Fungicides Developed on the Basis of the Life Cycles of Plant Pathogens

Abstract

There are 1, 200 crop diseases caused by pathogenic fungi in Japan. Control of these diseases is of vital importance to a sufficient and stable supply of foodstuff. The development of safe agricultural chemicals free of mammalian toxicity and environmental pollution are urgently needed. The authors believe the protection against processes of infection to be one of the most important factors in combatting fungal diseases. The processes of rain-borne and air-borne fungal infections were investigated with reference to various growth stages in their life cycles after they were noted on the surface of a host plant. We isolated antifungal substances, including citrinol and one of the phytoalexins, and their chemical structures were determined. Furthermore, studies were made on the response of host plants to stimulations by causal fungi. On the basis of information obtained, especially on the nature of the relationships between host plants and parasites, the successful development of two fungicides, soybean lecithin and sodium bicarbonate, was made. The former has a preventive effect against vegetable powdery mildews, and the latter has a curative effect against vegetable, rose, apple and pear powdery mildews in particular. Because of the non-mammalian-toxicity of both soybean lecithin and sodium bicarbonate, they are expected to be useful for application during crop harvest.