Pethybbidge and Laffebty — Dry-Rot of the Potato Tuber. 199 



Pratt 1 calls the rot due to F. radicicola "a field black-rot," and states that 

 this fungus is capable of causing a jelly-end rot, but that under field condi- 

 tions other factors are in part responsible. Both black-rot and jelly-end rot 

 appear to be field rather than storage rots. 



Haskell 8 isolated F. eumartii from tubers affected with a heel-end form of 

 dry-rot in New York, and he proved as the result of pure culture inoculations 

 that this species was capable of producing not only a wilt of the plant but 

 also a rot of the tuber. 



It will be clear from what has been said that considerable attention has 

 been devoted during recent years in the United States of America to the 

 various types of potato tuber dry-rot found there, but further critical study is 

 necessary to clear up the important discrepancies which at present appear to 

 exist between the results obtained by the various authors. 



Before concluding this survey it is necessary to refer briefly to certain 

 recent publications which deal with the question of the pathogenicity of some 

 of the better known species of Fusarium towards the potato. 



Wollenweber & Schlumberger 3 maintained in 1911 that, of the five species — 

 F. Solani (Mart.) A. & W., F. cceruleum (Lib.) Sacc, F. orthoceras A. & W., 

 F. subulatum A. & W., and F. discolor A. & "W., all were incapable of causing 

 a rot in tubers. In the case of the first two species, however, the conidia 

 used for inoculation did germinate within the tubers and caused some local 

 decay which did not spread, and in no case led to the rot of the whole 

 tuber. 



In a later report 4 from the same institution it is stated that preliminary 

 infection experiments with species of Fusarium had shown that F. discolor 

 var. sulphureum (Schlecht) and F. cceruleum (Lib.) were the species which 

 most energetically attacked the tuber. F. subulatum App. & Wr. and 

 F. rubiginosum App. & Wr. did so to a less degree, while F. Solani (Mart.) 

 App. & Wr., F. Martii App. & Wr., and other species, gave negative results. 

 Further trials showed that F. discolor var. sulphureum was distinctly the most 

 active parasite, followed by F. subulatum, F. metachroum and F. cceruleum. 

 Nine other species are mentioned which caused some damage to inoculated 



1 Pratt, O. A. A western field-rot of the Irish potato tuber caused by Fusarium 

 radicicola. Journ. Agric. Research, vi. No. 9. 1916, p. 297. 



2 Haskell, R. J. Potato wilt and tuber-rot caused by Fusarium eumartii. Phyto- 

 pathology, vi. No. 4. 1916, p. 321. 



3 Wollenweber u. Schlumberger. Infektionsversuche mit kartoffelbewohnenden Pilze. 

 Mitt. K. Biol. Anstalt f. Land u. Forstwirtschaft. Heft. 11. 1911, p. 15. 



4 Appel u. Fuchs. Zur Kenntniss der Fusariumfaule der Kartoffeln. Mitt. K. Biol. 

 Anstalt, Heft 14. 1913, p. 16. 



