Aspects of the enhanced biodegradation and metabolism of ethoprophos in soil

Enhanced biodegradation of ethoprophos was evident in a soil from a previou sly treated field in Northern Greece. However, enhanced biodegradation was specific to ethoprophos and there was no cross-enhancement leading to rapid degradation for any of the other organophosphorus (cadusafos, fenamiphos, fonofos, isazofos) or carbamate (aldicarb, oxamyl) nematicides registered i n Greece for the control of potato cyst nematodes. Studies with radio-label led ethoprophos showed that the adapted microflora in the soil from the pre viously treated field was able to degrade [propyl-1-C-14]ethoprophos rapidl y and mineralized about 60% of the initially applied nematicide. When [ethy l,1-C-14] ethoprophos was applied, the reduction in extractable radioactivi ty in the previously treated soil was coupled with evolution of lower amoun ts of [C-14] carbon dioxide and was similar to the amounts produced from th e previously untreated soils. It is suggested that degradation of ethoproph os in the soil from the previously treated field proceeds via hydrolysis of the P-S bond in the -S-propyl moiety of the ethoprophos molecule, which is then further mineralized by the adapted micro-organisms. Enhanced biodegra dation of ethoprophos in this specific previously treated soil in Northern Greece and under the local environmental conditions was still evident two y ears after the last ethoprophos field application. It appears that, once es tablished, enhanced biodegradation of ethoprophos can be quite stable. A po ssible solution to this problem might be the introduction of a rotation sch eme where other nematicides like fenamiphos, cadusafos, aldicarb or oxamyl are used as alternatives with ethoprophos application restricted to only on ce every three or four years. (C) 2000 Society of Chemical Industry.