Influence of Temperature and Wetness Duration on Infection of Immature Strawberry Fruit byPhytophthora cactorum

Abstract

Strawberry fruits (cv. Midway) inoculated with a sporangial suspension (400 ml) of P. cactorum were used to determine the effects of wetness duration and temperature on infection level. Infection increased with increased wetness duration (0-5 h) at all temperatures tested (6.degree.-30.degree. C). For each wetness duration, infection increased up to the optimum temperature (21.degree. C) and then declined. At temperatures between 17.degree. and 25.degree. C, > 1 for wetness resulted in > 80% infection. A multiple-regression, logistic model accurately described infection as a function of wetness duration and temperature. The model was validated under natural field conditions.