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Efficacy of the Seed Treatment ProShield
Against Corn Rootworm Larvae at Two
Locations in Illinois, 2000 |
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John T. Shaw,
Michael E. Gray, and Kevin L. Steffey
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Summary |
An
experiment was conducted at DeKalb and
Urbana to determine the efficacy of
ProShield against corn rootworm larvae
in 2000. Moderate root injury occurred
in the control plots in DeKalb (4.10)
and Urbana (4.15). In the DeKalb experiment,
average root injury ratings were kept
below 2.0 in plots treated with Aztec
2.1G (band) and Force 3G (band). Root
injury also was kept below the economic
injury index (3.0) in plots treated
with Counter 20CR (band) and Regent
4SC (microtube). In DeKalb, the average
root injury rating (3.70) for the ProShield
treatment was not statistically different
from the control. In Urbana, the average
root injury rating (3.0) for the ProShield
treatment was significantly lower than
the control. Average root injury ratings
were not statistically different among
ProShield (3.0), Lorsban 15G (2.7),
and Regent 4SC treatments. Poor consistency
ratings for roots treated with ProShield
at DeKalb (35%) and Urbana (65%) revealed
the highly variable level of control
afforded by this seed treatment. |
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Plot Information and Methods
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Locations
Corn rootworm insecticide trials were
established at the following locations:
1. Northern Illinois Agronomy Research
Center, DeKalb, Illinois.
2. University of Illinois, Crop Sciences
Research & Education Center, Field
EG-200 NE, Urbana, Illinois
Plot Size
Each insecticide was applied to one
row (40 feet long). Alleys (20 feet
wide) were established between all replications
at each location.
Experimental
Design
A randomized complete block with four
replications was utilized as the experimental
design at all locations. Two untreated
control plots were included within each
replication. Data collected from the
untreated control plots were averaged
for the analysis of variance (ANOVA).
Planting Dates and Agronomic
Factors
All seed (NK58 D-1) was furnished by
the Novartis Seed Company (Table 5.1).
Weather Information
See Appendix A, Tables
A.1 and A.2.
Stand Counts
Stand count data (Table 5.2) were determined
by recording the number of plants per
0.001 acre (17.4 linear feet of row).
Pre-Treatment Population
The DeKalb location was planted (1999)
as a trap crop (late-planted corn and
pumpkins) in an effort to enhance rootworm
oviposition and increase larval densities
in 2000. At the Urbana location a late-planted
cornfield was sprayed with a mixture
of buffalo gourd root powder and water
to increase the level of larval injury
in 2000.
Method of Application
for Granules at Planting Time
Granular insecticides were applied at
planting and metered through computer
controlled SmartBox (SBX) granular applicators
or Noble® units mounted
on each row of an ALMACO®
four-row precision planter. Insecticides
were applied in-furrow or in a 7-in.
band ahead of the firming wheels on
the planter. Spring tines mounted behind
each planter unit were used to incorporate
the insecticide. All rates are specified
as lb. (AI)/acre based on a 30-inch
row spacing.
Method of
Application for Liquids at Planting
Time
Regent 4SC was applied (0.13 lb. (AI)/acre)
during planting using microtubes directed
in the furrow and calibrated to deliver
2.1 gallons per acre (30 psi) at 3.0
mph.
Phytotoxicity
Symptoms of phytotoxicity were not observed
at the two locations for any of the
insecticide treatments.
Post-Treatment
Evaluation of Rootworm Injury
Five plants per treatment per replication
were dug, washed, and evaluated for
larval injury on July 13 and 25 for
Urbana and DeKalb, respectively (Table
5.3). The root-rating system used was
the Iowa State University root-rating
scale described by Hills and Peters
(1971):
- No visible damage or only a few
minor feeding scars
- Some roots with feeding scars
but none eaten off to within 1.5
inches of the plant
- Several roots eaten off to within
1.5 inches of the plant but never
the equivalent of an entire node
of roots destroyed
- One node of roots destroyed or
the equivalent
- Two nodes of roots destroyed or
the equivalent
- Three or more nodes of roots destroyed
The consistency ratings were based upon
the percentage of the total number of
roots examined for each treatment that
had root ratings less than 4.0 (Table
5.4).
Percent Lodging and
Yield
Plots in Urbana and DeKalb were harvested
and lodging estimates determined on
October 16 and 20, respectively. Lodging
data are shown for Urbana but not DeKalb
(Table 5.5).Yield data were obtained
by harvesting all four rows of the four
row plots with a combine equipped with
scales (Table 5.6).
