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.