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Ecology and Epidemiology

The Joint Action of Hydrogen Fluoride and Sulfur Dioxide on the Development of Common Blight of Red Kidney Bean. J. A. Laurence, Boyce Thompson Institute for Plant Research at Cornell University, Ithaca, NY 14853-1801; K. L. Reynolds, Boyce Thompson Institute for Plant Research at Cornell University, Ithaca, NY 14853-1801. Phytopathology 76:514-517. Accepted for publication 25 November 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-514.

Three-week-old Phaseolus vulgaris ‘California Light Red Kidney' plants were exposed to fluoride as HF at 0, 1, or 3 μg·m^-3 in filtered air. SO₂ at 0, 260, or 780 μg·m^-3 in filtered air, or all combinations of the two gases. Exposures were conducted continuously (HF) or for 6 hr daily (SO₂) for 5 days before, after, or before and after inoculation with Xanthomonas campestris pv. phaseoli. Diameters of lesions were measured when first visible and again 10 days after inoculation. Leaf-surface populations of the pathogen were established and assayed at 5-day intervals for 15 days. Preinoculation and postinoculation exposure to SO₂ caused significantly smaller lesions and longer latent periods. Postinoculation exposure to HF resulted in significantly longer latent periods. Interactions between the two gases occurred only when the exposures were concurrent. In general, the joint action of the two gases resulted in smaller lesions and longer latent periods. The pollutants did not significantly alter the growth of the pathogen in the resident phase.