Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.): Further field studies on the use of clean and contaminated seed potatoes and on the contamination of crop tubers

Abstract

Black scurf and stem canker of the potato were investigated in field trials in contaminated soil at Warburton, Cheshire, to determine the effect of planting clean and contaminated seed (vars. Arran Banner and Majestic) on crop yield and on the contamination of the crop tubers.Black‐scurf contamination was prevalent on crops grown from clean seed and was not significantly different from that occurring on plots planted with contaminated seed. It was severe on early‐dug tubers, but was more severe on late‐dug tubers. Produce grown with and without stable manure was heavily contaminated.Contaminated seed caused a check to tuber formation and an appreciable increase in stem canker and in the number of primary shoots killed. Nevertheless, the yields from the manured, contaminated seed plots were satisfactory and were not lower than those from the clean‐seed plots. There was no relation between the yield and the amount of black scurf on the produce.The results of a trial made in a field which had been in grass for at least 43 years, suggested that the soil contained little, if any, Corticium Solani. Heavy contamination occurred on tubers grown under relatively dry soil conditions.In all the trials misses and wilted shoots caused by Corticium were rare and there was no premature yellowing or death of the haulms on the clean or contaminated seed plots.The evidence obtained in the four seasons from 1941 to 1944 indicates that in this country satisfactory yields of early maincrop and maincrop varieties may be obtained despite the prevalence of C. Solani in the soil and on the seed, provided the soil and cultural conditions are reasonably good.