Insect pests of mushrooms: Phoridae

Phorids

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 12°C.  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.

Phorid life cycle

• After mating, adult females are attracted to developing mushroom mycelia in spawned compost.
• The compost remains attractive to adult females throughout the entire spawn-run period, and is particularly susceptible during the second week.
• Mycelial development, which occurs following casing, renews attraction to adult females.
• Each female can lay up to 50 eggs in close proximity to developing mycelia.
• Duration of the life cycle is temperature dependent and will vary in relation to the environmental conditions associated with cropping periods.
• Increased air temperatures associated with spawn-run and case-run periods facilitate life cycle completion in 24-26 days.
• The lower temperatures following breaking and during cropping periods may extend the life cycle to 40-50 days.