Apr. 8, 1918 



Relation of Soil Fungi to Potato Diseases 



rot, o per cent; common scab, 0.33 per cent; Rhizoctonia or russet scab, 

 o per cent; percentage of tubers infected, all diseases, by weight, 6.33 

 per cent. 



In 191 5 the averages for similar plots (10) were as follows: 



Plots on irrigated, previously cultivated land: Vascular infection, 26 

 per cent; tuber-rot, about 0.5 per cent; common scab, 4.7 per cent; and 

 Rhizoctonia or russet scab, about 2.8 per cent. 



On virgin desert land, irrigated: Vascular infection, 29.3 per cent; 

 tuber-rot, 5.6 per cent; common scab, 9.3 per cent; and Rhizoctonia or 

 russet scab, 11.3 per cent. 



No plots were planted on dry-farming land in 1915. In detail, the 

 percentages of disease observed in the 191 5 plantings are shown in 

 Table II. 



Table II. — Percentages of diseases of potatoes observed in the plantings in igi§ 



Plot I Re- 

 No. claimed. 



9 

 10 

 II 

 12 



13 

 14 

 15 



1910 



1907 



1907 

 1908 



1907 

 1908 



? 

 ? 



1915 

 1915 

 191S 

 191S 

 1915 

 1915 



Previous cropping. 



AT JEROME ST.^TION. 



1910, barley; 1911- 

 1914, alfalfa. 



Variety of potato. 



Average . 



IN COOPERATION WITH 

 IDAHO FARMERS. 



1907, wheat; 1908- 



19 14, alfalfa. 

 do 



1908-1915, orchard 

 land, cropped with 

 alfalfa and beans. 



1907, grain; 1908- 

 1914, alfalfa. 



1908, grain; 1909- 

 1913, idle; 1914, 

 grain. 



Alfalfa, long period 

 of years. 



do 



do 



Raw desert land 



do 



do 



do 



do 



do 



'Idaho Rural 



...do 



Netted Gem 



Rural New Yorker. 



Pearl 



People's 



Red Peachblow o 



.Burbank o 



Carmen 



Netted Gem. 

 do 



.do. 

 .do. 



^Red Peachblow. 



Netted Gem. 

 Idaho Rural. 



do 



Netted Gem. 



do 



Idaho Rural . 



do 



People's 



Percentage of hills infected. 



Com- 

 mon 

 scab. 



Rhi- 

 zoc- 

 tonia. 



0-37 



Tuber- 

 rot. 



Vascu- 

 lar in- 

 fection. 



o. 77 



46 



37 

 44 



