Efficacy of planting-time, pre-emergence,
and rescue insecticide treatments
for black cutworm control in Illinois, 1996

John T. Shaw and James W. Finger

Summary

Plot Information and Methods

Location

University of Illinois Foundation Shaw Farm, Urbana, Illinois.

Plot Size

Each plot consisted of 4 rows by 40-feet long, with treatments being applied to the center 2 rows, 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 8.1.

Barriers

Barriers were made of 14-gauge steel with sides that were 5 inches tall and 6 feet long. The barriers were placed in the field on September 16, after corn plants had reached the first true leaf stage. The center 2 treated rows were included within the 36-square feet barrier arena. Barriers were embedded in the ground to a depth of 1 inch. Soil was packed around the outer edges of each barrier to prevent the escape of BCW larvae. Barriers were kept free of weeds by hand weeding throughout the study.

Plant Stand Within Barriers

The average number of plants within each barrier arena was 15, with a range of 13 to 15. Plant counts were recorded on September 17, immediately before the release of BCW larvae in the arenas. Plants within the barriers that were to receive rescue treatments were again counted September 18, 24 hours after larval release and just prior to rescue treatments being applied. Corn plants within each barrier were in the V2 stage (Iowa State Special Report, No. 48), at the time of larval release.

Manual Cutworm Infestation

Fifteen third- to fourth-instar laboratory reared BCW larvae were placed in each barrier arena on September 17. The larvae used in this test were supplied by Dr. Armon Keaster and Mary Jackson of the University of Missouri.

Insecticide Application Dates

Planting-time treatments were applied on September 6, with pre-emergence treatments being applied September 9, and rescue treatments being applied on September 18, 24 hours after manual infestation.

Method of Insecticide Application

Planting-time granular insecticides were metered through Noble units mounted on each of the 2 center planter units. These 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 insecticides into the soil.

The planting-time liquid (Lorsban 4E) was applied with 2 8002 TeeJet flat fan nozzles (1 per row), in a 7-inch band, with a compressed-air system calibrated to deliver 5.75 gpa at 25 psi and a speed of 5 mph.

Pre-emergence insecticide treatments were applied with a CO₂ back-pack sprayer utilizing 3 8002VS nozzles calibrated to deliver 13.1 gpa at 25 psi, over the center 2 rows of the 4 row plots.

Rescue insecticide treatments were applied utilizing the same equipment used for the pre-emergence treatments over the center 2 rows of the 4 row plots.

Phytotoxicity

There were no indications of phytotoxicity in the 1996 trial.

Assessment of Insect Damage

The cumulative number of cut plants in each barrier arena was determined on September 20 and 24 and October 1 and 8. These dates correspond to 3, 7, 10, and 14 days after manual cutworm infestation ( DAI), or 2, 6, 9, and 13 days after application of rescue treatments. The condition of the plants cut by BCW larvae in all treatments was also determined on October 11; that is, cut plants were classified as either "dead" or "recovered" from previous cutting (Table 8.3). The recovered plants were assumed to contribute to the final yield.

Weather Information

See Appendix A, Table A.2

Statistical Analysis

Data were analyzed with the Pesticide Research Manager version 5.0, from Gylling Data Management, Inc.(GDM). Means were separated by Fisher's LSD test (P=0.05).

Results and Discussion

A total of 1.32 inches of rain fell between the application of rescue treatments and the final sampling date (Appendix A, Table A.6 and Table A.7). The maximum soil temperature at the 4 inch level ranged from 61°F to 81°F. These conditions along with cool air temperatures created ideal conditions for BCW establishment. At the final evaluation period the untreated controls had a mean percentage of plants cut of 55.42%. All 3 rates of Decis 1.5EC, Pounce 3.2EC (0.1 lb[AI]/A), Baythriod 2EC ( 0.031 lb[AI]/A), and Scout X-tra (0.9EC 0.016 lb[AI]/A), applied as rescue treatments performed exceptionally well, holding the mean percentage of cut plants below 10% for the entire evaluation period. Baythroid 2EC (0.031 lb[AI]/A) applied as a pre-emergence treatment was the only non-rescue treatment to hold the percentage of cut plants below 25%. All rescue treatments had fewer percentage of cut plants than any planting-time treatments. However, Force 3G (0.10 lb[AI]/A) and NAF-287 30G (1.0 lb[AI]/A), both banded at planting, performed better than all pre-emergence treatments except for Baythroid 2EC (0.031 lb[AI]/A), holding percentage of cut plants below 30%.

