Injury of Three Ornamental Flower Crops from Simulated Acidic Fog. Patrick M. McCool, Statewide Air Pollution Research Center, University of California, Riverside 92521. Robert C. Musselman, and Jerry L. Sterrett. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, 240 West Prospect, Fort Collins, CO 80526, and Statewide Air Pollution Research Center, University of California, Riverside 92521. Plant Dis. 74:310-312. Accepted for publication 20 November 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0310.

Flowering plants of carnation (Dianthus caryophyllus ‘Lillipot’), chrysanthemum (Chrysanthemum × morifolium ‘Florida Marble’), and zinnia (Zinnia elegans ‘Liliput’) were exposed in separate experiments to simulated acidic fog, with treatment pH ranging from 1.8 to 5.6. For all three ornamentals, flower injury was assessed to determine damage response levels. Response of carnation and chrysanthemum to acidic fog was similar. The most severe injury occurred near pH 1.8–2.0, and no injury was observed above approximately pH 3.8–4.0. Injury of zinnia was also most severe at pH 2.0 but was approximately 40% less severe than that of carnation or chrysanthemum at this acidity. In addition, zinnia, unlike the other flower species, developed flower injury at pH as high as 4.0. All flowers tested were injured at ambient acidity levels measured in many of the primary cut flower production areas of California. Acidic fog may have an economic impact on ornamental flower crops.