After a presentation by Dominick Ninivaggi, superintendent of the county’s Division of Vector Control, members of the East Hampton Town Board decided not to act on calls by several residents to ask the county to stop using the chemical methoprene to spray for mosquitoes in salt marshes here.
Mr. Ninivaggi said there was “a lot of misinformation and misunderstanding of what the scientific data show.”
The county vector control program was adopted in 2007 after an extensive review of its details, including an environmental review of the chemicals to be used, he said. “Methoprene was looked at very thoroughly,” and a secondary review was performed by outside agencies such as the State University at Stony Brook and the United States Geological Survey. Sampling of salt marshes that have been sprayed, Mr. Ninivaggi said, showed that the amount of the chemical remaining in the marsh is “extremely minute, and disappears very quickly.”
“This is by no means any kind of deadly poison or environmental concern.” And, he said, “the amount of material that we use is far below the amount of material that would be deleterious. The margins of safety are several hundredfold.”
There are no known effects to shellfish, he said, or to humans.
Methoprene has been used since 1995, Mr. Ninivaggi said, along with a biological larvicide, Bacillus thuringiensis, or Bti, which some have suggested could be used exclusively as a safer substitute for methoprene.
“Bti alone does not do the whole job,” Mr. Ninivaggi said. Alternating the agents of attack prevents mosquitoes from becoming resistant to one of the substances, he added.
Besides the West Nile virus, which is spread by mosquitoes, of particular concern, he told the board, is a virulent strain of equine encephalitis called Triple-E, which has a 50 to 75-percent mortality rate in humans and often leaves survivors with neurological damage. “It’s important to remember that there is more than one mosquito-borne disease,” he said.
Mosquitoes that carry both diseases live in local salt marshes, and the most effective strategy is to kill larvae in the marsh, he said. Once adult mosquitoes reach residential neighborhoods, an “adulticide” — a broad-spectrum pesticide — must be used to kill them, he said. Because that chemical is “toxic to a lot of different species of insects,” and the spraying exposes residents, county vector control tries to avoid the need to treat adult mosquitoes. “We do very little of that.”
West Nile was found this year in mosquitoes from the Three Mile Harbor and Beach Hampton areas of East Hampton Town, he said. Salt marshes around Napeague and Accabonac Harbors, as well as in Beach Hampton, are the areas of the town routinely treated by the county, he said.
Although in 2007 the East Hampton Town Board adopted a resolution asking the county to discontinue the use of methoprene here, Mr. Ninivaggi explained to the board that local municipalities are “specifically pre-empted” by state law from enacting their own laws regarding pesticide use.
“There’s always more to be learned. There’s always a possibility of some very subtle or sub-lethal effects that nobody’s seen,” the county official said of methoprene. But, he said, “we are 30 years in” to its use, “and you have to consider the alternatives.”
Board members said after Mr. Ninivaggi’s presentation that, given the information he had provided, they felt comfortable with the county’s spraying program.