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Are ticks developing resistance to permethrin?

What appears to be an increase in ticks on Shelter Island and the East End, including the two control sites where data is collected — Mashomack Point and North Haven — raises questions whether observations are an anomaly or a trend. The ability of pesticides, particularly permethrin, to control tick populations in the long-term is under debate once again.

The Island hasn’t used permethrin since the New York State Department of Environmental Conservation in 2019 banned use of 4-poster units — feeding stands that brush deer with permethrin — which had been deployed since 2008. Shelter Island’s 4-poster program represents the longest blacklegged tick control program in the nation, according to a study on the “Susceptibility of Blacklegged Ticks on Shelter Island to Permethrin.”

The report was presented to the Deer & Tick Committee July 7 by James Burtis, Ph.D., from Cornell University’s Department of Entomology. It was researched and written in conjunction with Scott Campbell, Ph.D., lab director of the Suffolk County Department of Health Services and a member of the Shelter Island Deer & Tick Committee; Animal Control Officer Beau Payne; Laura Harrington, Ph.D., professor of entomology at Cornell University; and Joseph Peggi, a Cornell research technician. The research to date is aimed at providing a baseline for comparisons with future studies, Mr. Burtis said.

Pesticide resistance is a global issue that could affect efforts to control ticks, Mr. Burtis said, noting there are few effective pesticides for tick control. Ticks collected in the field on Shelter Island were compared with those in lab populations and suggest reduced susceptibility to permethrin.

But the reduced susceptibility isn’t extreme enough to generally conclude that resistance is occurring and more research is necessary, Mr. Burtis said.

While the study dealt with blacklegged ticks, Mr. Campbell said there’s an effort to do a similar study with lone star ticks.

Deer population numbers

Numbers were slightly revised on the number of deer that remain on the Island, according to Dr. James Bevilacqua, D&T Committee chairman. The deer population had been estimated at between 1,400 and 1,500. Judging from a flyover count at the end of January this year, the population was estimated to be 497. Dr. Bevilacqua said the “Nuisance Wildlife Control Officers” hunt — a specially licensed hunt — in February and March reduced the herd by 137. After the fawning period in the spring, when does give birth, the population is believed to be at 750, one third of which are does, one third bucks and one third fawns, he said.

Deer counts are never an exact science, but are estimated based on the effectiveness of a flyover and anecdotal evidence of deer presence, such as plants destroyed by the animals feeding on them. This year’s flyover drew high praise from the committee for its professionalism.

Membership changes

Alex Navarro, who has been Mashomack Preserve’s representative on the Deer & Tick Committee, has been promoted by The Nature Conservancy to a position in Connecticut. His last meeting was July 7 and the committee anticipates that a replacement will be selected by Mashomack Director Jeremy Samuelson.

Two other members have resigned. Chuck Tiernan and Hank Amann have both left the committee and the Town Board can select their replacements.


The Committee will be present at the town’s August 21 Green Expo, spreading the word about how people can protect themselves from tick bites. After a presentation from member Julia Weisenberg on the subcommittee’s educational efforts to date, members praised what has been done and agreed to step up the educational component of work in the future.