The infection of potatoes byPhytophthora infestans during simulated washing and its control using a hot water treatment

Abstract

A single blighted tuber released on average 1.39 mg ofP. infestans mycelia and sporangia during simulated washing. In subsequent experiments up to 100% of tubers were infected when healthy tubers were washed in a suspension ofP. infestans equivalent to a concentration of 1.65 μg ml−1, i.e. that calculated to be in a commercial washing plant after washing a potato stock with approximately 1% of tubers infected with blight for 4 hours. Immature tubers were more prone to infection during washing than mature tubers. Damaging tubers, irrespective of their maturity, increased the incidence of tuber infection. The viability ofP. infestans isolates was significantly reduced byin vitro immersion in water at 44°C for 5 minutes. The infection of daughter tubers dipped in a suspension ofP. infestans for 3 minutes was prevented when the suspension temperature was 44°C. There was no indication of tuber damage at this temperature.