Hi I'm Stan DeFreitas, Mr. Green Thumb. Fungus gnats, kind of a major problem for our indoor plants. Now there's a couple of things you can do. One is start off with a sterile potting soil. Remember, pearlite exploded about 1800 degrees, it's all the white material you see in a potting soil. Fermiculite also is a material that's exploded at a high temperature. Peat moss, peat moss should be sterile. Now fungus gnats like the organic matter. Many of our soils will have up to 25% organic matter in that potting soil and because of that, you have a place that fungus gnats may start to develop. If it gets real bad, well throw the soil out and start again. But you can use plastic over some of the containers during the middle of summer to help solarize the soil or you could get your sprayer out and use something like neem oil that you can spray around the base of your plants, around that soil area to help kill those fungus gnats. Remember some of the pesticides you'll use you'll have to use outside and of course as always, read the label directions. The directions are the law and that's how you need to apply the material. For askmrgreenthumb.com, I'm Stan DeFreitas.