Mosquitoes are one of those summertime annoyances that many have just learned to "deal with" perhaps effectively, perhaps not. But whatever annoyances they cause you, think of your animals that don't have the benefit of screened windows or DEET. Mosquitoes can be dealt with effectively, and you likely are the beneficiary of the unsung heroes of local government, your county vector (mosquito) control district. Without their efforts, mosquito populations and the diseases they carry would be horrific, like they are in the Third World. Mosquitoes have killed more people than all the wars ever fought so the dangers are very real, as we have found in the U.S. with Encephalitis and West Nile.
But less than horrific can still be pretty bad so being a little "skeeter" savvy can go a long way to reducing the problem on your property. Like pest flies, mosquitoes have very specific requirements so minimizing mosquito reproduction in your local area almost always offers the biggest benefit for the least amount of effort.
There are hundreds of mosquito species in the U.S. but they all fall into two general categories. Ones that reproduce in intermittent still water like gullies, ditches, depressions and catch basins that only have water periodically (lasting more than 3 days), then dry out are called Floodwater Mosquitoes. If you look closely you’ll see they have a pointed abdomen. The other mosquito type reproduces in permanent still water such as ponds, stock tanks and marshes and are called Semi Permanent Mosquitoes. These have a rounded abdomen.
A Floodwater Mosquito takes a minimum of 72 hours (3 days) to get to the adult stage at the optimum temperature of 80-90℉, so the intermittent water must remain for at least that long. In urban areas a foreclosed house with an abandoned swimming pool can drive the whole neighborhood crazy with mosquitoes. Mosquitoes do not reproduce in moving water, streams or rivers unless there are still areas.
If you are getting bit during the daytime, and only occasionally, then it’s most likely Floodwater Mosquitoes that came from intermittent water. If you are getting bit constantly and mostly just before dusk and just before sunrise, then those probably are Semi-Permanent Mosquitoes and came from continuous water that is nearby. The Floodwater Mosquito can go quite a distance as they drift with the breeze until they detect CO2 from a mammal and then head upwind towards it for a meal. The Semi Permanent type does not range as far, typically 1/4 mile, so they are likely reproducing near to you and you can do something to prevent that.
Prevention comes from either removing or changing standing water every 3 days (when in doubt, dump it out) or by stopping the reproduction in the water by adding a Mosquito Torpedo Bti dunks or mosquito-eating fish (Gambusia). Remove all unnecessary standing water like unused troughs, pots, buckets, etc. Add Blue Bird houses since they consume many insects including mosquitoes. It doesn't take a lot of water to produce thousands of mosquitoes so look carefully and eliminate all you can. Mosquitoes cannot tolerate wind speeds higher than 7 mph so fans can help too. Call your county vector control office for tips specific to your area.
Like flies, mosquitoes use weeds to rest in out of the sun, so keep things well trimmed near you and your animals and force the bugs to rest elsewhere. Mosquitoes don't tolerate wave action so removing the plants growing in the water at the edges of ponds and lakes can help too.
Flood irrigation can be a big source of mosquitoes if the water “ponds” on the surface for 3 days. Ponding that long often means you are wasting water and creating a mosquito problem at the same time. Turn the water off when two-thirds of the field is flooded and it will generally cover the whole field anyway.
Be aware that if you dump out your horse's water trough every few days, you could be creating a fly factory, if you dump it where manure is, that now will be kept damp. Dump or drain the trough away from manure, or put a Torpedo in it once every 60 days – but not the round BT dunks you get from a hardware store.
For mosquitoes that are traveling in from afar, or if you happen to be in their territory (meal time) repellents can help, but so can wearing a white shirt and hat, instead of dark colors. Mosquitoes and many other biting flies don't see white, but are attracted to dark moving shapes. Never use DEET on your pets as cats and dogs are very sensitive to DEET and may develop severe neurological problems if it's used on them. If the product containing DEET does not explicitly say it's approved for use with horses, don't use it on them either.
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