US EPA

14944 

Journal Article 

Injury to herbaceous plants by smog or air pollution 

Middleton, JT; Kendrick, JB, Jr; Schwalm, HW 

1950 

0 

Plant Disease Reporter
ISSN: 0032-0811 

34 

245-252 

English 

Smog is a term coined from smoke and fog. According to the report of the Stanford Research Institute, smog occurs when a peculiar set of weather conditions in which natural haze and man-made contaminants of the air mingle to produce an unpleasant, murky atmosphere. This condition results in reduced visibility; in irritation to eyes, nose, and throat; and in injury to herbaceous plants. Although the term smog is widely used, it is perhaps more correct to refer to this condition in the south coastal area as air pollution, for whereas a mixture of smoke and fog is not unusual or confined to any particular region, the air pollution in this area is indeed unique. This condition has developed with population and industrial expansion during and since the recent war years. According to reliable sources, the population of Los Angeles County has nearly doubled since 1940; the number of industries in Los Angeles area has increased from 15,000 before World War II to about 100,000 at the present time, and employment in this area has doubled in the last eight years. Injury to crops was first noted in 1984, when certain vegetables were observed to have leaf injury. The cause of such injury was unexplained and it was thought to be due to the presence of sulfur dioxide or other air pollutants. The type of injury observed was not identical with the symptoms usually reported for sulfur dioxide injury. Further study and observation in the Los Angeles area soon revealed that the problem of injury to crops was one of general air pollution and not of specific damage from sulfur dioxide as originally believed. Injury to vegetable crops and other herbaceous plants has become more extensive and more pronounced each year. Unusual amounts of damage occurred in 1947, 1948, and 1949.