I have tried this a few times. If you live in the woods with lots of standing water, then it has literally no effect. I bought a giant supply of bacillus thurengensis pellets and put them in every body of standing water around the property weekly for a whole summer and still got annihilated by mosquitos. Now I spray, and while I hate pouring chemicals all over the property, it works fantastically well.

I could imagine it working alright if you live in the city or maybe a suburban area.