have eaten their way through more than 1 million acres of timber and residential trees since 1980, according to the state's Department of Agriculture.

Governments fight back by spraying insecticides. The two most common ones either eat up gypsy moths' insides or inhibit their growth.

Wet, cool weather has hampered the spread of the moths this year, said Daniel Parry, a spokesman for the U.S. Department of Agriculture's Animal and Plant Health Inspection Service.

Two of the gypsy moth's worst natural enemies - the nucleopolyhedrosis virus, or NPV, and the Entomophaga maimaiga fungus - appear to fare well in those conditions.

"During a gypsy moth outbreak, caterpillars become more susceptible to (the nucleopolyhedrosis virus) disease because they are stressed from competing with one another for food and space," according to a Michigan State University explanation of pathogens. "Typically, 1 to 2 years after an outbreak begins, the NPV disease causes a major die-off of caterpillars."

Cadavers of caterpillars killed by NPV dry up, clump together in a V shape and fall to the ground.

Bob Tichenor, the chief of forest pest management for the Maryland Department of Agriculture, said the prevalence of gypsy moths is determined by counting egg masses. The percentage of oak trees and the use of the land are considered, too.

All signs this year point to a smaller gypsy moth population, he said.

Maryland sprayed 39,616 acres in 14 counties and Baltimore City last year. That will drop to 14,077 acres in 12 counties this year.

Last year, the state sprayed about 5,200 acres in Washington County, but will spray just 115 acres this year.

West Virginia plans to spray 4,256 acres this year, compared with 74,584 last year.

In the Eastern Panhandle, the state will spray 891 acres in Berkeley County, compared with 2,525 last year, and 56 acres in Morgan County, compared with 4,820 acres last year.

The state sprayed 802 acres in Jefferson County last year, but has no plans to spray there this year.

A few Jefferson County residents signed up for spraying this year, but "the egg mass counts were not high enough," said Quentin "Butch" Sayers, the gypsy moth program manager for the West Virginia Department of Agriculture.

At a cost of $1.5 million, the Pennsylvania Department of Conservation and Natural Resources' Bureau of Forestry sprayed 58,461 acres last year. The previous year, the state sprayed 169,112 acres, including more than 5,300 acres in Franklin and Fulton counties.

This year, nothing.

"Spraying can help contain the widespread gypsy moth damage we have seen in the past," State Forester James R. Grace said last month in announcing the decision not to spray, "but the major controlling favor is, and will continue to be, the prevalence of a fungus in our woodlands."

Entomophaga maimaiga has "decimated" the gypsy moth population, Grace said.

The Pennsylvania conservation agency said the number of defoliated state forest acres dropped the three previous years from 837,600 to 237,600 to 55,800.

"Egg-mass counts last year, coupled with reduced defoliation, lead to the shared belief that there will not be a lot of defoliation in the state this year," Larry D. Rhoads, supervisor of the Bureau of Forestry's Pest Suppression Section, said in a prepared statement last month.

The bureau is not sure how the recent drought will affect fungi, Rhoads said.

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