How to safely kill houseplant fungus gnats?

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For the second year, I finally confirmed that a particular brand of houseplant potting soil does indeed contain or breed fungus gnats. I am looking for a natural solution to permanently solve this problem

  4 answers
  • Joy30150932 Joy30150932 on Oct 06, 2018

    There is a fungus gnat powder you can purchase. Fungus gnats come up put of the soil when you water. Just sprinkle some powder on the surface of the soil after watering and they will die. Any other remedy may kill off the plant too.

    • Dow33154311 Dow33154311 on Oct 06, 2018

      Thank you for your prompt response. I am planning to try all of the recommendations that I receive on this forum. I'm guessing I might be able to find this powder you suggested at a farm supply store. We don't have nurseries nearby

  • Wma7908878 Wma7908878 on Oct 06, 2018

    Have not tried it but a lady gave this remedy which works for her. Sprinkle cinnamon over the dirt in the pot.

    • Dow33154311 Dow33154311 on Oct 06, 2018

      Thank you for your prompt response, Wma7908878. I am going to try this. We sprinkle cinnamon on our coffee grounds prior to brewing and several foods for its health benefits. Will be interesting to see if it has the opposite effect on insects

  • Fiddledd224 Fiddledd224 on Oct 06, 2018

    Fungus gnats thrive on moist soil. Let the soil on all of your house plants dry completely before rewatering. Also, make sure that all damp areas of your house (including the bottoms of sinks and tubs) are dried. Once the moisture is gone, the gnats will leave for another damp spot.

    • Dow33154311 Dow33154311 on Oct 06, 2018

      Thank you for your prompt response, Fiddledd224. Tried your suggestion...unintentionally, on two separate occasions while we were out-of-town for over a week each time this past the summer. Plants were very thirsty to the point of wilting leaves. Seems like it didn't kill the gnats, since the eggs are buried in the soil. Soon after watering the plants, the bugs emerged. I also read online that this particular brand of potting soil (new bags) has been known to harbor the fungus gnats...ongoing with each new year's supply. I thought I was being ridiculous in suspecting the soil was contaminated last year when I first encountered the problem. I wasn't

      I have used Windex for over a decade to kill all indoor pests, as well as hornets and wasps and have even sprayed it on the leaves and soil prior to watering. It successfully and safely eliminates topical and flying insects, but does not touch the larvae/eggs in the soil

  • Fiddledd224 Fiddledd224 on Oct 06, 2018

    That's great that something works. As for contaminated soil, you can microwave it to kill whatever's in there that shouldn't be. (Make sure you clean the microwave afterward in case some of the soil gets into it - you don't want those bugs in your food!)

    • Em Em on Oct 06, 2018

      That would require unpotting, completely washing ALL dirt off of the roots, microwaving, then repotting. The gnat larvae are already in the soil. And how would they get in your food if they are dead???

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