Uptake, translocation and degradation of [¹⁴C]cymoxanil in tomato plants

[¹⁴C]Cymoxanil was applied to either the root system or to the foliage of tomato plants and its uptake, translocation and degradation was followed using autoradiography, combustion and thin-layer chromatographic analyses of water or methanolic extracts. Cymoxanil was taken up by the root system within 1 h and translocated to cotyledons, stem and leaves within 16 h. The compound was degraded, mostly to glycine, within 16-44 h, in the root and all parts of the shoot. When applied to the surface of leaf 2 of five-leaf plants, enhanced uptake, translocation and degradation (mainly to glycine) of [¹⁴C]cymoxanil was observed in plants treated with a mixture of oxadixyl and [¹⁴C]cymoxanil, compared with plants treated with [¹⁴C]cymoxanil alone. Root application data confirm that cymoxanil is a systemic compound with a short persistance in tomato plants. Foliage application data suggest that the well-documented synergistic interaction between cymoxanil, oxadixyl and mancozeb in controlling plant diseases caused by Peronosporales does not result from a delayed degradation of cymoxanil in the presence of the other fungicides; the mechanism of synergism has not yet been elucidated.