Q.Hi I have a problem with fungus gnats
I heard you could use sand as “top soil” but when I watered my plants the sand and soil just completely mixed how can i prevent the mixing or what is a better way to fight these gnats.. thanks a lot ?
Certified GKH Gardening Expert
They are a very beneficial, natural ally in the soil. They don't really like to come out of the soil where they are exposed, but will do so to avoid suffocation from being saturated. In short, they come out when the plant is overwatered, since they would suffocate in the soil.
They do what they are named for, however. They eat rotting material, or fungus. They will not harm living plant matter, but the fact that there are so many would signal an overabundance of fungus in the soil. Usually, fungal infections are caused by overwatering and saturated soil.
First, make sure that you let the soil dry out very thoroughly down to about 2 inches. Do this between every watering. Treat with a fungicide. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
Once the soil contamination is controlled, they will move on to another source of rotting soil, since they will no longer have any food source. Removing them before the soil is treated will lead to further infection, since there is nothing controlling it.