Fusarium in Tuber Rot and Wilt of Potato 15 



tardy in coming up. Fusarium spp. were isolated from such lesions. 

 These lesions are identical in appearance with lesions found on 

 potato stems and roots in the field which often are designated as 

 "foot disease" and ascribed to the activity of Rhizoctonia. 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 F. trichothccioidcs, 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, but no inoculum was applied. 

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

 while the controls remained healthy. There was no spreading 

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

 inoculum was applied. 



The affected sprouts reminded one forcibly of affected sprouts 

 in potato fields in the spring. Here and there in the fields one 

 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 of 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, but whose sprouts 

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

 develop into branches on such decapitated sprouts, only to be 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 Rhizoctonia and bacteria. Infection experi- 

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

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



