PROGRESS REPORT ON THE EUROPEAN CORN BORER 
53 
was made between the production of ears and nubbins by infested 
and noninfested plants growing in each of seven fields. Examina- 
tions were made in representative parts of each field, all the plants 
in a section of row being examined. The results are shown in 
Table 12. 
Table 12. — Effect of injury to stalks of sweet com upon the number of market- 
able ears produced 
Field 
No. 
Variety- 
Per 
cent 
stalks 
in- 
fested 
Per 
cent 
ears 
in- 
fested 
Total 
plants 
exam- 
ined 
in 
each 
lot 
Infested 
plants 
Noninfested 
plants 
Loss in mar- 
ketable ears 
Town (Mass.) 
Num- 
ber 
of 
mar- 
ket- 
able 
ears 
Num- 
ber 
of 
nub- 
bins 
Num- 
ber 
of 
mar- 
ket- 
able 
ears 
Num- 
ber 
of 
nub- 
bins 
Num- 
ber 
Per 
cent 
1 
2 
3 
4 
5 
6 
7 
Golden Bantam. .. 
Early Crosby 
Quincy Market ... 
Golden Bantam, __ 
do 
58 
35 
47 
100 
86 
94 
63 
18 
17 
11 
52 
66 
36 
37 
25 
25 
25 
200 
200 
200 
200 
41 
27 
47 
190 
110 
232 
236 
32 
35 
35 
130 
92 
92 
107 
49 
39 
47 
263 
193 
248 
264 
26 
28 
40 
129 
52 
80 
124 
8 
12 

73 
83 
16 
28 
16.33 
Medford 
30.77 
Do- 
0.00 
Do 
27.76 
43.01 
Do 
Golden Giant 
Golden Dawn 
6.45 
Do 
10.61 
Total- 
875 
883 
1523 
1,103 
479 
220 
Average 
::.... 
19.94 
i 
1 Increase in nubbins of infested plants equals 9.1 per cent. 
All of these fields were of the early plantings and the infestation 
consisted almost entirely of first-generation individuals. The data 
for fields 1 to 3 were obtained in 1921, and for fields 4 to 7 in 1922. 
In field 4 it was necessary to include a number of slightly infested 
plants among the " noninfested " group owing to the difficulty of 
finding strictly noninfested plants. 
Table 12 indicates that in the fields under consideration there 
was a reduction of 19.94 per cent in the number of marketable 
ears produced by infested plants as compared with the noninfested 
plants in the same fields. An increase of 9.19 per cent of nubbins 
was noted as a result of corn-borer injury to the plants. 
In fields of sweet corn showing maximum infestation (figs. 24 
and 25 ) the reduction in marketable ears was much more pronounced 
than these figures indicate. In such areas, however, practically 
100 per cent of the plants were badly infested, which fact did not 
permit an accurate comparison between ear production of infested 
and noninfested plants. 
PERCENTAGE OF BROKEN-OVER STALKS AND EAR STEMS DUE TO LARVAL INJURY 
Reference has previously been made to the breaking over of stalks 
and ear stems as a result of the tunneling of corn-borer larvae. 
Although the effect upon grain formation of such breaking over is 
exceedingly variable, and no definite economic importance can be 
assigned to this type of injury, it was thought desirable to present 
figures showing the extent of its occurrence. The counts shown 
in Table 13 were obtained from examinations of average stalks and 
ears in the experimental plats of flint and dent corn at Medford, 
Mass., during 1920. 
