Effects of Nitrogen and Potassium Fertilization on Infection of Florists’ Carnation by Gibberella zeae. R. W. Stack, Former Graduate Student, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. R. K. Horst, Professor, Department of Plant Pathology, and R. W. Langhans, Professor, Department of Floriculture and Ornamental Horticulture, Cornell University, Ithaca, NY 14853. Plant Dis. 70:29-31. Accepted for publication 27 July 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-29.

Carnation plants growing under commercial glasshouse conditions received three levels of nitrogen and three levels of potassium fertilization. Levels of nitrogen and potassium were monitored by soil tests and by foliar analysis. Cut stubs left from crop harvest were inoculated with Gibberella zeae, causal agent of Fusarium stem rot. Incidence and severity of disease were determined 60 days after inoculation. As levels of balanced nitrogen and potassium were increased from low to intermediate to high, incidence of infection increased significantly (25, 35, and 47%, respectively). There were many more severe infections (19%) in the high-nitrogen + low-potassium treatment than in any other treatment (2.3–3.5%).