Stimulation of Two Pathogenic Fungi by High Dilutions of Fungicides

Abstract

At very high dilutions, a wide range of fungicidal chemicals stimulates conidial germination, growth, and infectivity of the pathogenic form of Colletotrichum coffeanum Noack. Stimulation of germination is independent of nutrition; its degree is dependent on viability, the relation being logarithmic and identical with that between viability and nutrition. Germination of the uredospores of Hemileia uastatrix Berk. & Br. is also stimulated by fungicides at high dilution; again the degree of stimulation is greatest with spores of low viability. It is suggested that the physiological mechanism leading to stimulation may be the same for all fungicidal substances.