On the Fungicidal Action of Capillary Active Substances upon the Conidia of Ophiobolus Miyabeanus

Abstract

1. In this paper, the results of experiments on the relations between chemical structures as well as capillary activities and fungicidal (fungistatic) actions upon the conidia of Ophiobolus Miyabeanus Ito et krib. of monobasic fatty acid soaps of carbon number 4∼18 and other capillary active substances were described. For evaluating the fungicidal action the conidia were submerger in the solution of fungicide for 4 hours at temperature 28°C, then submitted for germination after washing with water.2. The fungicidal action of the monobasic saturated fatty acid potassium soaps increased gradually with increasing carbon numbers and reached maximum at the capric (C10) and lauric (C12) acid soaps, then diminished again. There were some correlations between the fungicidal actions and the capillary activities of these soaps. The solutions of cepric and lauric acid potassium soap showed some difference in their dissociation degrees, while their fungicidal actions were equally powerful in the same molecular concentration, viz. about 90% of conidia were fungistatic with 0.01M solutions.3. The potassium soaps of monobasic unsaturated oleic, linolic and linoleic acids with carbon numbers 18 showed smaller fungicidal power than those of the saturated acids, and any correlation of fungicidal power with capilary activities was hard to find. The increase of the unsaturated double bonds in the molecule of the soaps having the same carbon numbers (C18) promoted the fungicidal power slightly.4. No difference in the fungicidal actions was found between the sodium and potassium soaps of monobasic saturated fatty acids.5. Naphthenic and abietic acid soaps, while showing similar physical properties with fatty acid soaps, had low fungicidal power.6. Detergents such as Igepon T, Nekal BX and sodium salt of sulfate of ricinoleic acid showed very weak fungicidal power, though their capillary activities were very strong.7. The cation active soap containing cetyl-dimethyl-benzyl-ammonium chloride had considerable capillary activity and also strong fungicidal action in concentration as low as 0.004%.