Control of Mildew on Bean Plants by Means of an Antibiotic

Abstract

When an aqueous soln. of actidione a product isolated from Strepto-myces griseus by the Upjohn Co. at 10 ppm. was sprayed on Red Kidney bean plants affected by mildew, the grayish-white patches on the upper surface of the leaves disappeared completely within 48 hrs., indicating that the mycelium and the conidia of the fungus (Erysiphe polygonii) were destroyed. Expts. were then conducted in order to find the lowest effective concn. The most satisfactory formulation seems to be an aqueous dispersion of 0.25% methylcellulose (1500 cp. viscosity type) to which is added 5 ppm. of actidione. Since lesions remain after leaves once have been attacked by mildew and since these restrict growth of the plant even after the parasite has been destroyed, it seemed advisable to use actidione prophylactically. If the first spray application was made to the primary leaves of bean plants 10-12 days old, and treatment continued at intervals of 6-10 days, corresponding to the production rate of the trifoliate leaves, these plants were protected during their lifetime against mildew even when closely surrounded by heavily infected control plants.