Influence of Chronic Sulfur Dioxide Exposures on Early Blight of Tomato. R. J. Lotstein, Former Graduate Student, Department of Plant Pathology and Center for Air Environment Studies, Pennsylvania State University, University Park 16802. D. D. Davis, Professor, Department of Plant Pathology and Center for Air Environment Studies, Pennsylvania State University, University Park 16802. Plant Dis. 67:797-800. Accepted for publication 15 December 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-797.

Potted tomato plants were grown outdoors in the presence of airborne Alternaria solani inoculum and were either sprayed with chlorothalonil fungicide or left unsprayed. Plants were moved into controlled-environment chambers and exposed to 393 μg^-3 (0.15 ppm) SO₂ or charcoal-filtered air for 72 continuous hours per week for 4 wk. After exposures, plants were returned to their original outdoor positions. Interactions were observed between SO₂ exposure and fungicide treatment for the number of acceptable fruits per plant and mean individual fruit weight per plant. The combined exposure to SO₂ and infection by A. solani resulted in a decrease in fruit number and an increase in mean individual weight of remaining fruit.