IN-SITU ASSESSMENT OF PESTICIDE GENOTOXICITY IN AN INTEGRATED PEST-MANAGEMENT PROGRAM I - TRADESCANTIA-MICRONUCLEUS ASSAY

The genotoxicity induced by pesticides applied in an integrated pest m anagement (IPM) program was evaluated with the Tradescantia micronucle us assay (Trad-MCN). Three pesticide application rates were prescribed as follows: (a) Low, no field pesticide spray; (b) Medium, IPM test r ate: banded cyanazine plus metolachlor (2.7 kg a.i. and 2.3 I a.i./ha of herbicides, respectively); and (c) High, a preventative pesticide a pplication program: broadcast cyanazine plus metolachlor (same applica tion rates as above) plus chlorpyrifos (1 kg a.i./ha of insecticide). The Trad-MCN was employed for the assessment of (a) the formulated com pounds, singly and in combinations; (b) pesticide residues extracted f rom soils sampled before and after application, and (c) in situ exposu res (14-h exposure to pesticide-sprayed field), All pesticides showed clastogenic potency at doses between 10 and 50 ppm. Aqueous extracts o f the two pesticide-sprayed soils were clastogenic, but the unsprayed soil extracts were not. Plants exposed in situ to pesticide-sprayed so ils (inside a chamber receiving vapors from the soil) also showed sign ificant increases in micronuclei frequency in relation to controls exp osed to unsprayed soil, In general, there was no significant reduction in the genotoxic effects from the High to the Medium treatment levels of the IPM pro ram. This suggests that the reduction in pesticide app lication rates attained with the implementation of the proposed IPM pr ogram was not sufficient to abate the genotoxicity of the pesticides, as perceived with the sensitive assays employed. The results indicate that replacing genotoxic compounds may be the only effective remediati on measure to eliminate the risks imposed by mutagenic compounds in th e agricultural environment. (C) 1998 Elsevier Science B.V.