حسین مددی

Bacillus thuringiensis Berliner is a gram positive and endospore- forming soil bacterium that has the production ability of different kinds of endogenous crystal proteins, during its sporulation. B. thuringiensis (commonly known as 'B.t.') is an insecticidal bacterium and it is used worldwide for control of many important plant pests. Larvae of Sciaridae flies (Diptera: Sciaridae) especially the genera Bradysia spp. and Lycoriella spp. are among the major pests of mushroom Agaricus bisporus (Lange) Imbach. That cause direct damage to basidiocarps, via tunneling galleries and turning them unsuitable for commercialization. They may reduce yield in mushroom production up to 75%. In this research, native isolate of B.t . were isolated from different field soil. Insecticidal effect of these isolates was evaluated against 2 nd instar larvae Bradysia ocellaris at 23±1°C, 60 ± 5% R.H. and photoperiod of 0: 24 (L: D) h under laboratory controlled conditions. Mortality and feeding of B. ocellaris larvae was monitored and evaluated up to 3 weeks. The results indicated significant difference (81.72%) between mortality of flies’ larvae compare to control reaching to its maximum (40%) on 5 th days after inoculation. Referring to feeding inhibitory effects of B.t. and reducing developmen tal rate of B. ocellaris that shows sublethal effect of B.t. it seems B.t. has efficient potential as a biological control agent against the Sciarid flies, in mushroom production