Lull in gypsy moth population may reduce spraying

April 13, 1991|By Luther Young

Maryland's annual spraying program for the gypsy moth caterpillar is about to get under way, amid predictions that a natural lull in the pest's boom-and-bust population cycle will limit statewide tree damage this year.

But property owners concerned about individual trees should act now to protect them with sticky barriers against the leaf-eating caterpillars that are just beginning to emerge in the warm spring weather, according to the Maryland Department of Agriculture.

"If you're going to do it, this weekend is about the latest you can wait," said Robert H. Tichenor Jr., chief of forest pest management. The sticky bands around tree trunks trap the still-tiny caterpillars as they make their initial migrations in search of foliage.

Last year, a record 133,062 acres of trees were defoliated in the state, the first time damage exceeded 100,000 acres. The gypsy moth arrived in Maryland in 1969 after a century-long advance from New England and caused its first significant defoliation here in 1981.

But when inspectors went out last fall to conduct their surveys of gypsy moth egg masses -- a predic

tor of this spring's populations -- they found dramatically reduced numbers in Central Maryland.

"They're seeing the same reductions into south-central Pennsylvania, sort of a bottoming-out in this four- to five-year cycle," said Mr. Tichenor, referring to a periodic retreat of the pest thought to be caused by overpopulation stresses and dis

ease. Although last year's record spraying of 187,700 acres largely prevented defoliation in treated areas, the state is not taking credit for the anticipated decrease.

"Even in areas where we didn't spray, they're down this year," Mr. Tichenor said.

RF "We can't stop the gypsy moth. All we do is try to protect tree re

sources considered the most valuable and worth saving."

Maryland has an estimated 1.6 million acres of hardwoods, such as oaks, that are susceptible to the gypsy moth.

Severe defoliation -- defined as the loss of more than 60 percent of the leaves -- doesn't automatically cause death, but it can weaken a tree and make it vulnerable to drought, disease, insects and further defoliation.

The $2.5 million spraying program, scheduled to begin on the Eastern Shore in the last week in April, is targeting approximately 160,000 acres in 21 counties, down nearly 15 percent from the 1990 acreage and the smallest total since 1987.

And the number of property owners included in spray zones this year is off 50 percent from 1990, to about 43,000, indicating a decreased focus on heavily populated suburban areas that have received extensive treatment in recent years.

Mr. Tichenor said the state will spray 8,261 acres in Baltimore County, compared with 16,459 acres last year. Towson and Reisterstown are off the spray list, but White Marsh and Middle River -- with gypsy moths still "as heavy as ever" -- will receive major attention.

Anne Arundel County has reduced its targeted acreage from 13,490 last year to 11,867 acres, and Baltimore City has no plans for aerial spraying. The moth continues to advance into Southern Maryland, but infestations there are still low.

And populations on the Eastern Shore and in the three westernmost counties in Maryland -- which last year accounted for nearly half the statewide defoliation -- are expected to remain stable, Mr. Tichenor said.

Some of the reduction in spray acreage for 1991 results from budget cuts in the counties, which match the state's contribution of 25 percent of the spraying cost. The federal government contributes the remaining 50 percent of the "cooperative suppression" program.

Prince George's County will spray only 1,000 of 6,000 acres identified by the state as infested. Howard County dropped 1,400 acres from 5,000 originally targeted. Montgomery County is spraying about half the 20,500 acres treated last year.

And the 160,000 acres statewide don't include trees sprayed by private contractors. Mr. Tichenor said fewer than two dozen of the 43,000 property owners contacted asked

to be omitted from the program, compared to hundreds who angrily questioned the safety of the pesticides in 1988 and 1989 when widespread spraying began in the Baltimore area.

"It's just been a gradual education process," he said, adding that the same two pesticides, Dimilin and Bacillus thuringiensis, or Bt, are to be applied this year.

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