Adult phorids are slightly smaller (2-3 mm) but more robust flies than sciarids.
They are darker in colour with a hump-backed appearance with no obvious differences between male and
female flies.
Adult flies tend to remain on the compost surface or in close
proximity to the cropping area. They are very active in the presence of light and have a characteristic
rapid, jerky movement.
The flight of adult phorids is limited by temperature
and they are unable to fly when air temperature is below 12oC. Therefore, wild populations do not normally
invade mushroom production houses between November and March and adults are most abundant in September
- October.
Each female can lay up to 50 eggs in close proximity to developing mycelia. Phorid
larvae are off-white, legless maggots without a distinct head capsule (cf sciarid larvae). The anterior
region narrows to a point while the posterior is blunt with small protuberances.
An
economic threshold for phorids has not been determined but it is estimated that 50-60 larvae/125g of
compost would cause 0.5% total yield loss.
The duration of phorid
development is temperature dependent and may vary between 15 days (24-27oC) to
50 days (16-21oC). Larval development accounts for approximately 1/3 of the development time and the
remainder is spent in pupation. (
Phoridae Life-Cycle)
