Q: A year ago I used unsterilized potting soil for my indoor plants so ended up with little flies (like fruit flies). I spoke to someone at a plant store and she suggested that I take all the plants out of the soil and hose them off and then put them into the proper soil. I did that but in the last 5 months, the little flies have come back. Is there some solution that I can put into the soil to kill these?
You most likely are dealing with a fungus gnat. Irritating little flies
that can be detrimental to your plants because they feed on the roots.
They are a short lived fly but their reproductive skills are impressive
and that's why it seems like there is a continuum of an growing
population. Although there is commercial insecticides available at your
local Garden center that will control fungus gnats in the soil of your
houseplants, one of the best methods of control is simply by letting the
top layer of the soil of your houseplants dry. You may even want to
consider scratching the surface of the soil to help it dry out faster
and more evenly. Fungus gnats can only reproduce within a moist soil
environment and so eliminating the breeding ground is essential to