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The
Effectiveness of Bt-corn Varieties
for the Control of European Corn Borer
in Illinois, 2000 |
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John T. Shaw,Kevin
L. Steffey,and Michael E. Gray
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Summary |
A
trial was established near the University
of Illinois, Champaign, to compare the
effectiveness of different Bt-corn varieties
with their non-Bt corn isolines for
control of European corn borer. At least
70% of the non-Bt plants were injured
by corn borers. All Bt varieties had
significantly less damage and fewer
European corn borer larvae than most
of the non-Bt isolines for all parameters
measured. Few differences were observed
among Bt varieties. However, CBH-351
Bt had a significantly higher percentage
of plants injured (27.5%) than the other
Bt hybrids. |
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Plot Information and Methods
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Location
University of Illinois Cruse Farm, Champaign,
Illinois.
Plot Size
Four rows 25 ft for each treatment,
with 30 plants per row after thinning.
Between each of the replications was
a 10-ft alley.
Experimental
Design
Randomized complete block with four
replications.
Planting
Date and Agronomic Factors
Refer to Table 6.1.
Manual
Infestation of European Corn Borer Larvae
Manual infestations of European corn
borer (ECB) larvae were made to all
plants in each of the middle two rows
of each four-row plot. Manual infestations
to simulate the first-generation were
made on July 11 and 12 by applying five
egg masses (black-head stage) per plant
whorl on each of the two days. Corn
plants were in the V6 leaf stage (Ritchie
et al. 1993). Manual infestations to
simulate the second generation were
made to the same plants in the same
two rows, at corn anthesis (V18 - VT
corn stage, Ritchie et al. 1993). Three
egg masses (black-head stage) per plant
per day were applied on August 16 and
18.
Post-Infestation Evaluations of Injury
Caused by First- and Second-Generation
ECB
Evaluation of first-generation corn
borer injury:
On July 31, 10 plants in each of the
center two rows that had been manually
infested were evaluated using the 0-9
modified Guthrie scale:
0 No visible leaf feeding
1 Small amount of pin-hole or fine
shot-hole injury on a few leaves
2 Small amount of shot-hole injury
on a few leaves
3 Shot-hole injury common on several
leaves
4 Several leaves with shot holes
and elongated lesions
5 Several leaves with elongated lesions
6 Several leaves with elongated lesions
about 2.5 cm long
7 Long lesions common on about one-half
of the leaves
8 Long lesions common on about two-thirds
of the leaves
9 Most leaves with long lesions
Evaluations of first- and second-generation
corn borer injury:
On September 9 and 10, five corn plants
from each of the middle two rows were
split with a corn knife for evaluation.
Evaluations of injury to the ear, ear
shank, stalk above the ear, and stalk
below the ear were recorded separately
for each plant. The mean percentages
of plants with cavities, mean numbers
of cavities per plants, mean lengths
of stalk tunneling (cm) per plant and
mean numbers of live larvae per plant
were recorded.
Weather
Information
Refer to Appendix A, Tables
A.1, A.2,
A.3.
Statistical Analysis
Data were analyzed with Agriculture
Research Manager (ARM) version 6.1.6,
from Gylling Data Management, Inc. (GDM).
Means were separated by Duncan’s
New Multiple Range Test (MRT) (P = 0.05).
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Results and Discussion |
All plots were examined periodically
throughout the growing season for signs
of infestation and/or injury caused
by insects other than European corn
borer. Nothing was found in sufficient
quantity to analyze, so the data are
not presented.
Results from evaluations of first-generation
European corn borer injury are presented
in Table 6.2. The mean Guthrie ratings
for all Bt hybrids were significantly
lower than the mean Guthrie ratings
for the non-Bt isolines. There were
no significant differences in Guthrie
ratings among the Bt hybrids tested.
The percentages of plants injured by
European corn borer larvae are presented
in Table 6.3. The mean numbers of larvae,
mean numbers of cavities, and mean cavity
lengths (cm) per plant are presented
in tables 6.3 (whole plant), 6.4 (plant
below the ear), and 6.5 (plant above
the ear). The mean numbers of larvae
per shank and ear, mean numbers of cavities
per shank, and mean percentage of ears
injured are presented in Table 6.6.
