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Besides its known systemic activity, triadimefon acts in the vapour phase.This vapour phase activity of triadimefon was shown for powdery mildew on cucumbers and barley in greenhouse experiments at concentrations recommended for use in the field (I00 and 250 pg/ml) and also at substantially lower concentrations.The degree of vapour phase activity is dependent on the distance from the spray deposit.In experiments with radiolabelled triadimefon, it was observed that gaseous material was deposited on untreated barley plants, thus either keeping them free from attack or reducing infection.

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With three plant pathogens, Botrytis cinerea, Venturia inaequalis and Puecinia graminis f. sp. tritici, the time course of sterol biosynthesis during spore germination was examined by labeling experiments along with the question whether this pathway could be inhibited by triazole fungicides. Conidia of B. cinerea and V. inaequalis are able to synthesize sterols immediately after the beginning of the germination process when the germ tubes have not yet emerged. On the contrary uredospores of P. graminis start sterol biosynthesis after 6 to 8 h germination time almost at the end of the germ tube phase, indicating that sterol reserves of the spores are likely to be used for the germ tube growth.The sterol C-14 demethylation appeared to be the rate limiting step within the sterol biosynthetic pathway: the half life of 24-methylenedihydrolanosterol was less than 1 h for B. cinerea. It was more than 1 h for V. inaequalis and 3 h for P graminis. Independent of these differences in the time course of sterol biosynthesis and in the C-14 demethylation rate, the synthesis of sterols in germinating spores was strongly inhibited by triazole fungicides in all three pathogens examined. In contrast to P. graminis, this inhibition could be demonstrated with B. cinerea and V. inaequalis even in ungerminated conidia, indicating that the fungicides were rapidly taken up and reached their target within 1 or 2 h. These results are discussed along with the question whether spore germination can be used as a bioassay for the estimation of sensitivities of triazole fungicides.

The uptake of triadimenol was investigated by offering radio‐labelled chemical exclusively through the caryopsis in a special experimental design with single seed grains in plexiglass holders. In totally‐treated caryopses about 5% and, in partially‐treated caryopses (embryo untreated), 4.5% of the applied radioactivity reached the winter wheat shoots after 21 days up to the third leaf stage. Uptake of active ingredient through the pathway pericarp‐testa‐endosperm‐scutellum‐seedling up to the third leaf stage D(13) was therefore confirmed. Furthermore, [14C] triadimenol was also translocated through the caryopses into the roots and was released to the nutrient solution.