D. R. Clifford

The enantiomeric composition of triadimenol produced during metabolism of triadimefon by fungi: III. Relationship with sensitivity to triadimefon

Abstract Fifteen species of fungi, grown in shake culture in a liquid nutrient medium containing a 50:50 mixture of the 1 R and 1 S enantiomers of triadimefon, reduced triadimefon to triadimenol, the extent of reduction varying from 95% according to species. Each produced its own characteristic pattern of two or more of the four possible enantiomers of triadimenol and the stereoselectivity and stereospecificity of the reduction is discussed. The sensitivity of each fungus to individual enantiomers and a mixture of enantiomers of triadimefon and of triadimenol was assessed. Three broadly defined groups of fungi were found: (i) sensitive to both triadimefon and tridimenol, (ii) insensitive to both, and (iii) insensitive to triadimefon but moderately sensitive to triadimenol. In many cases it was possible to predict, at least semiquantitatively, the sensitivity of an organism to triadimefon from a knowledge of its characteristic metabolism to triadimenol and its sensitivity to the individual triadimenol enantiomers. No evidence for synergism or antagonism was found.

Distribution and performance of chemicals injected into trees for the control of fungal diseases

Control of Dutch elm disease (DED) and of powdery mildew, by injecting formulations of carbendazim and other compounds into the trunk of elm or apple trees, was limited by irregular distribution of fungitoxicant within the tree.The acid (but not methanol) content of carbendazim formulations influenced protectant activity against DED; no material tested was effective as an eradicant.Thiabendazole hypophosphite was phytotoxic to elms, gave control of DED inferior to carbendazim and was ineffective against powdery mildew on apple.