There are several methods for treating for mosquitoes around a home. One is making modifications to the landscape to level out areas that may collect water after a rain, another is removing sources of stagnant water like old flower pots, fire pits, bird baths, etc, another is treating areas with standing water with an IGR (insect growth regulator) like Methoprene, but the most popular is the use of a machine to emit a very fine mist of fog to your property.
The reason for the fog is because it takes the fight to the enemy. It attacks those mosquitoes at their home. See, during the heat of the day, mosquitoes rest under leaves and within the foliage, bushes, trees, etc. This is why just spraying doesn’t work. Mostly because the spray just runs off the top of the leaf and does not come into contact with the mosquito. Products that you attach to a hose that has material that kills mosquitoes are good examples of this kind of spray. With a fog you are more likely going to come into contact with the mosquito, killing it, and also placing the product to the underside of that leaf to either kill or repel any future mosquitoes from making that leaf it’s home. It’s a great way to crash a mosquito population around your yard and making your outside livable again.
On the other side of the coin, if you implement the measures above, you will get a noticeable decline in the nearby mosquito population, but if you have neighbors right next door with a ton of bushes, and foliage, then you may still have some activity. Also, don’t forget that mosquitoes are flyers, they can fly into your space and bite you regardless of treatment. Things like heavy rain can decrease the effectiveness of treatments, but overall it is a great tool to reduce populations.
The most effective frequency would be every 3 weeks, but some folks will go monthly, and others may just want one service to reduce the population of mosquitoes before a party, barbeque, or outdoor event.