Mar. i S . 1924 Wheat Scab , Corn Rootrot , and Crop Successions 877 
Fable X. —Data showing the field stands, percentages of vigorous plants, and acre yield 
from disease-susceptible and disease-resistant strains of Yellow Dent corn uninoculated 
and inoculated with Gibberella saubinetii, when grown on bluegrass sod at Blooming¬ 
ton, III., in 1921 
Character of 
corn. 
Seed inoculation. 
Num¬ 
ber of 
re¬ 
plica¬ 
tions. 
Number 
of 
plants. 
Per 
cent- 
age of 
field 
stand. 
Per 
cent- 
age of 
vigor¬ 
ous 
plants. 
Acre yield. 
Reduction in yield 
caused by inocu¬ 
lation. 
Disease-sus¬ 
ceptible. 
Disease-sus¬ 
ceptible. 
Disease-re¬ 
sistant. 
Disease-re¬ 
sistant. 
f Control. 
8 
4 
8 
4 
28 
14 
28 
14 
888 
386 
878 
38 s 
3,300 
572 
3, 2 59 
i ,556 
92.5 
80. 4 
9 i- 5 
80. 2 
98. 2 
93-6 
97.0 
92.6 
79.6 
59-4 
75-8 
S®- 9 
90.4 
80. 9 
87. 2 
78.2 
Busheh. 
59. i±i. 1 
48. 6± 1. 9 
54. 6±i. 4 
44 - 7 ±i. 3 
74 . 2 ± 0 . 9 
71. 6±i. 3 
72. i±o. 9 
7 o. 4 ±i. 1 
Bushels . 
Per ct. 
\G. saubinetii.. 
/ Control. 
IO. 5±2. 2 
17. 8 
\G. saubinetii.. 
(Control. 
9. 9 ±I. 9 
18. 1 
\G. saubinetii.. 
/ Control. 
2. 6±i. 6 
3-5 
\G. saubinetii.. 
1. 7±i. 4 
2.4 
CROP ROTATION FOR THE CORN BEET 
It is evident that wheat should not follow com in a rotation if wheat 
scab is to be held in check. Even though the stalks are removed and the 
field is plowed, some corn stubble will not be turned under and some will 
be pulled up again by the harrow. The wheat-scab infection hr this case 
will be mudi less than if most of the cornstalks were left on the field, but 
it will be higher than it would be if there had been no com preceding the 
wheat. 
In a four-year rotation, including one year of com and one year of 
wheat, there would be considerable advantage from the standpoint of 
controlling wheat scab and com rootrots in arranging the rotation so that 
the wheat will neither directly precede nor follow the com crop. Other 
small grains such as oats or barley, soybeans, clover or other legumes, or 
timothy, would be desirable to use as the intervening crops, as they are 
either immune or generally only slightly susceptible to the attacks of 
Gibberella saubinetii. 
In large parts of the Corn Belt it may be desirable to grow com more 
frequently than one year in four. In that case it seems best to use a five- 
year rotation with two years of com in succession. For the other three 
years the same plan as above can be followed. 
Some people insist on using a rotation of two years’ com in every four, 
with wheat as one of the intervening crops. In that case the wheat 
should immediately precede rather than follow the com crop, taking care 
to use the best disease-resistant seed com obtainable. It seems doubtful, 
however, whether a crop rotation of 50 per cent corn can be recommended 
from the standpoint of permanent crop improvement. 
SUMMARY 
Wheat scab was most severe where wheat followed corn in the rotation. 
The yield of com susceptible to rootrot was considerably reduced 
where corn followed badly scabbed wheat in the rotation. 
85606—24-6 
