Fungus gnats

(Question)

Every year when I bring in my tropical plants from the outdoors I get these little flies which I think are fungus gnats.  How can I get rid of them and stop them from invading my home?

(Answer)

Fungus gnats commonly develop in the soil of potted plants when the plant is overwatered.  Once you have these pesky little bugs it takes patience to be rid of them.  The small black adult insects that fly around the plant are a nuisance but are  harmless.  However, the larvae can damage the plant by attacking stems and roots.

Try the following:

  • Drench potting soil with insecticidal soap being careful to follow the manufacturers instructions.
  • Place yellow sticky traps that catch bugs around the plant
  •  If the numbers are very high, apply beneficial nematodes that will attack the larvae.  (Nematodes can be bought commercially at reputable garden centres)
  • Repot the plant using a sterile potting mix containing minimal organic matter

Tips:

Potting soil should be kept moist but not wet

Allow the water to drain out the bottom of the pot when watering

Provide good drainage

Do not let plant sit in water

Allow the top of the potting soil to dry out between waterings