PEsts: find out more SCIARID FLY

Sciarid fly

The Pest

Glasshouse sciarids or fungus gnats (Bradysia spp) can be a serious pest of some glasshouse crops.

Serious economic damage can be caused on some crops especially during seedling propagation and on fresh cuttings because the sciarid larvae attack the young roots. Large numbers can cause problems to more established plants and the presence of adults on produce during marketing is undesirable.  Adults may also carry fungal spores and transmit diseases such as Pythium and Phytophthora.

Situations vulnerable to sciarid attacks include, nursery stock propagation, seedlings in modules, some pot plants e.g. cyclamen and poinsettias, bedding plants, micropropagated material during weaning, and  herbs and ferns.

Sciarid fly adults on yellow sticky trap

Sciarid fly larva

Sciarid flies go through an egg stage, four larval stages, a pupal and an adult stage. At 24°C the life cycle takes 3-4 weeks. In cooler conditions it can take 8 weeks or more.

The adults are small (3-5mm) dark flies with long antennae and can be found moving around near the surface of the compost. The larvae are translucent white in colour with a distinctive black head. Larvae reach about 5mm in length and feed on decaying plant material and fungi.

Females are attracted to the smell of rotting vegetable matter and lay their eggs in the surface layer of the soil (100-300 eggs).  The larvae eat rotting algae, compost and occasionally seedlings and cuttings.

Sciarid fly
Adult