Also consumer-grade outdoor pesticide-foggers (ie: Yard Guard) do pretty much nothing positive at all unless you own stock in Black Flag, RAID or Ortho.
Mosquitoes and biting flies have mostly developed a tolerance to them and both are effectively immune, HOWEVER those same chemicals are very effective at killing/weakening beneficial insects, fish and birds.
All you accomplish spraying clouds of poison over your yard is causing toxic/carcinogenic pollution and potentially making the disease-carrying mosquito problem worse.