Little black flies buzzing around your pots and taking off when you water: these are sciarids, known as fungus gnats. The adults are mostly a nuisance; it’s their larvae — tiny white worms with black heads — that live in damp soil and feed on organic matter and sometimes young roots. The good news: they almost always point to overwatering, which is easy to correct.
Why they appear
- Soil that stays permanently damp on the surface.
- A potting soil very rich in organic matter, or a bag of potting soil that’s already contaminated.
- A planter or saucer where water sits.
Getting rid of them
- Let the surface dry to a depth of two to three centimetres between waterings: the larvae can’t survive in dry soil. This is the most effective measure.
- Water through the saucer: the soil drinks from below and the surface stays dry. Our planters with reservoir saucers are made for this.
- Cover the surface with a one- or two-centimetre mineral layer, such as pozzolana: the adults can no longer lay eggs in it.
- Trap the adults with yellow sticky traps pushed into the pots.
- If the infestation is heavy, repot in fresh, airy potting mix, such as our Signature Potting Mix, after removing the old soil.
Frequently asked questions
Are fungus gnats harmful to the plant?
For a healthy adult plant, rarely. For seedlings, cuttings and plants already weakened by overwatering, the larvae can damage the roots.
Are they fruit flies?
No: fruit flies, which are paler, hover around the kitchen and ripe fruit. Fungus gnats, black and slender, stay close to the pots.
Need an opinion?
Send a photo of your plant to our Plant Doctor: the whole plant, a close-up of a leaf (top and underside) and the surface of the soil. The diagnosis is free, and you can also drop by the studio at 6 Rue Zemmour, Aviation district, Rabat, Tuesday to Saturday, 10am to 6pm.
