Efficacy of seven BASF experimental insecticides applied at planting for control of corn rootworm larvae in Illinois, 1996

John T. Shaw and James W. Finger

Summary

Plot Information and Methods

Location

Northern Illinois Agronomy Research Center, DeKalb, Illinois.

Plot Size

Each treatment was applied to 2 rows 85 feet long and replicated 4 times.

Experimental Design

A randomized complete block with 4 replications was utilized as the experimental design. Included within each replication was 1 untreated control plot.

Planting Date and Agronomic Factors

See Table 6.1.

Pre-treatment Population

Trial area was planted to a trap crop (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 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 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.

Stand Counts

Stand count data were determined for each location by recording the number of plants per 0.001 acre (17.4 linear feet of row).

Phytotoxicity

There were no indications of phytotoxicity 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. The 4.0 rating was used because it more closely approximates the larval injury that current corn hybrids can tolerate without economic loss (research currently in progress by Michael E. Gray and Kevin L. Steffey).

Yield

Yields were determined from grain weights obtained by mechanically harvesting the remaining plants in both treated rows for all 8 replications. A Gleaner K combine with electronic scales mounted in the hopper was used. All weights were converted to 15.5% moisture and reported as bushels per acre (Table 6.3).

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.8, Table A.9 and Table A.10

Soil Information

See Appendix B.

Other Observations

All BWC compounds were observed to be quite dusty during calibration.

Statistical Analysis

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

Results and Discussion

Root Ratings
Treatment BWC00508 1.1G (0.10 lb [AI]/A) compared favorably with the 2 commercial standards Lorsban 15G and Aztec 2.1G with no significant differences in root ratings (Table 6.2). Only the BWC00600I treatment, which had no insecticide added to the granules, had root ratings that were not significantly different from the untreated control.

Yields
The untreated control had the lowest yield (Table 6.3) in this trial with a yield of 148.86 bushels per acre (bu/A). Five of the treatments, Lorsban 15G, BWC00506 1.1G, BWC00508 1.1G, BWC00104 2.5G and BWC00600I were not significantly different from the untreated control. However, only BWC00600I (with no insecticide) and the untreated control had yields that were significantly less than that of the highest yielding treatment (BWC00106 2.5G).

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 6.1: Agronomic factors for the BASF corn rootworm soil insecticide trial at DeKalb, Illinois, 1996

Variables

DeKalb

Planting date

May 3

Hybrid

Pioneer 3394

Plant population

26,100

Row spacing

30-inch

Soil condition
(top 2-3 inches)

moist

Wind

0-4 mph

Previous crop

trap crop- corn + pumpkins (95)

Soil insecticides

none (95)

Herbicides

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

Fertilizer

N 200 lb/A anhydrous
April 18

Fall tillage

disc chisel

Spring tillage

disc (twice)

Cultivation dates

none

Evaluation dates

July 31

Harvested

November 4

Table 6.2 Mean root rating and consistency ratings for the BASF corn rootworm soil insecticide trial at DeKalb, Illinois, 1996

Treatment

Rate¹

Placement²

Root ratings³

Consistency rating⁴

BWC00508 1.1G

0.10

band

2.15 c

100

Lorsban 15G

1.30

band

2.25 c

100

Aztec 2.1G

0.15

band

2.25 c

100

BWC00504I 0.5G

0.44

band

2.85 b

80

BWC00506 1.1G

0.10

band

2.90 b

75

BWC00106 2.5G

0.22

band

3.00 b

80

BWC00103 2.5G

0.22

band

3.25 b

60

BWC00104 2.5G

0.22

band

3.30 b

70

BWC00600I 0.0G

0.00

band

3.45 ab

45

Control

4.00 a

30

Table 6.3 Mean stand count and mean yeild for the BASF corn rootworm soil insecticide trial at, DeKalb, Illinois, 1996

Treatment

Rate¹

Placement²

Stand count³

Mean yield bu/A^4,5

BWC00106 2.5G

0.22

band

24.63

166.83 a

Aztec 2.1G

0.15

band

24.00

165.51 a

BWC00504I 0.5G

0.44

band

25.63

162.57 ab

BWC00103 2.5G

0.22

band

24.13

162.42 ab

Lorsban 15G

1.30

band

24.00

158.67 abc

BWC00506 1.0G

0.10

band

24.25

157.52 abc

BWC00508 1.1G

0.10

band

25.13

155.11 abc

BWC00104 2.5G

0.22

band

24.25

153.74 abc

BWC00600I 0.0G

0.00

band

23.75

149.74 bc

Control

24.63

148.86 c

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