Flies in mushroom houses act as carriers of various mushroom diseases. In addition, fly larvae break down the compost of the mushroom producing beds, in which the flies breed, and feed on the mushroom mycelia. In southern California, where mushrooms are grown throughout the year, the problem of fly reinfestation from the outside is always present. Phorid and sciarid flies are the most numerous, attracted by the odor of the beds immediately after spawning. Infestations are heaviest after wet weather or following irrigation of adjacent areas. Control is necessary both for protection of the mushrooms and from the standpoint of sanitation. Flies must be kept out of the producing houses and nearby dwellings. One large mushroom farm has developed a successful fly-control program.

The above progress report is based on Research Project No. 1338A.