The final percentage of plants that were dead or recovered is presented in Table 8.3. Of the 28 treatments only Pounce 3.2EC (0.10 lb[AI]/A) and Capture 2EC (0.01 and 0.015 lb[AI]/A), applied as pre-emergence treatments, were not significantly better than the untreated control for final dead plants. All 25 other treatments had 20% or fewer final dead plants.

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 8.1: Agronomic factors for black cutworm insecticide evaluations, Urbana, 1996

Variables

Urbana

Planting date
Temperature
Wind

September 6, 1996
85°
3-5 MPH

Hybrid

Pioneer 3394

Plant population

26,100

Row spacing

30-inch

Soil condition
(top 2-3 inches)

moist

Previous crop

soybeans 1995

Soil insecticides

none (1995)

Herbicides

none

Preemerge application date
Wind
Soil conditions

September 9,
0-3 mph
dry

Infestation

September 17
15 larva per barrier arena

Rescue application date
Wind
Soil conditions

September 18
0-5 mph
dry

Assessment of damage

September 20 and 24
October 1 and 8

Table 8.2 Cumulative mean percentage of plants cut per barrier by black cutworm larvae 3, 7, 10 and 14 days after manual infestation (DAI), Urbana, Illinois, 1996¹

Treatment

Rate²

Application

Code³

Mean % cut plants⁴

3 DAI

7 DAI

10 DAI

14 DAI

Decis 1.5EC

0.013

rescue

1.67 hi

1.67 k

1.67 l

1.67 j

Decis 1.5EC

0.01

rescue

0.00 i

3.59 jk

5.26 kl

5.26 ij

Pounce 3.2EC

0.1

rescue

5.51 ghi

5.51 ijk

5.51 kl

5.51 ij

Baythroid 2EC

0.031

rescue

7.20 f-i

7.20 h-k

7.20 jkl

7.20 hij

Decis 1.5EC

0.016

rescue

7.55 f-i

7.55 h-k

7.55 i-l

7.55 hij

Scout X-tra .9EC

0.016

rescue

7.16 f-i

8.83 g-k

8.83 h-l

8.83 hij

Baythroid 2EC

0.025

rescue

8.69 f-i

10.36 f-k

10.36 h-l

10.36 hij

Decis 120EC

0.013

rescue

11.91 e-i

11.91 e-k

11.91 g-l

11.91 g-j

Lorsban 4E

1.0

rescue

15.06 e-i

16.84 d-k

16.84 f-l

16.84 f-j

Decis 1.5EC

0.2

rescue

12.18 e-i

17.30 d-k

18.96 e-l

18.96 e-j

Baythroid 2EC

0.031

pre emerge

18.33 c-g

21.67 c-j

23.33 d-k

23.33 d-i

Lorsban 4E

0.5

rescue

16.67 d-h

24.17 c-i

26.25 c-k

26.25 c-i

Force 3G

0.13

band

21.67 b-g

26.67 b-h

26.67 b-k

26.67 c-i

NAF-287 30G

1.3

band

23.84 a-f

28.84 a-f

28.84 b-i

28.84 c-h

Mustang 1.5EC

0.037

pre emerge

15.00 e-i

28.33 a-g

28.33 b-j

28.33 c-h

Baythroid 2EC

0.025

pre emerge

25.27 a-e

26.67 b-h

29.23 b-h

29.23 c-h

Lorsban 4E

1.0

band

33.33 abc

33.33 a-d

33.33 a-g

33.33 b-g

Capture 2EC

0.02

pre emerge

