Oakes Irrigation Research Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Phone: (701) 742-2744, FAX: (701) 742-2700, E-mail: Walter.Albus@ndsu.edu

Fine Tuning Microrates for Early-Season Broadleaf Weed Control in Onion.

Harlene Hatterman-Valenti and Collin Auwarter.

Weed control in onion is essential to produce marketable bulbs and is compounded by the crop’s notoriously non-competitive nature, especially during establishment when onion can take anywhere from 4-10 weeks to reach the 2-leaf stage. Broadleaf weeds such as common lambsquartes and redroot pigweed gain a competitive advantage over the establishing onion crop if effective weed control methods are not implemented. Most preemergence (PRE) herbicide options are ineffective and no postemergence (POST) herbicides can be applied prior to the onion 2-leaf stage. This study was conducted at the Oakes Irrigation Research Facility near Oakes, ND to compare early-season weed control of bromoxynil (Buctril) and oxyfluorfen (GoalTender) applied at microrates to a standard pre-emergence treatment of DCPA (Dacthal) or ethofumesate (Nortron) in onion. ‘Sedona’ onion was planted May 14 as twin rows on 18” centers and a planting population of 175,000 seeds/a. PRE treatments included 1 or 2 lb/A ethofumesate and 13.33 lb/A DCPA and were applied 8 days after planting (DAP). Microrate applications began when broadleaf weeds were in the cotyledon to one-leaf stage, which corresponded to onion between the flag and one-leaf stage, 21 DAP. Bromoxynil and oxyfluorfen were applied at the 0.25X and 0.13X, respectively, of the lowest labeled rate along with 0.031 lb/A clethodim (Select) and applied as four or five weekly sequential applications. Petroleum oil-surfactant (Herbimax) (1 pt/a) was tank mixed with the microrate application. The pre-emergence treatments received Buctril at 1 pt/A and Goal at 2 pt/a when onion reached the five-leaf stage.

Table1. Herbicides applied and the application timings for the various treatments.

Trt No.

Trt Name

Rate Unit/A

App Code

Trt No.

Trt Name

Rate Unit/A

App Code

Trt No

Trt Name

Rate Unit/A

App Code

Buctril

floz

Buctril

Floz

Buctril

Floz

Select Max

floz

Select Max

Floz

Select Max

Floz

Herbimax

Buctril

floz

Buctril

Floz

Buctril

Floz

Select Max

floz

Select Max

Floz

Select Max

Floz

Herbimax

Buctril

floz

Buctril

Floz

Buctril

Floz

Goal Tender

floz

Select Max

Floz

Goal Tender

Floz

Select Max

floz

Herbimax

Select Max

Floz

Herbimax

Buctril

Floz

Herbimax

Buctril

floz

Select Max

Floz

Buctril

Floz

Goal Tender

floz

Herbimax

Goal Tender

Floz

Select Max

Floz

Buctril

Floz

Select Max

Floz

Herbimax

Select Max

Floz

Herbimax

Buctril

Floz

Herbimax

Floz

Buctril

Floz

Select Max

Floz

Goal Tender

Floz

Select Max

Floz

Herbimax

Select Max

Floz

Herbimax

Buctril

Floz

Herbimax

Buctril

Floz

Select Max

Floz

Goal Tender

Floz

Select Max

Floz

Herbimax

Select Max

Floz

Herbimax

Buctril

Floz

Herbimax

Buctril

Floz

Select Max

Floz

Goal Tender

Floz

Goal Tender

Floz

Herbimax

Select Max

Floz

Select Max

Floz

Buctril

Floz

Herbimax

Goal Tender

Floz

Goal Tender

Floz

Buctril

Floz

Select Max

Floz

Select Max

Floz

Goal Tender

Floz

Herbimax

Select Max

Floz

Buctril

Floz

Goal Tender

Floz

Herbimax

Goal Tender

Floz

Select Max

Floz

Buctril

Floz

Select Max

Floz

Herbimax

Select Max

Floz

Herbimax

Dacthal

Herbimax

Goal Tender

Floz

Buctril

Floz

Buctril

Floz

Goal

Select Max

Floz

Select Max

Floz

Select Max

Floz

Herbimax

Buctril

Floz

Goal Tender

Floz

Nortron

Select Max

Floz

Buctril

Floz

Buctril

Herbimax

Select Max

Floz

Goal

Buctril

Floz

Herbimax

Select Max

Floz

Goal Tender

Floz

Goal Tender

Floz

Herbimax

Select Max

Floz

Buctril

Floz

Nortron

Herbimax

Select Max

Floz

Buctril

Floz

Herbimax

Goal

Goal Tender

Floz

Goal Tender

Floz

Select Max

Floz

Select Max

Floz

Buctril

Floz

Herbimax

Select Max

Floz

Untreated

Herbimax

Goal Tender

Floz

Buctril

Floz

Select Max

Floz

Herbimax

Table 2. Spray application information.

Date:		5/22/12	6/4/12	6/12/12	6/21/12	6/27/12	7/2/12
TIme:		A	B	C	D	E	F
Sprayer:	GPA:	20	20	20	20	20	20
	PSI:	40	40	40	40	40	40
	Nozzle:	11002	8002	8002	8002	11002	11002
Air Temperature(F):		63	72	50	63	78	93
Relative Humidity (%):		53	60	81	73	74	53
Soil Moisture:		Adequate	Adequate	Adequate	Adequate	Adequate	Adequate
Wind (MPH):		11	6	4	8	9	5
Cloud Cover (%):		40	5	0	60	50	0
Onion Stage:		Seed Cracking	1 leaf	2 leaf	3 leaf	4 leaf	5 leaf

Table 3. Weed control and onion injury ratings.

