Title

Field pea response and weed control with fall application of metribuzin and pyroxasulfone at Hettinger, ND, 2025.

(Research Report, Hettinger REC, December 2025)

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Publication File:

Field pea response and weed control with fall application of metribuzin and pyroxasulfone at Hettinger, ND, 2025

Summary

Fall application of the herbicides metribuzin and pyroxasulfone were evaluated for both crop response and weed control in 2025 at Hettinger, ND (see Table 1 for treatments; Table 3 for description of applications). A fall application of glyphosate alone provided poor control of cheatgrass (26%) and addition of metribuzin did not improve cheatgrass control (28 to 32%). Application of glyphosate plus pyroxasulfone (Zidua SC) resulted in 86% control of cheatgrass and the addition of metribuzin only improved cheatgrass control when added at 8 oz/A. Kochia control with pyroxasulfone was 86 and 82% at 23 and 50 days after planting (DAP). Fall application of metribuzin provided similar control of kochia. The combination of pyroxasulfone and metribuzin improved kochia control to 95 and 91% (23 and 50 DAP) when applied at 8 oz/A. Wild buckwheat control with pyroxasulfone was 74 and 50% (23 and 50 DAP). Metribuzin at 4, 6, and 8 oz/A also resulted in poor wild buckwheat control (61 to 69%). Combination of pyroxasulfone and 8 oz/A of metribuzin improved wild buckwheat control to 81%. Wild oat was controlled 86% with pyroxasulfone. Metribuzin did not control wild oat. An application of clethodim (Section 3) was applied to the entire trial after the 23 DAP evaluation to control wild oat and cheatgrass. Prickly lettuce control with pyroxasulfone was poor (45%). Metribuzin improved control to 81 to 85%. Best control was with a combination of pyroxasulfone and 8 oz/A of metribuzin.

Lead Author

Lead Author:

Caleb Dalley

Availability

Availability:

Web only

Publication Sections

Table 1. Evaluation of fall application of metribuzin and pyroxasulfone for weed control in peas.

			Cheatgrass		Kochia				Wild buckwheat				Wild oat		Prickly lettuce
Treatment^a		Rate	23 DAP		23 DAP		50 DAP		23 DAP		50 DAP		23 DAP		50 DAP
		oz/A	–––––––––––––––––––––––––––– % control –––––––––––––––––––––––––––––––
1	Untreated Control	-	0	d	0	d	0	d	0	d	0	f	0	d	0	e
2	Roundup PowerMax3	22	26	c	0	d	0	d	0	d	0	f	0	d	0	e
3	Zidua SC	4	86	b	86	bc	82	c	74	ab	50	e	86	a	45	d
	Roundup PowerMax3	22
4	Metribuzin	4	28	c	85	c	85	bc	63	c	61	d	23	c	81	c
	Roundup PowerMax3	22
5	Metribuzin	6	32	c	88	bc	84	c	62	c	63	d	31	bc	84	bc
	Roundup PowerMax3	22
6	Metribuzin	8	29	c	89	bc	86	bc	66	bc	69	c	33	b	85	bc
	Roundup PowerMax3	22
7	Zidua SC	4	94	ab	91	ab	85	bc	79	a	76	ab	89	a	83	bc
	Metribuzin	4
	Roundup PowerMax3	22
8	Zidua SC	4	88	ab	90	abc	89	ab	69	bc	73	bc	82	a	88	ab
	Metribuzin	6
	Roundup PowerMax3	22
9	Zidua SC	4	95	a	95	a	91	a	81	a	80	a	88	a	95	a
	Metribuzin	8
	Roundup PowerMax3	22
LSD P=.05			7.7		5.7		4.7		9.4		6.1		9.8		6.8
Standard Deviation			6.3		4.7		3.9		7.8		5.0		8.1		5.7
CV			11.83		6.85		5.88		14.22		9.64		16.85		9.09
Treatment F			135.968		275.360		374.080		66.401		150.741		89.289		179.924
Treatment Prob(F)			0.0001		0.0001		0.0001		0.0001		0.0001		0.0001		0.0001

^aRoundup PowerMax3, glyphosate 4.8 lbae/gal; Zidua SC, pyroxasulfone 4.17 lbai/gal; metribuzin 75%DF. All treatments included AMS at 8.5 lb/100gal.
^bAbbreviations: DAP, days after planting; lbae/gal, pounds acid equivalent per gallon; lbai/gal, pounds active ingredient per gallon.

Fall herbicide treatments did not cause visible injury to peas (data not shown). Pea stand count was not affected by herbicide treatment. Pea height was reduced in treatments with poor weed control (especially with poor control of wild oat and cheatgrass). Pea yield was lowest in the untreated control and with a fall application of glyphosate alone. Pea yield was highest when a combination of pyroxasulfone and metribuzin was applied in the fall.

Table 2. Evaluation of fall application of metribuzin and pyroxasulfone for crop response in peas.

			Stand count		Pea height		Pea yield
Treatment^a		Rate	37 DAP		51 DAP
		oz/A	plants/A		inches		lb/A
1	Untreated Control	-	255000	-	10.2	e	996	d
2	Roundup PowerMax3	22	251000	-	10.2	de	983	d
3	Zidua SC	4	251000	-	11.8	abc	1925	b
	Roundup PowerMax3	22
4	Metribuzin	4	259000	-	11.0	cd	1425	c
	Roundup PowerMax3	22
5	Metribuzin	6	275000	-	11.4	bc	1869	b
	Roundup PowerMax3	22
6	Metribuzin	8	279000	-	11.8	abc	1842	b
	Roundup PowerMax3	22
7	Zidua SC	4	279000	-	12.2	ab	2352	a
	Metribuzin	4
	Roundup PowerMax3	22
8	Zidua SC	4	279000	-	12.2	a	2380	a
	Metribuzin	6
	Roundup PowerMax3	22
9	Zidua SC	4	299000	-	12.2	a	2433	a
	Metribuzin	8
	Roundup PowerMax3	22
LSD P=.05			12.1		2.0		377.6
Standard Deviation			10.0		1.6		311.6
CV			15.06		5.58		17.37
Treatment F			0.679		6.250		12.940
Treatment Prob(F)			0.7051		0.0002		0.0001

Application Description		Application equipment
Date	Nov-4-2024	Equipment Type	Tractor mounted
Start Time	2:39 PM	Operation Pressure	42 PSI
Stop Time	3:02 PM	Nozzle Model	11002DG
Air Temperature Start, Stop	50, 50 F	Nozzle Spacing	20 IN
% Relative Humidity Start, Stop	37, 37	Boom Length	100 IN
Wind Velocity+Dir. Start	6 MPH, WSW	Boom Height	22.0 IN
Wind Velocity+Dir. Max	15 MPH, SW	Ground Speed	4 MPH
Soil Temperature	40 F	Carrier	WATER
% Cloud Cover	10	Application Amount	10 GAL/AC

Field pea response and weed control with fall application of metribuzin and pyroxasulfone at Hettinger, ND, 2025.

Table 1. Evaluation of fall application of metribuzin and pyroxasulfone for weed control in peas.

Table 2. Evaluation of fall application of metribuzin and pyroxasulfone for crop response in peas.

Table 3. Application environment and equipment for preemergence application of herbicide treatments for weed control in peas.

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