The life-history and epidemiology of American gooseberry mildew on black currants

It is shown that conidia of Sphaerotheca mors-uvae (Schw.) Berk, from gooseberry readily infect black currant; therefore it is unlikely that a new race of S. mors-uvae specifically pathogenic to black currants has recently appeared. However, the life-cycle on black currants differs from that on gooseberry. Incubation, infection and sporulation of the fungus have been examined under the optimum conditions of 18 °C and 100% relative humidity. The establishment of infections and sporulation was encouraged by a relatively low soil moisture content, temperatures above 15 °C, 60% relative humidity and good illumination-factors which promote vigorous plant growth. High phosphorus and high potassium nutrition also increased the susceptibility of black currants to infection.