May IS, 191S 



Phoma Betae 



173 



Table I. — Results of inoculating sugar-beet leaves of different ages with Phoma betae 

 and Phyllosticta betae — Continued 



" "Heart" leaves occupied the central portion of the plant. 



The data recorded in Table I (series 1,3, and 4) show that the old, 

 mature leaves of the sugar-beet plant or those leaves which are beginning 

 to yellow are the only ones that are susceptible to Phoma betae. In order 

 to corroborate this point, additional inoculations were made on leaves that 

 were deemed to be in this condition at the time of inoculating. Out of 48 

 inoculations with Phoma betae 32 typical spots were produced, and with 

 a like number of inoculations with Phyllosticta betae 23 infections devel- 

 oped. It will be noted in Table I (series 2) that the inoculations which 

 did not produce infections were made on leaves that were evidently not 

 correctly determined as to their degree of maturity, since, as a rule, they 

 had not yet attained this age at the time the infections should have 

 developed. The cultures in this series were obtained from reisolations 

 of Phoma and Phyllosticta infections of series i . 



The original cultures used for the inoculations with Phoma betae were 

 obtained from Mr. H. A. Edson, of the Bureau of Plant Industry, who 

 isolated the organism from rotted sugar beets kept in storage at Long- 

 mont, Colo. Those of Phyllosticta betae used in the inoculations were 

 obtained from heavily infected sugar-beet leaves that had been collected 

 in Colorado during the growing season of 191 3. Puncture inoculations 

 used exclusively in this experiment w^ere made from a suspension of 

 the pycnospores in sterile water. 



DISSEMINATION OF PHOMA BETAE 



Such agencies as beet balls,^ wind, irrigation water, insects, and dung 

 play an important part in the distribution of Phoma betae in the field. 



1 Edson, H. A. op. cit., p. 141. 



