Potato physiology and varietal efficiency in disease behaviour

First early Epicure potato crops escape the heavier losses from potato root celworm because of a differential effect of temperature on host and parasite "Varietal efficiency" of tuber production has been combined with yield, length of growth cycle, temperature and daylengths to show that a variety suitable for "celworm escape" must have a high efficiency during low temperatures and short, dull days whilst maintaining the efficiency at high temperatures and longer days. Differing reactions of Epicure and Kerr's Pink to late blight on the foliage and on the tubers are explained by their differing C_p/R_s ratio values which in turn reflect the varietal effeiency.