May 15, jgis Seedling Diseases of Sugar Beets 147 



since Phyllosticta spots were at no time observed upon the foliage of the 

 beets in question, which were grown in isolation and were under daily 

 observation. The following season (191 3) inoculations were made on 

 beets grown outdoors at Madison, Wis., in pots filled with soil from Garden 

 City, Kans., from Rocky Ford, Colo., and from Madison, Wis. Other 

 beets grown in the usual way in the field at Madison, at Garden City, and 

 at Rocky Ford were inoculated. In all cases this was done by placing a 

 large fragment of actively growing culture on sterilized beet blocks upon 

 the crown of the beet near the heart and a second portion in direct con- 

 tact with an abrasion on the crown just beneath the surface of the soil. 

 Through the courtesy of colleagues at Garden City and Rocky Ford it 

 was possible to have the beets watched at these points as carefully as 

 were those at Madison. At no time during the season did evidence of 

 infection appear on any of the beets under observation. 



Two lots of beets were grown in 191 3 from pasteurized seed. One lot 

 was isolated from other beets so as to be protected from infection. These 

 beets were stored in the fall in a warm basement, which offered very 

 favorable conditions for the development of Phoma storage-rot, as shown 

 by previous experience. They were examined from time to time during 

 the winter, spring, and summer for evidences of Phoma betae, with nega- 

 tive results. 



The other lot of seed was sown in proximity to breeding stock and 

 mother plants known to be infected with Phoma betae, and stored in a 

 cellar with infected material. These beets developed Phoma rot during 

 the winter. Phyllosticta appeared on seed plants grown from some of 

 these roots during the summer of 1914, and the seed produced was found 

 to carry the pycnidia and spores of Phoma. 



PERPETUATION OF THE FUNGUS 



The results of the various experiments coupled with field observations 

 lead to the opinion that Phoma betae is capable of infecting Beta vulgaris 

 L. only during periods of especial susceptibility, such as the early seed- 

 ling stage, or, in the case of the leaf, during physiological old age. It 

 may also be that the root is susceptible to infection during periods of low 

 vitality induced by unfavorable environment, but experimental proof is 

 lacking. It does appear, however, that this fungus is entirely capable 

 of living for a long time in a hidden condition upon the crown of the 

 beet, ready to take advantage of any diminished vitality in its host. 

 After infection has once occurred, the parasite may remain present in a 

 viable though inconspicuous condition, although the host appears to have 

 completely overcome the disease. The Phoma field-rot in the summer 

 and fall of 1913, in Wisconsin and Colorado, respectively, developing in 

 the first instance under conditions of excessive moisture and in the sec- 

 ond under severe drought, may be explained in this way. The crown 



