Pest Problems Explained – SCIARID FLIES (Fungus Gnats)

Sciarid Fly Description

The young are small, 4-6mm long, white larvae (maggots) with black heads, these can be found in the top few millimetres of soil or compost.

Adult Sciarids are 3-4mm long, black, midge like flies that can be seen jumping or hovering over the soil surface.

They are likely to be found in the greenhouse or around houseplants where compost is moist and warm, and where algae may have developed on the soil surface.

Sciarid Fly Damage

Seedlings are nibbled off at the base of the stem or just below the soil level. Roots of cuttings are eaten away. Damaged plants may succumb to rot.

Sciarid Fly Life Cycle

Adult females lay their eggs in the surface layer of the soil, and although short-lived they can lay between 100 & 300 eggs during a week.

The eggs hatch into maggots, which will eat rotting algae, compost, seedlings and cuttings.

Sciarid Fly Larva

The whole life cycle takes about 4 weeks at 20ºC (68ºF).

Scairids can be present in the greenhouse or conservatory at any time of the year.

Biological Control of Sciarid Flies

Sciarid flies can be controlled biologically inside by using their natural enemy, the predatory mite Hypoaspis miles.