Efficacy of registered and experimental insecticides
to control corn rootworm larvae in Illinois, 1996

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

Summary

Plot Information and Methods

Locations

Corn rootworm insecticide trials were established at the following locations:

1. Northern Illinois Agronomy Research Center, DeKalb
2. Northwestern Illinois Agricultural Research and Demonstration Center, Monmouth
3. University of Illinois Foundation Shaw Farm, Urbana

Plot Size

Each treatment was applied to a single row 100, 100, and 65 feet long at DeKalb, Monmouth, and Urbana, respectively. Furadan 4F was applied broadcast over two rows.

Experimental Design

A randomized complete block with 4 replications was utilized as the experimental design. Included within each replication at DeKalb, Monmouth, and Urbana were 3, 2, and 4 untreated control plots, respectively. Data collected from the untreated control plots were averaged for the ANOVA.

Planting Dates and Agronomic Factors

See Table 4.1.

Pre-treatment Population

All locations were planted as trap crops (late planted corn and pumpkins) in 1995 in an effort to enhance oviposition and increase larval densities in 1996.

Method of Application for Granules at Planting Time

Granular insecticides applied at planting were metered through computer controlled SmartBox (SBX) granular applicators or Noble units mounted on each of the 4 planter units (John Deere, 7000 series, 4-row Max-Emerge planter). The planting-time granules were applied in-furrow or in a 7-inch 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 30 inch row spacing.

Method of Application for Liquids at Planting Time

Liquid applications of Regent 80WG were delivered at planting through micro-tubes calibrated to deliver 2.2 qt per acre in-furrow.

Method of Application for Liquids at Cultivation Time

Furadan 4F was applied as a broadcast spray over the center 2 rows of a 4 row plot on May 30 for Monmouth and DeKalb. 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 4.2) were determined by recording the number of plants per 0.001 acre (17.4 linear feet of row).

Phytotoxicity

There were no indications of phytotoxicity in the 1996 trials at any of the 3 locations.

Other Observations

Two compounds CNOVA 15G and NAF-287 30G became very hard and lumpy after sitting in the noble unit containers for a day or two. All 3 BWC compounds and NAF-289 30G were quite dusty during calibration. No major problems were observed with any of the other compounds in regard to handling or calibration.

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 percentage of the total number of roots examined for each treatment that had root ratings below 4.0. The 4.0 rating was used because it more closely approximates the larval injury, current corn hybrids can tolerate without economic loss (research currently in progress by Michael E. Gray and Kevin L. Steffey).

Weather Information

See Appendix A:

• Table A.3 and Table A.4 for Urbana
• Table A.8 and Table A.9 for DeKalb
• Table A.11 and Table A.12 for Monmouth

Soil Information

See Appendix B

Statistical Analysis

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

Results and Discussion

1996 proved to be another atypical spring for all experimental locations in Illinois. While DeKalb and Monmouth were planted at a reasonably average planting date (Table 4.1), the Urbana planting date was delayed by 3 weeks due to the cool wet spring conditions. These cool wet conditions held soil temperatures well below normal for DeKalb and Urbana (Appendix A), as a result egg hatch and larval development was delayed. These delays caused researchers to dig and rate corn roots on 2 separate occasions at DeKalb and Urbana to insure there was maximum damage from larval feeding. The final mean root ratings for DeKalb, Monmouth, and Urbana were 4.15 (Table 4.3), 4.38 (Table 4.4), and 5.15 (Table 4.5), respectively in the untreated control plots. The consistency ratings (Table 4.6) are derived from the total number of roots that were rated for each treatment at each location that had a rating of 4.0 or lower for the last root dig. With only a few exceptions, the band application of most products provided better root protection than the in-furrow application of the same products applied at the same rate (Table 4.7). Post-emergence treatments did not perform well this year, probably due to the delayed egg hatch and the need for more accurate timing of application.

