Efficacy of Registered and Experimental Insecticides for Control of Second-Generation European Corn Borer in Illinois, 2000
John T. Shaw, Kevin L. Steffey, and Michael E. Gray

Summary

Plot Information and Methods

Location

University of Illinois Crop Sciences Research & Education Center, Field EG-400 NW, Urbana, Illinois.

Plot Size

Four rows (30-inrow spacing) ´ 50 ft for each treatment in each replication, with 20-ft alleys between each replication. Treatments were applied to the center two rows of each plot leaving two untreated rows between each plot.

Experimental Design

Randomized complete block with four replications with two untreated control plots in each replication. Data collected from the untreated control plots were averaged for the ANOVA.

Planting Dates and Agronomic Factors

Refer to Table 7.1.

Weather Information

See Appendix A, Table A.3.

Manual Infestation of ECB

Manual infestation of ECB larvae to simulate the second-generation were made at corn anthesis (V18 - VT corn stage: Ritchie et al. 1993) on August 16 and again on August 18. Five egg masses (black-head stage) were placed in the first leaf axils both above and below the ear nodes on 10 consecutive plants in each of the middle two rows of a four-row plot.

Pre-Treatment Densities of ECB

On August 21, just before insecticide application, 20 infested plants were examined for surviving ECB larva. An average of 4.2 first and second instars per plant was recorded. The percent of infestation from the first generation (natural infestation) was negligible and did not influence the counts for the second generation.

Method of Insecticide Application

All insecticide treatments were applied with a modified John Deere 6000 high-clearance vehicle (HCV). Liquid insecticides were applied on August 21, three days after the second manual infestations of ECB, with six 8003 TeeJet hollow cone nozzles (three per row). Two nozzles were directed toward the ear zone with drops and one nozzle directed over the row. A compressed-air system was calibrated to deliver 15.2 gpa at 20 psi and a speed of 2.5.

Post-treatment Evaluations of Injury

On September 21, five corn plants from each of the middle two rows were split with a corn knife for evaluation. Evaluations of injury to the ear, ear shank, stalk above the ear, and stalk below the ear were recorded separately for each plant. The mean percentages of plants with cavities, mean numbers of cavities per plants, the lengths of stalk tunneling (cm) per plant, and the number of live larva per plant were recorded.

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 Multiple Range Test (MRT) (P=0.05).

Results and Discussion

Results of all evaluations are presented in Table 7.2 and Table 7.3. Percentage of plants injured by corn borers and mean numbers of larvae, numbers of cavities, and cavity length per plant are shown in Table 7.2. Mean numbers of larvae, numbers of cavities, and cavity lengths per plant below the ear are shown in Table 7.3.

Survival of second-generation European corn borer larvae survival was quite high; at least 52% of the plants in all plots had cavities (Table 7.2). In addition, a natural infestation of second-generation European corn borers occurred several days after the insecticides were applied. Nevertheless, the percentages of injured plants in plots treated with Warrior T 1SC and Tracer 2SC at 0.015 lb (AI)/acre and 0.031 lb (AI)/acre were significantly lower than the percentage of injured plants in the untreated control plots.

In the untreated control plots, the mean number of larvae per plant, mean number of cavities, and mean cavity length were 3.3, 4.3, and 16.6 cm, respectively. The mean numbers of larvae per plant were significantly lower in plots treated with Mustang 1.5EC at 0.44 lb (AI)/acre, Warrior T 1SC, Y-1, and Tracer 2SC at 0.015 and 0.031 lb (AI)/acre than in the untreated control plots. The mean numbers of cavities per plant were significantly lower in plots treated with Warrior T 1SC, Y-1, and Tracer 2SC at 0.015 and 0.031 lb (AI)/acre than in the untreated control plots. The mean cavity lengths per plant were significantly shorter in plots treated with Warrior T 1SC and Tracer at 0.015 and 0.031 lb (AI)/acre than in the untreated control plots.

Measurements of numbers of corn borers and injury below the ear (Table 7.3) were similar to measurements for entire plants, with some exceptions. In the untreated control plots, the mean number of larvae per plant, mean number of cavities, and mean cavity length were 2.3, 2.3, and 8.3 cm, respectively. The mean numbers of larvae per plant were significantly lower in all insecticide-treated plots than in the untreated control plots. The mean numbers of cavities per plant were significantly lower in plots treated with Warrior T 1SC, Mustang 1.5EC at 0.03 lb (AI)/acre, and Tracer 2SC at 0.015 and 0.031 lb (AI)/acre than in the untreated control plots. The mean cavity lengths per plant were significantly shorter in plots treated with Warrior T 1SC and Tracer at 0.015 and 0.031 lb (AI)/acre than in the untreated control plots.

Although the percentages of injured plants were unacceptably high (from a producer's standpoint) in all insecticide-treated plots, some significant differences among treatments were apparent, particularly with regard to the numbers of European corn borer larvae per plant. Warrior T 1SC and Tracer 2SC significantly reduced the numbers larvae, numbers of cavities, and cavity lengths.

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.

