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Disease Control and Pest Management

Eradication of Xanthomonas campestris, the Causal Agent of Black Rot, from Brassica Seeds with Antibiotics and Sodium Hypochlorite. H. S. Humaydan, A joint contribution of the Harris Seed Co., Inc., Rochester, NY 14624; G. E. Harman(2), B. L. Nedrow(3), and L. V. DiNitto(4). (2)(3)New York State Agricultural Experiment Station, Geneva, NY 14456; (4)A joint contribution of the Harris Seed Co., Inc., Rochester, NY 14624. Phytopathology 70:127-131. Accepted for publication 30 July 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-127.

A method is needed for eradicating Xanthomonas campestris from Brassica seeds without causing damage to seeds or phytotoxicity to seedlings. The pathogen was eradicated from most lots of Brassica seeds by a 1 hr soak in a 500 μg/ml solution of either aureomycin, terramycin, or streptomycin. These treatments were phytotoxic, but if the antibiotic soak was followed with a water rinse and a soak for 30 min in 0.5% (w/v) NaOCl, the phytotoxicity was eliminated. Laboratory, greenhouse, and field tests indicated that a soak for 2 hr in a solution containing any one of these antibiotics followed by the water rinse and a NaOCl soak eradicated X. campestris from all seed lots tested and was not phytotoxic. When preceded with a reduced-pressure 0.2% (w/v) thiram soak for 24 hr, both Phoma lingam and X. campestris were eradicated from cabbage seeds with no loss of seed quality. By comparison, the standard hot water soak did not eradicate X. campestris from three of 11 lots tested, and it frequently damaged seed quality. A soak in 500 μg/ml of vancomycin HCl was not phytotoxic, but in field tests seeds treated with this antibiotic produced infected plants. Efforts are under way to register a seed soak in 500 μg/ml streptomycin for 2 hr followed by a water rinse and a 30-min soak in 0.5% NaOCl for eradication of seedborne X. campestris in the United States.