3o6 Journal of Agricultural Research voi. vi, no. 9 



Wollenweber * reports the isolation of F. orthoceras from jelly-end tubers 

 and thought it the probable cause of the disease. The writer has twice 

 isolated F. trichothecioides from such tubers fresh from the field. 



Artificial infection of the growing tuber with F. trichothecioides under 

 western conditions has never been accomplished. Under conditions of 

 high humidity Jamieson and Wollenweber ^ were able to produce an 

 infection in the growing tuber wuth this fungus, but their results are 

 not believed to be indicative of what actually takes place in nature in 

 the irrigated West. Tubers infected with jelly-end rot, when kept in a 

 moist chamber for a few days, invariably threw out tufts of F. radici- 

 cola through the lenticels, although from these same tubers with well- 

 advanced stem-end rot other fungi, notably F. oxysporum, have been 

 isolated from the interior of the tuber. Carpenter ^ has shown that F. 

 oxysporum is capable of producing a similar rot of the potato tuber, 

 and from its frequent occurrence in connection with jelly-end-rot- 

 infected tubers it must be considered as one of the factors involved in 

 producing this type of rot. Other Fusarium species, either indepen- 

 dently or in conjunction with F. radicicola, may be in part responsible 



for the disease. 



STORAGE EXPERIMENTS 



In the fall of 1914 two ordinary 2 -bushel sacks filled with Netted 

 Gems infected with jelly-end rot were secured. With a soft blue pencil, 

 a line was drawn around each tuber in such a manner that the blue line 

 separated the decayed from the healthy tissue. The tubers were then 

 sacked and put in storage in the potato cellar of the Jerome Experiment 

 Station, at Jerome, Idaho. Fifty tubers each of Pearls and Idaho 

 Rurals infected with stem-end and lenticel blackrot were secured. On 

 each tuber a blue line was drawn around the stem end at the margin of 

 the infected and healthy tissues. Lenticel infections were marked in 

 the same manner. The marked Pearl and Idaho Rural tubers were 

 then sacked and placed in storage near the similarly treated Netted 

 Gems infected with jelly-end rot. 



The storage period was from November 15, 191 4, to April 12, 191 5. 

 The temperature of the cellar during this period ranged from 32° to 

 48° F. During the last six weeks of the storage period the minimum 

 temperature was 36°, and for the greater part of this time the tem- 

 perature approached the maximum of 48°. On April 12 the tubers 

 were removed from the sacks and examined one by one to determine 

 whether the rot had continued to develop. In no case could any per- 

 ceptible advance in the decay be found. It is apparent that neither jelly- 



' Wollenweber, H. W. Studies on the Fusarium problem. In Phytopathology, v. 3, no. i. p. 24-50. 

 I fig., pi. s. 1913- 



2 Jamieson, Clara O., and Wollenweber, H. W. An external dry rot of potato tubers caused by Fusa- 

 rium trichothecioides, WoUenw. In Jour. Washington Acad. Sci., v. 2, no. 6, p. 146-152, illus. 1912. 



« Carpenter, C. W. Op. cit. 



