239 



Two sprays are in common use and have generally been found satis- 

 factory. These are Bordeaux mixture and lime-sulfur, both of which 

 are obtainable as commercial preparations or may be made up as needed. 

 When small quantities are wanted, commercially prepared Bordeaux mix- 

 ture is satisfactory; and when lime-sulfur is used, it is generally more 

 convenient to use a ready-made material. Descriptions of these sprays, 

 the methods of preparation, and the times of application are to be found 

 in publications of the Illinois Agricultural Experiment Station, especially 

 Circular No. 2T7, "Directions for spraying fruits in Illinois," published 

 jointly by the Department of Horticulture and the Natural History Sur- 

 vey in February, 1924. 



Diseases of Vegetable Crops 

 Potato 



In the production of potatoes Illinois held in 1922 the sixteenth 

 place, while in acreage it was twelfth. According to the Census reports 

 for 1920 there were 8G,38-1 acres devoted to potato-growing in the state. 

 The distribution of the commercial acreage as reported in 1922 is shown 

 on Map 9G, each dot representing approximately 500 acres. From this 

 map it appears that St. Clair county is the outstanding producer, with a 

 noticeable extension of the industry into counties immediatelv to the 

 north and south. A second area of intensive growing is found in north- 

 ern Illinois, beginning in Rock Island county and running more or less 

 continuously through the border counties of the state north, east, and 

 then south to include Will county, with Whiteside and Cook counties 

 leading in acreage. 



The potato crop is estimated to have ranged from 5,200,000 bushels 

 in 1919, valued at $10,192,000, to 9,568,000 bushels in 1923, valued at 

 $8,420,000. 



Earlv Blight 

 Caused by Alternaria solaiii { E. & M.) J. & G. 



Early blight is the commonest potato disease in Illinois. It appears 

 on the leaves as circular grayish to brownish spots, dry, dead, and con- 

 centrically marked. They first appear about the time the tubers begin 

 to form, and gradually increase in size and nuniber, coalescing and occu- 

 pying large areas of leaf tissue. In severe cases all the leaves on the 

 plants may be completely killed, leaving only the stem alive and green. 



Burrill recorded the presence of this di.sease in Cham])aign county in 

 1911. During 1922 and 1923 it was found in 15 counties, the distribu- 

 tion of which is shown on Map 97. It appears from this map that it is 

 more common in the southern half of the stale than northward. 



Crop reductions from early blight have been estimated at 1 per cent 

 in 1922 and 1.5 per cent in 1923, equivalent to (!S,()00 bushels valued at 

 $61,200 and 145,000 bushels valued at $127,600 for the years mentioned. 



