Malheur Experiment Station Information for Sustainable Agriculture

In 1999, four trials were conducted to evaluate new herbicides for weed control efficacy and potato tolerance. In all, 42 different herbicide treatments were investigated. These trials demonstrated that potatoes are tolerant to much higher rates of sulfentrazone than are necessary to achieve acceptable weed control. Potato tolerance to BAS 656 07 H and Dual Magnum was demonstrated, and yields were not reduced even when BAS 656 07 H and Dual Magnum were applied at two and four times the typical use rates. Postemergence combinations of Dual Magnum with Sencor or Matrix were shown to cause significant foliar injury, and the Sencor combination reduced marketable tuber yield. Under favorable environmental conditions, most of the herbicides evaluated provided exceptional weed control. Postemergence applications of Select provided good volunteer barley control without injury to the potatoes. Many of the herbicides investigated have promise for improving weed control in potatoes in the future.

Four trials were conducted at the Malheur Experiment Station to evaluate new herbicides for weed control efficacy and crop tolerance in potatoes. A trial evaluating postemergence grass herbicides for volunteer barley control was furrow irrigated while the other trials were sprinkler irrigated. The sprinkler irrigated trials were planted April 13 in a silt loam soil with pH 7.8 and 1.5 percent organic matter. The volunteer barley control trial was planted April 15 in a loam soil with pH 8.0 and 1.1 percent organic matter. For all trials, 'Russet Burbank' seed pieces were planted every 9 inches in 36- inch-wide rows. Experimental plots were four rows wide and 30 ft long. Plots were sidedressed with fertilizer on April 22, and beds were reshaped with a lilliston on April 23. Preemergence herbicides were applied April 30 and immediately incorporated with overhead irrigation. Postemergence applications were made June 4. Treatments were applied with a CO₂-pressurized backpack sprayer delivering 20 gpa at 30 psi. Plots were irrigated with sprinklers according to crop requirements throughout the season. Potato injury and weed control were evaluated throughout the season, and tuber yields were taken by harvesting the center two rows of each plot. Potatoes were harvested on September 20, 21, and 22.

Potato Response and Weed Control with Sulfentrazone Combinations

Sulfentrazone was applied alone at rates from 0.125 to 0.375 lb ai/acre and at 0.188 lb ai/acre in combinations with other herbicides including Sencor, Matrix, Eptam, Dual II Magnum, BAS 656 07 H, and Prowl. Treatments were replicated four times.

Preemergence Herbicides for Weed Control in Russet Burbank Potatoes

In this trial, treatments included combinations of different herbicides including BAS 656 07 H, Dual Magnum, Frontier, Eptam, Prowl, Sencor, and Matrix. Treatments were replicated three times. All treatments were applied preemergence, except for Dual Magnum combinations with either Sencor or Matrix, which were applied at the postemergence application time.

Tolerance of Russet Burbank Potatoes to BAS 656 07 H

This trial was conducted to evaluate BAS 656 07 H for crop injury at normal field use rates and at twice and four times the normal rate, and to compare it to other standard herbicides applied at twice their labeled rates. BAS 656 07 H is an active isomer of the herbicide Frontier (dimethenamid) and has been submitted to EPA for registration on potatoes. Treatments were replicated four times. The potato canopy covered the rows early this year, keeping us from hand weeding the plots. At the end of the season, weeds were apparent in some plots, but competitive effects were negligible.

Volunteer Barley Control with Select

Volunteer barley was broadcast over the entire trial on April 22. Prowl (0.75 lb ai/acre) was applied April 23 and incorporated with the lilliston. The lilliston also incorporated the barley seed. Prowl was used to control other weeds without having much impact on the barley. Grass herbicides were applied on June 4 when potatoes and barley both averaged 9 inches in height. Treatments were replicated four times. Potato injury and barley control were evaluated until the potato canopy outgrew the barley. Total potato yield was determined by harvesting the center two rows of each plot, but tubers were not graded.

In 1999, the spring weather was cool and dry and then warmed up shortly after planting. Potatoes emerged and quickly formed a canopy while weed germination was low. The low weed germination and early potato canopy resulted in excellent weed control from almost all of the preemergence herbicide combinations evaluated.

