Biodegradation of selected insecticides by Bacillus and Pseudomonas sps in ground nut fields

Bacterial cultures isolated by selective enrichment technique were identified as species of Bacillus and Pseudomonas. These isolates were tested for their ability to degrade the respective insecticides in mineral salts medium. Within 7 days of incubation, nearly 75% of chlorpyrifos and phorate and 50% of dichlorvos, methyl parathion and methomyl were degraded by cultures of soil bacteria. Qualitative analysis of chlorpyrifos and methyl parathion residues by gas chromatography revealed the formation of one unidentified metabolite in inoculated samples. Whereas no metabolite formation was detected in case of other insecticides inoculated samples. Moreover, dichlorvos and phorate were completely degraded by soil isolates at the end of 14 days. Order of microbial degradation of selected insecticides in the present experiment is as follows: phorate > dichlorvos > methyl parathion > chlorpyrifos > methomyl.