Efficacy of different formulations of Regent insecticide applied at planting to control corn rootworm larvae and first-generation European corn borer in Illinois, 1996

John T. Shaw, Michael E. Gray, Kevin L. Steffey and James W. Finger

Summary

Plot Information and Methods

Location

University of Illinois Foundation Shaw Farm, Urbana, Illinois.

Plot Size

Each treatment was applied to 2 rows 65 feet- long except for Furadan 4F which was applied broadcast over 2 rows and 1 treatment of Regent 80WG applied broadcast per plant incorporated over 4 rows.

Experimental Design

A randomized complete block with 4 replications was utilized as the experimental design. Included within each replication at were 2 untreated control plots. Data collected from the untreated control plots were averaged for the ANOVA.

Planting Date and Agronomic Factors

See Table 5.1.

Pre-treatment Population

This location was planted as a trap crop (late planted corn and pumpkins) in 1995 in an effort to enhance CRW oviposition and increase larval densities in 1996.

Method of Application for Granules at Planting Time

Granular insecticides applied at planting were metered through Noble units mounted on each of the center 2 rows of a 4-row planter unit (John Deere, 7000 series, 4-row Max-Emerge planter). The planting-time granules were applied in-furrow ahead of the firming wheels on the planter.

Method of Application for Liquids Pre-plant

One treatment of Regent 80WG was applied as a broadcast spray at a rate of 0.13 lb(AI)/A over a 4-row area with a CO₂ back-pack sprayer system calibrated to deliver 13 gpa at 22 psi. The incorporation was accomplished with a 10 foot section of a field cultivator set to incorporate the insecticide to a depth of 2-3 inches, just prior to planting. For individual treatment details see Table 5.2.

Method of Application for Liquids at Planting

All liquid treatments applied at planting utilized a compressed air system and were applied to the center 2 rows of the 4-row plots at a speed of 3 MPH. There were 10 Regent 80WG treatments, 5 of which utilized microtubs for low gallonage output and 5 which used standard liquid attachments. In the Regent 80WG treatments that included the addition of a fertilizer, the 80WG was mixed with water first, then added to the fertilizer. For individual treatment details see Table 5.2.

Method of Application for Post-emergence Liquids

Furadan 4F was applied as a broadcast spray over the center 2 rows of a 4-row plot on May 31. Furadan 4F was applied at a rate of 1 quart of product per acre over 2 rows with a CO₂ back-pack sprayer system calibrated to deliver 20.5 gpa at 20 psi.

Stand Counts

Stand count data (Table 5.3) was determined by recording the number of plants per 0.001 acre (17.4 linear feet of row).

Phytotoxicity

There were no indications of phytotoxicity with any of the treatments in this trial.

Manual ECB Infestations

On June 27, 15 connective plants in 1 of the middle 2 rows of a 4-row plot were infested by placing 2 ECB egg masses (black-headed stage) in the whorl of each plant. A second infestation with 2 ECB egg masses per plant was made the next day, June 28. On the day of infestation, the corn plants were in the V4 to V5 development stage (Richie et. al. 1993).

Post-Treatment Evaluation of Rootworm Injury

Five plants per treatment per replication were evaluated for rootworm injury. The root-rating system used was the Iowa State University root-rating scale described by Hills and Peters (1971):

1. No visible damage or only a few minor feeding scars.
2. Some roots with feeding scars but none eaten off to within 1.5 inches of the plant.
3. Several roots eaten off to within 1.5 inches of the plant but never the equivalent of an entire node of roots destroyed.
4. One node of roots destroyed or the equivalent.
5. Two nodes of roots destroyed or the equivalent.
6. Three or more nodes of roots destroyed.

The consistency ratings were based on the percent of the total number of roots examined for each treatment that had root ratings below 4.0.

Post-Treatment Evaluation of First Generation ECB Injury

On August 6, 10 manually infested plants were split to the base with a corn knife. The number of borer cavities per plant and the total length (inches) of cavities per plant were recorded (Table 5.5 and Table 5.6).

Weather Information

A prolonged, cool, wet spring caused delayed rootworm egg hatch, slower larval development, and may have contributed to the less than expected performance of some compounds. See Appendix A, Table A.3, Table A.4 and Table A.5

Statistical Analysis

Data were analyzed with the Pesticide Research Manager version 5.0, from Gylling Data Management, Inc.(GDM).

