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How to Control Fungus Gnats on Indoor Plants

By Stan DeFreitas Mr Green Thumb ; Updated September 21, 2017

Controlling fungus gnats on indoor plants can be done by using a sterile potting soil of peat moss, but many potting soil has at least 25 percent organic material. Keep an eye on indoor plants to avoid the development of fungus gnats with plant advice from an urban horticulturist in this free video on gardening.


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.


About the Author


Stan DeFreitas, also known as "Mr. Green Thumb," has experience as an urban horticulturist working for the Pinellas County Extension Service and has taught horticulture at the St. Petersburg College. "Mr. Green Thumb" has spread gardening know-how on radio, TV and newspaper columns in both the Clearwater Sun and the Tampa Tribune. DeFreitas is the number one gardening advisor in the state of Florida, was the first to establish a "community garden" in Pinellas County, and helped start the first Master Garden Program in Pinellas County. DeFreitas was also twice Jaycees Horticulture "Man of the Year," was awarded the landscape design award from the city of St. Petersburg Beach, and was the host of the highest rated garden show on local PBS.