Results from each location follow:

DeKalb

The DeKalb site had more than its share of wet cool weather this spring with 6.49, 5.26, and 8.65 inches of rainfall for May, June, and July respectively. For the most part all treatments performed well under these extreme conditions. All 23 treatments had mean root ratings below 4.0 and 16 of those had mean root ratings below 3.0. Only BWC00103 2.5G, Fortress 2.5G (0.16 lb[AI]/A), and Furadan 4F had root ratings that were not significantly different from that of the untreated control (4.15 root rating).

Monmouth

As with DeKalb, Monmouth too experienced cool wet weather early, with 5 inches above normal rainfall in May. Both Monmouth and were planted early (May 2) and both experienced cooler than normal soil temperatures early causing delayed egg hatch and slower larval development. This may have accounted for some of the erratic performance of a few soil insecticides at both locations. Monmouth experienced moderate to heavy rootworm feeding pressure in 1996 with a 4.38 mean root rating for the untreated controls. Of the 24 treatments at the Monmouth site one half (12) had mean root ratings below a 3.0. However, only Furadan 4F, Fortress 2.5G (0.12 lb[AI]/A), BWC00301 2G, and Thimet 20G were not significantly different from the untreated control.

Urbana

Urbana experienced the same cool wet spring as did DeKalb and Monmouth. As with DeKalb two sets of root ratings were necessary at the Urbana site. Both sets of root ratings were analyzed and are shown in Table 4.5. The Urbana site had the greatest amount of rootworm feeding pressure of all 3 sites in Illinois in 1996 with a 5.15 mean root rating for the untreated control plots. Of the 26 treatments 16 had mean root ratings below 3.0 Only Chlorofos 15G had a root rating (4.95) that was not significantly different from the untreated control. The in-furrow applications of some of the registered insecticides (Aztec 2.1G, Aztec 2.5G, and Force 3G) did not perform as well as expected. This could be due to the delayed corn rootworm (CRW) egg hatch, and the corn plant growing roots beyond the treated zone, allowing for more root damage. Unlike DeKalb and Monmouth all Fortress treatments performed well at the Urbana site.

References 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.

Table 4.1: Agronomic factors for corn rootworm soil insecticide evaluations at three locations, Illinois, 1996

Variables

DeKalb

Monmouth

Urbana

Planting date

May 3

May 2

May 20

Hybrid

Pioneer 3394

Pioneer 3394

Pioneer 3394

Plant population

26,100

26,100

26,100

Row spacing

30-inch

30-inch

30-inch

Soil condition
(top 2-3 inches)

moist

moist

moist

Wind

0-4 mph

0-5 mph

20-30 mph

Previous crop

trap crop- corn + pumpkins (95)

trap crop- corn + pumpkins (95)

trap crop- corn + pumpkins

Soil insecticides

none(95)

none(95)

none(95)

Herbicides

2 lb Bladex DF,
3 qt Lasso,
2 lb Aatrex 90

2.4 qts/A Bicep 2

Dual II 2.5 pt/A
2 qt/A Atrazine,
1 qt Crop Oil post emergence

Fertilizer

N 200 lb/A anhydrous April 18

N 180 lb/A anhydrous April 3

N 150 lb/A anhydrous
May 17

Fall tillage

disc chisel

chisel plow

chisel plow

Spring tillage

disc(twice)

field cultivator (once)
disk (once)

disk (twice)
tilthmaster (once)

