Apr. 3, 1916 Climatic Conditions and Cercospora beticola 25 



that had been slightly covered or buried from i to 5 inches in the ground 

 the life of the fungus was entirely extinct after 12 months (experiments 

 II to 18). The death of the fungus in material plowed under is due in 

 all probability to the rapid disorganization which results under favor- 

 able temperature and moisture conditions, such, for instance, as those 

 which prevailed at Rocky Ford through the winter of 191 2-13. During 

 that period there was insufficient moisture to permit severe freezing, 

 but there was a daily extreme variation of soil temperature, indicating 

 that the air temperature produced the changes through the more or less 

 dry soil. In the experiments at Madison there was only a partial dis- 

 integration of the buried beet tops six months after harvest, but other 

 factors impaired the vitality of the fungus and its life appeared to be 

 entirely extinct; consequently, notwithstanding the great differences in 

 soil factors, comparable results as to the life of the fungus were obtained 

 from the experiments at both places. 



Table II. — Effect of desiccation and overwintering on the viability of Cercospora beticola 

 in infected sugar-beet tops under field conditions at Rocky Ford, Colo., and Madison, 

 Wis. 



a Herbarium specimens for this test were furnished by Barrett, Illinois; Clinton, Connecticut; WheUel, 

 New York; Pammel, Iowa; Norton, Maryland; and Cook, New Jersey. 

 * 39S colonies. 