21.67 b-g

31.67 a-e

33.33 a-g

33.33 b-g

Mustang 1.5EC

0.024

pre emerge

23.33 a-f

33.33 a-d

33.33 a-g

33.33 b-g

NAF-289 30G

1.3

band

25.48 a-e

32.14 a-d

33.81 a-f

33.81 b-f

Pounce 3.2EC

0.1

pre emerge

23.33 a-f

33.33 a-d

35.00 a-f

35.00 a-f

Warrior 1EC

0.02

pre emerge

20.00 b-g

31.67 a-e

35.00 a-f

35.00 a-f

Aztec 2.1G

0.15

band

27.44 a-e

35.77a-d

35.77 a-f

39.10 a-e

NAF-288 30G

1.3

band

35.47 ab

38.93 abc

40.60 a-e

40.60 a-e

Lorsban 15G

1.3

band

35.00 ab

40.00 abc

41.67a-d

41.67 a-d

Capture 2EC

0.01

pre emerge

31.67 a-d

40.00 abc

46.67 abc

46.67 abc

Mustang 1.5EC

0.03

pre emerge

31.67 a-d

46.67 ab

48.33 ab

48.33 abc

Capture 2EC

0.015

pre emerge

38.33 a

46.67 ab

53.33 a

53.33 ab

Control

39.47 a

47.81 a

54.58 a

55.42 a

Table 8.3 Mean percentage of plants recovered and the final percentage of dead plants after manual infestation of black cutworm larvae, Urbana, Illinois 1996¹

Treatment

Rate²

Application

Code³

Percentage

recovered

Percentage

dead

Pounce 3.2EC

0.1

rescue

50.00 abc

0.00 g

Decis 1.5EC

0.016

rescue

50.00 abc

0.00 g

Baythroid 2EC

0.025

rescue

75.00 ab

1.67 fg

Decis 1.5EC

0.013

rescue

0.00 c

1.67 fg

Scout X-tra .9EC

0.016

rescue

62.50 ab

1.78 fg

Baythroid 2EC

0.031

rescue

75.00 ab

2.08 fg

Decis 1.5EC

0.01

rescue

25.00 bc

3.34 efg

Force 3G

0.13

band

90.83 a

3.34 efg

Decis 120EC

0.013

rescue

56.25 abc

5.00 d-g

Lorsban 4E

1.0

rescue

70.83 ab

5.93 d-g

Warrior 1EC

0.02

pre emerge

81.43 ab

6.67 d-g

Lorsban 4E

1.0

band

87.50 a

6.67 d-g

NAF-289 30G

1.3

band

79.17 ab

6.79 d-g

Baythroid 2EC

0.025

pre emerge

73.88 ab

7.51 d-g

NAF-288 30G

1.3

band

76.61 ab

8.57 d-g

Decis 1.5EC

0.2

rescue

50.00 abc

8.59 d-g

Baythroid 2EC

0.031

pre emerge

39.58 abc

10.00 d-g

Mustang 1.5EC

0.024

pre emerge

64.58 ab

10.00 d-g

NAF-287 30G

1.3

band

55.95 abc

11.92 d-g

Mustang 1.5EC

0.037

pre emerge

60.72 ab

11.67 d-g

Capture 2EC

0.02

pre emerge

65.73 ab

18.62 b-f

Lorsban 4E

0.5

rescue

67.14 ab

15.42 c-g

Mustang 1.5EC

0.03

pre emerge

65.18 ab

18.33 b-f

Lorsban 15G

1.3

band

56.07 abc

18.33 b-f

Aztec 2.1G

0.15

band

55.21 abc

20.00 b-e

Pounce 3.2EC

0.1

pre emerge

35.36 abc

21.67 a-d

Capture 2EC

0.015

pre emerge

47.67 abc

28.33 abc

Capture 2EC

0.01

pre emerge

24.24 bc

36.67 a

Control

38.65 abc

33.69 ab

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