Postharvest Control of Botrytis cinerea on Cut Rose Flowers with Pyrrolnitrin. Philip E. Hammer, Department of Horticulture, The Pennsylvania State University, University Park 16802. Kathleen B. Evensen, and Wojciech J. Janisiewicz. Department of Horticulture, The Pennsylvania State University, University Park 16802, and USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430. . Plant Dis. 77:283-286. Accepted for publication 19 November 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0283.

Pyrrolnitrin, an antibiotic isolated from Pseudomonas cepacia, was tested for postharvest control of Botrytis cinerea infections on cut Sonia and Royalty rose flowers. After pyrrolnitrin was applied as a bud dip, buds were inoculated with conidia of B. cinerea and stored for 7 days at 2 C. Dip treatments of 12–200 mg/L significantly reduced lesion development during storage at 2 C and promoted poststorage fresh weight gain (an index of cut flower quality). No phytotoxicity was observed on leaves or petals at concentrations of pyrrolnitrin up to 200 mg/L. Dip treatment with 100 mg/L reduced lesion development by about 90% compared to inoculated control flowers and prevented poststorage flower rot. This degree of disease control was comparable to that achieved with 1,800 mg of vinclozolin per liter (the maximum label rate).