Fungus gnats lay their eggs in the soil of potted plants.People who have a lot of houseplants sometimes are plagued by annoying little black flies that seem to hover near water sources. These are fungus gnats (
Sciara
), which lay their eggs in the soil of potted plants. The adults don't live in the soil, but they don't go far. Once eggs hatch, larvae feed on decaying organic matter in the soil for about 10 to 14 days, then pupate and become adults. All the while, other adults lay eggs (100 to 300 per female), so the cycle goes on.
Adult gnats, which live about two weeks, like a humid environment, such as the kitchen and bathroom. Larvae, too, like moisture and thrive in houseplants that are kept constantly moist.
Allowing the soil to dry out for several days will kill larvae and help stop the cycle because adults won't lay eggs on dry soil. It's also a good practice to let the soil dry out between waterings.
To help control adults, place sticky traps near plants. There is a biological control called
with the active ingredient
Bacillus thuringiensis israelensis
.
Bti
is a bacterium that attacks the gnat larvae. Use it as a spray or soil drench. Although fungus gnats are a nuisance, they rarely damage plants.
-- Homes & Gardens staff
If you want to automatically receive a free daily homes and gardens tip, sign up at OregonLive.com's newsletters subscription site.