Some landscape sites, especially in highly urbanized area, are subjected to significant levels of air pollution. The most damaging of these pollutants are sulfur dioxide, ozone, and peroxyacetyl nitrate (PAN). Symptoms of sulfur dioxide injury include necrotic (dead) spots between the major veins, where the tissue turns light tan and papery in texture. Annuals sensitive to sulfur dioxide include aster, begonia, bachelor’s button, china aster, coleus, cosmos, geranium, marigold, poppy, and zinnia. The most common symptom of exposure to ozone is the formation of tiny, light-colored flecks or spots (similar to spider mite damage) on the upper surfaces of affected leaves. Annuals sensitive to ozone include ageratum, aster, begonia, marigold, pansy, petunia, and salvia. Symptoms of PAN injury are expressed as silvering, glazing, or bronzing of the lower leaf surfaces and sometimes leaf death. Annual flowers sensitive to PAN include aster, impatiens, petunia, salvia, and snapdragon.

Prepared by: Erv Evans, Consumer Horticulturist

© 2000 NC State University
Images © by Erv Evans