Cultivation dates

none

June 16

June 20

Stand counts

June 17

June 17

June 18

Furadan application

May 30

May 30

May 31

Evaluation dates

July 31 and
August 19

July 22

July 15 and
August 2

Table 4.2 Mean stand counts for rootworm insecticide trials, Illinois, 1996

Treatment

Rate¹

Placement

DeKalb

Stand count^2,3

Monmouth

Stand count^2,3

Urbana

Stand count^2,3

Aztec 4.7G

0.15

Band-SBX

---

---

26.00

Aztec 2.1G

0.15

Band

23.25

26.00

26.75

Aztec 2.1G

0.15

Furrow

25.25

25.50

29.75

Aztec 4.7G

0.15

Furrow-SBX

---

---

26.00

BWC00103 2.5G

0.2

Band

23.75

25.50

26.50

BWC00301 2G

0.17

Band

23.25

23.00

26.75

BWC00506 1G

0.087

Band

24.25

25.75

25.75

Chlorofos 15G

1.3

Band

---

---

25.75

CNOVA 15G

1.3

Band

24.50

24.00

24.25

Counter CR

1.3

Furrow

24.00

25.50

26.25

Counter CR

1.3

Band

24.75

25.25

26.25

Force 3G

0.13

Band

24.75

25.00

27.50

Force 3G

0.13

Furrow

23.75

25.50

25.75

Fortress 2.5G

0.12

Band

22.75

25.50

25.50

Fortress 5G

0.12

Furrow-SBX

25.75

18.00

25.00

Fortress 5G

0.16

Band

---

---

27.00

Fortress 5G

0.16

Band-SBX

---

---

26.50

Fortress 5G

0.16

Furrow

23.00

26.50

26.50

Fortress 5G

0.16

Furrow-SBX

---

---

25.50

Fortress 2.5G

0.16

Band

24.25

24.25

28.00

Furadan 4F

1.0

Broadcast

24.50

25.00

---

Lorsban 15G

1.3

Band

26.00

24.75

26.50

NAF-287 30G

1.3

Band

26.50

27.25

26.25

NAF-288 30G

1.3

Band

24.00

24.75

26.50

NAF-289 30G

1.3

Band

24.50

26.00

25.00

Regent 3G

0.13

Furrow

25.00

25.00

---

Regent 80WG

0.13

Micro-tubes

22.25

25.50

---

Regent 1.5G

0.13

Furrow

26.50

24.75

---

Thimet 20G

1.3

Band

24.75

26.00

26.00

Control

23.38

23.88

25.50

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing.
² Stand counts are based on the number of plants per 0.001 acres (17.4 linear feet of row). Counts were made on June 17 for DeKalb and Monmouth and June 18 for Urbana.
³ Means for all three locations were not significant (P=0.05)

Table 4.3 Mean root ratings for 2 sample dates for corn rootworm soil insecticide evalutations, DeKalb, Illinois, 1996

Treatment

Rate¹

Placement²

Root ratings

July 31³

Root ratings

August 19³

Lorsban 15G

1.3

Band

2.40 e-h

2.25 d

Counter CR

1.3

Band

1.95 gh

2.40 d

Force 3G

0.13

Band

2.13 fgh

2.40 d

Aztec 2.1G

0.15

Furrow

2.20 fgh

2.40 d

BWC00506 1G

0.087

Band

2.20 fgh

2.45 d

Counter CR

1.3

Furrow

1.85 h

2.60 d

NAF-288 30G

1.3

Band

2.25 fgh

2.60 d

NAF-287 30G

1.3

Band

2.45 e-h

2.60 d

Aztec 2.1G

0.15

Band

2.15 fgh

2.60 d

NAF-289 30G

1.3

Band

2.65 def

2.60 d

Regent 3G

0.13

Furrow

2.70 c-f

2.65 d

Thimet 20G

1.3

Band

2.40 e-h

2.80 cd

Regent 80WG

0.13

Micro-tubes

2.50 d-h

2.85 cd

Regent 1.5G

0.13

Furrow

2.60 d-g

2.87 cd

CNOVA 15G

1.3

Band

2.25 fgh

2.90 cd

Force 3G

0.13

Furrow

2.30 e-h

2.90 cd

Fortress 5G

0.12

Furrow-SBX

2.73 c-f

3.33 bc

Fortress 5G

0.16

Furrow

2.60 d-g

3.40 bc

Fortress 2.5G

0.12

Band

3.30 abc

3.40 bc

BWC00301 2G

0.17

Band

3.10 bcd

3.40 bc

BWC00103 2.5G

0.2

Band

2.95 b-e

3.70 ab

Fortress 2.5G

0.16

Band

3.35 ab

3.85 ab

Furadan 4F

1.0

Broadcast

3.80 a

3.87 ab

Control

3.77 a

4.15 a

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing.
² Regent 80WG application and Fortress 5G SmartBox (SBX) applications were applied at planting on May 3. Furadan 4F was applied broadcast over 2 rows on May 30.
³ Means in a column followed by the same letter do not significantly differ (P=0.05; Duncan's New MRT).