Other Observations

Even though the Regent 80W was mixed with water prior to adding the fertilizer, this mix caused problems with delivery and handling.

No major problems were observed with any of the other treatments in regard to handling or calibration.

Results and Discussion

Rootworms
>Only Fortress 5G, Aztec 2.1G, Counter 20CR, and Force 3G, (all applied in-furrow) had mean root ratings that were below 3.0 and were significantly better than the untreated control (Table 5.4). Only 4 Regent treatments had root ratings below 4.0, and none were significantly better than the untreated control. However, in the regular rootworm trials conducted at DeKalb and Monmouth (Table 4.3 and Table 4.4) Regent 1.5G, 3G and 80W all had significantly better root ratings than the untreated controls in the respective trials.

European corn borer
Eight of the 15, Regent treatments (Table 5.5) had a mean percentage of the plants with ECB cavities significantly lower than that of the untreated controls 67.5%. Eleven of the 15 treatments had significantly fewer cavities per plant than the untreated control, but there were no significant differences in the mean cavity length from that of the untreated control.

References Cited

How a Corn Plant Develops, Special Report, No. 48, Iowa State University of Science and Technology, Cooperative Extension Service, Ames, Iowa. Ritche et al. Reprinted June, 1993.

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.

Table 5.1: Agronomic factors for corn rootworm/European corn borer soil insecticide evaluations at Urbana, 1996

Variables

Urbana

Planting date

May 22

Hybrid

Ill. Foundation Seeds

Plant population

26,100

Row spacing

30-inch

Soil condition
(top 2-3 inches)

moist

Wind

0-2 mph.

Previous crop

trap crop - corn+pumpkins (95)

Soil insecticides

none(95)

Herbicides

Dual II 2.5pt/A, 2 qt/A Atrazine,
1 qt Crop Oil (postemergence)

Fall tillage

chisel plow

Spring tillage

disk (twice) Tilthmaster (once)

Stand counts

June 17

ECB infestation dates

June 27 two egg masses per plant
June 28 two egg masses per plant

Root ratings

July 15

Stalk ratings (ECB)

August 6

Table 5.2 Application methods for rootworm/European corn borer soil insecticide evaluation at Urbana, 1996

Treatment

Formulation

Rate¹

Placement²

Output

Regent
(PPI)

80WG

0.13

broadcast
pre-plant incorporated (PPI)

13 GPA
22 psi

Regent

80WG

0.13

band

2-650067 nozzles
34 psi
4.22 GPA

Regent

80WG

0.13

in-furrow

2-650067 nozzles
34 psi
4.22 GPA

Regent

+
10-34-0 fertilizer
water

80WG


---
---

0.13


6.60 qt. product/A
---

in-furrow

2-250067 nozzles
34 psi
4.20 GPA
33%
67%

Regent

80WG

0.13

2" x 2"

1/4 inch microtube
in-line orifice #27
21 psi
4.10 GPA

Regent

+
10-34-0 fertilizer

80WG


---

0.13


---

2" X 2"

1/4 inch microtube
in-line orifice #27
21 psi
4.10 GPA
100%
18 GPA

Regent

80WG

0.13

in-furrow

2-250017 nozzles
30 psi
1.04 GPA

EXP60145A-SC

1.67SC

0.13

in-furrow

2-250017 nozzles
30 psi
1.04 GPA

EXP61196A-EC

2.5EC

0.13

in-furrow

2-250017 nozzles
30 psi
1.04 GPA

Regent

+
10-34-0 fertilizer
water

80WG


---
---

0.13


2.0 qt product/A
---

in-furrow

2-250017 nozzles
30 psi
1.04 GPA
33%
67%

Regent

80WG

0.13

in-furrow-stream

1/8 inch microtube
24 psi
0.98 GPA

Regent

80WG

0.13

in-furrow-stream

1/8 inch microtube
10 psi
0.54 GPA

Regent

+
10-34-0 fertilizer
water

80WG


---
---

0.13


0.67 qt. product/A
---

in-furrow-stream

1/8 inch microtube
10 psi
0.54 GPA
33%
67%

¹ All rates are in lb (AI)/acre (based on 30-inch row spacing) unless otherwise designated.
² Placement of treatments with 2x2 is 2 inches to one side of the row and 2 inches deep. The PPI is a pre-plant incorporated treatment.

