May 29, 1916 Fieldrot of Potato Tubers 299 



usually showed tufts of F. radicicola. Infected tubers of Idaho Rural 

 potatoes kept 10 days in a moist chamber at room temperature are 

 shown in Plate XXXV, figures 4 and 5. Tufts of F. radicicola have 

 appeared. Inoculations in 191 5 left no doubt in the writer's mind that 

 F. radicicola was capable of causing both types of rot. 



DISTRIBUTION AND ECONOMIC IMPORTANCE 



F. radicicola is apparently widely distributed. Wollenweber ^ states 

 that its habitat is "on partly decayed tubers and roots of plants, 

 such as Solanum tuberosum in Europe and America (collected by Wollen- 

 weber) and Iponwea batatas in the United States of America (collected 

 by Harter and Field)." Carpenter^ makes the following statement as 

 to its habitat: "On partly decayed tubers and roots of plants. Cause 

 of potato dryrot and jelly-end rot. Identified from the following: 

 Ipomoea batatas (collected by Mr. L. L. Harter) ; Musa sapientum (col- 

 lected by Mr. S. F. Ashby, Jamaica, Porto Rico) ; Cucumis sativus (col- 

 lected by Mr. F. V. Rand, West Haven, Conn.); soil (collected by Mr. 

 F. C. Werkenthin, Austin, Tex.)." 



The writer has isolated F. radicicola from the roots of poplar trees 

 (Populus deltoides) at Jerome, Idaho, where he found it associated with 

 crownrot. The fact that the fungus appears on potato tubers when 

 disease-free seed potatoes are planted on raw desert lands suggests that 

 it may be well distributed throughout the desert soils. Orton ^ in 

 1909 reported jelly-end rot of potatoes from the San Joaquin Valley, in 

 California. 



F. radicicola has been reported on potatoes from Idaho, Oregon, 

 and California by Wollenweber * and from Idaho, Oregon, California, 

 Nevada, Mississippi, New York, Virginia, and the District of Columbia 

 by Carpenter.^ The writer has isolated this fungus from decayed potato 

 tubers from the following localities in Idaho: Idaho Falls, Blackfoot, 

 Aberdeen, Rupert, Murtaugh, Twin Falls, Filer, Kimberly, Jerome, 

 Wendell, Gooding, King Hill, and Caldwell, and has observed the rot in 

 potato fields in many other localities in the State. The disease appar- 

 ently appears at its worst under dry-land-farming conditions and in raw 

 desert land planted to potatoes before having been in other crops. On 

 comparing rotted tubers collected by himself in Idaho with specimens 

 sent to the Department of Agriculture from California and Oregon he 

 was convinced that the rots were of one and the same nature. He has 

 also observed rots identical in outward appearance with those found in 

 Idaho, in Portland, Oreg., Seattle, Wash., and British Columbia. 



' Wollenweber, H. W. Identification of species of Fusarium occurring on the sweet potato, Ipomoea 

 batatas. In Jour. Agr. Research, v. 2, no. 4, p. 257. 1914. 



2 Carpenter, C. W. Op cit., p. 206. 



•■' Orton, W. .v. Potato diseases in San Joaquin County, Cal. U. S. Dept. Agr., Bur. Plant Indus. Circ. 

 23, 14 p. 1909. . 



* Wollenweber, H. W. Op. cit. 



' Carpenter, C. W. Op. cit. 



