Fungus gnat

Bradysia spp. and Lycoriella spp.

1. Identification

• Common name: Fungus gnat
• Scientific name: Bradysia spp. and Lycoriella spp.
• Order: Diptera
• Family: Sciaridae

2. Pest description

• Small adults (2–4 mm), dark body and transparent wings.
• Slow movement and weak flight, often observed close to the soil or substrate.
• Whitish larvae, with a black head, develop in moist organic matter.
• They feed on fungi, young roots and decomposing tissues.
• Pupation in the soil or substrate, in shallow chambers.

3. Main hosts

• Greenhouse crops: vegetables, ornamentals and nurseries.
• Plants in pots and substrates rich in organic matter.
• Saprophytic fungi present in moist soils.
• A frequent problem in protected environments with high humidity.

4. Symptoms and damage

• Wilting and stunted growth of seedlings.
• Damage to young roots caused by the larvae.
• Greater susceptibility to root diseases (e.g.: Pythium, Fusarium).
• Significant losses in nurseries and the production of young plants.
• Adults may act as mechanical vectors of pathogens.

5. Biological cycle

• Rapid cycle under conditions of high humidity and mild temperatures.
• Eggs laid in the moist substrate.
• Larvae develop over 1–2 weeks.
• Pupation in the soil, followed by the emergence of the adults.
• Multiple annual generations, continuous in greenhouses.

6. Monitoring

• Yellow or blue chromotropic traps for detection of adults.
• Observation of the substrate to identify larvae and pupae.
• Assessment of soil humidity and the presence of saprophytic fungi.
• Frequent monitoring in nurseries and greenhouses.
• Recording of environmental conditions favourable to development.

7. Management measures

• Cultural: reduction of excessive humidity, improved drainage, removal of decomposing organic matter and avoiding excessive watering.
• Biological: use of Steinernema feltiae, Bacillus thuringiensis israelensis (Bti) and predatory mites such as Stratiolaelaps scimitus.
• Integrated protection: continuous monitoring, sticky traps, careful management of watering, application of authorised biological agents and integration of cultural practices to reduce population pressure.

Bibliographic references

• EPPO Global Database – Bradysia spp. and Lycoriella spp..
• CABI Invasive Species Compendium – Sciaridae in protected environments.
• Harris, M. A. et al. (1996). Biology and control of fungus gnats.
• Cloyd, R. A. et al. (2004). Management of Sciaridae in greenhouse crops.