Uptake and metabolism of a systemic fungicide (triadimenol) by pre-veraison grapes

Triadimenol (1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4,-triazol-1-yl)butan-2-ol, formulated as Bayfidan® 250 EC), is one of the most frequently used systemic fungicides in viticulture. However, little is known about the behaviour of this compound once applied to Vitis vinifera sp. and hence strategies to use this fungicide are hard to optimise in an informed manner. Accordingly, uptake and metabolism of triadimenol applied to berries of Vitis vinifera cultivars Chardonnay, Cabernet Sauvignon and Riesling was investigated. Triadimenol rapidly became resistant to removal by washing with aqueous solutions in all cultivars studied, indicating that this fungicide is unlikely to succumb to rain wash erosion after spraying. Metabolism of triadimenol by grapevines was also investigated using 14C-triadimenol by thin layer chromatography/autoradiography. Direct conversion of a minor proportion of triadimenol into polar conjugates, and into conjugates of its oxidation product, was evident. Although similar patterns of triadimenol metabolism were observed with all three cultivars, the proportion of triadimenol metabolised differed, possibly due to minor differences in berry maturity. Metabolism of triadimenol in grapes does not involve breakdown of the fungicide into simpler and smaller compounds, but rather, does result in formation of bigger, conjugates with the original fungicide structure largely conserved