JOMAlOFAGliiamiliALffiSMCH 



Vol. XVI Washington, D. C, March 17, 191 9 No. 11 



FUSARIUM-BLIGHT OF POTATOES UNDER IRRIGATION 



By H. G. MacMillan 



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

 of Plant Industry, United States Department of Agriculture 



HISTORY OF FUSARIUM-BLIGHT 



The Irish potato {Solanum tuberosum) has been one of the most 

 profitable crops grown in the Greeley district of northern Colorado. 

 In this fertile, irrigated section, one of the oldest in the coimtry, the 

 potato gave large yields for many years before any serious setbacks 

 occurred. From 1908 to 1912 the inroads of disease threatened the 

 industry severely, and in 191 1 and 1912 the crops were failures. In 

 1 91 5 a laboratory was established at Greeley for the study of potato 

 troubles, but since that year the yearly losses have been light. Fusarium- 

 blight has been present, however, as a conspicuous malady. 



Fusarium-blight, or potato-wilt, is well recognized in nearly all the 

 potato-growing regions of the country, except in the extreme North- 

 eastern States. It is caused most frequently by the fungus Fusarium 

 oxysporwn Schlect., though other species of this genus have been found 

 involved. In 1899^ Smith {15Y first proved that species of this genus 

 would cause plant-wilts, and in 1904 Smith and Swingle {16) described 

 a potato-wilt and tuber-rot due to F. oxysporum. It was believed by 

 them that the F. solani of Pizzigoni {10) and of Wehmer {ly) was iden- 

 tical with their species. The confusion which existed over the definition 

 of species was largely removed by the taxonomic investigations of 

 Appel and Wollenweber (j), Carpenter {2), Sherbakoflf {14), and Wollen- 

 weber (20). Manns (6), Orton (9), Pratt {11), Wilcox {18), and others 

 have continued to reveal the great losses which species of Fusarium 

 cause in the potato industry and have suggested methods of control. 



' Smith, Erwin F. The watermelon disease of the south. (Abstract.) In Proc. Amer. Assoc. Adv. 

 Sci. 43d Meeting, 1894, p. 2S9-290. 1895. 



The following papers are likewise contributory: 



Smith, Erwin F. The spread of plant diseases. A consideration of some of the ways in which para- 

 sitic organi:ms are disseminated. In Trans. Mass. Hort. Soc. 1896, pt. i, p. 117-133. 1896. 



. The fungous infestation of agricultural soils in the United States. In Sci. Amer. Sup., v. 48, 



no. 1246, p. 19931-19982. 1899. 



' Reference is made by number (italic) to " Literature cited," pp. 301-303. 



Joiunal of Agricultural Research, Vol. XVI, No. 11, 



Washington, D. C. Mar. 17, 1919 



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