Potential effects (efficacy, phytotoxicity, antagonism) of tank-mixing the soybean herbicide Resource with registered insecticides 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

Plots were 40 feet x 50 feet for each treatment in each of 4 replications.

Experimental Design

A randomized complete block design with 4 replications was utilized. An untreated control block was included in each replication.

Planting Date and Agronomic Factors

See Table 3.1.

Pre-treatment Infestation

All plots were sampled on August 27, just prior to treatment. An average of 1.4 bean leaf beetles (BLB) per 20 sweep (n = 100) was recorded. The average number of corn rootworm adults per 20 sweeps were; Northern corn rootworms (NCR) = 12.4, western corn rootworms (WCR) = 12.0, and southern corn rootworms (SCR) = 2.8.

The average height for velvet leaf weeds were 20 inches.

Method of Pesticide Application

A 20-foot boom was mounted to the rear of a modified John Deere 6000 high-clearance sprayer (boom height = 17 inches above the crop canopy). Flat fan spray tips (12-XR TeeJet 8002VS, Spraying Systems Co.) were spaced 20 inches apart on the boom. A compressed-air system was calibrated to deliver 19.7 gpa at a pressure of 30 psi and a speed of 2.5 mph. All treatments were tank-mixed prior to application and included the crop oil concentrate Agrodex.

Post-Treatment Samples

Insect control was determined by taking sweep net counts at 7, 14, and 21 days after treatment (DAT). Twenty sweep-net samples were taken from each plot. The standard 15-inch diameter sweep-net was used for all sampling.

The percentage of weed control was determined at 7 DAT and 21 DAT, based on a visual percentage of dead plants observed for the entire plot in each replication. Weeds were identified to species for each plot, however, only the velvet leaf was in sufficient numbers in all plots to analyze. Select herbicide was applied post-emergence for grass control on August 6.

Weather Information

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

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

The initiation of this test was later than planed due to the low densities of bean leaf beetle adults needed for insect control determinations. This delay caused the broadleaf weed population to become 18 to 24 inches tall, at the time of treatment application, resulting in somewhat reduced control of the Resource herbicide. Orthene appeared to have a synergistic effect on the Resource herbicide with significantly better velvet leaf control for the Resource + Orthene tank-mix than with the Resource alone for both 7 DAT and 21 DAT ratings (Table 3.5). By 21 DAT the Resource + Ambush and the Resource + Pounce were also significantly better than the Resource alone for velvet leaf control. All treatments that included Resource had significantly shorter soybean plants than did the same treatments without Resource.

The addition (tank-mix) of Resource had no effect on the performance of the insecticides Ambush 2.0EC or Pounce 3.2EC for bean leaf beetle, western corn rootworm, or northern corn rootworm adult control (Table 3.2, Table 3.3, and Table 3.4).

Table 3.1: Agronomic factors for soybean herbicide and insecticide interaction study, Urbana, Illinois, 1996

Variables

Urbana

Planting date

July 2, 1996

Hybrid

Pioneer 9362

Row spacing

30-inch

Previous crop

Corn (95)

Herbicide

August 6
Select herbicide 6 oz/A + COC (Agrodex)
postemergance (for grass control)

Treatment date
Temperature
Wind

August 27
80°F
0-5mph

Evaluation dates

September 3
September 10
September 17

Table 3.2 Mean number of bean leaf beetles, northern corn rootworm, western corn rootworm, and southern corn rootworm adults per 20 sweeps, 7 days after treatment (DAT) Urbana, 1996

Treatment¹

Rate²

Bean Leaf

Beetles^3,4

7 DAT

NCR + WCR

Rootworms^3,4,5

7 DAT

NCR+WCR+SCR

Rootworms^3,4,5

7 DAT

Resource .86EC
Ambush 2.0EC
COC

4.0
10.0
0.5% v/v

0.50 b

7.25 b

10.25 b

Pounce 3.2EC
COC

6.0
0.5% v/v

0.50 b

8.25 b

10.25 b

Ambush 2.0EC
COC

10.0
0.5% v/v

1.16 b

9.83 b

10.67 b

Resource .86EC
Pounce 3.2EC
COC

4.0
6.0
0.5% v/v

1.50 b

5.50 b

7.75 b

Resource .86EC
Orthene 75SP
COC

4.0
16.0
0.5% v/v

4.96 a

10.88 b

12.92 b

Orthene 75SP
COC

16.0
0.5% v/v

5.75 a

26.50 ab

28.75 ab

Resource .86EC
COC

4.0
0.5% v/v

7.00 a

13.50 b

19.00 b

Control

5.50 a

35.75 a

40.00 a

¹ All treatments were tank-mixed prior to application. COC=Crop Oil Concentrate (Agrodex)
² All rates specified as oz/acre unless noted otherwise.
³ All counts are based on 20 sweeps.
⁴ Means in a column followed by the same letter do not significantly differ (P=0.05, Duncan's New MRT).
⁵ NCR= northern corn rootworm, WCR=western corn rootworm, SCR=southern corn rootworm.

