Studies on powdery scab of potatoes-I. factors affecting disease development

Surveys undertaken in the Simla hills from 2,000 to 3,300 meters above sea level during 1973 to 1975, showed that the incidence of powdery scab of potato caused by Spongospora subterranea (Wallr.) Lagerh. was up to 14.5 per cent. The incidence was more at higher elevations. Artificially inoculated tubers showed 70–80 per cent infection at 10° to 15°C. Under controlled conditions, soil temperature of 15°C associated with high soil moisture (0.1 to 0.2 atm tension) was found to be the optimum for disease development.