A foul smelting soft rot of the upper stalk and leaves of sorghum was observed in Isabela, Puerto Rico, during the summer of 1985. The bacterium from infected rotting sorghum whorls was isolated in pure culture and inoculated to sorghum, maize (Zea mays L.), and sugarcane (Saccharum officinarum L.) in the field and to potato (Solanum tuberosum L.) and pineapple [Ananas comosus (L.) Merr.] in vitro. Results of pathogenicity and 23 phenotypic tests suggested Erwinia chrysanthemi p.v. zeae Burk., McFadden & Dimock as the causal agent of the bacterial whorl blight and stalk rot of sorghum. Twenty-two antibiotics were tested for in vitro control of our strain of the whorl blight pathogen. Zones of inhibition around antibiotic impregnated discs on bacteria, seeded on Muller Hinton Agar, showed high pathogen sensitivity to senociclin, chloramphenicol, kanamycin, gentamicin, carbenicillin, cefotaximine, tetracycline, amikacin, and tobramycin. Members of the penicillin family appeared ineffective for controlling this bacterium. TAM 428 and SC 120, dwarf sorghums with moist sweet stems, were severely damaged when fungicide treated. Mean incidence of visible bacterial whorl blight reached 25%. Yield losses ranged from 34 to 56%. Dry stemmed sorghums, SC 307 and SC 212, showed less than 5% whorl blight and no yield loss.