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Black Fly Control

About our Black Fly Control Program

The Town of Caroga conducts a Black Fly Control Program using harmless Bti (Bacillus thuringiensis israelensis) every spring. We use Vectobac 12AS from Valent BioSciences containing 11.6% Bti. You can click on the Vectobac 12AS link and read the product label for detailed information. Our Field Technicians (5 people) monitor all moving waterways in the town. Bti is applied when needed in the targeted area at various times beginning March 1st and ending July 31st. The Town has conducted this program for more than twenty years.

What do we do?

The program began 23 years ago by identifying moving waterways that adult female black flies might select to lay their eggs. Any moving water, from a 4-inch wide trickle to one the size of Caroga Lake outlet is a potential breeding area for black flies. Field Technicians surveyed over 50 square miles of the town to catalog waterways. The best map you can buy shows less than 50% of the waterways, so we made our own maps. We have identified over 150 such streams in the town. After the female 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 found in most local waters! The larvae attach to any secure anchor and filter food from the water as it moves by. That is why we don’t monitor or treat non-flowing waters. If the water does not flow, the larvae starve and die. 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. In the 20+ years of Caroga’s Black Fly Control program, Field Technicians have catalogued over 140 miles of waterways in our town. 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. In the four stages of the Black Fly life cycle they are only susceptible to Bti as larvae. Black Fly eggs do not eat, and larvae that have entered into the pupae stage do not eat. Adult flies are out of the water looking for a blood meal. Only the larvae actively feed in the streams.

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. Once they discover larvae, they measure the size of the stream, the depth, the temperature, and the speed of the flow. Using proven scientific formulas, we calculate how much Bti to add to the stream and at what distance intervals. Very precise amounts of Bti are mixed with stream water in a mixing jug and added at appropriate intervals. By adding Bti in very low concentrations (5-25 parts of Bti per million of stream water) depending on stream conditions, 90-100% of the larvae are killed. Bti only kills the larvae. Once they grow into pupae 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 prevents the flies from continuing to develop into biting adults. To determine the effectiveness of their work, Field Technicians return to each stream frequently thru the spring/summer months monitoring for larvae. This allows us to maintain larvae-free streams and interrupt the Black Fly life cycle. Eliminating as many larvae as possible eliminates biting adult flies. Larvae continue to emerge from eggs all season long. The eggs may have over-wintered or may been laid in spring. Streams are usually treated between 2- 10 times per season.

How successful is the program?

The comprehensive, season-long approach to controlling Black Flies is very well received in town. There are significantly fewer black flies as a result of the program. We cannot completely eliminate Black Flies. Residents, visitors, business owners and elected officials remain in favor of continuing this approach to control Black Flies. Years ago aerial spraying was used to control adult flying Black Flies. But this method also killed other insects and was controversial for Adirondackers. Hand treating our streams targets only Black Fly larvae, mosquito larvae (usually not found in flowing waters), and a certain small biting midge larvae. Bti is safe for humans and other animals, because they don't have the same combination of an alkali gut and the specific enzymes necessary for a reaction. The only creatures which have the right combination, are black flies, mosquitoes, fungus gnats and a few types of midges. Bti is considered one of the safest natural Black Fly pesticides on the market. Besides being non-toxic to humans and other animals, Bti has the advantage that it degrades quickly and doesn't persist in the environment Who else uses Bti? 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, 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. Aerial spraying of broad- spectrum chemicals for black fly control is a thing of the past. The Towns of Caroga, Keene, Colton, Indian Lake, Horicon, Chestertown, Inlet and Newcomb have had programs for over 20 years. Several other states use Bti. Because it is extremely specific, Bti is considered one of the safest insect control agents ever developed. Other insects, birds, fish and mammals (including humans) do not have the stomach chemistry to be affected by Bti.

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. The NYS Regional Forester has given us written permission to use Bti on state lands within the town.

What do the Field Technicians do on my property?

We may ask to have access to your property for several reasons. You may have moving water on your property (or border moving water) 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 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. We wear high rubber boots so we can examine leaves, weeds, stones, sticks, in streams, take readings and measurements of stream flow. We carry backpacks with our measuring devices and log books for calculations. Even if you have no moving water on your property, 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 tax dollars. All work conducted by Field Technicians is on foot. No trails are cut; no blazes are made. No motorized vehicles are used. We occasionally will use a kayak or canoe to access an inlet stream on the far side of a large body of water. Plastic flagging may be used temporarily but will be removed at the end of the season. We leave no trash on your property. We are all woodsmen and enjoy not seeing trash on waterways.

What do our work days look like?

Some of us are retired from the regular working world and do our woods walking during the week. Some of us have full time work weeks at other jobs and do our woods walking on weekends or holidays. All of us walk the woods in daylight. We walk some remote streams mostly alone and chose our path carefully. We usually park along the road at a stream crossing. We will walk upstream and downstream from the bridge or culvert, monitoring or treating the stream if larvae are found. We lock our vehicles but if you look inside on the seat you will be able to see a letter from the Town of Caroga stating why we are parked there and showing the Town’s pesticide license triangle. We may ask your permission to park on your property to avoid parking our vehicle on a dangerous stretch of highway or you might have a dirt road that will get us closer to a stream we would like to monitor. That would be your decision to allow us to park on your land. Our Black Fly Control program starts March 1 st and ends July 31 st . Our field work depends greatly on weather. If streams are ice covered in early March obviously we cannot monitor or treat. If there is deep snow on the ground we cannot easily get around and it is dangerous to transit from a three foot high snow bank down into a stream bed with snow shoes. Water temperatures are near freezing when we start in March so we certainly don’t want to get wet from falling into a stream.

What is our training to work with Bti and treat streams?

We use research-proven scientific methods to treat streams. All our Field Technicians must attend a 30-hour classroom course registered and approved by the NYS DEC. After the 30-hour course, we must sit for a general pesticide use exam and a specific Category 5B exam covering Aquatic Insect Control given by New York State. An annual summary of town-wide Bti use must be sent to DEC each November 1. A highly-specific report must be sent to DEC each February 1 detailing what quantity of Bti was put into each stream treated by date, quantity, and location. This report must be backed up by stream side worksheets that show our measurements and calculations for Bti treatments.

Contact Information

The town’s Black Fly Control Director is Michael Kunath. He can be reached thru the Town Hall or is happy to be contacted by home phone. He can meet you at the town hall for an information session or meet you at your stream. Please contact him with any questions you have about Black Fly Control.

Black Fly
Control Director

  Michael Kunath
(518)752-6287 (home)

Links of Interest

Black Fly Life Cycle
Blood sucking scourge of the Adirondacks

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