Effects of soil temperature and moisture on stem canker (Rhizoctonia solani) disease of potatoes

Potato seed pieces bearing one sprout were inoculated wit h cultures of Rhizoctonia solani, planted in pots of compost at 45, 60, 75 or 90 % water holding capacity (whc) and incubated at 5, 10 or 15 degrees C. Shoots emerged after 2 - 3 wk at 15 degrees C, 3 - 4 wk at 10 degrees C and after 9 - 11 wk at 5 degrees C and stem canker recorded after emergence, was severe at 10 and 15 degrees C but slight at 5 degrees C. Soil moisture had less effect on emergence but stem canker was more severe in dry (45 % whc) than moist soils (75 and 90 % whc). The relationship between time of shoot emergence and stem canker severity is discussed.