Black Fly Control Program

About the Black Fly Control Program

The Town conducts a Black Fly Control Program using Bti (Bacillus thuringiensis israelensis) every spring. Our Field Technicians work on all moving waterways in the targeted area at various times beginning late March and ending by late July. The Town has conducted this program since 1994.

Contact Us

Department Hours (In Season)

February 1 - July 15
Monday through Friday
8:00 am to 4:00 pm
Located on third floor of Town Hall

(During the off-season please leave a message, voice mail will be checked.)


How does it begin?
It begins with finding moving waterways that adult female black flies might select to lay their eggs. Any moving water, from a 4-inch wide trickle to a river larger than the Ausable is a potential breeding area for black flies. Beginning in the fall of 1993, Field Technicians have now surveyed over 100 square miles of the town to catalog waterways. The best map you can buy shows less than 50% of the waterways we are looking for so we had to make our own. After a black fly lays her eggs in moving water, those eggs settle through the water, attach and begin to grow into the next stage of their development - small, worm-like creatures called larvae. Larvae are what we look for. (And they are easy to find in local waters!) The larvae attach to any secure anchor and filter food from the water as it moves by. Following their development stage as larvae they mature into pupae. The pupae mature and emerge from the water as the familiar adult black fly. The adult female will search until she finds a warm-blooded donor to bite. Once she has a blood meal, she starts the egg laying cycle again.
Why look for larvae?
In the larval stage of their life cycle the black fly population is easy to find, identify and treat with Bti. Field Technicians catalogued over 250 miles of waterways in the target area. Now we know where to systematically look for larvae in streams. While the larvae are busy filtering food from the water they will also eat any microscopic particles of the liquid Bti formulation we put in the stream. Because of the unique conditions in the stomach of a black fly larvae, most notably a very alkaline pH, when the larvae eats Bti it will die, usually within a day.
What does the fieldwork involve?
Field Technicians are constantly monitoring the streams assigned to them to see if black fly eggs have hatched into larvae yet. Once they see larvae they measure the size of the stream and add very precise amounts of Bti. By adding Bti in very low concentrations (5-20 parts of Bti per million parts of stream water) 90-100% of the larvae are killed. However, Bti only kills the larvae. Once they grow into pupae the larvicide Bti does not work. So the Technicians must get to the streams before the larvae grow into pupae or it is too late. The killing of larvae, or larviciding, prevents the flies from continuing to develop into biting adults. To determine the effectiveness of their work Field Technicians return to each stream after treatment to count the number of dead larvae before they detach and wash downstream. This allows us a simple way to confirm a successful treatment. Streams are regularly monitored for more larvae and treated as needed. Larvae continue to emerge from eggs all season long. The eggs may have over-wintered or may been laid in spring. Streams are treated 2-10 times per season as needed.
How successful is the program?
The comprehensive, season long approach to controlling black flies has been very well received in town. There are significantly fewer black flies as a result of the program. Residents, visitors, business owners and elected officials remain in favor of continuing this approach to control.
What about Bti? Who else uses it?
Bti was discovered in Israel in the late 1970's. Since then tons of Bti have been applied to rivers in South Africa to combat a parasite carried by black flies that was a leading cause of blindness there. Large-scale programs are conducted on major rivers in the United States. What makes Bti programs in mountainous regions like the Adirondacks challenging is that there are many breeding waterways for black flies and they're spread out across all sorts of terrain. It takes very little Bti and lots of legwork to get the job done right. Bti was introduced in the Adirondacks in 1982 during a NY State Museum Science Survey study in the hamlet of Onchiota in the Town of Franklin. Programs have been developed in over 30 communities since then. 
What does the New York State Department of Environmental Conservation have to say?
Bti is the only pesticide the NYS DEC allows to be used on State Forest Preserve lands for control of biting insects. This is because Bti is extremely specific in targeting black fly larvae and is non-persistent in the environment. It is also because of the carefully controlled ground application method we use. All of our Field Technicians are licensed by the DEC.
What are the Field Technicians going to be doing while they are on my property?
We may ask to have access to your property for several reasons. You may have moving water on your property that may host larvae which we'd like to include in our treatment activity. Remember, we consider even a trickling little brook something to keep a watch over. Your property may have seasonal running water on only the wettest of springs, but we still will want to monitor in the event it is a banner year and the stream hosts larvae. Even if you have no moving water on your place we may write and ask permission to include it in our work. Why? Your lot may provide a good shortcut to walk to another lot that does have a waterway on it. This saves us time and that saves your tax dollars. All work conducted by Field Technicians is on foot. No trails are cut; no blazes are made. We use canoes by state access on the Chubb River south of the Averyville Road. A motor boat is use on Lake Placid; boat access is used only with pre-arranged, written docking privileges. Flagging may be used temporarily but will be removed at the end of the season.
Where are the Field Technicians working in the Town of North Elba?
The area we work in begins at the North end of Lake Placid in Whiteface Landing. It extends east and south through the Mt. Whitney area and into the Sentinel Mountain range. We work as far east as the North Country School and the Mt. Van Hovenberg Sports Complex. From there we head west covering the area south of the ends of John Brown and Averyville Roads, and the Village of Lake Placid. Our work area in the western section of town extends to Scarface Mountain south of Ray Brook, and continues North to McKenzie Pond Road to the edge of Saranac Lake. All of the area North of Rte 86 in Ray Brook is included and we continue east to the Whiteface Inn Road then up the west shore of the lake to Undercliff. That's 100 square miles and 250 miles of waterways for 15-17 weeks!
Why do I need to return a Response Form?
While it may be a nuisance to return your Response Form, it is best if you tell us directly what your preference is regarding the program. The only way to be sure we know what you want is if you tell us. If we could get a response from everyone we contact it would greatly simplify our work. Please help us by promptly returning the Response Form in the postage paid envelope. This will save us time by reducing paperwork, lowering postage costs and saving administrative expenses - all paid for with your taxes. Your time and cooperation is most sincerely appreciated.


Program Director:
John Reilly
(518) 523-9516 ext. 141