JOIMAL OF AGRlCilDRAL RESEARCH 



Vol. XIII Washington, D. C, April 8, 1918 No. 2 



SOIL FUNGI IN RELATION TO DISEASES OF THE IRISH 

 POTATO IN SOUTHERN IDAHO 



By O. A. Pratt 



Assistant Pathologist, Cotton, Truck, and Forage Crop Disease Investigations, Bureau 



of Plant Industry, United States Department of Agriculture 



INTRODUCTION 



In a former paper it was shown that planting disease-free seed pota- 

 toes (Solatium tvherosum) on lands never before in cultivation could not 

 be considered a guarantee of a disease-free product (10) } Research 

 studies with the powdery-dryrot organism (Ftisarium trichothecioides 

 Wollenw.) (9) and with Fusarium radicicola WoUenw., the cause of a 

 blackrot {11) of the Irish potato tuber, indicated that these organisms 

 might be well distributed in the desert soils. From the results of the 

 1 91 5 plantings it was assumed that the infection which was observed in 

 the harvested crop must have proceeded from organisms already present 

 in the virgin desert soil, but since no attempts had been made to isolate 

 any of the organisms concerned, this assumption remained unverified. 



In an attempt to verify previous conclusions, plantings of disease-free 

 seed were again made in 191 6 on lands never before planted to potatoes, 

 and isolations of fungi were made from the soils. It is the purpose of 

 this paper to set forth the results obtained from the plantings of 191 6 

 and to report the fungi obtained from these isolations. 



19 16 PLANTINGS 



In the spring of 191 6 eight plots (No. 1-8) were planted with disease- 

 free seed potatoes on irrigated land previously cropped vvdth grain and 

 alfalfa or clover, or with grain alone, but never with potatoes; one 

 (No. 9) on irrigated virgin desert land never before in any crop; one 

 (No. 10) on dry-farming land previously in grain but never in potatoes; 

 and four (No. 11-14) on dry-farming land reclaimed from the desert in 

 the spring of 1916 for the special purpose of planting these plots. Two 

 of these plots (No. 7-8) were planted on the grounds of the experiment 



1 Reference is made by number (italic) to "Literature cited," p. 98-99. 



Journal of Agricultural Research, Vol. XIII, No. a 



Washington, D. C. Apr. 8, 1918 



mw Key No. G-139 



(73) 



