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Leaf Spot of Marigold Caused by Seed Contaminated with Pseudomonas syringae pv. tagetis in North Carolina. D. L. Strider, Department of Plant Pathology, North Carolina State University, Raleigh 27695-761 6. Plant Dis. 68:1016. Accepted for publication 17 August 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-1016d.

Bacterial leaf spot of marigold (Tagetes erecra L.). incited by Pseudornonassyringae pv, targetis, Young, Dye. & Wilkie, was severe on cultivars Lemondrop. Petite Spray, and Petite Yellow in greenhouses in North Carolina during 1983 and 1984. Koch's postulates were successfully completed. Less than 1% of Lemondrop seedlings from a lot of naturally infested seed showed initial symptoms on cotyledons, but spread from these seedlings was rapid, and the lot yielded only 21.5% marketable bedding plants. A 30-min seed soak in 0.5% sodium hypochlorite did not reduce germinability of Lemondrop, Petite Spry. or Petite Yellow. Sufficient naturally infested Lemondrop seed for efficacy studies were unavailable. For marigold to remain a popular bedding plant seedsmen must recognize the pathogen's destructive potential and rogue seed fields to produce pathogen-free seed.
References: Hellmers. E. Acta gric. Scand. 5: 185, 1955. Styer. D. J. et al. Plant Dis. 64: 101, 1980.