An article in Sunday's Metro section about efforts to control the spread of gypsy moths incorrectly listed the chemicals being used in some areas of Montgomery County. The county is using the pesticide Dimilin on about 1,000 acres in the north and the biological pesticide Bt on 1,400 acres in such areas as Bethesda, Chevy Chase, Rockville and Silver Spring.
For many Washington area residents, there are three sure signs of spring's arrival: cherry trees blooming, out-of-town relatives visiting and local governments spraying for leaf-eating gypsy moths.
Although there are still large areas untouched by the moth's voracious caterpillars, the pest is rapidly spreading through area woodlands. But in Arlington County, some residents are expressing fears that one of the pesticides used to combat the moths may be harmful.
"I don't particularly like being the person who's going to be a guinea pig for Dimilin," said Sherry Icenhower, who is among the more than 60 Arlington residents who are not allowing their properties to be sprayed with the chemical. "I don't believe Dimilin should be used until every other possibility is tried."
State and local officials reject her fears, saying that Dimilin is the most effective pesticide against the month. Icenhower refuses to accept their statements. The county, she said, is "presenting it as being as safe as taking an aspirin. But I think that's far from the truth." She said she and others are concerned about the possible cancer-causing components of the chemical.
There is no dispute that a lot of the chemical and Bt, another pesticide, will be used in the region this spring. In Virginia, officials sprayed 1,000 acres last year and plan to spray 26,000 acres this year, most of them in Northern Virginia. Arlington and Loudoun counties are heavily infested.
In Maryland, where six years ago there were only three known infested acres, the state this year expects to spray about 100,000 acres, about a quarter of them between the Washington suburbs and Baltimore, and extending to Frederick and Howard counties.
"There's been a considerable explosion of gypsy moths in Northern Virginia. We're keeping our fingers crossed for a cold, wet spring" to hamper the moth's spread, said Dan Schweitzer of the Virginia Department of Agriculture.
Bob Tichenor, the Maryland agriculture department's gypsy moth expert, described his state's problem as "a little bit worse" than 1985. Maryland plans to spend $1.25 million to fight the moth this year while Virginia is budgeting about $325,000.
The costs of programs in the two states, however, may depend upon a ruling by a federal judge in Oregon who, on a technicality, temporarily has barred federal aid to states who use Dimilin in their spraying programs.
Officials in every local jurisdiction have developed gypsy moth combat plans ranging from search-and- destroy missions to monitoring the number of the moth's buff-colored egg masses which will begin appearing on trees in late April. In May, the eggs will hatch into leaf-eating, dark gray caterpillars with red and blue dots.
Depending on the severity of the infestation -- said to be "astronomical" in Arlington -- officials in most localities said they plan to spray in lightly infested areas with the nontoxic biological pesticide known as Bt, and with Dimilin, a more potent chemical pesticide.
State and federal health and environmental officials say Dimilin and Bt can be used around humans and animals, but they note that Dimilin has "a very low" toxicity that primarily affects aquatic life.
The Virginia Health Department said in a statement that the cancer risk level of Dimilin is "100 to 1,000 times below the one-in-a-million . . . cancer risk associated with smoking two cigarettes in a lifetime."
"If my woods were sprayed with Dimilin , I would make my kids stay in during the spraying, and then let them go out after . . . but I'd expect absolutely no reaction if they stayed out there" during the spraying, said Paul Schroeder, the U.S. Environmental Protection Agency's expert on Dimilin and a Fairfax County resident.
Dimilin, which destroys the moth's larvae by interfering with their skeletal growth, is considered the most effective pesticide because one application every three years kills 99 percent of the larvae while it takes three Bt sprayings to get 85 percent control.
The EPA last year cleared Dimilin for use in heavily populated areas, according to state and federal officials.
"Nothing is used unless the EPA approves it," said Max Heppner, a spokesman for the U.S. Department of Agriculture, adding that "very few substances have been subjected to as thorough an examination" as Dimilin.
States wanting to use Dimilin may have to forgo federal aid to their spraying programs unless the federal judge in Oregon lifts his injunction. The judge barred the use of federal funds for programs using four chemical pesticides because an appendix to an environmental impact statement on a spraying program in Oregon was written in such a way that he declared it too confusing for the typical reader. He ordered a rewrite.
That ruling, state and federal officials emphasize, did not involve any finding that Dimilin or the other chemicals were unsafe and it did not impose any ban on their use.
Most area jurisdictions also plan to fight the pest with parasitic wasps that eat the moth's larvae and with "lure tapes," which confuse the male and disrupt mating.
Alexandria, Prince George's County and the National Capital Park Service are not planning to spray because infestation levels in their jurisdictions are low. The District, also reporting very low levels, plans to use Bt in isolated areas.
An official said Fairfax County is expecting "fairly low levels" of infestation and will use only Bt on about 2,400 acres in Vienna and the Chesterbrook Woods area of McLean. Prince William County plans to use Dimilin on about 100 acres near Haymarket and Bull Run Mountain.
In Montgomery County, where 2,400 acres are to be sprayed, officials plan to use Dimilin on about 1,000 acres in such areas as Bethesda, Chevy Chase, Rockville and Silver Spring.
Maryland agriculture officials had threatened to bypass Montgomery and Prince George's counties because of laws the two enacted requiring the posting of warning signs when chemical pesticides are used. The agriculture officials subsequently relented, however. Since then, the state legislature upheld those laws, although only Montgomery is participating in the spraying program this year.
Arlington appears to be the only area jurisdiction encountering opposition to the use of Dimilin.
Nancy Zerbey Gray, the county's gypsy moth field coordinator, said of the more than 7,500 homeowners whose properties are to be sprayed, 61 have been exempted because of objections to Dimilin. As a result, the property of the opponents' neighbors also will not be sprayed with that pesticide.