Air pollution injury of potato in Michigan

A disorder of Michigan potatoes tentatively called speckle leaf is associated, in part, with air pollution injury. The disease is characterized by reduced yields following early vine maturity, premature vine death, and yellowing of the lower leaves. Necrotic spots developed on the upper surface of leaves, followed by bronzing, and upward leaf rolling. Severely affected leaves became chlorotic and remained attached to the stem. Potato plants were grown in two plastic houses through which was blown either ambient field air or ambient air filtered through activated charcoal. Plants grown in the plastic house receiving ambient air developed symptoms similar to nearby field plants. Plants grew normally in filtered ambient air and remained free of speckle leaf and air pollution injury symptoms. The potato varieties Haig, Norchip, and Superior were most sensitive, Sebago was intermediate, and Kennebec and Katahdin were most tolerant. Tobacco plants in ambient non-filtered air developed symptoms typical of ozone injury. Bean leaves became bronzed with brown necrotic flecks on both surfaces, and severely affected leaves dropped. Neither tobacco nor bean was affected in the filtered air.