.Mar. is, 1924 
Wheat Scab , Corn Rootrot, and Crop Successions 871 
vested. The acre yield of the disease-resistant com was 2.7 bushels, 
or 4.8 per cent, less on the field in which the previous crops of wheat, 
oats, and com had been grown, than on the virgin sod, while the acre 
yield of the disease-susceptible corn was 9.4 bushels, or 17.8 per cent, less. 
The difference in yield of 13 per cent, then, was due very likely to disease- 
producing organisms in the soil. But here again, as previously explained, 
the actual difference probably was a little larger on account of the fact 
that some reduction in yield of the resistant com also was chargeable to 
the attacks of Gibberella saubinetii. These data clearly indicate that 
ordinary susceptible dent corn may suffer a significant reduction in 
yield when grown after a crop of badly scabbed wheat. 
CORN INOCULATIONS WITH GIBBERELLA SAUBINETII 
THE ORGANISM 
During the season of 1919, over 2,000 scabbed wheat heads collected 
in the survey in the six States included in the rotation studies mentioned, 
as well as from seven other States, were sent to the laboratory at Madison, 
Wis., for identification of the organisms. As reported by Dickson, 
Johann, and Wineland (5), 94per cent of the scab was found to be caused 
by Gibberella saubinetii , while the remaining 6 per cent was caused prin¬ 
cipally by Fusarium culmorum var. leteius Sher. and Fusarium avenaceum 
(Fr.) Sacc. These latter came principally from northern Wisconsin and 
Minnesota where com is not generally grown. During that season no 
perithecia of Gibberella saubinetii could be found on any of the corn refuse 
in these northern sections, while in the Com Belt, perithecia of this 
fungus were very abundant. In 1920, a large number of scabbed wheat 
heads were collected from the States included in the Corn Belt and sent 
to Madison. During this season 98 per cent of the scab was found to be 
caused by Gibberella saubinetii , while most of the remaining 2 per cent 
was caused by Fusarium avenaceum. 
The isolation studies would indicate, therefore, that Gibberella saubinetii 
is the principal organism concerned. In fact, it probably is the only 
one of economic importance in the production of wheat scab in the 
United States and therefore has been used in all of the inoculation 
experiments. 
Inoculation experiments with corn growing under field conditions have 
been conducted for a number of years at Bloomington, Ill. It has been 
reported by Holbert, Dickson, and Biggar (9) that germination was 
lowered, early growth retarded, relative vigor throughout the season 
reduced, and grain production lessened by inoculation with Gibberella 
saubinetii. Since that report, inoculation experiments have been con¬ 
ducted on a larger scale and methods of technique have been improved. 
Some of the later results are given by Holbert et al. (12 6 ). The funda¬ 
mental facts first reported (9) have held true. Summarized data on 
some of the largest and most significant experiments will be given here. 
methods 
Experiments 7 were conducted in 1921 at Bloomington, Ill., with a 
strain of Gibberella saubinetii isolated from wheat kernels. The inocula¬ 
tions were made with 3-day-old cultures grown on potato dextrose agar 
6 Holbert, J. R., and others, op. cit. 
7 Merle T. Jenkins, Scientific Assistant, Office of Cereal Investigations, rendered valuable assistance in 
•conducting this experiment. 