Potato Response and Weed Control with Sulfentrazone Combinations

Sulfentrazone alone and in combination with other herbicides did not cause significant potato injury (Table 1). All of the treatments provided at least 87 percent control of redroot pigweed, common lambsquarters, and hairy nightshade. Barnyardgrass was not present at high enough populations to be evaluated. Sulfentrazone at the lowest rate evaluated provided at least 99 percent control of all three weed species. Matrix alone provided slightly less redroot pigweed control than the other treatments. On September 1, Matrix alone and Sencor plus Matrix had slightly lower control of common lambsquarters and hairy nightshade than the other treatments, except for Sencor alone. Total tuber yields were not different among treatment (Table 2). All treatments increased U.S. Number One and total marketable tuber yields in comparison to the untreated check. Sulfentrazone plus Dual II Magnum had higher U.S. Number One and total marketable yields than sulfentrazone at the highest rate (0.375 lb ai/acre), sulfentrazone plus Sencor or Matrix or Eptam, Sencor plus Matrix, and Matrix alone. The results suggest that potatoes are tolerant to sulfentrazone at rates higher than needed for effective weed control.

Preemergence Herbicides for Weed Control in Russet Burbank Potatoes

Postemergence applications of Dual Magnum in combination with Matrix or Sencor caused significant foliar injury, with the injury being more severe with the Dual Magnum plus Sencor combination (Table 3). None of the preemergence treatments caused visible injury. Injury from the postemergence treatments became less apparent as the season progressed. On June 15, Dual Magnum applied preemergence and Dual Magnum plus Matrix applied postemergence provided the least control of redroot pigweed. The postemergence combination improved as the season progressed, but the preemergence application of Dual Magnum still had only 80 percent redroot pigweed control on September 1. All other treatments provided greater than 90 percent redroot pigweed control. Common lambsquarters and hairy nightshade control was also poor with the postemergence application of Dual Magnum plus Matrix at the early evaluation, but was among the best by the September evaluation. BAS 656 07 H plus Sencor, Prowl plus Sencor, and Sencor alone had greater than 95 percent control of redroot pigweed, common lambsquarters, and hairy nightshade throughout the entire season. All treatments increased total yields (Table 4) compared to the untreated check except for Dual Magnum plus Sencor. The reduced total yield may have been due to the severe injury early in the season. Prowl plus Sencor and Eptam plus Sencor had among the highest yields of U.S. Number One and total marketable tubers while Dual Magnum alone preemergence and Dual Magnum plus Sencor postemergence were not different from the untreated for total marketable yield. Prowl plus Sencor yielded higher than Prowl plus Matrix for total U.S. Number One and total marketable potato yields. Prowl plus Matrix (167 cwt/acre) produced more undersize tubers than plots treated with Prowl plus Sencor (139 cwt/acre). Slightly lower weed control with the Prowl and Matrix combination may have resulted in the lower yields.

Tolerance of Russet Burbank Potatoes to BAS 656 07H

No potato injury or differences in potato yield and quality were observed when BAS 656 07 H, Frontier, Dual II Magnum, and Prowl were applied at twice the labeled field rate (Table 5). Even at 4 times the typical use rate, BAS 656 07 H and Dual II Magnum did not cause significant injury or reduce potato yields. These results suggest that potato tolerance to the herbicides evaluated is very high. Although not significant, low weed pressure in the untreated check may have depressed yields for that treatment.

Volunteer Barley Control with Select

Herbicide activity was slow because the barley was so large when the postemergence treatments were applied. On June 18, barley control (Table 6) was greatest with Select at the high rate (0.188 lb ai/acre). Poast alone and Select combined with Sencor provided the least control. The addition of Sencor to Select appeared to decrease early control. However, by June 23, barley control was similar for all Select treatments but lower with Poast. All herbicide treatments increased potato yield compared to the untreated check. Select would be useful for postemergence control of volunteer barley and other grass species in potatoes.

Table 1. Weed control and potato injury on June 15 and September 1 with sulfentrazone combinations, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

