12 Diseases of Economic Plants 



presence of the disease germs is manifest. In the case of 

 Sumatra tobacco under shade, or lettuce grown under 

 canvas, the money expended to prepare for the crop may 

 aggregate from $700 to $1000 or even more per acre the 

 first year. The capture of such acreage by the lettuce 

 drop or the tobacco wilt is a far more serious matter than 

 a plant disease is usually considered to be. 



The diseases which develop on the product after harvest, 

 while in storage, are of peculiar destructiveness since they 

 cause the loss of a large percentage of the finished agricul- 

 tural yield. "*• '" Thus a large part of the total yield of sweet 

 potatoes is lost. Those diseases that develop in transit entail, 

 in addition to the loss of the product, also the freight charges 

 and many hundreds of thousands of dollars in litigation. 



Some of the losses caused by diseases of a few crops are 

 given below, merely as illustrative instances. The authority 

 is named with each estimate. These losses are in many 

 instances much larger than is indicated, due to increase in 

 market value of the product. 



The California vine disease in 1892, $10,000,000. Pierce. 



Wheat rust in the United States, 1898, $67,000,000. Galloway. 



Wheat rust in Illinois, 1885, $1,875,000. Burrill. 



Violet leaf-spot in the United States, 1900, $200,000. Dorsetf. 



Peach leaf-curl in the United States, 1900, $2,335,000. Pierce. 



Potato late-blight in New York, 1904, $10,000,000. Stewart. 



Oat smut in the United States, annual, $6,500,000. Orton. 



Wheat loose smut. United States, annual, $3,000,000. Orton. 



Wheat bunt in the United States, annual, $1 1,000,000. Orton. 



Potato blight in the United States, annual, $36,000,000. Orton. 



Wheat, 1917, all diseases, 64,440,000 bu. Lyman.a 



Oats, 1917, all diseases, 153,973,000 bu. Lyman. 



Corn, 1917, all diseases, 175,344,000 bu. Lyman. 



Potato, 1917, all diseases, 117,174,000 bu. Lyman. 



Sweet potato, 1917, all diseases, 41,707,000 bu. Lyman. 



Cotton, 1917, all diseases, 1,866,000 bales. Lyman. 



