'Tough to get at.' Mosquito expert concerned about conditions in Wellfleet

Could there be a repeat of Wellfleet's 2021 mosquito plague this year? The early signs seem a bit ominous.

In 2021, Wellfleet resident Jodi North Birchall told the Cape Cod Times that the mosquito conditions in her yard were like a "horror movie." She recently posted on her Facebook page that mosquito conditions are "WAY WORSE this year."

Reached by phone, Birchall said current mosquito conditions were "terrible" outside her house. "They're giant and they're hungry," she added. "It's going to be bad this year."

The unfortunate vampiric era of 2021 buzzed to life when high tide washovers at Duck Harbor brought Cape Cod Bay water inland, creating a sizable mosquito nursery. The resulting population boom sent ravenous swarms to backyards and beaches in the area, causing consternation and indoor retreat for irked residents.

A cooperative effort between the Cape Cod National Seashore and the Cape Cod Mosquito Control project helped reduce mosquito populations after the 2021 boom. Larvicide was applied in the area and the clearing of ditches helped restore water flow and flushing action.

Landscape changes, overwash at Duck Harbor

Since then, there have been significant changes to the landscape near Duck Harbor. Saltwater intrusion from the continuing overwash situation killed trees and vegetation in a forested area behind Duck Harbor Beach.

The Cape Cod National Seashore and Ducks Unlimited partnered on a project to remove the dead vegetation from a roughly 125-acre area. An additional 25 acres in the nearby High Toss Road area was also recently cleared.

A recent visit to the cleared area by a Cape Cod Times reporter lasted only a short time, as numerous mosquitoes made a foray outside the car quite unpleasant.

The goal of the clearing efforts was to restore "conditions favorable for salt marsh vegetation," according to a release from the Seashore, and new salt marsh vegetation has been observed in the area.

Debris is covering standing water

Clearing efforts left a considerable amount of woody debris behind, with much of the landscape covered by what looks like chunky mulch. In places, the debris is covering standing water, and the setup is proving challenging for Cape Cod Mosquito Control crews as they try to apply larvicide in the area.

"The woody debris is thick, and it's hard for us to get through it into the water," said Gabrielle Sakolsky, superintendent of the Cape Cod Mosquito Control Project..

According to a statement from the Cape Cod National Seashore, the amount of seawater that continues to roll inland has played a large role in producing mosquito breeding habitat this year. "The issue is not necessarily the mulching, but the increased volume of water coming through Duck Harbor during overwash events, which were particularly large from January through April, and the poor drainage," the statement said.

Regarding a question about the clearing project, the Seashore replied, "The situation would have been far worse if the trees were left standing. Water would continue to pool in Duck Harbor due to the increased overwash events and would drain even slower with the vegetation still standing. Additionally, access to treat those areas for mosquitoes would have been that much more difficult."

Access issues plague Mosquito Control crews

Gaining access to uncleared areas has been a challenge for Cape Cod Mosquito Control crews. Water from the overwashes has reached places that host an almost impenetrable tangle of soggy vegetation, making control efforts nearly impossible. "It's tough to get at those mosquitoes," said Sakolsky.

The Seashore said it will continue to work with the Cape Cod Mosquito Control throughout the summer to address conditions in the area. Sakolsky said she was "very concerned" about the situation around Duck Harbor and would be monitoring it closely. "We are putting a lot of time and personnel into it, but it is a large area," said Sakolsky.

Eric Williams, when not solving Curious Cape Cod mysteries, writes about a variety of ways to enjoy the Cape, the weather, wildlife and other subjects. Contact him at ewilliams@capecodonline.com. Follow him on X: @capecast.

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This article originally appeared on Cape Cod Times: Mosquitoes in Wellfleet: Standing water from overwash raises concerns