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Ecology and Epidemiology

Relationship of Numbers of Zoospores of Phytophthora cryptogea to Infection and Mortality of Watercress. D. J. Mitchell, Associate Professor, Department of Plant Pathology, University of Florida, Gainesville, FL 32611; M. E. Kannwischer(2), and E. S. Moore(3). (2)(3)Graduate Research Assistant, and Technician, respectively, Department of Plant Pathology, University of Florida, Gainesville, FL 32611. Phytopathology 68:1446-1448. Accepted for publication 3 May 1978. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1446.

Suspensions of motile zoospores were added to individual, 2-wk-old watercress plants growing in flooded vermiculite. Percentages of infection after 7 days at 25 C in a growth room were 18, 26, 46, 56, 65, 81, and 100 at 50, 100, 200, 300, 500, 103, and 104 zoospores per plant. After 21 days percentages of dead plants were 30, 51, 67, and 81 at 103, 104, 105, and 106 zoospores per plant.

Additional keywords: inoculum density, Nasturtium officinale.