Sciarids

These are very common locally and are active throughout the year. They are small black flies about 2 mm long and run rapidly over the surface of the compost of casing with their long thin antennae held upright. The adults are attracted to newly peak heated compost at the cooling stage and each female lays about 150 eggs in the compost. The eggs hatch within 3 or 4 days and the larvae have a shiny black head. These larvae can feed for 3 to 4 weeks. They can travel into the stalk of mushrooms or feed in the casing and damage the mycelium and cause button mushrooms to turn brown and die. Adults maturing in the cropping house lay their eggs in the casing, if heavy larval populations emerge they can prevent the development of young pinheads. As well as direct damage to the crop the flies can also spread mites and disease, especially Verticillium as the spores of this disease are sticky they easily adhere to the bodies of the flies.

1. Efficient composting and peak heating.

2. Exclusion of adults by filters and tight fitting doors. It is important that doors are not left open as an aid for ventilation.

3. Disposal of crops debris at a distant location from the farm.