Mayis, I9IS Phoma Betae 



177 



ENSILAGE 



The process of siloing infected beet tops has been found to be sufficient 

 to kill Phoma betae. In the ensilage experiments carried on during the 

 winters of 191 2 and 191 3 it was ascertained that the organism was viable 

 at the time the silage was made, but could not be isolated after the tops 

 had been ensiled for two months. A medium composed of somewhat 

 diluted silage material was also inimical to the growth of the fungus. 

 Detailed data will be published later in connection with the relation of 

 Cercospora beticola to ensiled beet tops. 



SUMMARY 



A typical spot of Phoma betae (Oud.) Fr. is light brovra in color, i to 2 

 cm. in diameter, and has scattered over its surface numerous pycnidia, 

 at times concentrically arranged. Such spots on a normal beet plant 

 usually appear during July and August on the old leaves near the ground. 

 If the plant is physiologically low, all except the heart leaves may become 

 infected. 



Phoma betae produces a characteristic infection on leaves that have a 

 stomatal count of 60 to 100 per sq. mm. of upper leaf surface. 



The pycnospores of the fungus may be disseminated by such agencies 

 as beet balls, wind, irrigation water, insects, and dung. 



The thermal death point of Phoma betae in the leaf tissue exposed for 

 one-half hour to dry heat is between 80° and 90° C. The fungus is dead 

 in infected leaves after three months' storage in soil in boxes exposed to 

 outdoor conditions, while its life becomes extinct in leaves buried in the 

 ground only after five to eight months, depending on the depth of cover. 

 The fungus can not survive the process of ensiling the beet tops. 



