Fenaminosulf applied as a single soil drench soon after planting strawberries, cv. Merton Princess, and growing the plants on ridges 305 mm high decreased the incidence and severity of red core (Phytophthora fragariae). Pre-plant treatment with dazomet and growing plants on raised rows 100 mm high were ineffective. The percentage of diseased roots was the most useful estimate of disease in evaluating the efficacy of treatments and the interaction of disease and yield. The relationship between disease and yield was highly significant, negative and apparently linear. Disease accounted for a higher proportion of the variation in yield in the first fruiting year than in the second. There was a close correlation between plant size in June and yield in July.