Evaluation of the efficacy of Bacillus thuringiensis in the biological control of Dipteran pests of mushroom in the laboratory and the farm

As the mushroom dipterans flies are permanent pests of mushroom farms, the growers frequently use the chemical pesticides. Since the mushroom growers and the consumers are always at the risk of chemical pesticides contamination, introducing non-chemical and biological methods is therefore necessary. This research was conducted with two experiments in the mushroom farm conditions. In the first experiment, a commercial formulation (Bioflash®) based on Bacillus thuringiensis subsp. israelensis was tested along with a number of common insecticides on composts. First experiment was carried out in a completely randomized design with seven treatments including Dimilin® 0.75 & 1 g/l, Bioflash® 1 & 2 ml/l, Tracer® 0.3 & 0.6 g/l and the control (the usual method of controlling flies with oreganophosphate insecticides) each with 10 replications. Based on the results of the first assay, an experiment was conducted in the mushroom farm conditions in three stages including Bioflash® incorporated into compost simultaneously with spawn inoculation, Bioflash® spray in precasing and Bioflash® drench into casing in comparison with the control. The results of the first experiment showed that all test insecticides were effective in decreasing the pest population, so that the average efficiencies of Dimilin® (1g/l), Tracer® (0.6 g/l) and Bioflash (2 ml/l) on 15 days after treatment were 67.9%, 74.2% and 79.9%, respectively with no significant difference among them. Farm experiment results showed that the application of Bioflash® drench into casing at six days after casing had the highest efficiency with 79.3% reduction in the population.