Plant and Soil 84,445-449 (1985). Ms. 5994 9 1985 Martinus Ni/hoff/Dr W. Junk Publishers, Dordrecht. Printed in the Netherlands. Enhanced degradation of carbofuran by Pseudomonas cepacia and Nocardia sp. in the presence of growth factors K. VENKATESWARLU* and N. SETHUNATHAN Laboratory o f Soil Microbiology, Central Rice Research Institute, Cuttack-753 006, Orissa, India Received 11 July 1984. Revised October 1984 Key words Carbofuran Degradation Nocardia sp. Pseudomonas cepaeia Soil extract Yeast extract Summary Pseudomonas cepacia and a Nocardia sp., isolated from flooded alluvial soil amen- ded with carbofuran, metabolized ring- ~4C-carbofuran fairly rapidly in mineral salts medium or soil extract, stlpplemented with yeast extract. When the two isolates were incubated with soil extract together with 500vg ml -~ yeast extract, about 40 to 62% of the radioactivity was recovered as water-soluble products. The degradation of carhofuran by Nocardia sp. led to the formation of coloured, water-soluble and non-extractable metabolites. Introduction Recent build-up of brown planthopper (Nilaparvata lugens Stal.), a major pest of rice neces- sitated the extensive and intensive use of Fnradan 3G (3% carbofuran; 2,3-dihydro-2,2-di- methyl-7-benzofuranyl N-methylcarbamate) in rice culture. Perusal of the literature on carbo- furan reveals only indirect involvement of microorganisms in its metabolism in soils2'3'*'* . Apart from our earlier study on the bacterial degradation of earbofuran, after an initial tag of about 20 days, in mineral salts medium s , virtually no information is available on the meta- bolic fate of this insecticide by pure cultures of microorganisms. This report describes the increased metabolism of ring- t4C-carbofuran in the presence of soil extract and yeast extract by Pseudomonas eepaeia and Nocardia sp., isolated from flooded alluvial soil. Materials and methods Chemicals Uniformly ring-labelled 14C-carbofuran (specific activity, 2.20mCi/mmol; 98% pure), technical grade earbofuran, earbofuran phenol (2,3-dihydro-2,2-dimethyl-7-hydroxybenzo- furan) and 3-hydroxyearbofuran (2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran) and 3-hydroxycarbofuran (2,3 - dihydro- 2,2- dimethyl- 3 -hydroxy- 7-benzofuranyl methylcar- bamate) were gifted by FMC Corporation, Middleport, NY. Stock solution was prepared by dissolving the labelled carbofuran in 100ml acetone. The solvent from aliquots of this stock solution was evaporated completely at room temperature and the residues were then equili- brated with distilled water for 8 h before being sterilized by membrane filtration. Incubation studies An enrichment culture was prepared in test tubes (25 • 200 mm) by adding 1 mg of the technical grade carbpfuran to 20 g alluvial soil samples under flooded conditions (25 ml distilled water) at 15-day intervals. After four additions of the insecticide, a bacterium capable of * Department of Botany, Nagarjuna University, Nagarjuna Nagar-522 510, India. 445