Reduction in biological efficacy of ethoprophos in a soil from Greece due to enhanced biodegradation: comparing bioassay with laboratory incubation data

Soils were collected from a potato-growing area in Serres, Northern Greece, where the nematicide ethoprophos was reported to have lost its effectivene ss against cyst nematodes following 30 years of regular use. Incubation stu dies with ethoprophos and two bioassays using root-knot nematodes demonstra ted that, in this heavily treated soil, the nematicide was degraded rapidly and nematicidal activity persisted only up to 14 days. In soil from an adj acent field with no known history of nematicide use during the preceding 14 years, ethoprophos was degraded more slowly and retained its nematicidal a ctivity for more than 35 days. Ethoprophos efficacy was extended when the s oil that had been treated in the field was autoclaved, although the effect was only transitory. The addition of 'preconditioned' soil from the previou sly treated field to samples of soil from the previously untreated field re sulted in a significant acceleration of ethoprophos degradation compared wi th that observed in unamended soil from the previously untreated field. (C) 1999 Society of Chemical Industry.