i 7 8 
Journal of Agricultural Research 
Vol. XXVII, No. 4 
nubbin ears only (PL 2, A, B). Often imperfectly developed ears are 
observed at a number of nodes on a stalk and more frequently multiple- 
ear production occurs at one node (PI. 2, C), showing futile attempts at 
prolificacy. These manifestations, and large succulent stalks should be 
included, are the readily apparent symptoms associated with the black- 
bundle disease of com and can be noted in any commercial field. When 
plants having any of these symptoms are cut open, blackened vascular 
bundles can nearly always be found in the nodes and internodes near the 
base and sometimes throughout the stalk (PI. 1 and PI. 3, B). Occasionally 
the fundamental tissue outside the blackened vascular tissue becomes 
browned or blackened, but usually in only one internode of a stalk. 
However, the number of plants having these symptoms (excluding the 
black-bundle symptom) represents only a small part of the total number 
of plants affected by the disease. Plants, including the ears, may 
appear outwardly healthy and yet be infected from the crown to the 
tassel and every kernel on fine looking ears may have the organism in¬ 
ternally. In these cases the presence of the black vascular bundles 
within the stalks is the most distinguishing symptom. The ears may be 
diagnosed by plating the kernels or by germination in conjunction with 
microscopic examination. 
Apparently good seed ears selected from apparently normal stalks 
and producing 100 per cent of strong plants on the germinator may 
produce high percentages of purple plants in the field. No microscopic 
examination of seedlings on the germinator was made to determine 
infections. In these cases plant growth records during the first half 
of the season usually indicated strong rows. Table I shows in detail the 
record of an ear of the kind described and compares it with the records 
of four other ears. Among other things, it is an illustration of the 
statement that no appreciable indications of this group of symptoms 
are to be found during the first half of the growing season. 
Table I. —Field performance of an infected ear row (row 3) compared with adjacent 
uninfected ear rows; Funk Ninety-Day corn planted May 24, IQIQ, in brown silt loam 
soil of medium fertility, at Bloomington, III. 
Condition of seed and accession numbers of seed ears. 
Notations at different dates. 
Uninfected. 
Infected. 
Uninfected. 
Row 1, 
No. 5794 * 
Row, 2, 
No. 5831. 
Row 3, 
No. 5824. 
Row 4, 
No. 5887. 
Row 5, 
No. 5897. 
Stand and early vigor, June 13: 
Total stand. 
Z46 
123 
136 
i 43 
138 
Per cent stand. 
97 
82 
91 
95 
92 
Number strong plants. 
107 
61 
96 
108 
71 
Number weak plants. 
6 
11 
12 
7 
5 
Number blighted plants. 
1 
3 
0 
1 
1 
General condition. 
Good. 
Medium. 
Good. 
Good. 
Good. 
Condition, July 11 and 12: 
Color of foliage. 
Dark green. 
Dark green. 
Dark green. 
Dark green. 
Dark green. 
Uniformity of growth. 
Uniform. 
Variable. 
Uniform. 
Uniform. 
Uniform. 
Number leaning plants. 
3 
3 
2 
22 
16 
Condition, Aug. 6: 
Number plants with wilting or dead 
leaves. 
3 
IS 
5 
3 
27 
Preharvest data, Sept, ii: 
Number good ears. 
131 
99 
40 
133 
117 
Number mid-sized ears. 
1 
2 
10 
1 
6 
Number nubbins. 
2 
9 
18 
5 
2 
Number barren plants.*.. 
6 
22 
54 
2 
9 
Number smutted plants... 
6 
7 
7 
3 
2 
Number prematurely dead plants. 
0 
0 
7 
0 
a 
Percentage of purple plants. 
0 
0 
85 
0 
0 
Acre yield in bushels. 
90 
57-8 
27-4 
69.7 
62 