The percentages of non-Bt plants with
injury caused by European corn borer
larvae indicated that the infestation
in our trial was severe; 70 to 100 %
of the non-Bt plants were injured (Table
6.3). The percentages of plants injured
by corn borer larvae were significantly
lower for all Bt hybrids than for all
non-Bt isolines. One Bt hybrid (CBH-351)
had a significantly higher percentage
of injured plants than the other Bt
hybrids. All Bt hybrids had significantly
fewer cavities per plant than the non-Bt
isolines. The mean numbers of larvae
per plant were significantly lower in
all Bt hybrids than in all but two non-Bt
isolines (LEPOTD 11 and CBH-351 non-Bt).
There were no significant differences
in mean numbers of larvae per plant
among the Bt hybrids. The mean cavity
lengths per plant were significantly
lower in all Bt hybrids than in all
but one non-Bt isoline (LEPOTD 11).
There were no significant differences
in mean cavity length per plant among
the Bt hybrids.
Evaluations of the amount of injury
below and above the ears are presented
in tables 6.4 and 6.5, respectively.
The mean numbers of larvae per plant
and mean numbers of cavities per plant
below the ear for all Bt hybrids were
significantly lower than in all but
one non-Bt isoline (Y non-Bt–larvae;
CBH-351 non-Bt–cavities) (Table
6.4). There were no significant differences
in numbers of larvae or numbers of cavities
per plant below the ear among the Bt
hybrids. The mean cavity lengths per
plant below the ear for all Bt hybrids
were significantly lower than in all
but two non-Bt isolines (LEPOTD 11 and
CBH-351 non-Bt) (Table 6.4). There were
no significant differences in mean cavity
lengths per plant below the ear among
the Bt hybrids.
The mean numbers of larvae per plant
above the ear for all Bt hybrids were
significantly lower than in all but
two non-Bt isolines (Y non-Bt and CBH-351
non-Bt) (Table 6.5). There were no significant
differences in numbers of larvae per
plant above the ear among the Bt hybrids.
The mean numbers of cavities per plant
above the ear for all Bt hybrids were
significantly lower than in all but
one non-Bt isoline (CBH-351 non-Bt)
(Table 6.5). There were no significant
differences in numbers of cavities per
plant above the ear among the Bt hybrids.
The mean cavity lengths per plant above
the ear for all Bt hybrids were significantly
lower than for all non-Bt isolines (Table
6.5). There were no significant differences
in mean cavity lengths per plant above
the ear among the Bt hybrids.
Evaluations for numbers of European
corn borer larvae and amount of injury
to shanks and ears are shown in Table
6.6. There were no larvae, and consequently
there was no injury in any of the shanks
of the Bt hybrids. The numbers of larvae
and numbers of cavities in the non-Bt
isolines were very low. No corn borer
larvae were found in any of the ears
of the Bt hybrids. However, 2.5% of
the ears of one Bt hybrid (CBH-351 Bt)
have evidence of injury, although not
significantly more than the amount of
injury in the other Bt hybrids. There
were no significant differences in the
mean numbers of larvae and mean numbers
of cavities per shank, the mean numbers
of larvae per ear, and the mean percentages
of ears injured among the Bt hybrids.
Few stalks were broken either above
or below the ears, and no ears were
found on the ground at evaluation time.
Also, we observed no differences in
the amount of stalk rot at the time
of evaluation.
Similar to our results from Bt-corn
efficacy trials in the past, the Bt-corn
varieties in this year’s trial
were quite effective in reducing the
numbers of European corn borer larvae
and the amount of injury they caused
to the stalks, shanks, and ears. However,
CBH-351 Bt had a significantly higher
percentage of plants injured (27.5%)
than the other Bt hybrids.
Reference Cited
Ritche, S.W., J.J. Hanway, and G.O.
Benson. 1993. How a corn plant develops.
