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Infection Rates of Cercospora apii in Mixed Populations of Susceptible and Tolerant Celery. R. D. Berger, Associate Professor of Plant Pathology, Institute of Food and Agricultural Sciences, University of Florida, Agricultural Research and Education Center, Belle Glade 33430; Phytopathology 63:535-537. Accepted for publication 13 November 1972. DOI: 10.1094/Phyto-63-535.

Disease incidence and infection rates for blight in susceptible celery decreased as the percentage of blight-tolerant plants in the population increased. This protective effect was largely lost at disease incidences above 25%. Tolerant celery in mixed populations had increasing blight incidence as the percentage of susceptible plants increased but infection rates did not truly reflect such an increase. There was no significant difference in infection rates between susceptible and tolerant celery for a major portion of the epidemic suggesting that the tolerance was effective against only low levels of spore arrivals.