Bendiocarb and diflubenzuron as substitute insecticides for endosulfan in commercial mushroom growing

Summary Diflubenzuron and bendiocarb treatments of compost and casing soil at a rate of 1 g a.i./m2 each, resulted in comparable or even improved compost and casing soil colonisation over endosulfan treatments (at a rate of 1.5 g a.i./m2). Alternating diflubenzuron/bendiocarb treatments were preferable to the reverse treatments, which tended to diminish total yield of mushrooms significantly by 1.4–3.9 kg/m2. This effect was due to the casing soil treatment with diflubenzuron and not due to the compost treatment with bendiocarb after spawning. The effectiveness of these substitutes for endosulfan was tested on five commercial mushroom farms, where a similar or improved control of Megaselia halterata (Diptera: Phoridae) was obtained over control (endosulfan) treatments. If present, Lycoriella auripila (Diptera: Lycoriidae) was very effectively controlled by the substitute insecticides compared with endosulfan. Relatively high numbers of M. halterata were occasionally observed in endosulfan‐treated houses, indicating that a certain level of resistance towards this insecticide may already have developed. This assessment of tolerance in M. halterata emphasised the need for substitute insecticides with different modes of action, in addition to environmental reasons. The chemicals should be alternately applied within individual crops to avoid resistance development.