Fusarium in Tuber Rot and Wilt of Potato 15 



tardy in coming up. Fusarium spp. were isolated from such les- 

 ions. These lesions arc identical in appearance with lesions found 

 on potato stems and roots in the field winch often are designated as 

 "foot disease" and ascribed to the activity of Rhisoctonia. Late 

 in May other series were started and the soil was infected with rice 

 and spore suspensions. No infections resulted at all. even though 

 the inoculum was derived from the same source as that used in 

 earlier experiments. 



On March 12. sprouts that were just breaking through the 

 ground were uncovered and smeared with rice infected either with 

 F. oxysporum or with /•. trichothecioides, 6 sprouts being used in 

 each set. The plants were wounded no more than was inevitable 

 in removing- the soil. The soil was then replaced. The soil in the 

 controls was removed in the same way, hut no inoculum was applied. 

 Idle 12 sprouts to which inoculum had been applied were killed, 

 while the controls remained health). There was no spreading 

 of the disease to other sprouts, even where an abundance of 

 ini iculum was applied. 



The affected sprouts reminded one forcibl) of affected sprouts 

 in potato fields in the sprint;. Mere and there in the fields ne 

 finds sprouts that look sickly and small, which usually wilt and die 

 or remain sickly and small. Upon examination of such sprouts, 

 prominent brownish, watery lesions are found. At times such 

 sprouts overcome the trouble and make a fair growth, at least 

 until transpiration becomes excessive. These lesions also account 

 for many of the "poor stands" or failures id" potatoes to come 

 up evenly. If one digs in where a sprout ought to have come up, 

 one can often find a tuber that has sprouted, hut whose sprouts 

 have been cut off entirely by such lesions. Often lateral buds 

 develop into branches on such decapitated sprouts, only to he cut 

 off again. If such a tuber finally manages to get a shoot above the 

 ground, the shoot is sickly and backward. In 1912, 1913, and 1914 

 the writer plated the inner tissue of many such sprouts and almost 

 invariably obtained cultures of various Fusarium spp., although 

 often associated with Rhisoctonia and bacteria. Infection experi- 

 ments conducted with Rhisoctonia in 1912-1913 gave almost uni- 

 formly negative results. The writer was at first inclined to refer 



