Factors influencing the development of potato pink rot (Phytophthora erythroseptica)

In affected crops sampled in the Lothian Region of Scotland during 1973–74, the incidence of pink rot (Phytophthora erythroseptica Pethybr.) increased during the latter part of the growing season. The number of plants with tuber symptoms increased but the number of rotted tubers per plant usually remained small. Earlier lifting usually resulted in the development of more pink rot in storage because tubers carrying inoculum or latent infection could not be detected or discarded. Application of fertiliser to the drill tended to give slightly more pink rot than broadcast application, perhaps because chemical damage to roots and stolons facilitated entry of the pathogen. Dry seasons may aggravate this effect. Disinfection of seed tubers, or selection of seed from healthy plants instead of from plants showing diseased tubers, did not significantly influence infection in the subsequent crop. Tests on varietal susceptibility showed differences, some inconsistent, among cultivars, but all those investigated were susceptible to infection by P. erythroseptica. Arran Pilot and Home Guard seemed the most susceptible; Record and Stormont Enterprise the least susceptible.