Bacterial Blight of Carnation Caused by Pseudomonas woodsii and Susceptibility of Carnation Cultivars. E. E. TRUJILLO, Professor; Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu 96822. N. M. NAGATA, Junior Researcher, Department of Plant Pathology, University of Hawaii, 3190 Maile Way, Honolulu 96822. Plant Dis. 78:91-94. Accepted for publication 10 September 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0091.

Pseudomonas woodsii was shown to be the cause of a blight of carnation on 10 Maui farms during 1989 and 1990. Small, water-soaked, yellow specks that appeared 6 days after inoculation were the initial symptoms on potted plants. When plants were inoculated with 2.9 × 106 cfu/ ml, the specks appeared in 6 days and enlarged to 2- to 3-mm-diameter discrete spots 4 days after initial symptoms were visible; at 4.5 × 108 cfu/ml, however, lesions coalesced, causing extensive blight. Plants inoculated with 106 to 108 cfu/ml produced comparable numbers of lesions when incubated for 24-48 hr in a moist chamber or outdoors at ambient relative humidities. The lowest inoculum level to initiate disease was 2.9 × 103 cfu/ml. Streptomycin sulfate at 250 and 500 ppm a.i., oxytetracycline at 204 and 407 ppm a.i., and fosetyl Al at 4,800 and 9,600 ppm a.i. significantly reduced the number of leaf spots, but treatments did not economically control the disease. Of 66 cultivars evaluated in the field, Cal Red and Cal Improved White showed high disease resistance.