Soil and Atmospheric Moistures Associated with Fusarium Crown Rot and Leaf Blight of Poa pratensis. R. W. Smiley, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. D. C. Thompson, Former Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Plant Dis. 69:294-297. Accepted for publication 22 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-294.

Kentucky bluegrass (Poa pratensis) sod produced in the field was used to study the sequential effects of turfgrass watering regimes and atmospheric humidities on the incidence and severity of Fusarium diseases in the greenhouse. Severity of leaf blight was significantly increased by drought stress, especially when followed by periods of flooding, high humidity, or both. Plants that had not been predisposed by drought were resistant to leaf blight even when subsequently flooded but sustained low levels of infection during prolonged periods (up to 8 days) of high relative humidity. Fusarium spp. were principal colonists of crowns but not of tiller bases, whereas the reverse was true for Nigrospora spp. Inoculating the turfgrass with a conidial suspension of mixed Fusarium spp. did not increase disease levels above those in uninoculated treatments of field-produced sod.