1981 Volume 6 Issue 2 Pages 201-209
Sodium bicarbonate (SBC) has a control effect against citrus penicillium decay and several other plant diseases. However, the inhibitory effect varies because of crystallization of the chemical on the plant. A SBC preparation to which an emulsifier used as a food additive was added was considered to be a practical control chemical against powdery mildew of cucumber, egg plant, strawberry, etc. For the purpose of clarifying the characteristic effect of the chemical, a study was made of its effect on cucumber powdery mildew fungus, Sphaerotheca fuliginea, at various growth stages and the following results were obtained. 1) Direct spray of SBC at a concentration of 2, 000ppm inhibited 80-100% of conidial germination. 2) In hyphal elongation, there was little difference between this treatment and water-treatment, and no great inhibitory effect was observed. 3) The chemical did not to control conidiophore formation very well, the control percentage being only 38%. 4) The number of conidia formed per conidiophore in about 20 hours was 5 in untreated sections, whereas in the SBC treated sections no conidia were formed. 5) Treatment of new conidia with SBC resulted in the formation of small projections on the surface and rupture of the cell wall under a slight pressure, with subsequent projection of the contents. Such conidia could not infect cucumber plant and the SBC preparation greatly inhibited conidial dispersion.
