Cecids

The three most common species of cecids which infect the mushroom crop are Heteropeze pygmaea, Mycophila speveri and Mycophilia barnesi.

The adults are minute flies which are rarely seen, and it is usually the larvae which are about 1 mm long that are first noticed through the plastic bag. The commonest species is Heteropeza pygmaea which has white larvae whereas the Mycophila species have orange larvae.

Each larva becomes a 'mother larva' which can give birth to 12-20 daughter larvae within a week of its own birth, without any adult midge being present. This ability to multiply so rapidly results in enormous numbers of larvae in the compost and when the food supply becomes limiting within the compost the larvae swarm and go onto the mushrooms, especially after the crop has been watered. Large numbers of larvae especially of the orange type make the mushrooms unsaleable. The larvae also carry a bacterium which causes increasing losses due to the degradation of mushrooms.

Cecids and their larvae are only killed when temperatures throughout the compost reach 55°C for 5 hours or 60°C for 3 hours.

If all larvae are killed during pasteurisation, infestations at cropping usually indicate that pests have entered the bags after filling. If there is a cecid problem on the farm it is vital to isolate infested houses by disinfecting tools, knives, buckets etc. Clean overalls should be worn in each house. Filters should be replaced at the end of each crop and doors should be tight fitting and not left open as an increased aid for ventilation. As per usual the area where casing is to be unloaded should be disinfected. Any bags that are visibly infected with cecids during cropping should be sprayed with a disinfectant, sealed and dumped at a distant location, the same applies for crop debris.

Before the bags are emptied they should be sprayed with disinfectant, after emptying the interior of the house should be washed out.