BIOLOGICAL CHARACTERIZATION OF UPTAKE, TRANSLOCATION, AND DISSIPATION OF DIFENOCONAZOLE (CGA-169374) IN WHEAT, PEANUT, AND TOMATO PLANTS

Uptake and translocation of the triazole fungicide difenoconazole (CGA 169374) were evaluated on peanut, wheat, and tomato plants with Alternaria solani, Cercospora arachidicola, and Erysiphe graminis f. sp. tritici as test organisms. Persistence and penetration studies were carried out on peanut and tomato plants with Cladosporium cucumerinum as indicator fungus for the bioautographic in vitro assay. Sufficient quantities of difenoconazole penetrated into plants sprayed with 50-mu-g a.i./ml to give excellent disease control. Translaminar movement after leaf band application as well as acropetal translocation out of the treated zone towards the leaf tip were demonstrated. Uptake by the root system and upward translocation to foliage, however, was low. After leaf-dipping and stem-painting treatments, the symplastic and apoplastic transport of difenoconazole was also insignificant when judged by disease development on upper leaves. Persistence of difenoconazole on the surface of leaves seems to be plant-dependent. At the last sampling, 21 days after treatment, 50% of the applied activity was found on peanut leaves, whereas on tomato leaves only 10% was observed. Rate of penetration was similar for both plant systems.