I manage a historic site in Brunswick, Ga. We are directly on the marsh and have problems with biting flies (deer flies, black flies, yellow flies), mosquitos and sand gnats. I began using a DynaFog Mini-lite 2990 ulv sprayer last year. The primary chemical that I used was permethrin. I had a good deal of success controlling biting flies but was less successful with mosquitos. I am attempting to spray around 40 acres. Our landscape with lots of live oak trees providing plenty of shade. Being on the marsh the environment is, of course, very wet. What chemical or chemicals would you recommend for these insects in my application?
First it sounds like you have ideal equipment but the Permethrin would not be my choice of active to apply. It would explain the mixed results you achieved though based on the size of the area involved, you really need to isolate what we call "mosquito pockets" to get control of this specific pest. More on that later..
For starters, I would change to BIFEN. It's more cost efficient, requires a lot less material to be mixed per tank (good for the environment) and works a lot better compared to permethrin. I use it exclusively for my 1 acre lot (located on the Hootch) and it takes care of everything including roaches and ants so it's plenty strong.
Now if I found that the Bifen alone wasn't lasting long enough, I'd get some NYLAR and add that to the tank mix. This will no doubt interfere with the juveniles of all the pests you mention which in turn would prevent them from developing to breeding adults. This would really help for the long term.
Lastly, if you find yourself hesitant to spray close to the wetlands in fear of contaminating any sensitive areas, get some ECO IC. This active is a "green" product made from essential oils. It's federally exempt yet highly effective for all the pests you want to control. And since it can be applied to sensitive areas without concern of contamination, it's a great choice for these sites where pests are no doubt living and thriving and might otherwise be missed. These are in fact what can turn out to be "mosquito pockets". Marsh land, potted plants, areas with man made irrigation or sprinkler systems, etc. Many times a small pocket can breed thousands of mosquitoes and be missed.
To catch such locatins, it's important to think small which can get tough to do when dealing with 40 acres. But my gut tells me if you look really close to where the mosquito activity is centered, you'll find the hot spot. As our MOSQUITO CONTROL article explains, they don't travel far to find food and basically, can't. That means they must be somewhere close to where people are being bit so be sure to treat these areas well.
Here are direct links to the information and products listed above:
Mosquito Control: http://www.mosquitoes.net/mosquito-control