STUDIES OF DISEASE PRODUCING SPECIES OF FUSARIUM. 25 1 



When it is considered that a vast number of spores may be 

 produced on one diseased bud the necessity for great care in 

 this work becomes apparent. 



Summary. 



Species of Fusarium occur on a large number of host plants. 

 A part of these fungi are destructive parasites. Ov^^ing to the 

 confused condition or the classification of the species of this 

 genus it is frequently difficult to distinguish a parasitic species 

 from a saprophyte which has some similar characteristics. In 

 many cases the same fungus has been described under a number 

 of different names. In order to compare the fungi from differ- 

 ent sources, it is necessary to grow them in culture under the 

 same conditions. However, there is a wide difference in the 

 value of different media for this purpose. Liquid media and 

 agars give an abnormal growth as compared with the growth of 

 the fungus on more favorable media such as cylinders of vege- 

 tables and other plant parts. Wollenweber * considers stems 

 of plants the best medium for normal development of species of 

 Fusarium. 



In order to determine the extent of the parasitism of a given 

 species it is necessary to carry out inoculation experiments. In 

 some cases the same morphological species occurs on more than 

 one host plant and it is only by inoculations that the question 

 can be answered as to whether the strains occurring on one host 

 can cause disease in another. 



Two species of Fusarium have been isolated from Maine 

 apples and it has been found that each of these is capable of 

 causing decay. One of these, F I, agree quite closely with the 

 organism received as F. piitrefacicns, and which was described 

 by Osterwalder as a cause of apple decay in Europe. The same 

 fungus was isolated from diseased glumes of wheat, F VIII, 

 and from potato stem, F XXXVIII. These strains also caused 

 rot of apple fruit upon inoculation. One of the species, F II 

 and F IV, from apple produces o'bovate spores similar to conidia 

 of Sporotrichum in addition to typical septate Fusarium spores. 

 This fungus resembles very closely in cultural characters the 

 fungus which was described as the cause of a rot of carnation 



* Wollenweber, H. W. Studies on the Fusarium Problem. Phyto- 

 pathology 3 : 25, 1913. 



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