I spent a few hours researching black fly/buffalo gnat control measures. The options aren't great, but they
are expensive.
As you know, black flies are attracted by carbon dioxide, but I also found out they're also attracted to dark, moving objects. Like nestling eaglets. About the only thing they don't like is wind. Which suggests a fan - a big one - with a long extension cord. On the flip-side, some of the residential traps are vacuum-assisted. If scaled up to treat an acre of woods, it could get very noisy for the nestlings. But they are used to the hatchery's lawnmowers...
Commercial controls include flypaper. Some sticky pages can be scented or contained in colorfully patterned cardboard boxes. The theory is that black flies are attracted to certain patterns, like flowers, that might be found in nature. Flypaper is a relatively cheap option but horribly labor-intensive. And nothing guarantees that flies will land on the sticky paper.
Carbon dioxide traps may be an effective option, but they're expensive and could be labor-intensive. The most reliable source of CO
2 is propane, followed by dry ice and then by a titanium dioxide catalyst. The theory is that if you can't shoo away black flies you can give them an alternative source of CO
2 to lure them away from the area you want cleared.
I ignored the sites suggesting the use of DEET (recommended for your backyard parties, though). Likewise, beneficial nematodes were ignored because the black fly life cycle near eagle nests doesn't depend on soil, which is where nematodes are applied and live naturally. Black fly larvae depend on oxygenated, running waters, but I ignored suggestions of damming the creek or making it hypoxic.
However, there are a couple of options that focus on the aquatic, larval stages of black flies, namely dragonflies and a bacteria (Bacillus thuringiensis var. israelensis or "Bti"). I have no idea how dragonflies could be introduced into an area where none are already, but they're voracious and nymphs can and do feed under water. Bti can also be safely applied in aquatic environments. The only warning is to make sure the body of water being treated isn't a drinking water source. (I presume the warning means a "direct" drinking water source, since almost all waters can and do eventually become drinking water.) If water treatment becomes a viable option, then timing is everything and the local life cycle of black flies needs to be nailed down.
Similarly, fish (e.g., carp, suckers) are extremely good at feeding on black fly larvae. Perhaps the hatchery might have a few suggestions? Other predators include beetles, caddisflies and stoneflies (see the paper at the end of the articles).
Black Flies ("Buffalo Gnats")
http://www.idph.state.il.us/envhealth/pcblackflies_buffalognats.htmBlack fly
https://en.wikipedia.org/wiki/Black_flyHow To Control Black Fly
https://www.arbico-organics.com/category/black-fly-controlCarbon Dioxide Mosquito Traps No Magic Bullet, Say UF Experts
https://www.sciencedaily.com/releases/2005/06/050607013042.htmCO2 Traps
http://www.mosquitocontrol.org/co2-trapsCarbon dioxide baited mosquito traps
http://labs.russell.wisc.edu/mosquitosite/preventing-mosquito-bites/carbon-dioxide-baited-mosquito-traps/Dynatrap DT1000 and DT2000XL
http://www.mosquitoreviews.com/dynatrap-dt1000-dt2000xl.htmlBest Mosquito Trap Reviews. Propane, CO2 and Electric Traps
https://insectmurderer.com/best-mosquito-trap-reviews/Gnats in a Pond
https://homeguides.sfgate.com/gnats-pond-50754.htmlAQUABAC 200G Granular Bti Mosquito Control
https://www.arbico-organics.com/product/aquabac-bti-mosquito-control-granular-bacillus-thuringiensis-israelensis-btiWhat Do Dragonflies Eat?
https://www.dragonfly-site.com/what-do-dragonflies-eat.htmlDipteran predators of Simuliid blackflies:a worldwide review
https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2915.2003.00431.x