A novel fungicide, LY177206 [3-(1,1-dimethylpropyl)-1-oxo-1H-indene-2-carbonitrile], has demonstrated activity as a protectant against certain plant pathogens under greenhouse conditions. The compound controlled squash downy mildew (Pseudoperonospora cubensis) and grape downy mildew (Plasmopara viticola) at a rate range of 25 to 50 ppm. Activity against wheat leaf rust (Puccinia recondita) and bean rust (Uromyces phaseoli) was demonstrated on intact plants at rates of 50 to 100 ppm. Better efficacy was obtained with an aqueous suspension (A.S.) of LY177206 than with an emulsifiable concentrate (E.C.), especially for residual control. Scanning electron microscopy (SEM) revealed that crystallization was occurring on the leaf surface with the E.C. formulation.
Attempts to improve the characteristics of the A.S. under rainfall conditions were performed by adding different polymers or surfactants to the formulation. Under simulated rainfall conditions in the greenhouse, addition of a resin hydrophobe, Polyfac MT603, to the LY177206 aqueous suspension resulted in the greatest efficacy enhancement when compared to the original aqueous suspension containing no additive. SEM studies comparing the A.S. formulations revealed subtle differences in the distribution and agglomeration properties of the active ingredient on the leaf surfaces.