Fungus Gnats - Houseplants Pests and how to Control them

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houseplant Pest, Fungus gnat

Fungus Gnats

Fungus gnats are a major problem in houseplants. The small, black, flying adult is harmless. The problem is that it lays eggs in the soil which hatch into tiny, black-headed maggots which are harmful. These normally feed on organic matter in the soil but they can devour young roots. The gnats are troublesome in over-damp conditions. They multiply very fast and easily spread from one plant to another. Be on the look out for these black fly-like insects and take immediate control as they can infest your entire houseplants collection.

  • To prevent infestation, cover the soil surface with a layer of sand or ornamental stones and let the soil slightly dry out between waterings.
  • Where there is infestation, repot the plant in fresh soil, avoid overwatering the plant and institute the prevention measures.
  • Use yellow sticky traps to trap the adults and keep them from laying eggs.
  • Drench the infected soil with a solution of 4 parts water to 1 part rubbing alcohol. Repeat the treatment until the problem is cleared.
  • Drench the infected soil with a solution of 1 part hydrogen peroxide to 4 parts water and repeat as necessary.
  • Sprinkle Mosquito bits over the surface of the infected soil and water them in. Repeat until the problem is cleared.
  • Lightly spray all the plant surfaces with a Pyrethrin-based insecticidal spray and spray the infected soil to thoroughly moisten the surface. Allow the top 2 in. of soil to dry out before watering.
  • Drench the infected soil with an insecticidal solution as per the manufacturer's recommendations.

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