STUDIES OF DISEASE PRODUCING SPECIES OF FUSARIUM. 2.0"] 



Fusarium may attack the apple fruit in 2 ways. Both of 

 the species isolated in 1908 were first found growing in wounds 

 on the surface of the fruits. Associated with them were other 

 fungi, part of which proved to be parasites and part saprophytes 

 when inoculations were made into apple fruits. Later each of 

 the two species was found growing in the cavity around the 

 seeds and spreading into the surrounding tissues to cause decay 

 just as Osterwalder described for F. putrefaciens. In such 

 cases the fungus enters the seed cavities through the canal which 

 extends down from the blossom end and which does not become 

 closed in some varieties. Apples which appear sound may show 

 when cut open a growth of mycelium around the seeds. If such 

 apples are kept in cold storage, the fungus cannot grow but 

 when the apples are subjected to a higher temperature for sev- 

 eral days the mycelium spreads into the surrounding tissues 

 causing the loss of the fruit. Either F I or F II may be respon- 

 sible for such decay. As will be shown later Fusarium forms 

 from a nurrtber of sources are capable of causing rot of apple 

 fruits upon inoculation but these two species are the only ones 

 which have been found to occur on the fruit in nature to such 

 an extent as to cause much loss. A third form was isolated 

 from a decaying apple in 1909 but has not been found again. 



While these species of Fusarium are to be regarded as causes 

 of storage rot of ripe apples, that part of the infection which 

 takes place through the blossom end probably occurs in most 

 cases before the apples are placed in storage. In some cases, 

 infection through wounds may also occur before harvesting as 

 in apples injured by insects or by hail. Wounds caused by rough 

 handling also serve as a place of entrance for these as for other 

 rot fungi. In a few cases green apples on the tree showing 

 growth of Fusarium on wounded places have been found. Fig. 

 105 shows the appearance of such an apple. The fungus was 

 isolated from this apple and has been grown for more than two 

 years in comparison with Fusarium I with the result that the two 

 strains are regarded as belonging to the same species. This 

 has been isolated a number of times from apples. In one lot of 

 Milden apples which were under observation in 1912 mycelium 

 of a Fusarium was found in the core in many cases. Later an 

 attempt was made to isolate the fungus from each of 20 of the 

 apples which were either partially or wholly decayed and in 