Table 4.4 Mean root ratings for corn rootworm soil insecticide evalutation, Monmouth, Illinois, 1996

Treatment

Rate¹

Placement²

Root ratings³

Counter CR

1.3

Band

2.15 i

Aztec 2.1G

0.15

Band

2.25 hi

Force 3G

0.13

Band

2.45 ghi

BWC00506 1G

0.087

Band

2.45 ghi

Aztec 2.1G

0.15

Furrow

2.50 f-i

Counter CR

1.3

Furrow

2.55 f-i

Force 3G

0.13

Furrow

2.70 e-i

Fortress 5G

0.12

Furrow-SBX

2.79 e-i

CNOVA 15G

1.3

Band

2.80 e-i

NAF-289 30G

1.3

Band

2.80 e-i

NAF-288 30G

1.3

Band

2.85 d-i

Lorsban 15G

1.3

Band

2.90 d-i

Fortress 5G

0.16

Furrow

3.00 d-h

Regent 80WG

0.13

Micro-tubes

3.10 c-g

Regent 3G

0.13

Furrow

3.20 b-g

NAF-287 30G

1.3

Band

3.20 b-g

Regent 1.5G

0.13

Furrow

3.26 b-f

BWC00103 2.5G

0.2

Band

3.45 b-e

Fortress 2.5G

0.16

Band

3.60 bcd

Furadan 4F

1.0

Broadcast

3.80 abc

Fortress 2.5G

0.12

Band

3.80 abc

BWC00301 2G

0.17

Band

3.90 ab

Thimet 20G

1.3

Band

3.95 ab

Control

4.38 a

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing.
² Regent 80WG application and Fortress 5G SmartBox (SBX) applications were applied at planting on May 3. Furadan 4F was applied broadcast over 2 rows on May 30.
³ Means in a column followed by the same letter do not significantly differ (P=0.05, Duncan's New MRT).

Table 4.5 Mean root ratings for 2 sample dates for corn rootworm soil insecticide evalutations, Urbana, Illinois, 1996