Table 3.3 Mean number of bean leaf beetles, northern corn rootworm, western corn rootworm, and southern corn rootworm adults per 20 sweeps, 14 days after treatment (DAT) Urbana, 1996

Treatment¹

Rate²

Bean Leaf

Beetles^3,4

14 DAT

NCR + WCR

Rootworms^3,4,5

14 DAT

NCR+WCR+SCR

Rootworms^3,4,5

14 DAT

Ambush 2.0EC
COC

10.0
0.5% v/v

3.49 c

24.45 ab

28.04 ab

Pounce 3.2EC
COC

6.0
0.5% v/v

3.75 c

11.75 b

18.25 b

Resource .86EC
Ambush 2.0EC
COC

4.0
10.0
0.5% v/v

4.25 c

12.25 b

17.00 b

Resource .86EC
Pounce 3.2EC
COC

4.0
6.0
0.5% v/v

6.25 c

15.50 b

22.50 b

Orthene 75SP
COC

16.0
0.5% v/v

8.00 bc

33.00 a

40.25 a

Resource .86EC
COC

4.0
0.5% v/v

14.75 a

15.25 b

21.00 b

Resource .86EC
Orthene 75SP
COC

4.0
16.0
0.5% v/v

16.24 a

14.35 b

18.69 b

Control

¹ All treatments were tank-mixed prior to application. COC=Crop Oil Concentrate (Agrodex)
² All rates specified as oz/acre unless noted otherwise.
³ All counts are based on 20 sweeps.
⁴ Means in a column followed by the same letter do not significantly differ (P=0.05, Duncan's New MRT).
⁵ NCR= northern corn rootworm, WCR=western corn rootworm, SCR=southern corn rootworm.

Table 3.4 Mean number of bean leaf beetles, northern corn rootworm, western corn rootworm, and southern corn rootworm adults per 20 sweeps, 21 days after treatment (DAT) Urbana, 1996

Treatment¹

Rate²

Bean Leaf

Beetles^3,4,5

21 DAT

NCR + WCR

Rootworms^3,4,5

21 DAT

NCR+WCR+SCR

Rootworms^3,4,5

21 DAT

Resource .86EC
Ambush 2.0EC
COC

4.0
10.0
0.5% v/v

1.50 b

7.25 b

24.25 b

Ambush 2.0EC
COC

10.0
0.5% v/v

1.79 b

13.39 b

29.05 ab

Pounce 3.2EC
COC

6.0
0.5% v/v

2.75 b

7.25 b

25.00 b

Resource .86EC
Pounce 3.2EC
COC

4.0
6.0
0.5% v/v

3.25 b

8.75 b

31.00 ab

Resource .86EC
COC

4.0
0.5% v/v

12.00 a

8.25 b

25.75 ab

Orthene 75SP
COC

16.0
0.5% v/v

15.00 a

25.00 a

46.00 ab

Resource .86EC
Orthene 75SP
COC

4.0
16.0
0.5% v/v

20.00 a

12.75 b

37.75 ab

Control

18.00 a

22.50 a

48.25 a

¹ All treatments were tank-mixed prior to application. COC=Crop Oil Concentrate (Agrodex)
² All rates specified as oz/acre unless noted otherwise.
³ All counts are based on 20 sweeps.
⁴ Means in a column followed by the same letter do not significantly differ (P=0.05, Duncan's New MRT).
⁵ NCR= northern corn rootworm, WCR=western corn rootworm, SCR=southern corn rootworm.

Table 3.5 Mean number of bean leaf beetles, northern corn rootworm, western corn rootworm, and southern corn rootworm adults per 20 sweeps, 21 days after treatment (DAT) Urbana, 1996

Percentage velvet leaf control³

Plant heights³

(inches)

Treatment¹

Rate²

7 DAT

21 DAT

21 DAT

Resource .86EC
Orthene 75SP
COC

4.0
16.0
0.5% v/v

52.5 d

75.0 d

32.49 c

Resource .86EC
Ambush 2.0EC
COC

4.0
10.0
0.5% v/v

17.5 b

65.0 c

34.13 bc

Resource .86EC
Pounce 3.2EC
COC

4.0
6.0
0.5% v/v

17.5 b

65.0 c

32.52 c

Resource .86EC
COC

4.0
0.5% v/v

32.5 c

55.0 b

32.92 c

Ambush 2.0EC
COC

10.0
0.5% v/v

0 a

0 a

34.66 ab

Orthene 75SP
COC

16.0
0.5% v/v

0 a

0 a

34.78 ab

Pounce 3.2EC
COC

6.0
0.5% v/v

0 a

0 a

36.02 a

Control

0 a

0 a

36.00 a

¹ All treatments were tank-mixed prior to application. COC=Crop Oil Concentrate (Agrodex)
² All rates specified as oz/acre unless noted otherwise.
³ Means in a column followed by the same letter do not significantly differ (P=0.05, Duncan's New MRT).

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