If they lay eggs only once, this fact could help in eradicating them. If one has an extra pot of soil without a plant in it and waters this one day before watering the plants, then this pot may be targeted first for laying eggs. The next day the potted plants can be watered with less chance of having eggs laid in them. The plantless pot of soil could be thrown out every week along with the fresh eggs thereby avoiding a generation of gnats.

This requires that you water your plants infrequently so that the soil in the planted pots are not attractive to the gnats.

Would this work?

  • 1
    Welcome to the site. Interesting concept you have here...
    – GardenerJ
    Jan 25, 2016 at 14:33

1 Answer 1


Fungus gnats have a busy but short life. As this site indicates

An adult fungus gnat lays up to 200 eggs during the one week it spends as an adult winged gnat. The adult then dies. Legless larvae hatch out in about four days. After two weeks of feeding, larvae spend about three to four days as pupae before emerging as the next generation of adults

Using another area as a trap or decoy can work with some pests. If you have a plant with fungus gnats then they will not move to a trap area as they are weak fliers. Also the effort to set the soil trap does not seem practical for larger interiorscapes or greenhouses.

For fungus gnats control measures focus on the larvae as

most of the fungus gnat’s life is spent as a larva and pupa in organic matter or soil, so the most effective control methods target these immature stages rather than attempting to directly control the mobile, short-lived adult

  • Ensuring the soil medium is not always wet
  • yellow sticky traps
  • soil drenches with soap and water or other pesticide
  • a chunk raw potato can be placed on the soil and removed. Evidently it is attractive to the larvae
  • 1
    Diatomaceous Earth, in conjunction with keeping the soil dry can also do some damage to larvae / pupae.
    – renesis
    Jan 25, 2016 at 18:12

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