Table 7.1: Agronomic factors and evaluation dates for insecticide efficacy trials for control of second-generation European corn borer Urbana, Illinois, 2000

Variables

Urbana

Planting date

June 7, 2000

Hybrid

Pioneer 34G81

Plant population

28,500 plants per acre

Row spacing

30 inches

Soil condition (top 2-3 inches)

Moist

Previous crop

Soybeans

Soil insecticide

Force 3G applied at planting

Infestation Dates

August 16 and 18

5 egg masses (black-head stage) per plant per date

Treatment date

August 21

Air temperature

75°F

Wind

0 - 5 mph

Evaluation date (Stalk splitting)

September 21

Table 7.2 Mean numbers of corn borer larvae, number of cavities, and cavity length (cm), per plant for the second-generation European corn borer efficacy trial, Urbana, Illinois, 2000

Treatment

Rate¹

%
Damaged
plants

Mean no. of
larvae
per plant²

Mean no. of
cavities
per plant²

Mean cavity
length (cm)
per plant²

Mustang 1.5EW

0.044

85.0

a

1.5

b

2.5

a-e

11.5

ab

Warrior T 1SC

0.025

62.5

bc

0.9

b

1.2

cde

4.5

bc

X-1

0.025

90.0

a

1.5

ab

2.9

abc

12.7

a

X-2

0.030

87.5

a

2.0

ab

2.8

a-d

12.7

a

X-3

0.035

95.0

a

2.1

ab

3.5

ab

14.8

a

Y-1

0.030

82.5

ab

1.3

b

2.3

b-e

9.8

abc

Mustang 1.5 EW

0.030

92.5

a

1.7

ab

2.8

a-d

11.3

ab

Tracer 2SC

0.015

52.5

c

0.6

b

1.0

e

3.4

c

Tracer 2SC

0.031

55.0

c

0.5

b

1.1

de

4.7

bc

Control

92.0

a

3.3

a

4.3

a

16.6

a

¹ All rates are specified as lb (AI)/acre.
² Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT).

Table 7.3 Mean numbers of corn borer larvae, numbers of cavities, and cavity length (cm) per plant below the ear for second-generation European corn borer insecticide efficacy trial, Urbana, Illinois, 2000

Treatment

Rate¹

Injury below the ear²

Mean no. of
larvae
per plant

Mean no. of
cavities
per plant

Mean cavity
length (cm)
per plant

Mustang 1.5EW

0.044

0.8

b

1.2

abc

4.8

ab

Warrior T 1SC

0.025

0.4

b

0.5

c

1.6

b

X-1

0.025

0.9

b

1.4

abc

5.7

ab

X-2

0.030

1.0

b

1.5

abc

5.5

ab

X-3

0.035

1.0

b

1.8

ab

7.1

a

Y-1

0.030

0.8

b

1.3

abc

5.4

ab

Mustang 1.5 EW

0.030

0.6

b

1.2

bc

4.9

ab

Tracer 2SC

0.015

0.4

b

0.6

c

1.6

b

Tracer 2SC

0.031

0.3

b

0.6

c

1.9

b

Control

2.3

a

2.3

a

8.3

a

¹ All rates are specified as lb (AI)/acre.
² Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's New MRT).

Table 7.4 Mean numbers of corn borer larvae, numbers of cavities, and cavity length (cm) per plant above the ear for second-generation European corn borer insecticide efficacy trial, Urbana, Illinois, 2000

Treatment

Rate¹

Injury above the ear²

Mean no. of
larvae
per plant

Mean no. of
cavities
per plant

Mean cavity
length (cm)
per plant

Mustang 1.5EW

0.044

0.6

a

1.3

a-d

6.7

ab

Warrior T 1SC

0.025

0.5

a

0.7

cde

2.9

cd

X-1

0.025

0.7

a

1.5

abc

7.0

ab

X-2

0.030

1.0

a

1.3

a-d

7.2

ab

X-3

0.035

1.1

a

1.7

ab

7.7

ab

Y-1

0.030

0.5

a

0.9

b-e

4.3

bcd

Mustang 1.5 EW

0.030

1.1

a

1.6

ab

6.3

abc

Tracer 2SC

0.015

0.2

a

0.4

e

1.8

d

Tracer 2SC

0.031

0.2

a

0.6

de

2.8

cd

Control

1.0

a

1.9

a

8.3

a

¹ All rates are specified as lb (AI)/acre.
² Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's New MRT).

Table 7.5 Mean numbers of corn borer larvae and cavities in the shank, and percentage ear damage and larvae in the ear for second-generation European corn borer insecticide efficacy trial, Urbana, Illinois, 2000

Treatment

Rate¹

Shank damage²

Ear damage²

Mean no. of
larvae
per plant

Mean no. of
cavities
per plant

Mean no. of
larvae
per ear

% Damage

Mustang 1.5EW

0.044

0.3

ab

0.5

a-d

0.3

bcd

65.0

ab

Warrior T 1SC

0.025

0.0

b

0.2

de

0.4

a-d

70.0

ab

X-1

0.025

0.3

ab

0.6

abc

0.6

ab

85.0

a

X-2

0.030

0.2

ab

0.4

a-e

0.4

a-d

80.0

a

X-3

0.035

0.3

ab

0.4

a-e

0.6

abc

80.0

a

Y-1

0.030

0.1

ab

0.3

b-e

0.3

d

77.5

a

Mustang 1.5 EW

0.030

0.3

ab

0.6

ab

0.4

bcd

75.0

a

Tracer 2SC

0.015

0.1

b

0.1

e

0.2

d

35.0

c

Tracer 2SC

0.031

0.1

ab

0.3

cde

0.3

cd

42.5

bc

Control

0.4

a

0.7

a

0.7

a

90.0

a

¹ All rates are specified as lb (AI)/acre.
² Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's New MRT).

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