Trt

-----------6/12/2012-----------

-----------6/21/2012-----------

-----------6/27/2012-----------

-----------7/9/2012-----------

--------------------------------------------------------------------- % -------------------------------------------------------------------

CHEAL*

AMARE

Injury

CHEAL

AMARE

Injury

CHEAL

AMARE

Injury

CHEAL

AMARE

Injury

88 ab

94 a

18 a

94 ab

99 a

15 a

94 a

89 a

6 ab

93 ab

99 a

0 a

80 ab

91 ab

13 a

86 bc

96 a

11 a

88 ab

91 b

5 ab

93 ab

100 a

0 a

71 b

85 c

14 a

81 cd

95 a

9 a

78 c

98 a

2 b

89 b

100 a

0 a

94 a

95 a

15 a

98 a

96 a

12 a

96 a

99 a

6 ab

100 a

0 a

86 ab

94 a

16 a

84 c

100 a

12 a

84 bc

98 a

4 ab

89 b

100 a

0 a

88 ab

86 bc

16 a

71 e

76 b

13 a

94 a

95 ab

9 a

94 ab

98 a

0 a

90 a

93 a

20 a

75 de

94 a

14 a

95 a

95 ab

7 ab

99 a

100 a

0 a

88 ab

94 a

16 a

73 e

90 a

10 a

95 a

95 ab

6 ab

96 ab

99 a

0 a

78 ab

90 abc

13 a

89 abc

94 a

10 a

84 bc

94 ab

3 b

90 b

98 a

0 a

95 a

15 a

96 a

11 a

96 a

99 a

3 b

100 a

0 a

93 a

94 a

15 a

98 a

99 a

11 a

96 a

5 ab

98 a

0 a

0 c

0 d

0 b

0 f

0 c

0 b

0 d

0 c

0 a

LSD(P=.05)

11.7

4.4

6.1

6.3

8.5

6.4

6.0

3.3

5.2

5.0

3.4

0.0

*Abbreviations: CHEAL = common lambsquarters, AMARE = redroot pigweed.

Table 4. Treatment effects on onion yield and grade.

-------------------------------------------2 Double Rows X 6’------------------------------------------

Trt

----<1”----

-1” – 2.25”-

-2.25” – 3”-

---3” – 4” ---

----- >4” -----

----Total----

Lbs

CWT/A

0 a

1 ab

0.2 ab

9 ab

3.8 a

15 abc

11 bc

0.5 a

0.6 a

26.3 b

15.4 bc

372 bc

0 a

3 ab

0.4 ab

14 ab

5.3 a

20 ab

14 abc

0.3 a

36.5 ab

20.4 abc

493 abc

0 a

7 ab

1.1 ab

16 a

5.2 a

5 cd

3 cd

0.0 a

28.0 ab

9.75 c

236 c

0 a

2 ab

0.4 ab

9 ab

3.3 a

18 abc

14 abc

1.8 a

2.2 a

31.0 ab

20.1 abc

485 abc

0 a

5 ab

0.8 ab

15 a

5.5 a

9 bcd

5 cd

0.0 a

29.0 ab

11.5 c

278 c

0 a

3 ab

0.5 ab

10 ab

3.6 a

15 abc

12 bc

2.0 a

2.7 a

29.0 ab

18.5 abc

447 abc

0 a

1 ab

0.2 ab

5 bc

2.0 ab

18 abc

14 abc

1.3 a

1.6 a

25.8 b

17.3 abc

418 abc

0 a

2 ab

0.4 ab

5 bc

2.0 ab

24 a

19 ab

2.0 a

2.4 a

32.8 ab

23.2 ab

562 ab

0 a

11 a

1.5 a

9 ab

3.2 a

7 bcd

4 cd

0.0 a

25.5 b

8.8 c

213 c

0 a

1 ab

0.1 ab

9 ab

3.5 a

28 a

23 a

0.8 a

1.0 a

38.3 a

27.1 a

655 a

0 a

2 ab

0.4 ab

12 ab

4.6 a

16 abc

11 bc

0.0 a

30.0 ab

16.0 abc

387 abc

0 a

0 b

0.0 b

0 c

0 b

0 d

0.0 a

0.0 c

0.0 d

0 d

LSD (P=.05)

5.9

0.8

5.4

2.1

8.9

6.8

2.0

2.5

7.3

7.2

175

Treatments that included bromoxynil during at least one of the application timings provided better common lambsquarters control throughout the trial compared to treatments without bromoxynil. In contrast, the treatment with oxyfluorfen applied alone had poor common lambsquarters control. However, applying bromoxynil at the 0.0625 lb/A followed by tank mixes of bromoxynil and oxyfluorfen at 0.0625 lb/A provided the best common lambsquarters control compared to all other treatments. Applying bromoxynil at the 0.031 lb/A followed by tank mixes of bromoxynil and oxyfluorfen at the 0.0625 lb/A had significantly less control of common lambsquarters.

The highest yielding treatment was when bromoxynil was applied at 0.0625 lb/A followed by tank mixes of bromoxynil and oxyfluorfen at 0.0625 lb/A with 655 CWT/A. The lowest yielding treatment besides the untreated, which didn’t produce any marketable bulbs, was when bromoxynil was applied at 0.031 lb/A followed by tank mixes of bromoxynil and oxyfluorfen at 0.0625 lb/A with 213 CWT/A. The preemergence conventional treatment of ethofumesate at 1 lb/A had the second highest yield of 562 CWT/A.

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