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Etiology

Effect of Simulated Saline Cooling Tower Drift on Tree Foliage. B. A. Francis, Former graduate research assistant, Department of Botany, University of Maryland, College Park, 20742; C. R. Curtis, professor, Department of Plant Science, University of Delaware, Newark, 19711. Phytopathology 69:349-353. Accepted for publication 27 September 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-349.

Wet cooling towers used by industries and utilities to dissipate waste heat often release a saline aerosol drift into the surrounding atmosphere. To simulate saline drift, water from a cooling tower basin was sprayed repeatedly during the growing season on small trees of Virginia pine (Pinus virginiana), tulip tree (Liriodendron tulipifera), California privet (Ligustrum ovalifolium), Norway spruce (Picea abies), white ash (Fraxinus americana), and flowering dogwood (Cornus florida). Only dogwood leaves showed significant injury. The intensity of tip and marginal necrosis and Na⁺ and Cl^– concentrations increased with the number of sprays per season. The Cl^– concentration ranged from 3,145 to 9,000 μg/g dry weight (dw) for mild to severe foliar necrosis, respectively. Corresponding Na⁺ concentrations ranged from 167 to 1,418 μg/gdw. Injury was not related to K⁺ or Ca⁺⁺ concentrations. Dogwood may be a useful bioindicator of saline drift.