Warmer winter prompts communities to deploy Bti pesticide against black flies earlier than in past years
In late February this year, Andrea Malik looked around at open streams and bare grounds in the town of Colton and began to count down. Although it was still winter, the black fly program director knew waters in the area were unusually warm, allowing eggs to hatch.
For 38 years, the so-called “black fly diva” has treated waters around Colton with the pesticide Bacillus thuringiensis israelensis (Bti) to kill larvae. The small juveniles grow into the biting insects typically known to swarm Adirondack forests throughout May and June.
This year is different, she said. The team, which includes Malik and three others, normally start in mid-April. The technicians began treating streams at the beginning of March.
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![black fly treatment team](https://www.adirondackexplorer.org/wp-content/uploads/2024/04/Bti-crew-2-900x675.jpeg)
“This is the earliest ever,” Malik, who also leads Bti training programs around the park, said.
![black fly diva Andrea Malik](https://www.adirondackexplorer.org/wp-content/uploads/2024/04/Andrea_1-600x800.jpeg)
The treatment is applied to streams as narrow as 4 inches wide to rivers like the Ausable. First discovered in the 1970s, the bacterium kills both black fly and mosquito larvae. Research shows Bti is generally not toxic to wildlife and humans.
Permits for applying the pesticide are issued by the state Department of Environmental Conservation. Bti is the only pesticide allowed by the DEC on forest preserve for the control of biting insects, according to a landowner notice letter.
More than a dozen towns in the park have Bti permits this year, public documents show.
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In the town of Webb, black fly program director Jason Villiere said he wanted to start Bti treatment ahead of the date stamped on his permit but abided by the set rules. Water temperatures in the town and around Old Forge were warm enough the first week of March to begin.
“This is unusual,” Villiere said. “Generally, we’ve been starting, in the last five years or so, maybe the third week of March if not more towards even April for us.”
As the climate changes, warmer temperatures are causing mild winters that disrupt natural cycles for insects like black flies. Eggs laid in the fall hatch in streams once water temperatures reach about 50 degrees. Larvae numbers are average in towns the Explorer reached.
North Elba began treating waters a couple of weeks early this year, black fly program director John Reilly said. The winter warm-ups and thaws shifted Bti application times from early April to mid-March.
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Malik said the appearance of ticks is also a concern as winters become more mild. About 10 years ago, the program invested in permethrin-treated clothing to repel the bugs.
“I used to run around in the grass, roll around in the grass, I don’t dare doing that now,” she said.
The warming from El Niño this year likely contributed to temperatures this season, though Malik said she noticed gradual warming over the nearly 40 years she has spread Bti.
Malik recalled a time about at least a decade ago when she skied on a river under a full moon in mid-March. Snow and ice covered the ground and black flies were far from her mind. Now, late winter looks different in Colton.
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“We don’t have the winters we used to have,” Malik said.
I can feel them crawling on me already…
El nino is not climate change. Stop pushing that ponzi scheme you call climate change.
Nobody anywhere in this article said El Nino was climate change. It merely mentioned the phenomenon as adding to the increased heating of climate change. Quit being a climate change denier and wake up before you and all life on Planet Earth are dead.
hook, line and sinker I see.
Thanks for your help in reducing those biting black flies .
Killing off the food for the fish (particularly trout), bats, insects such as Dragonflies, Damselflies, and Wasps. Not counting the numerous aquatic and terrestrial insects that feed on them, because you cant deal with the bites? Protect yourself
Shane, you might want to read the study finding that the predators of black fly larvae prey on alternate food sources in the stream quite well if black fly larvae are less. You may be used to fending off the smaller amount of flying black flies because of a successful treatment plan in your area and think this isn’t so bad. BTi does not get all the larvae, only reduces their numbers. I suggest you talk a walk near Mason Lake/Miami River in June if you want to see what a un-treated area is like.
Liked “generally nontoxic”