				Weed control
			Potato Injury	Redroot  pigweed		Common lambsquarters		Hairy nightshade
Treatment	Rate		6-15	6-15	9-1	6-15	9-1	6-15	9-1
	lb ai/acre		-------------------------------------------%-----------------------------------------------
Sulfentrazone	0.125		6	99	99	100	100	99	100
Sulfentrazone	0.188		0	100	100	100	100	98	98
Sulfentrazone	0.25		8	100	99	99	100	99	99
Sulfentrazone	0.375		6	100	100	100	100	99	100
Sulfentrazone + Sencor	0.188 + 0.5		3	100	100	100	100	100	100
Sulfentrazone + Matrix	0.188 + 0.016		6	99	100	100	100	93	96
Sulfentrazone + Eptam	0.188 + 3.0		3	100	98	100	100	98	98
Sulfentrazone + Dual II Magnum	0.188 + 1.0		0	100	99	100	100	98	99
Sulfentrazone + BAS 656 07 H	0.188 + 0.64		0	100	100	100	100	96	100
Sulfentrazone + Prowl	0.188 + 1.0		1	99	100	100	100	99	100
Sencor + Matrix	0.5 + 0.016		0	100	100	94	90	99	87
Eptam + Sencor	3.0 + 0.5		0	100	96	100	100	100	96
Sencor	0.5		0	100	96	93	97	99	92
Matrix	0.016		0	94	88	94	91	91	88
Sulfentrazone	0.188		3	98	100	100	100	100	96
Untreated			0	0	0	0	0	0	0
LSD (0.05)			NS	3	4	6	5	6	7

Table 2. Russet Burbank tuber yield^† and grade in response to sulfentrazone combinations, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

			U.S. Number One					Total no. 2	Total marketable	Total yield
Treatment	Rate		4-6 oz	6-12 oz	> 12 oz	Total	%
	lb ai/acre		--------------------cwt/acre------------------				%	-------------cwt/acre-------------
Sulfentrazone	0.125		135	221	60	416	72	13	429	577
Sulfentrazone	0.188		143	215	48	405	72	8	413	561
Sulfentrazone	0.25		129	225	54	408	74	8	417	549
Sulfentrazone	0.375		134	196	53	383	69	12	395	550
Sulfentrazone + Sencor	0.188 + 0.5		144	195	58	396	73	7	404	541
Sulfentrazone + Matrix	0.188 + 0.016		125	194	59	378	71	14	391	531
Sulfentrazone + Eptam	0.188 + 3.0		134	200	57	391	71	8	399	552
Sulfentrazone + Dual II Magnum	0.188 + 1.0		141	234	65	440	76	14	454	578
Sulfentrazone + BAS 656 07 H	0.188 + 0.64		151	226	49	427	75	5	432	569
Sulfentrazone + Prowl	0.188 + 1.0		145	223	38	406	72	6	412	563
Sencor + Matrix	0.5 + 0.016		129	213	48	390	73	7	397	535
Eptam + Sencor	3.0 + 0.5		154	194	50	397	70	7	404	566
Sencor	0.5		145	207	49	401	72	8	409	558
Matrix	0.016		153	201	32	386	70	10	396	548
Sulfentrazone	0.188		140	215	51	405	73	7	412	554
Untreated			143	164	26	333	68	9	342	490
LSD (0.05)			NS	NS	NS	44	4	NS	45	NS

^†Potatoes were harvested on September 21 and 22.

Table 3. Potato injury and weed control with preemergence and postemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

					Weed control
				Injury	Redroot  pigweed		Common lambsquarters		Hairy nightshade
Treatment	Rate	Timing		6-15	6-15	9-1	6-15	9-1	6-15	9-1
	lb ai/acre			--------------------------------------------%---------------------------------------------
Frontier + Sencor	1.17 + 0.5	PRE		2	99	97	84	95	79	85
BAS 656 07 H + Sencor	0.64 + 0.5	PRE		2	100	100	100	100	100	100
BAS 656 07 H + Matrix	0.64 + 0.016	PRE		0	92	97	90	87	99	93
BAS 656 07 H + Prowl	0.64 + 1.0	PRE		0	99	90	92	92	85	83
Prowl + Eptam + Sencor	1.0 + 3.0 + 0.5	PRE		3	100	100	100	100	98	90
Prowl + Sencor	1.0 + 0.5	PRE		0	100	97	98	100	100	97
Prowl + Matrix	1.0 + 0.016	PRE		0	96	100	90	95	85	86
Eptam + Matrix	3.0 + 0.016	PRE		0	100	96	100	100	97	80
Eptam + Sencor	3.0 + 0.5	PRE		2	100	100	100	100	97	95
Dual Magnum + Matrix	1.6 + 0.016	POST		23	77	100	70	94	83	100
Dual Magnum + Sencor	1.6 + 0.5	POST		33	92	100	90	100	84	97
Dual Magnum	1.6	PRE		0	75	80	99	93	88	83
Sencor	0.5	PRE		0	100	100	100	100	93	93
Matrix	0.016	PRE		0	95	97	95	93	100	95
Sencor + Matrix	0.5 + 0.016	PRE		0	100	100	100	100	100	93
Untreated				0	0	0	0	0	0	0
LSD (0.05)				4	7	8	11	7	15	15

