Some factors affecting the activities of dinitrophenol fungicides. II.—Use of g.l.c. partition data in studies of chemical structure/fungicidal activity against powdery mildew

The application of partition data, derived by a gas-liquid chromatographic (g.l.c.) technique, to the study of the activities of members of homologous 4-(l-substituted alkyl)-2,6-dinitrophenol series against cucurbit and apple powdery mildews (caused by Oidium sp. and Podosphaera leucotricha respectively) is discussed. The correlation between the possession of high protectant activity and a favourable πglc value for maximum ‘zonal’ movement within the leaf surface is stressed. This criterion is more important than vapour-phase activity in this context; it may well rival in importance the possession of optimum conidial penetration properties.