Special Report No. 48, Iowa State University
of Science and Technology, Cooperative
Extension Service, Ames |
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Table 6.1. |
Agronomic
factors and evaluation dates for the
Bt-corn efficacy trial for control of
European corn borer Champaign, Illinois,
2000 |
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Variables |
Urbana |
| Planting
date |
June
9, 2000 |
| Hybrids
|
Various
Bt and Non-Bt hybrids |
| Plant
population |
30
plants per 25 row feet after thinning
|
| Row
spacing |
30
in |
| Soil
condition (top 2-3 inches) |
Moist
|
| Soil
temperature (4-inch level) |
68o
F |
| Air
temperature |
79o
F |
| Wind
|
0—5
mph |
| Previous
crop |
Soybeans
|
| Soil
insecticide |
None
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| Herbicides
|
Dual
+ Atrazine |
| Infestation
dates |
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First generation |
July
11 and 12, 2000 (V6 plant stage)
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5
egg masses per plant per date
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Second Generation |
August
16 and 18 (Anthesis) |
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3
egg masses per plant per date
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| Evaluation
dates |
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| Guthrie
Rating |
July
31, 2000 |
| Stalk
splitting |
September
9 and 10, 2000 |
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Table 6.2. |
Guthrie
ratings for the Bt-corn efficacy trial
for control of first-generation European
corn borer Champaign, Illinois, 2000 |
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Treatment1 |
Guthrie rating2
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Cry 1F / TC1507 / M2722 |
0.01 |
c |
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M2722 non-Bt isoline |
5.70 |
a |
|
Y Bt |
0.05 |
c |
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Y non-Bt isoline |
5.60 |
a |
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LEPOTD 11 non-Bt |
0.55 |
c |
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LEPOTD 12 |
0.00 |
c |
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LEPOTD 13 |
0.05 |
c |
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LEPOTD 14 |
0.00 |
c |
|
LEPOTD 18 |
0.15 |
c |
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LEPOTD 19 non-Bt |
5.95 |
a |
|
CBH-351 Bt |
0.10 |
c |
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CBH-351 non-Bt isoline |
3.80 |
b |
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1
Cry 1F and its isoline was supplied
by Dow AgroSciences; all LEPOTD hybrids
were supplied by Monsanto; and the
CBH-351 hybrids were supplied by Aventis.
2 The modified Guthrie
rating scale is explained in the text.
Means in a column followed by the
same letter are not significantly
different (P=0.05; Duncan’s New
MRT) |
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Table 6.3. |
Mean
numbers of larvae, cavities, and cavity
length (cm) per plant for the Bt-corn
efficacy trial for control of first
and second-generation European corn
borer Champaign, Illinois, 20001,
2000 |
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| Treatment |
% Injured plants
|
Mean no. of
larvae per plant |
Mean no. of
cavities per plant |
Mean cavity
length (cm) per plant |
| Cry
1F / TC1507 / M2722 |
0.0
|
e |
0.0
|
c |
0.0
|
d |
0.0
|
e |
| M2722
non-Bt isoline |
92.5
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ab
|
0.8
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b |
2.3
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bc
|
8.2
|
bc
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| Y Bt
|
2.5
|
e |
0.0
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c |
0.1
|
d |
0.1
|
e |
| Y non-Bt
isoline |
100.0
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a |
1.2
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b |
2.8
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b |
10.5
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b |
| LEPOTD
11 non-Bt |
70.0
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c |
0.6
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bc
|
1.7
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c |
3.3
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de
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| LEPOTD
12 |
5.0
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e |
0.0
|
c |
0.1
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d |
0.1
|
e |
| LEPOTD
13 |
2.5
|
e |
0.0
|
c |
0.0
|
d |
0.0
|
e |
| LEPOTD
14 |
2.5
|
e |
0.0
|
c |
0.0
|
d |
0.0
|
e |
| LEPOTD
18 |
0.0
|
e |
0.0
|
c |
0.0
|
d |
0.0
|
e |
| LEPOTD
19 non-Bt |
96.7
|
a |
2.0
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a |
4.8
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a |
15.2
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a |
| CBH-351
Bt |
27.5
|
d |
0.1
|
c |
0.3
|
d |
1.0
|
e |
| CBH-351
non-Bt isoline |
80.0
|
bc
|
0.7
|
bc
|
1.7
|
c |
5.5
|
cd
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1 Cry 1F and its
isoline was supplied by Dow AgroSciences;
all LEPOTD hybrids were supplied by
Monsanto; and the CBH-351 hybrids were
supplied by Aventis.
