Transfer of Phytophthora infestans from blighted set tubers into the haulm of Potato (

main source of inoculum leading to transference of Phytophthora infestans (Mont.) d By from one season to another. The way in which the pathogen actually invades the plant foliage is less clear, and different reports follow one of the three views mentioned in early literature: (a) direct penetration, from tubers to haulms (Melhus, 1915); (b) indirect infection, from tubers to soil and then to haulms (Salmon and Ware, 1926); (c) indirect infection from tubers to soil, and then as air-borne inoculum to plants (De Bary, 1876). These views on the mode of infection were derived from observations rather than from con-