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A Comparison of Inoculation Methods of Erwinia chrysanthemi in Greenhouse Ornamentals. R. A. Haygood, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650. D. L. Strider, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 66:461-463. Accepted for publication 24 July 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-461.

Concentrations of 2 × 106 and 2 × 108 colony-forming units per milliliter and undiluted inoculum of Erwinia chrysanthemi were inoculated to wounded and unwounded, attached and detached leaves of 29 greenhouse ornamentals. Asplenium nidus, Begonia semperflorens, Begonia × hiemalis, Brassaia actinophylla, Crassula argentea, Kalanchoe blossfeldiana, Pelargonium × hortorum, and Peperomia argyreia were new hosts of E. chrysanthemi. Unwounded attached and detached leaves of A. nidus, C. argentea, K. blossfeldiana, and Philodendron selloum were susceptible to E. chrysanthemi when inoculated with high inoculum concentrations, but wounding was usually required for infection of other cultivars. Stab-inoculation of stems and inoculation of wounded attached leaves with undiluted inoculum resulted in similar responses except for Caladium × hortulanum, Chrysanthemum morifolium, Dracena marginata, Dracena sanderiana, Euphorbia pulcherrima, Pelargonium × hortorum, and Peperomia argyreia. Wounded detached leaves in sand of Caladium × hortulanum, Coleus blumei, E. pulcherrima, and Pelargonium × hortorum became infected with undiluted inoculum, but attached leaves did not. Wounded leaves of several species developed extensive soft rot in petri plates but did not become infected in sand.

Keyword(s): bacterial blight, floral crops, foliage plants.