2 Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT) |
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Table 6.4. |
Mean
numbers of, larvae, cavities, and cavity
length (cm) per plant, below the ear
for the Bt-corn efficacy trial for control
of first and second-generation European
corn borer Champaign, Illinois, 2000 |
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Treatment2 |
Injury below
the ear1 |
|
Mean no. of
larvae per plant |
Mean no. of
cavities per plant |
Mean cavity
length (cm) per plant |
|
Cry 1F / TC1507 / M2722 |
0.0 |
d |
0.0 |
e |
0.0 |
d |
|
M2722 non-Bt isoline |
0.5 |
bc |
1.3 |
c |
4.7 |
b |
|
Y Bt |
0.0 |
d |
0.1 |
e |
0.1 |
c |
|
Y non-Bt isoline |
0.9 |
b |
2.1 |
b |
8.0 |
a |
|
LEPOTD 11 non-Bt |
0.1 |
cd |
0.5 |
de |
0.9 |
c |
|
LEPOTD 12 |
0.0 |
d |
0.1 |
e |
0.1 |
c |
|
LEPOTD 13 |
0.0 |
d |
0.0 |
e |
0.0 |
c |
|
LEPOTD 14 |
0.0 |
d |
0.0 |
e |
0.0 |
c |
|
LEPOTD 18 |
0.0 |
d |
0.0 |
e |
0.0 |
c |
|
LEPOTD 19 non-Bt |
1.3 |
a |
3.2 |
a |
10.4 |
a |
|
CBH-351 Bt |
0.1 |
d |
0.3 |
e |
0.8 |
c |
|
CBH-351 non-Bt isoline |
0.4 |
bcd |
1.1 |
cd |
3.5 |
b |
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1 Means
in a column followed by the same letter
are not significantly different (P=0.05;
Duncan’s New MRT).
2 Cry 1F and its isoline
was supplied by Dow AgroSciences;
all LEPOTD hybrids were supplied by
Monsanto; and the CBH-351 hybrids
were supplied by Aventis |
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Table 6.5. |
Mean
numbers of larvae, cavities, and cavity
length (cm) per plant above the ear
for the Bt-corn efficacy trial for control
of first and second-generation European
corn borer Champaign, Illinois, 2000 |
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Treatment2 |
Injury above
the ear1 |
|
Mean no. of
larvae per plant |
Mean no. of
cavities per plant |
Mean cavity
length (cm) per plant |
|
Cry 1F / TC1507 / M2722 |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
M2722 non-Bt isoline |
0.3 |
bc |
1.0 |
bc |
3.5 |
ab |
|
Y Bt |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
Y non-Bt isoline |
0.4 |
bc |
0.7 |
bc |
2.4 |
bc |
|
LEPOTD 11 non-Bt |
0.4 |
ab |
1.1 |
ab |
2.3 |
bc |
|
LEPOTD 12 |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
LEPOTD 13 |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
LEPOTD 14 |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
LEPOTD 18 |
0.0 |
c |
0.0 |
d |
0.0 |
d |
|
LEPOTD 19 non-Bt |
0.7 |
a |
1.6 |
a |
4.7 |
a |
|
CBH-351 Bt |
0.0 |
c |
0.1 |
d |
0.1 |
d |
|
CBH-351 non-Bt isoline |
0.2 |
bc |
0.5 |
cd |
2.0 |
c |
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1Means
in a column followed by the same letter
are not significantly different (P=0.05;
Duncan’s New MRT).
2 Cry 1F and its
isoline was supplied by Dow AgroSciences;
all LEPOTD hybrids were supplied by
Monsanto; and the CBH-351 hybrids
were supplied by Aventis. |
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Table 6.6. |
Mean numbers of larvae
and cavities per shank, and mean numbers
of larvae per ear and of ears injured
percentage for the Bt-corn efficacy
trial for control of first and second-generation
European corn borer Champaign, Illinois,
2001 |
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| Treatment2
|
Mean no. of
larvae per shank |
Mean no. of
cavities per shank |
Mean cavity
length (cm) per shank |
% of ears injured
|
|
Cry 1F / TC1507 / M2722 |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
M2722 non-Bt isoline |
0.2 |
a |
0.3 |
bc |
0.4 |
a |
50.0 |
a |
|
Y Bt |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
Y non-Bt isoline |
0.3 |
a |
0.5 |
a |
0.3 |
ab |
35.0 |
a |
|
LEPOTD 11 non-Bt |
0.0 |
bc |
0.2 |
cd |
0.2 |
bc |
17.5 |
b |
|
LEPOTD 12 |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
LEPOTD 13 |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
LEPOTD 14 |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
LEPOTD 18 |
0.0 |
c |
0.0 |
d |
0.0 |
c |
0.0 |
b |
|
LEPOTD 19 non-Bt |
0.2 |
a |
0.4 |
ab |
0.3 |
a |
43.3 |
a |
|
CBH-351 Bt |
0.0 |
c |
0.0 |
d |
0.0 |
c |
2.5 |
b |
|
CBH-351 non-Bt isoline |
0.2 |
ab |
0.2 |
bcd |
0.2 |
bc |
13.3 |
b |
|
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1Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT).
2 Cry 1F and its isoline
was supplied by Dow AgroSciences; all
LEPOTD hybrids were supplied by Monsanto;
and the CBH-351 hybrids were supplied
by Aventis. |
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