Sciarid flies (Sciaridae) are a difficult pest, especially in young plant material. They can cause damage to seedlings, rootstock and cuttings of many plant species. In the cultivation of mushrooms they can be very annoying as well and cause both direct and indirect damage. Sciarid flies are often found in moist, organic environments.
Sciarid flies go through seven stages, namely egg, four larval stages, pupa and adult fly. Adults are noticed when they appear in large numbers. Eggs are deposited in the soil. Larvae generally eat rotting plant material, algae and fungi that are present in or on the soil. Pupation takes place in the soil as well.
Direct damage can occur to young and/or weak plants in a moist, organic environment, when larvae chew the plants' roots. This reduces the uptake of water and nutrients, causing the plants to die. Strong plants are only affected at very high levels of infestation.
Indirect damage is caused when larvae transmit mites, nematodes, viruses and fungal spores. Adult sciarid flies can also transmit various fungal spores. The spots where larvae have chewed the plant are also potential spots where fungi can take hold. The damage can be lethal to the plant.