Last summer I repotted my plants with new soil I bought from a garden store which will remain nameless, and the soil brought in indoor fungus gnats, or nasty-gnats as I like to call them. How do I know it was the soil? Only 2 out of my 5 plants got infected, and they were the ones I repotted with the new soil - the gnats never infected the other pots. Once fall came and I brought my plants inside, clouds of gnats were hovering around my plants. And my face.
The worst part was how annoying those gnats were - soon they expanded their horizons and were found throughout the whole house! They aimed for moist orifices of people's faces, like nostrils, mouths, and tear ducts. On the worst day I killed about 50 in just a few hours without even trying too hard!
While developing new and exciting swatting techniques like the one-handed squish and the clap-and-rub, I also scoured the internet for how to get rid of those damn things.
For months I tried every suggestion I could find out there, from watering my plants with soapy water to setting vinegar traps everywhere and letting the soil dry out between waterings, and nothing worked. I didn't want to spray my plants with DEET, and I sure as hell wasn't going to repot them again, so the next thing I was going to try was an expensive organic insecticidal bacterial solution.
Thankfully, I didn't waste my money. The reason why letting the soil dry out should work is because gnats breed on moist soil, and the reason it wasn't working for me was because the problem was so severe that there were always enough survivors to repopulate my house after waterings. Not only that, by doing that I was also selecting for a new breed of drought-resistant supergnats! So I tried a new approach -- what if the top of the soil was always dry? Then the gnats could never breed. But how to do that without killing my plants? Here's the solution:
It's so simple. I started watering the plants without getting the top of the soil wet by carefully watering them around the edges of the pot. And if that didn't work, I'd carefully dig a moat-like trench with my finger along the sides of the pot and filled it with water. Ta-dah! Dry soil on top!
Two months on and I'm still watering my plants this way, but the fact is that I haven't seen one gnat in weeks! And this was a lot less work than having to search all over the city for a gardening store with a solution, not to mention a hell of a lot cheaper and healthier. Amazing.
DEATH TO GNATS!!!