Statistical
Analysis
Data were analyzed with the Agriculture
Research Manager (ARM) version 6.1.6,
from Gylling Data Management, Inc.(GDM).
Means were separated by Duncan’s
New MRT test (P=0.05). |
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Results and Discussion |
On June 1, the number of plants per
0.001 acre (17.4 linear feet of row)
was not statistically different among
treatments in DeKalb (Table 5.2). On
June 5, significantly fewer plants (0.001
acre) were found in the Urbana plots
in which the ProShield treatment was
used compared with the control.
Moderate root injury occurred in the
control plots at the DeKalb (4.10) and
Urbana (4.15) locations (Table 5.3).
In the DeKalb experiment, average root
injury ratings were kept below 2.0 in
plots treated with Aztec 2.1G (band)
and Force 3G (band). Root injury also
was kept below the economic injury index
(3.0) in plots treated with Counter
20CR (band) and Regent 4SC (microtube).
In DeKalb, the average root injury rating
(3.70) for the ProShield treatment was
not statistically different from the
control. In Urbana, the average root
injury rating (3.0) for the ProShield
treatment was significantly lower than
the control. Average root injury ratings
were not statistically different among
ProShield (3.0), Lorsban 15G (2.7),
and Regent 4SC treatments.
Poor consistency ratings (Table 5.4)
for roots treated with ProShield at
DeKalb (35%) and Urbana (65%) revealed
the highly variable level of control
afforded by this seed treatment. Root
protection provided by the use of Regent
4SC (microtube) also was more variable
compared with Aztec 2.1G, Counter 20CR,
and Force 3G.
The percentage of plants that lodged
(Table 5.5) in DeKalb and Urbana was
negligible and no differences among
the treatments were observed.
No significant differences in yield
were detected among the insecticide
treatments at the DeKalb location; however,
all treatments had significantly greater
yields than the control (Table 5.6).
In Urbana, none of the yield estimates
among the insecticide treatments differed
significantly from the control. In Urbana,
significantly more bushels per acre
were harvested in plots treated with
Aztec 2.1G (173 bushels per acre) compared
with Counter 20 CR plots (140.9 bushels
per acre).
Reference Cited
Hills, T.M., and D.C. Peters. 1971.
A method of evaluating post-plant insecticide
treatments for control of western corn
rootworm larvae. J. Econ Entomol. 64:
764-765. |
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Table 5.1. |
Agronomic factors and evaluation dates
at two locations for ProShield corn
rootworm efficacy trial, Illinois, 2000. |
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Variables |
DeKalb |
Urbana |
| Planting
date |
May
17, 2000 |
April
28, 2000 |
| Hybrid
|
NK58
D-1 |
NK58
D-1 |
| Plant
population
|
28,500
seeds per acre |
28,500
seeds per acre |
| Row
spacing
|
30
inches |
30
inches |
| Soil
condition
(top 2-3 inches)
|
Moist
|
Dry
|
| Soil
temperature
(4-inch level)
|
60oF
|
61oF
|
| Air
temperature
|
70oF
|
65oF
|
| Wind
|
8-10
mph |
2-4
mph |
| Previous
crop |
trap
crop — corn + pumpkins (1999)
|
trap
crop — corn (1999) |
| Soil
insecticides |
None
|
None
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| Herbicides
|
Degree
(pre-emergence) Balance + Aatrex
(post-emergence) |
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| Fertilizer
|
Anhybrous
180 lbs. |
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| Fall
tillage |
Coulter
Chisel |
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| Spring
tillage |
Mulch
finisher twice |
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| Cultivation
date |
June
8 |
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| Evaluation
dates |
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| Stand
counts |
June
1 |
June
5 |
| Root
ratings |
July
25 |
July
13 |
| Yield
|
October
19 |
October16
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Table 5.2. |
Mean
stand counts for ProShield corn rootworm
efficacy trial at two locations, Illinois,
2000 |
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Treatment |
Rate1
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Placement |
Stand Counts2
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DeKalb |
Urbana |
| ProShield
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seed
treatment |
25.75
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ab |
25.11
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b |
| Force
3G |
0.130
|
band
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25.50
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b |
28.00
|
ab
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| Force
3G |
0.130
|
furrow
|
--- |
27.75
|
ab
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| Aztec
2.1G |
0.150
|
band
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29.00
|
a |
32.75
|
a |
| Lorsban
15G |
1.300
|
band
|
--- |
31.25
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ab
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| Counter
20CR |
1.300
|
band
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27.53
|
ab |
30.00
|
ab
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| Regent
4SC |
0.130
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microtube
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26.50
|
ab |
30.00
|
ab
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Control |
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27.25 |
ab |
32.00 |
a |
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1Rates are specified as
lb (AI)/acre, except ProShield which
is expressed as mg/seed.
2Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT) |
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Table 5.3. |
Mean
root ratings for ProShield corn rootworm
efficacy trial at two locations, Illinois,
2000. |
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Treatment |
Rate1
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Placement |
Root Ratings2
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DeKalb
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Urbana |
| ProShield
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|
seed
treatment |
3.70
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ab
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3.00
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b
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| Force
3G |
0.130
|
band
|
1.44
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e
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2.00
|
d
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| Force
3G |
0.130
|
furrow
|
--- |
2.01
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d
|
| Aztec
2.1G |
0.150
|
band
|
1.70
|
de
|
2.20
|
cd
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| Lorsban
15G |
1.300
|
band
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--- |
2.70
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bc
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| Counter
20CR |
1.300
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Band
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2.53
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cd
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2.03
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d
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| Regent
|
0.130
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microtube
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2.86
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bc
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2.95
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b
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Control |
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4.10 |
a |
4.15 |
a |
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1Rates
are specified as lb (AI)/acre, except
ProShield which is expressed as mg/seed.
2Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT) |
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Table 5.4. |
Mean
consistency ratings for ProShield corn
rootworm efficacy trial at two locations,
Illinois, 2000. |
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Treatment |
Rate1
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Placement |
Consistency
Ratings2,3 |
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DeKalb |
Urbana |
| ProShield
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|
seed
treatment |
35
|
65
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| Force
3G |
0.130
|
band
|
100
|
100
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| Force
3G |
0.130
|
furrow
|
---
|
100
|
| Aztec
2.1G |
0.150
|
band
|
100
|
90
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| Lorsban
15G |
1.300
|
band
|
---
|
70
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| Counter
20CR |
1.300
|
band
|
87
|
100
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| Regent
4SC |
0.130
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microtube
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74
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75
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Control |
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35 |
20 |
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1Rates are specified
as lb (AI)/acre, except ProShield which
is expressed as mg/seed.
2Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT).
3Consistency rating is the
percentage of the total number of roots
examined with a root rating less than
4.0. |
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Table 5.5. |
Mean
percentage lodging for ProShield corn
rootworm efficacy trial at two locations,
Illinois, 2000. |
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Treatment |
Rate1
|
Placement |
% Lodging2
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DeKalb3
|
Urbana |
| ProShield
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|
seed
treatment |
---
|
0.50
|
a
|
| Force
3G |
0.130
|
band
|
---
|
0.75
|
a
|
| Force
3G |
0.130
|
furrow
|
---
|
1.50
|
a
|
| Aztec
2.1G |
0.150
|
band
|
---
|
1.25
|
a
|
| Lorsban
15G |
1.300
|
band
|
---
|
5.00
|
a
|
| Counter
20CR |
1.300
|
band
|
---
|
1.50
|
a
|
| Regent
4SC |
0.130
|
microtube
|
---
|
2.04
|
a
|
|
Control |
|
|
---
|
4.75 |
a |
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1Rates are specified as
lb (AI)/acre, except ProShield which
is expressed as mg/seed.
2Yield was determined by
machine harvesting (converted to 15.5%
moisture).
3Means in a column followed
by the same letter are not significantly
different (P=0.05; Duncan’s New
MRT) |
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Table 5.6. |
Mean
yield for ProShield corn rootworm efficacy
trial at two locations, Illinois, 2000 |
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Treatment |
Rate1
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Placement |
Yield bu/acre2,
3 |
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DeKalb |
Urbana |
| ProShield
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|
seed
treatment |
157.7
|
a
|
151.3
|
ab
|
| Force
3G |
0.130
|
band
|
168.8
|
a
|
157.0
|
ab
|
| Force
3G |
0.130
|
furrow
|
--- |
152.7
|
ab
|
| Aztec
2.1G |
0.150
|
and
|
162.6
|
a
|
173.0
|
a
|
| Lorsban
15G |
1.300
|
band
|
--- |
157.3
|
ab
|
| Counter
20CR |
1.300
|
band
|
165.5
|
a
|
140.9
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b
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| Regent
4SC |
0.130
|
microtube
|
151.6
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a
|
154.3
|
ab
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|
Control |
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|
132.7 |
b |
167.8 |
ab |
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1Rates
are specified as lb (AI)/acre, except
ProShield which is expressed as mg/seed.
2Yield was determined
by machine harvesting (converted to
15.5% moisture).
3Means in a column
followed by the same letter are not
significantly different (P=0.05; Duncan’s
New MRT). |
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