In 2018 when fall arrived, I brought my plans back indoors. With them came fungus gnats. I could not get rid of them even with an apple cider vinegar solution. I left it out for over a week and not a single catch.
In 2020 when fall arrived, I brought some strawberry clippings indoors. They had a few weeks in small pots to establish roots. But like 2018, when they came in, so did fungus gnats.
I tried H2O2 rinse of the soil; that didn't work. I tried a soapy solution along the bottom of the planters and wetting the topsoil surfaces. That also did not work. I tried a dusting of diatomaceous earth and saw no reduction in gnats.
Lastly I tried my own sugary water solution to attempt to catch the gnats and much to surprise, this works quite well. I think I will try this along with another H2O2 rinse.
The mixture consists of 4 cups of brown sugar mixed with 1 gallon of water
