Getting rid of black flies isn't easy. A large portion of this article is dedicated to simply protecting yourself from black flies. If you thought mosquitoes were persistent, you probably haven't met our little friend the black fly, otherwise known as the buffalo gnat or the turkey gnat. Black flies are a considerable problem along the Canadian shield and in the northeastern states, near rivers and streams where black fly larvae find the running water necessary to complete their life cycle and become adult black flies. Black fly populations have gotten so bad in some areas, in fact, that the provincial government of Alberta (that's in Canada) has reported infestations where livestock, like cattle, have died from swarms of black flies. People have died. Several cases have been reported from New England where unwary travelers have been swarmed by black flies, accidentally inhaling the flies, and then dying from the resulting anaphylactic shock. Black flies are no joke.
Black flies have become a problem so serious in some states that conservation offices are starting statewide and countywide programs to help reduce the populations of black flies by treating lakes and streams with a bacterial toxin known as BTI, or Bacillus thuringiensis subspecies israelensis. But we'll talk more about this in the latter half of the article. For now, let's talk about ways to keep black flies off your person or persons, and then move on to possible ways to reduce the number of black flies in and around your homestead.
Chemical & Physical Black Fly Control
Pyrethrin-based insect foggers, like Raid Yard Guard Outdoor Fogger and Spectracide Bug Stop Insect Killer, provide an immediate, but temporary, relief from black flies. Some people will tell you that this should be your last resort when controlling any insect population in your yard, but pyrethrins biodegrade quite readily. In other words, you don't need to worry about poisoning your family or the environment when you're using pyrethrins. This doesn't mean you shouldn't use caution; cats are particularly sensitive to pyrethrins. Just remember that this is a temporary form of black fly control, and black flies are known to fly several miles before finding a blood meal.
Insect repellents will usually get rid of black flies from your personal space, but that isn't a guarantee. Black flies are tenacious little jerks, and when they're hungry enough, they will go to great lengths to find a blood meal. There are days when even the highest concentration of DEET in your repellent won't stop black flies from biting. Nevertheless, if you are going out into the woods in the morning or late afternoons during the peak black fly season, you should probably find a brand of insect repellent that contains the highest concentration of DEET you can get. Some examples of such insect repellents would be: Sawyer Maxi DEET, Fite Bite 30, Muskol, and Cutter Max 100—all of which are 100% DEET, except for the Fite Bite 30. Off! Deep Woods is a rather common 24% DEET repellent, as well. You don't need to apply this stuff to your face, but the back of your neck, ears, and forehead are common places for black flies to bite.
Lighter shades of clothing are supposed to keep black flies away, or at least make you look less delicious. I don't know if there's actually been any scientific studies done on the color range that black flies find less inviting, but white, off-white, and light tan colored shirts and pants seem to attract less black flies than darker colors like blue, red, black, green, or brown. Why is this? You're asking the wrong person. How do we know it works? Anecdotal evidence provided by hunters, campers, and people who spend a lot of time in the woods suggests that it does. Other than word-of-mouth evidence, there doesn't appear to be any research supporting this claim, but it's worth a shot. Oh, and remember to tuck your shirts and socks in; black flies like to get in your pants and bite you right behind your kneecap.
If lighter clothing isn't cutting it for you, there are brands of outdoor clothing that are impregnated with repellents to get rid of black flies. These are perhaps your backup to lighter clothing and repellents that can be applied to your skin because of the cost of this special clothing and the tediousness of maintaining this type of clothing. Such clothing is usually treated with permethrin, a synthetic form of the natural insecticidal properties discovered in Chrysanthemum flowers. An example of clothing brands that offer such garments would be Buzz Off Insect Repellent Apparel. A well known company called Sawyer also makes a product called Premium Insect Repellent Clothing Treatment that you may apply to your own clothing. This is probably the most cost effective means of obtaining treated clothing.
Head nets are probably a last resort (or maybe your first) when it comes to getting rid of black flies outdoors. Head nets are perhaps the most effective physical control of black flies in your immediate personal space. We don't know who exactly the genius was that wrapped his or her head in mosquito netting before going outdoors one day, but we have plenty of companies that are willing to solve your black fly problem on the cheap with this rather basic invention. As we've mentioned in the article about mosquito bites, we would recommend either Cabela's Mosquito Head Net (shown to your right), or Coghlan's Mosquito Head Nets—both of which are cheap ways to ensure you don't ever swallow another black fly again.
BTI & Black Fly Control
What we're about to suggest here is for educational (almost hypothetical, really) purposes only. The hypothesis is this: BTI (Bacillus thuringiensis subspecies israelensis) has been shown to kill black fly larvae before they mature into adults; under certain conditions, it may be possible to reduce black fly populations within a small area or location, so long as black flies are not a strongly established pest. In other words, if you have a small stream in your backyard, and black flies are a problem but not a very big problem in your region, you may be able to apply BTI to the stream/creek and reduce the black fly population significantly—but only if the application of BTI is timed properly.
BTI for consumer use is usually sold as something called Mosquito Dunks. They are donut-shaped cakes that contain roughly 10% concentrations of bacillus thuringiensis israelensis—a bacterium that acts as a larvicide. When applied to small ponds, swamps, or lakes, these cakes can be effective for up to 30 days. Of course, concentrations and lifespan are most likely reduced if these BTI dunks are applied to a small stream or creek. So, you will have to keep an eye on these dunks, checking periodically to see whether or not they've completely dissolved. To be on the safe side, you may want to reapply mosquito dunks once every 15 days. You should also consider applying BTI at various points in the stream or creek, to ensure that BTI is being dispersed throughout the entirety of the water supply. You might start at the head of the creek and work your way down, dropping a dunk in every 50–100 feet or so—depending on your budget.
Before you even consider trying to apply BTI to a water source, you need to consult your local conservation office or extension service to make sure you're not breaking any laws. While you're at it, you may want to consult said offices about possibly starting a BTI control program in your community. This is probably a better idea than trying to control black flies on your own property due to the black fly's propensity for traveling several miles before finding a human to bite. Generally speaking, BTI black fly control programs are most effective when managed at the state or county level. Planes and helicopters are usually employed to dust or spray BTI over large areas. Significant progress is being made with regard to the practice of BTI-based management in certain parts of the country where black fly populations are traditionally higher.