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Acute Foliar Injury of Eastern White Pine Induced by Sulfur Dioxide and Ozone. A. C. Costonis, Plant Pathologist, USDA, Forest Service, Southeastern Forest Experiment Station, Asheville, North Carolina 28802. Phytopathology 60:994-999. Accepted for publication 27 January 1970. DOI: 10.1094/Phyto-60-994.

Ramets of eastern white pine (Pinus strobus) were exposed to both SO₂ and O₃ in a controlled-environment chamber. Current needles between 4 and 5 weeks old were acutely injured by SO₂ at dosages ranging from 15 ± 5 parts/hundred million (pphm) for 2 hr to concentrations as low as 5 ± 1.5 pphm for 1 hr. These results demonstrated that certain strains of eastern white pine trees are extremely sensitive to low levels of SO₂. New needles on different branchlets of the same tree could be independently injured by either O₃ or SO₂ at approximately 25 ± 5 pphm for 2 hr. Sulfur dioxide was considerably more phytotoxic than O₃. Macroscopic differences in development of injury on new needles induced by both gases are discussed. No histological differences of diagnostic significance were noted between the two kinds of injury.