Reliability of methods of assessing the degree of tuber attack by common scab of potatoes

Summary Four methods of assessing the degree of tuber attack by common scab caused byStreptomyces scabies (Thaxt.) Waksman and Henrici were compared in five experiments, over three years at two locations. The experiments were conducted on light, naturally infested soils in counties Wexford and Carlow. Comparison of the coefficients of variation showed that the cover score method gave the least consistent results. The other three methods gave consistent results. Of these the visual assessment (0–10) of tubers in the field and the highest scab method were the easiest and quickest methods to operate.