Greenhouse evaluation of chemicals for control of powdery mildews

Abstract

SUMMARYExperiments in the greenhouse with surface‐active agents for control of apple and barley powdery mildews indicated that cationic compounds were of particular interest. On barley, significant protective disease control was given only by agents providing good wetting; on apple, even good wetting was not necessarily followed by good protection. Didecyldimethylammonium bromide (DDAB) and domiphen bromide were among the most effective agents, giving a high degree of protection at 0·05%; curative action on apple was extremely good even at 0·025%, especially by DDAB. The latter was outstanding among many fungicides for protection of strawberry foliage against powdery mildew in the greenhouse, but more prolonged protection was given by lime sulphur or dinocap in a late‐season field trial.DDAB caused no damage on foliage of any of these three host species, except on strawberry where a non‐ionic agent was also included in the formulation. But disease control was reduced when certain cationic agents, including DDAB, were used to formulate several pure fungitoxicants, e.g. captan or dodine acetate.