Page:Popular Science Monthly Volume 78.djvu/481

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CONTROL OF PLANT DISEASES
PSM V78 D481 Chestnut trees destroyed by bark disease.png
Fig. 3. Large Chestnut Trees killed by the Bark Disease.

wave of disease. It to-day causes loss estimated at $36,000,000 annually in the United States. New York alone has incurred a loss of $10,000,000 in one year.

The asparagus rust prohibited successful asparagus culture in several states and threatened that industry in California, where the crop occupies yearly over 7,000 acres of land, until means of control were devised by scientific men. The rice smut was recognized in its

PSM V78 D481 Distribution of chestnut bark disease by county and state.png

Fig. 4. Map showing the Distribution of the Chestnut Bark Disease. Black shows area of severe infection; round dots, presence of disease prior to 1909; + indicates the spread of the disease during 1909. After Metcalf.