Treatment

Rate¹

Placement²

Root ratings
July 15, 1996³

Root ratings
August 2, 1996³

Fortress 2.5G

0.16

Band

2.00 i

2.05 h

Fortress 5G

0.16

Furrow-SBX

2.20 hi

2.15 gh

Fortress 5G

0.16

Furrow

2.18 hi

2.34 fgh

Fortress 5G

0.16

Band

2.25 hi

2.45 fgh

Fortress 2.5G

0.12

Band

2.17 hi

2.45 fgh

Fortress 5G

0.16

Band-SBX

2.20 hi

2.55 fgh

Force 3G

0.13

Band

2.70 d-h

2.65 fgh

Counter CR

1.3

Furrow

2.51 e-i

2.68 fgh

Aztec 4.7G

0.15

Band-SBX

3.10 b-f

2.70 fgh

Fortress 5G

0.12

Furrow-SBX

2.38 ghi

2.70 fgh

Lorsban 15G

1.3

Band

2.60 d-i

2.70 fgh

CNOVA 15G

1.3

Band

2.50 e-i

2.80 e-h

NAF-289 30G

1.3

Band

2.65 d-i

2.85 e-h

BWC00506 1G

0.087

Band

2.80 c-h

2.90 e-h

Aztec 2.1G

0.15

Band

2.85 c-h

2.90 e-h

Counter CR

1.3

Band

2.45 f-i

2.90 e-h

Aztec 4.7G

0.15

Furrow-SBX

3.00 c-g

3.00 d-g

Thimet 20G

1.3

Band

3.05 b-f

3.10 c-f

NAF-288 30G

1.3

Band

3.15 b-e

3.60 b-e

NAF-287 30G

1.3

Band

3.20 bcd

3.65 b-e

Force 3G

0.13

Furrow

2.65 d-i

3.65 b-e

Aztec 2.1G

0.15

Furrow

2.95 c-g

3.80 bcd

BWC00301 2G

0.17

Band

3.65 ab

3.85 bc

BWC00103 2.5G

0.2

Band

3.45 bc

4.00 b

Chlorofos 15G

1.3

Band

4.20 a

4.95 a

Control

4.13 a

5.15 a

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing.
² SBX=applications made with the SmartBox at planting on May 20.
³ Means in a column followed by the same letter do not significantly differ (P=0.05; Duncan's New MRT)

Table 4.6 Consistency ratings for corn rootworm soil insecticide trials, Illinois, 1996

Treatment

Rate¹

Placement²

DeKalb consistency rating
8-19-96³

Monmouth consistency rating
7-22-96³

Urbana consistency rating
8-2-96³

Aztec 4.7G

0.15

Band-SBX

---

---

90

Aztec 2.1G

0.15

Band

95

100

65

Aztec 2.1G

0.15

Furrow

93

100

25

Aztec 4.7G

0.15

Furrow-SBX

---

---

75

BWC00103 2.5G

0.2

Band

35

50

10

BWC00301 2G

0.17

Band

55

35

10

BWC00506 1G

0.087

Band

95

100

80

Chlorofos 15G

1.3

Band

---

---

0

CNOVA 15G

1.3

Band

80

90

90

Counter CR

1.3

Furrow

90

95

90

Counter CR

1.3

Band

100

100

90

Force 3G

0.13

Band

100

100

90

Force 3G

0.13

Furrow

70

85

45

Fortress 2.5G

0.12

Band

45

30

90

Fortress 5G

0.12

Furrow-SBX

73

74

80

Fortress 5G

0.16

Band

---

---

100

Fortress 5G

0.16

Band-SBX

---

---

85

Fortress 5G

0.16

Furrow

73

75

97

Fortress 5G

0.16

Furrow-SBX

---

---

100

Fortress 2.5G

0.16

Band

35

55

100

Furadan 4F

1.0

Broadcast

40

40

---

Lorsban 15G

1.3

Band

100

75

85

NAF-287 30G

1.3

Band

95

70

30

NAF-288 30G

1.3

Band

95

90

60

NAF-289 30G

1.3

Band

100

90

80

Regent 3G

0.13

Furrow

85

60

---

Regent 80WG

0.13

Micro-tubes

90

65

---

Regent 1.5G

0.13

Furrow

87

68

---

Thimet 20G

1.3

Band

80

30

65

Control

20

20

0

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing.
² Regent 80WG and the SmartBox applications of Fortress 5G and Aztec 4.7G were all applied at planting.
³ The consistency rating is the percentage of the total number of roots examined with a rating below 4.0.

Table 4.7 Mean root ratings for band versus furrow application, Illinois, 1996

Placement

Treatment

Rate¹

Band

Furrow

URBANA - August 2

Aztec 2.1G

0.15

2.90

3.80

Aztec 4.7G

0.15 SBX

2.70

3.00

Counter CR

1.3

2.90

2.68

Force 3G

0.13

2.65

3.65

Fortress 5G

0.16

2.45

2.34

Fortress 5G

0.16 SBX

2.55

2.15

Control

5.15

DEKALB - August 19

Counter CR

1.3

2.40

2.60

Aztec 2.1G

0.15

2.60

2.40

Force 3G

0.13

2.40

2.90

Control

4.15

MONMOUTH - July 22

Counter CR

1.3

2.15

2.55

Aztec 2.1G

0.15

2.25

2.50

Force 3G

0.13

2.45

2.70

Control

4.38

¹ All rates are specified as lb (AI)/acre, based on 30-inch row spacing. SBX=applications made with the SmartBox.

Soybean Aphid Workshop Download and view powerpoint presentations from the workshop....