Inoculation and Evaluation of Strawberry Plants with Phytophthora fragariae. S. W. George, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. R. D. Milholland, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616. Plant Dis. 70:371-375. Accepted for publication 23 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-371.

Strawberry plants were inoculated effectively by spraying the roots with nonmotile (encysted) zoospores at 3 × 10⁴/ml. Oospore formation in the stele was used to measure disease development. Infection increased on the susceptible cultivar Tennessee Beauty as inoculum density was increased, but the cultivars Stelemaster and Surecrop remained resistant even when inoculated with 10 × 10⁴ zoospores per milliliter. The optimum temperature range for both zoospore germination on host roots and oospore development in host tissue was 15–20 C. A temperature of 25 C encouraged zoospore germination but greatly inhibited oospore formation. Both pathogen race and duration of flooding significantly influenced zoospore production in culture.