Name: Shore fly – Scatella australiae
Indirectly damages plants by spreading Pythium and other soft rot organisms. Adult flies leave faecal material on leaf and flower surfaces, causing downgrading of ornamental plants, particularly seedlings.
Egg: Very small, ovoid, white. Laid on algae growing on potting mix, pots, benches and floors.
Immatures: Opaque, yellowish-brown maggots, found close to the surface of potting media. No distinct head. Feed on algae.
Adult: Small, black fly with reddish eyes, short legs and antennae. Wings dusky, each with five pale spots. Makes short flights (doesn’t hover).