784 
Journal of Agricultural Research voi. xxiu. No. 10 
PLANT PARASITES 
Close observations have been made for evidences of bacteria and fungi. 
While the first group has not yet been found consistently associated with 
the disease at any stage of its development, certain fungi have been 
found under certain conditions associated with the diseased plants 
in the later stages of their development, and also with the plants in the 
fall previous to the development of the rosette disease in the spring. 
All of these parasitic forms, however, have been found associated 
to a greater or less extent with plants not showing rosette disease. 
Owing to the fact that the disease was not reported until rather late in 
the spring of 1919, investigations were not started until May of that 
year. Previous to starting the investigation and also afterwards, the 
pycnidia of Septoria tritici Desm. were found to be rather numerous on the 
leaves of many plants affected by rosette disease and also on the leaves 
of plants not showing the disease in question. This organism, however, 
was not consistently associated with all plants showing the rosette 
disease. In the spring of 1920 this organism was not often found in the 
field, probably on account of unfavorable winter conditions. During 
1921 it was again prevalent in the experimental plots and elsewhere. 
Although this organism seems to be a leaf parasite primarily, the ques¬ 
tion of its possible parasitic relation to the roots and crown of the wheat 
plant is being investigated. 
Upon starting the work in May, 1919, 14 it was found that a Helmintho- 
sporium of the Helminthosporium sativum type was almost always present 
within the tissues of diseased plants collected near Granite City, Ill., add 
the same organism was found associated to some extent with plants 
affected with the rosette disease from other parts of Illinois and from 
Indiana. On the other hand, the organism also was found rather prev¬ 
alent upon plants free from the rosette disease. Many other forms of 
fungi were isolated from the basal tissues of plants showing the advanced 
stages of the rosette disease, but these wer$ in the minority and less con¬ 
sistently associated with the diseased plants. 
At that time of year (May) the presence of Helminthosporium in the 
tissues of plants affected by rosette disease was not considered especially 
significant, as this organism was not confined to plants showing the dis¬ 
ease in question, or to the infested fields. Further, this organism had 
been known for a considerable time to be pathogenic on wheat, according 
to Johnson ( 13) and Bolley (r) and to be responsible for many of the wheat 
troubles in the winter- and spring-wheat belts, but these troubles differ 
in a number of respects from the rosette disease. 
During the season of 1920 an intensive field study of the disease was 
made by the writer. Observations were started on March 24, just as 
wheat was coming out of the dormant condition. As soon as the disease 
made its appearance (March 26) platings were made from the basal 
tiller and root tissue of both diseased and healthy plants. This plating 
was conducted by the writer in the field laboratory located at Granite 
City, Ill., and by Mr. R. W. Goss, then with the Office of Cereal Investiga¬ 
tions, located in the Department of Plant Pathology at the University of 
Wisconsin. Material used in the field laboratory was plated out within 
from one to two hours after the plants were taken from the soil. Material 
sent to the Wisconsin laboratories was collected just in time to make the 
11 Credit is due Mrs. Edith Seymour Jones for assistance in connection with the laboratory work done 
during the spring and summer of 19 iq » 
