Coop Scoop Blog
PERSISTENTLY PROBLEMATIC PESTS: FUNGUS GNATS
by Ben Goldberg
At our house we have battled fungus gnats, probably acquired when we brought plants back into the house for winter or on plants purchased from a greenhouse. Although these gnats serve as food for birds and bats, and although they don’t bite people or pets or directly damage plants, eventually their larva can damage plants. The pests can also be pretty difficult to get rid of, but most of us try to avoid using toxic chemicals that might harm...well, everything!
The following is a summary of what our family has learned so far about safely battling these critters. And remember: persistence pays!
Got gnats? You’ll know them when you see them—flying around, landing in your drink, on your food, on your Kindle, etc. But what kind of gnat is sharing your food, drink, and novel? It can be helpful to know your enemy. The most common varieties are the gnat-like fruit fly, the drain gnat, and the fungus gnat. (For more identifying info, Google “what type of gnats do I have?”)
Assuming you have fungus gnats, they will most likely be found living happily, if pestily, in your houseplants, where they consume organic matter. You may see them rise up like an ominous cloud when you pet your plants. (You do pet your plants, don’t you???) Here are a few nontoxic actions to try, alone or in some benevolent combo.
- Since fungus gnats thrive on wet soil, let your plants dry out thoroughly between waterings, and do not overwater.
- Mix a few drops of liquid soap (Dr. Bronner’s, anyone? Always available in many flavors at the Co-op) in a cup of water. Spray the mixture on the top of your plant’s soil every few days.
- Remove the top ¼ to ½ inch of soil from your plants and replace it with horticultural sand or gravel to discourage gnats from laying eggs in it.
- Place a cut potato on the soil with the cut side down to entice some of the larvae from the soil. Replace every few days.
- Buy or make apple cider vinegar traps. (Can also be used for fruit flies.) Replace regularly.
- Deploy sticky pest traps. These will provide the added benefit of gluing your sleeve to the trap when you open and close your window curtains. What fun!
- Mix 3% household (NOT industrial strength) hydrogen peroxide and water in a 1 (peroxide) to 4 (water) ratio. Spray onto dry soil, wetting the soil a few inches deep; or simply water with the solution. (Ignore the fizz and foam. It’s harmless fun.)
- Try neem oil, a safe and effective herbicide, diluted to the manufacturer’s directions.
- Apply food-grade diatomaceous earth. Let the soil dry out and—while wearing a mask—sprinkle the DE thinly onto the soil, and rake it gently in.
- Apply beneficial nematodes, a benign biological control agent, according to directions.
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All that TMI said, if you have any level of gnat infestation, you might want to consider starting with some of the simpler approaches and escalating (albeit not to chemicals, please) to one of the more “sophisticated attacks” if necessary. Then enjoy—sans gnats—your food, drink, and latest Kindle-ized mystery novel.
Ben Goldberg lives and celebrates in Albany.