Shore flies (Scatella stagnalis) are small insects that frequently occur in greenhouses all around the world and can be present all year round. Shore flies do not directly damage plants but they decrease plant marketability.
Shore fly larvae feed on rotting plant material, algae and other microscopic unicellular organisms and do not directly attack living plants like fungus gnats do. The adults leave their excrement on plants, which lowers the plant’s aesthetic value. The high reproduction rate of shore flies can result in a swarm of adults, which also render products unattractive to costumers. Very large number of adult shore flies can also become a major nuisance to people working in greenhouses.
Shore flies are usually found in the vicinity of water; moist to wet conditions and the presence of algae and moss in potting mix, pots, benches and floors are favourable to their development. Its life cycle includes six stages, i.e. egg, three larval stages, pupa and adult. Development from egg to adult takes between 9 and 14 days. Larvae have a yellowish or brownish colour and can reach about 0,5 mm in length at the end of the 3rd stage. The adult fly is about 0,5 cm long, has short legs, short antennae and dark wings with clear spots.