Efficacy of the Seed Treatment ProShield Against Corn Rootworm Larvae at Two Locations in Illinois, 2000
John T. Shaw, Michael E. Gray, and Kevin L. Steffey

Summary

Plot Information and Methods

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, Table A.1 and Table 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 NobleŽ units mounted on each row of an ALMACOŽ 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):

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 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).

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).

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 5.1: Agronomic factors and evaluation dates at two locations for ProShield corn rootworm efficacy trial, Illinois, 2000.

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)

60°F

61°F

Air temperature

70°F

65°F

Wind

8 - 10 mph

2 - 4 mph

Previous crop

trap crop - corn + pumpkins (1999)

trap crop - corn (1999)

Soil insecticides

None

None

Herbicides

Degree (pre-emergence)
Balance + Aatrex (post-emergence)

Fertilizer

Anhybrous 180 lbs.

Fall tillage

Coulter Chisel

Spring tillage

Mulch finisher twice

Cultivation date

June 8

Evaluation dates:

Stand Counts

June 1

June 5

Root ratings

July 25

July 13

Yield

October 19

October 16

Table 5.2 Mean stand counts for ProShield corn rootworm efficacy trial at two locations, Illinois, 2000

Treatment

Rate¹

Placement

Stand Counts²

DeKalb

Urbana

ProShield

seed treatment

25.75

ab

25.11

b

Force 3G

0.130

band

25.50

b

28.00

ab

Force 3G

0.130

furrow

---

27.75

ab

Aztec 2.1G

0.150

band

29.00

a

32.75

a

Lorsban 15G

1.300

band

---

31.25

ab

Counter 20CR

1.300

band

27.53

ab

30.00

ab

Regent 4SC

0.130

microtube

26.50

ab

30.00

ab

Control

27.25

ab

32.00

a

¹ Rates are specified as lb (AI)/acre, except ProShield which is expressed as mg/seed.
² Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).

Table 5.3 Mean root ratings for ProShield corn rootworm efficacy trial at two locations, Illinois, 2000

Treatment

Rate¹

Placement

Root Ratings²

DeKalb

Urbana

ProShield

seed treatment

3.70

ab

3.00

b

Force 3G

0.130

band

1.44

e

2.00

d

Force 3G

0.130

furrow

---

2.01

d

Aztec 2.1G

0.150

band

1.70

de

2.20

cd

Lorsban 15G

1.300

band

---

2.70

bc

Counter 20CR

1.300

band

2.53

cd

2.03

d

Regent 4SC

0.130

microtube

2.86

bc

2.95

b

Control

4.10

a

4.15

a

¹ Rates are specified as lb (AI)/acre, except for ProShield which is expressed as mg/seed.
² Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).

Table 5.4 Mean consistency ratings for ProShield corn rootworm efficacy trial at two locations, Illinois, 2000

Treatment

Rate¹

Placement

Consistency Ratings^2,3

DeKalb

Urbana

ProShield

seed treatment

35

65

Force 3G

0.130

band

100

100

Force 3G

0.130

furrow

---

100

Aztec 2.1G

0.150

band

100

90

Lorsban 15G

1.300

band

---

70

Counter 20CR

1.300

band

87

100

Regent 4SC

0.130

microtube

74

75

Control

35

20

¹ Rates are specified as lb (AI)/acre, except ProShield which is expressed as mg/seed.
² Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).
³ Consistency rating is the percentage of the total number of roots examined with a root rating less than 4.0.

Table 5.5 Mean percentage lodging for ProShield corn rootworm efficacy trial at two locations, Illinois, 2000.

Treatment

Rate¹

Placement

% Lodging²

DeKalb³

Urbana

ProShield

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

¹ Rates are specified as lb (AI)/acre, except ProShield which is expressed as mg/seed.
² Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).
³ The % lodging in the DeKalb trial was not enough to analyze.

Table 5.6 Mean yield for ProShield corn rootworm efficacy trial at two locations, Illinois, 2000

Treatment

Rate¹

Placement

Yield bu/acre^2,3

DeKalb

Urbana

ProShield

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

band

162.6

a

173.0

a

Lorsban 15G

1.300

band

---

157.3

ab

Counter 20CR

1.300

band

165.5

a

140.9

b

Regent 4SC

0.130

microtube

151.6

a

154.3

ab

Control

132.7

b

167.8

ab

¹ Rates are specified as lb (AI)/acre, except ProShield which is expressed as mg/seed.
² Yield was determined by machine harvesting (converted to 15.5% moisture).
³ Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).

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