WELLFLEET — It’s not just you — even the county’s mosquito control experts say 2024 is shaping up to be a bad year for the bugs. They’re also worried that a series of petitions calling for pesticide reductions could create laws that hamper their organic measures to control mosquito breeding.
Only preliminary numbers are available this early in the summer, but they already paint a pretty clear picture. Last year, a trap set in Provincetown by the Cape Cod Mosquito Control Project (CCMCP) collected about 200 insects in the last week of May and the first two weeks of June. This year, over the same period, they got around 2,000. Slightly higher numbers were found at another trap in Truro.
According to entomologist Gabrielle Sakolsky, CCMCP’s superintendent, high rainfall and floods are behind the boom. “It’s so wet all over Cape Cod,” she said. “My crews are busy no matter where they are.”
Typically, mosquito numbers grow over the course of the summer. So far, those in the traps have mostly been the brackish water-breeding ones, which Sakolsky said is normal, as they emerge before freshwater mosquitoes do. Their populations could peter out only if we have a period of less rain and fewer storms coinciding with high tides.
Wellfleet is dealing with the effects of saltwater inundations around High Toss, Pole Dike, and Bound Brook Island roads during the winter and spring. The saltwater has ended up inland since an overwash at Duck Harbor in 2021 eroded the dunes there, allowing high-tide storm surges to flow up the Herring River floodplain. It’s been a boon to the brackish water-breeding mosquitoes.
The 2021 Duck Harbor overwash drove a mosquito outbreak in Wellfleet that year. But that boom originated around Duck Harbor itself, where Mosquito Control staff were not able to gain access and apply larvicide because they lacked permission from the National Seashore.
This year, they have permission to spray in those areas, but the overwash area has since grown, and with vegetation cleared around Duck Harbor saltwater is flowing farther upstream. So, the mosquitoes are breeding farther up the Herring River, too, and sometimes in areas that are too densely vegetated for Mosquito Control to reach.
A Petition’s Possible Effects
In the last eight months, Orleans, Eastham, and Wellfleet have approved home-rule petitions aimed at limiting pesticide use. These petitions, if approved by the state legislature, would ban the use of all synthetic pesticides — that is, those made by chemically altering mineral, animal, or plant products — except in a handful of cases such as for indoor pest control, personal insect repellents, and pet flea and tick sprays.
According to Laura Kelley of Eastham, who wrote the petitions, the hope was to encourage a reduction in pesticide use. “I have a right to not be exposed to pesticides from someone else’s property,” she said, adding that ponds and bees have the same right.
Sakolsky said she understands the motivations behind the petitions and agrees there should be more limits on pesticide use. She is worried, however, that these laws could make her agency’s future mosquito control efforts more complicated. “They would very much limit what we could do when applying the larvicides,” she said. She notes, however, that the ban would not apply within the limits of the National Seashore.
The CCMCP relies on a Bacillus thuringiensis israelensis (Bti)-based larvicide to control mosquitoes. It is a naturally occurring bacterium that kills larvae during their development, and besides mosquitoes, it kills only a handful of other flies, leaving humans and other animals completely unharmed.
While the bacterium itself is considered nonsynthetic, Sakolsky said, the process that turns it into a sprayable pesticide means the final product is classed as synthetic, so use of the larvicide would be prohibited under the home-rule petition.
In its current form, the petition includes a waiver that would allow town select boards to exempt some synthetic pesticides from the ban on a case-by-case basis, specifically to control invasive plants and mitigate public health emergencies. It is unclear whether CCMCP could get a waiver to use larvicide, but Sakolsky said she would apply for one if the bill were to pass at the state level.
Still, none of that is likely to happen quickly. To become law, each home-rule petition needs to become a bill approved by the Joint Committee on Environment and Natural Resources, then passed in the state House and Senate, and signed by the governor within two years of reaching the committee. The Orleans petition has already been turned into a bill and has been before the Joint Committee since March 14.
And there’s still room for the exemptions that Mosquito Control would need. If the petition were to pass, it would likely change before it reached the governor’s desk. It allows the legislature to discuss the petition with the select board and amend it.