Table 4. Tuber yield^† and quality in response to preemergence and postemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

			U.S. Number One					Total no. 2	Total marketable	Total yield
Treatment	Rate	Timing	4-6 oz	6-12 oz	> 12 oz	Total	%
	lb ai/acre		---------------------cwt/acre------------------				%	-------------cwt/acre-------------
Frontier + Sencor	1.17 + 0.5	PRE	145	217	30	392	72	7	399	546
BAS 656 07 H + Sencor	0.64 + 0.5	PRE	147	249	34	430	74	12	443	581
BAS 656 07 H + Matrix	0.64 + 0.016	PRE	142	229	42	412	72	7	419	570
BAS 656 07 H + Prowl	0.64 + 1.0	PRE	149	223	46	417	72	8	425	577
Prowl + Eptam + Sencor	1.0 + 3.0 + 0.5	PRE	144	239	52	435	75	11	447	581
Prowl + Sencor	1.0 + 0.5	PRE	156	253	42	451	74	16	467	610
Prowl + Matrix	1.0 + 0.016	PRE	143	215	32	391	69	9	400	568
Eptam + Matrix	3.0 + 0.016	PRE	148	208	37	393	70	7	400	565
Eptam + Sencor	3.0 + 0.5	PRE	151	253	46	450	77	7	457	587
Dual Magnum + Matrix	1.6 + 0.016	POST	148	256	38	443	78	8	451	570
Dual Magnum + Sencor	1.6 + 0.5	POST	145	223	24	392	76	2	394	518
Dual Magnum	1.6	PRE	142	215	26	383	70	7	390	550
Sencor	0.5	PRE	144	244	42	429	75	10	439	571
Matrix	0.016	PRE	148	244	45	436	74	8	443	589
Sencor + Matrix	0.5 + 0.016	PRE	139	253	40	432	75	10	442	575
Untreated			127	180	26	333	68	10	343	486
LSD (0.05)			NS	38	NS	51	5	NS	53	49

^†Potatoes were harvested on September 20.

Table 5. Potato injury and yield^† in response to preemergence herbicide applications, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

Injury

U.S. Number One

Total

Treatment

Rate

Field rate

5-29

6-29

4-6 oz

6-12 oz

>12 oz

Total

%

Two's

Market- able

Yield

lb ai/acre

---------------------cwt/acre------------------

%

------------cwt/acre----------

Frontier 6.0	2.34	2X	4	3		126	198	29	353	67		14	368	526
BAS 656 07 H	0.64	1X	6	3		129	165	22	316	63		13	329	499
BAS 656 07 H	1.29	2X	11	4		133	185	33	351	66		18	369	529
BAS 656 07 H	2.58	4X	9	5		132	190	22	344	66		21	365	524
Dual II Magnum	2.6	2X	4	0		140	179	23	343	64		21	364	533
Dual II Magnum	5.2	4X	4	1		130	190	22	342	65		23	365	524
Prowl	3	2X	1	1		144	180	31	355	66		26	381	537
Untreated	-	-	3	3		133	184	19	336	67		18	354	498

LSD (0.05)

NS

NS

NS

NS

NS

NS

NS

NS

NS

NS

^†Potatoes were harvested on September 21 and 22.

Table 6. Volunteer barley control with postemergence grass herbicides, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Injury				Barley control			Potato yield†
Treatment	Rate	6-18	6-23	7-7		6-18	6-23	7-7
	lb ai/acre	----------------------------------------%-----------------------------------------							cwt/acre
Select + COC	0.094 + 1 qt	0	3	0		60	80	85	518
Select + COC	0.125 + 1 qt	0	3	0		60	77	82	552
Select + COC	0.188 + 1 qt	0	3	0		67	73	83	499
Select + Sencor + COC	0.125 + 0.38 +  1 qt	3	8	0		48	72	83	520
Poast + COC	0.188 + 1 qt	3	5	0		50	60	65	564
Untreated		0	0	0		0	0	0	366
LSD (0.05)		NS	NS	NS		5	9	17.6	78

^†Potatoes were harvested on September 22.

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Malheur Agricultural Experiment Station

Last updated  Tuesday July 30, 2002 .