Table 5.3 Stand counts for plots treated with a soil insecticide for corn rootworm/European corn borer efficacy trials, Urbana, Illinois, 1996

Treatment

Rate¹

Placement²

Stand count

Aztec 2.1G

0.15

furrow

23.54

Counter CR

1.3

furrow

22.50

EXP60145A-1.67SC

0.13

1.04 GPA
furrow

23.25

EXP60655A-clay 1.5G

0.13

furrow

22.00

EXP61196A-2.5EC

0.13

1.04 GPA
furrow

22.75

EXP61216A-clay 3.0G

0.13

furrow

24.87

Force 3G

0.13

furrow

24.75

Fortress 5G

0.16

furrow

24.00

Furadan 4F

1.0

Broadcast
May 31

23.50

Regent 80WG

0.13

0.98 GPA
m-tube

21.75

Regent 80WG

0.13

4.22 GPA
band

24.25

Regent 80WG

0.13

1.04 GPA
furrow

23.00

Regent 80WG
+10-34-0 fert.

0.13
6.60 qt/A

4.20 GPA
furrow

22.25

Regent 80WG
+10-34-0 fert.

0.13
2.0 qt/A

1.04 GPA
furrow

22.00

Regent 80WG

0.13

0.54 GPA
m-tube

21.64

Regent 80WG-PPI

0.13

13 GPA
PPI 2"-4"

24.25

Regent 80WG

0.13

4.1 GPA
m-tube
2" x 2"

21.25

Regent 80WG

0.13

4.22 GPA
furrow

24.00

Regent 80WG
+ 10-34-0

0.13
100%

4.1 GPA
m-tube
2" X 2"

21.50

Regent 80WG
+ 10-34-0

0.13
0.67 qt/A

0.54 GPA
m-tube

23.25

Control

21.50

Table 5.4 Mean root ratings and consistency ratings for plots treated with a soil insecticide for corn rootworm/European corn borer efficacy trials, Urbana, Illinois, 1996

Treatment

Rate¹

Placement²

Root ratings³

Consistency rating⁴

Fortress 5G

0.16

furrow

2.13 e

100

Aztec 2.1G

0.15

furrow

2.73 de

86

Counter CR

1.3

furrow

2.73 de

80

Force 3G

0.13

furrow

2.80 de

93

Furadan 4F

1.0

Broadcast
May 31

3.33 cd

47

Regent 80WG

0.13

0.54 GPA
m-tube

3.53 bcd

47

Regent 80WG
+10-34-0 fert.

0.13
2.0 qt/A

1.04 GPA
furrow

3.60 bcd

40

Regent 80WG

0.13

1.04 GPA
furrow

3.70 abc

40

Regent 80WG

0.13

4.22 GPA
band

3.87 abc

20

Regent 80WG

0.13

4.22 GPA
furrow

4.07 abc

13

Regent 80WG

0.13

0.98 GPA
m-tube

4.07 abc

13

EXP61196A-2.5EC

0.13

1.04 GPA
furrow

4.07 abc

13

EXP61216A-clay 3.0G

0.13

furrow

4.10 abc

10

EXP60655A-clay 1.5G

0.13

furrow

4.20 abc

7

Regent 80WG
+10-34-0 fert.

0.13
6.60 qt/A

4.20 GPA
furrow

4.27 abc

7

Regent 80WG-PPI

0.13

13 GPA
PPI 2"-4"

4.33 ab

13

Regent 80WG

0.13

4.1 GPA
m-tube
2" x 2"

4.40 ab

7

EXP60145A-1.67 SC

0.13

1.04 GPA
furrow

4.47 ab

7

Regent 80WG
+ 10-34-0

0.13
100%

4.1 GPA
m-tube
2" X 2"

4.47 ab

0

Regent 80WG
+ 10-34-0

0.13
0.67 qt/A

0.54 GPA
m-tube

4.60 a

0

Control

4.27 abc

7

Table 5.5 Mean percentage of plants with cavities, mean number of cavities per plant, and percentage control for plots treated with a soil insecticide for corn rootworm/European corn borer efficacy trials, Urbana, Illinois, 1996¹

