Evaluation of efficacy of selected conventional and experimental insecticides for control of corn earworm and European corn borer on sweet corn in Illinois, 1996

John T. Shaw, Rick Weinzierl and James W. Finger

Summary

Plot Information and Methods

Location

University of Illinois Cruse Farm, Champaign, Illinois

Plot Size

Each plot consisted of 4 (30-inch wide) rows 50 feet long. Thirty-foot wide alleys were established between each of the 4 replications. Insecticides were applied to the middle 2 rows of each plot leaving 2 untreated rows between each plot.

Experimental Design

A randomized complete block design with four replications was utilized. Two untreated control plots were included in each replication and were averaged for the ANOVA.

Planting Date and Agronomic Factors

See Table 11.1.

Weather Information

See Appendix A, Table A.4, Table A.5 and Table A.6

Soil Information

See Appendix B

Insecticide Application Dates

Because of the high numbers of European corn borer adults all treatments were applied on August 15, prior to any silking of the corn plants. All subsequent applications were made every 4 to 5 days beginning on August 20, at 12% silk (Table 11.1).

Method of Insecticide Application

All insecticide treatments were applied with a modified John Deere 6000 high-clearance vehicle (HCV) with a rear mounted boom. Six Conejet (TX VS-8) hollow cone nozzles (3 per row) were calibrated to deliver 29.5 gpa at 40 psi and a speed of 2.5 mph, with a compressed air system. Four nozzles (2 per row) were attached to drops and directed the spray towards the ear zone area, a third nozzle (1 per row) was mounted directly over the row with the spray being directed into the whorl (tassel) area.

The adjuvant Bond was added to the 2 treatments of Talstar at a rate of 0.025% v/v.

Post-Treatment Evaluations of Injury

Twenty-five ears were harvested from the middle two rows of each treatment for each replication on September 10 and 11. Ears were examined and the number of damaged ears, pest species, larval size, and location of ear damage (tip or side) was recorded for each ear.

Statistical Analysis

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

Results and Discussion

Densities of ECB were very high (Table 11.4) during this trial period with nearly 100% of the ears damaged and an average of 2.9 larva per ear for the untreated controls. In general most treatments were very effective in controlling ECB larvae. All sixteen treatments had significantly fewer ECB larvae and CEW larvae than the untreated control plots (Table 11.2). Also all sixteen treatments had a greater percentage of clean ears than the untreated control (Table 11.3). Notably were Talstar 0.67F, Capture 2EC, and Warrior 1EC all of which held the mean percentage of damaged ears below 20%. However, no treatment held the mean percentage of damaged ears below 10%.

Table 11.1: Agronomic factors for sweet corn efficacy trials, Illinois, 1996

Variables

Urbana

Planting date

June 26

Hybrid

'Flag-ship' (MarketMore Seeds)

Plant population

26,100

Row spacing

30-inch

Plot size

4 rows x 75 feet

Experimental Design

Randomized Complete block with four replications

Previous crop

Sweet corn (95)

Soil insecticide

None

Herbicides

Dual II (pre-plant)

Fertilizers

N 150 lb/A anhydrous

1st application date
Wind
Temperature

August 15
0-2 mph
75°F

Silking date

August 18 (1%)

2nd application date
Wind
Temperature

August 20 (12% silk)
0-5 mph
80°F

3rd application date
Wind
Temperature

August 24
0-2 mph
70°F

4th application date
Wind
Temperature

August 28
0-2 mph
70°F

5th application date
Wind
Temperature

September 1
0-2 mph
75°F

6th application date
Wind
Temperature

September 6
2-5 mph
70°F

Evaluation date (harvest)

September 10-11

Table 11.2 Mean number of European corn borer (ECB) and corn earworm (CEW) for harvested samples from insecticide treated and untreated sweet corn, Illinois, 1996¹

Treatment

Rate²

Mean ECB Larvae per 25 Ears³

Mean CEW Larvae per 25 Ears³

Capture 2EC

0.04

0.09 d

0.25 g

Talstar 0.67F +

Bond

0.04

0.025% v/v

0.50 cd

0.50 fg

Warrior 1EC

0.025

0.50 cd

0.75 efg

Talstar 0.67F +

Bond

0.03

0.025% v/v

0.00 d

0.75 d-g

Capture 2EC

0.03

1.00 bcd

1.00 d-g

Baythroid 2EC

0.031

0.50 cd

1.00 d-g

Scout X-Tra .9EC

0.016

3.50 b

1.00 d-g

Decis 1.5EC

0.016

2.24 bcd

1.22 d-g

Mustang 1.5EC

0.05

1.58 bcd

1.56 c-g

Mustang 1.5EC

0.0375

1.75 bcd

1.75 b-g

Capture 2EC

0.025

1.00 bcd

1.75 b-f

NAF-295 4E

0.068

0.75 bcd

2.50 b-e

Pounce 3.2EC

0.2

2.00 bc

2.75 bcd

Baythroid 2EC

0.025

1.00 bcd

3.75 bc

NAF-295 4E

0.045

0.50 cd

4.50 bc

Pounce 3.2EC

0.15

0.25 cd

4.50 b

Control

74.88 a

11.13 a

Table 11.3 Mean percentage of damaged ears, and mean number of ears with tip and side damage for insecticide treated and untreated sweet corn Illinois, 1996¹

Treatment

Rate²

Mean tip damage per 25 ears^3,4

Mean side damage per 25 ears^3,4

Mean percent damaged ears^3,4

Talstar 0.67F +
Bond

0.04
0.025% v/v

2.50 j

0.00 d

10.00 f

Capture 2EC

0.04

2.54 ij

0.08 cd

10.52 f

Capture 2EC

0.03

3.25 hij

1.25 bcd

15.00 f

Warrior 1EC

0.025

4.25 ghi

0.25 bcd

18.00 ef

Capture 2EC

0.025

4.75 gh

0.00 d

19.00 ef

Talstar 0.67F +
Bond

0.03
0.025% v/v

5.25 fg

0.00 d

21.00 def

Mustang 1.5EC

0.05

7.49 ef

0.28 bcd

29.86 cde

Mustang 1.5EC

0.0375

8.00 ef

1.00 bcd

33.00 cd

Baythroid 2EC

0.031

8.50 de

0.00 d

33.00 cd

NAF-295 4E

0.068

8.00 ef

1.50 bc

36.00 c

NAF-295 4E

0.045

9.75 cde

0.75 bcd

38.00 c

Decis 1.5EC

0.016

10.16 cde

0.28 bcd

43.19 c

Pounce 3.2EC

0.2

14.00 bc

0.25 bcd

57.00 b

Baythroid 2EC

0.025

14.50 bc

0.50 bcd

58.00 b

Scout X-Tra .9EC

0.016

13.25 bcd

1.25 b

58.00 b

Pounce 3.2EC

0.15

15.50 b

0.50 bcd

63.00 b

Control

24.88 a

18.25 a

99.00 a

Table 11.4 European corn borer light trap counts and corn earworm pheromone trap counts, Champaign, Illinois, 1996

Dates for the month of August

ECB light trap counts

CEW pheromone trap counts

6

X

7

102

12

8

190

6

9

175

35

10

95

--

11

280

78

12

X

--

13

X

--

14

164

129

15

215

35

16

163

75

17

X

--

18

X

--

19

X

165

20

105

256

21

135

320

22

X

370

23

125

450

24

X

--

25

X

760

26

6

160

27

X

380

28

20

--

29

8

600

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