Plants relatively sensitive to sulfur dioxide injury are soybeans, dry edible beans, alfalfa, small grains and many vegetable crops. The symptoms of sulfur dioxide injury may resemble damage from frost, other air pollutants, chemical sprays or herbicide residues in soils. This often makes it very difficult to identify the cause of injury. Positive identification can be made only after all foliar symptoms and related evidence have been considered. In general, symptoms are either chronic or acute, depending on the rate of sulfur accumulation in the leaf tissues.
Chronic injury is characterized by a slow accumulation causing a general chlorotic appearance.
Some plants may be ivory or white, while others show a strong reddish brown or black coloration. Later symptoms resemble normal senescence. Acute injury appears as marginal areas of dead tissue, which at first have a grayish green, water-soaked appearance. Later these areas take on a leached ivory color in most plants. In small grains, tip dieback is a common symptom.