148 Journal of Agricultural Research voi. iv, no. 2 



infections originating from the seed readily explain the source of the spores 

 producing the outbreaks of Phyllosticta, which appear to be much more 

 common in regions of low humidity, where, as Pool and McKay (34) have 

 shown, viable spores of this fungus are common in the air. In this con- 

 nection, attention should be especially called to observations during the 

 seasons of 1912 and 1913 in Colorado, Idaho, and Wisconsin, since they in- 

 dicate a direct connection between the occurrence of Phyllosticta on the 

 leaves and seed stalks of mother beets and the presence of Phoma on the 

 seed they produce. Phyllosticta was quite prevalent in the Idaho-Colorado 

 region, but escaped detection by the same observer in Wisconsin. Tests 

 upon seed produced in these regions during both seasons have shown 

 that the more western seed was quite generally infected to an extent 

 comparable to that from European sources, while that grown in Wis- 

 consin showed only a very slight infection. 



Pool and McKay, who kindly continued the observations at Madison 

 during the absence of the author in the season of 1914, found the Phyl- 

 losticta form on the leaves and stalks of seed beets and also on first-year 

 beets. In the absence of fruits the causal fungus was identified by cul- 

 tural methods. In other instances pycnidia were produced. The spots 

 were, as a rule, less clearly defined and less numerous than those in the 

 Idaho-Colorado region, which are similar to those seen in Europe in 1914, 

 where they were common on both field and mother beets. Since the 

 leaf form of the disease occurred in Wisconsin in 191 4, it is probably safe 

 to assume that it existed there on seed beets, undetected, in the two 

 preceding years. However, if the absence of Phyllosticta infection in 

 Wisconsin in 191 2 and 191 3 be assumed, the presence of the small amount 

 of Phoma betae on the seed produced there may still be accounted for in 

 at least three different ways. The seed balls may have been infected at 

 any time between blossom and maturity by air-borne spores developing 

 in the crown. The fungus may have spread from the crown of the 

 mother plants on the surface of the seed stalks to the racemes and infected 

 the fruit, or it may have passed through the vascular system of the stem 

 to the seed. 



CONTROL OF THE FUNGUS 



It is apparent that Phoma betae is one of the most serious obstacles 

 which the growers of beet seed in America have to face. Its ravages on 

 mother beets during the winter may be largely overcome by favorable con- 

 ditions of storage, but in case the mother beet escapes destruction the 

 infection remains to proceed to the leaves and seed stalks and to infect 

 the seed. Since the fungus sometimes inhabits the vascular region of 

 the root, it may possibly progress through the stem, as well as on the 

 surface. In any event, it is an undoubted fact that it finds its w^ay into 

 the young seed ball, where it starts with the seed upon another 2 -year 

 cycle. 



