570 Journal of Agricultural Research vol. vi, no. is 



in the laboratory room (23 ), and decay was completed in 10 days. 

 From these results there is a wide range of temperatures at which decay 

 by this organism will take place. It is apparent, however, that the 

 optimum lies somewhere between 32 to 35 and the minimum at 

 approximately 4 . The maximum temperature was not determined, 

 but in view of the fact that a slight decay of the blocks occurred in 

 chamber 20 (39. 3 ), it must be somewhat higher. 



It is interesting to note in this connection that the dasheens in most 

 of the chambers were more promptly decayed in this experiment than the 

 turnips. In other experiments of a similar nature both in the laboratory 

 room and in the thermostat chambers this has not always been the case. 

 In fact, it has frequently happened that the turnips, and carrots also 

 when they are included in the tests, were more promptly decayed than 

 the dasheens. While a strain (3616) originally obtained from dasheens 

 was used for inoculating the blocks, turnips and carrots inoculated with 

 this strain in moist chambers were generally more speedily decayed than 

 dasheens. While no positive explanation of such a condition will be 

 attempted, it has been apparent throughout the whole course of the 

 work that the condition of the material when used plays no little part 

 in the results to be obtained. It has been noticed that fresh turnips 

 and carrots decay after inoculation more readily than those that have 

 been kept in the ice box or elsewhere under conditions permitting the 

 escape of moisture and eventual withering. Dasheens, on the other 

 hand, lose moisture more slowly and remain suitable for such experiments 

 a much longer time. 



SUMMARY 



(1) There are four storage rots of economic aroids: Java blackrot 

 caused by Diplodia tuber icola, Diplodia maclurae, Diplodia gossypina, 

 and Diplodia sp. from Mangifera indica; powdery gray rot caused by 

 Fusarium solani; sclerotium-rot caused by Sclerotium rolfsii; and 

 softrot caused by Bacillus carotovorus. 



(2) All of the species of Diplodia cause a rot identical in character. 



(3) All the causal organisms are wound parasites. 



(4) The parasitism of each organism has been established by inocula- 

 tion experiments. 



(5) F. solani from the Irish potato produces a rot identical with the 

 rot produced by F. solani from the dasheen. 



(6) Several other organisms were studied, none of which were found 

 parasitic. 



(7) The Java blackrot organism produced decay better under relatively 

 dry conditions. 



(8) It was necessary to apply sterile water once or twice to the tubers 

 and corms after inoculation with F. solani, S. rolfsii, and B. carotovorus. 

 After decay had started, no further application of water was required. 



