Question
I have some little black flies in my apartment and today noticed there were more of them gathering around my ficus plant...the soil in the pot. Without using chemicals, can you tell me how to rid my home of this pestilence! Thanks.
Nina
San Francisco
Answer
Those little buzzing pests are fungus gnats. They become a problem when houseplants (or greenhouse plants) are over-watered or when the soil stays constantly moist. Overly moist soil is more relevant to the gnats indoors because the temperatures stay warm. The adult gnats lay eggs in the soil. The larvae hatch and begin to feed on the decaying organic matter of the soil (and can sometimes harm roots if their numbers are great). They pupate and then emerge as the annoying gnats to start the cycle again.
The cycle can be broken if the soil is kept drier, allowing more time between watering. Repotting a plant into fresh soil will also help. There is also a product called Gnat Exterminator. They are beneficial nematodes (microscopic soil dwelling "worms") that prey on the gnat larvae. They are applied as a spray to the infected foliage. Sloat also carries a miniature sticky trap, called Gnat Sticks that can be placed in the pot to trap the adult gnats.
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