Treatment

Rate²

Placement³

Mean number cavities per plant⁴

Mean percent plants with cavities⁴

Percentage control⁵

EXP60655A-clay 1.5G

0.13

furrow

0.13 d

12.50 d

82

EXP61196A-2.5EC

0.13

1.04 GPA
furrow

0.13 d

12.50 d

82

Regent 80WG
+ 10-34-0

0.13
100%

4.1 GPA
m-tube
2" X 2"

0.15 d

15.00 d

79

Regent 80WG

0.13

4.1 GPA
m-tube
2" x 2"

0.15 d

15.00 d

79

Regent 80WG
+ 10-34-0

0.13
0.67 qt/A

0.54 GPA
m-tube

0.17 cd

16.85 cd

76

EXP60145A-1.67SC

0.13

1.04 GPA
furrow

0.18 cd

17.50 cd

75

EXP61216A-clay 3.0G

0.13

furrow

0.22 bcd

21.85 bcd

69

Regent 80WG

0.13

0.54 GPA
m-tube

0.28 bcd

27.50 bcd

61

Regent 80WG

0.13

4.22 GPA
furrow

0.30 bcd

30.00 a-d

57

Regent 80WG

0.13

4.22 GPA
band

0.30 bcd

30.00 a-d

57

Regent 80WG

0.13

0.98 GPA
m-tube

0.33 bcd

32.50 a-d

54

Regent 80WG-PPI

0.13

13 GPA
PPI 2"-4"

0.45 a-d

45.00 a-d

36

Regent 80WG
+10-34-0 fert.

0.13
2.0 qt/A

1.04 GPA
furrow

0.55 abc

55.00 abc

21

Regent 80WG
+10-34-0 fert.

0.13
6.60 qt/A

4.20 GPA
furrow

0.55 abc

55.00 abc

21

Regent 80WG

0.13

1.04 GPA
furrow

0.60 ab

60.00 ab

14

Control

0.70 a

67.50 a

0

Table 5.6 Mean cavity length per plant and the mean cavity length for plots treated with a soil insecticide for corn rootworm/European corn borer efficacy trials, Urbana, Illinois, 1996¹

Treatment

Rate²

Placement³

Mean cavity length per plant (inches)⁴

Mean cavity length (inches)⁴

EXP61196A-2.5EC

0.13

1.04 GPA
furrow

0.22 d

1.50 b

EXP60655A-clay 1.5G

0.13

furrow

0.28 cd

1.92 ab

Regent 80WG

0.13

4.1 GPA
m-tube
2" x 2"

0.31 cd

1.19 b

EXP60145A-1.67SC

0.13

1.04 GPA
furrow

0.32 cd

1.15 b

Regent 80WG
+ 10-34-0

0.13
100%

4.1 GPA
m-tube
2" X 2"

0.35 cd

2.44 ab

Regent 80WG

0.13

0.54 GPA
m-tube

0.41 cd

0.76 b

EXP61216A-clay 3.0G

0.13

furrow

0.42 cd

1.34 b

Regent 80WG

0.13

4.22 GPA
band

0.50 bcd

1.14 b

Regent 80WG

0.13

4.22 GPA
furrow

0.51 bcd

1.86 ab

Regent 80WG

0.13

0.98 GPA
m-tube

0.54 bcd

1.86 ab

Regent 80WG
+10-34-0 fert.

0.13
2.0 qt/A

1.04 GPA
furrow

0.88 a-d

1.66 b

Regent 80WG
+10-34-0 fert.

0.13
6.60 qt/A

4.20 GPA
furrow

1.04 abc

1.94 ab

Regent 80WG
+ 10-34-0

0.13
0.67 qt/A

0.54 GPA
m-tube

1.18 b

1.11 b

Regent 80WG-PPI

0.13

13 GPA
PPI 2"-4"

1.22 ab

3.40 a

Regent 80WG

0.13

1.04 GPA
furrow

1.42 a

1.78 ab

Control

1.51 a

2.12 ab

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