Malheur Experiment Station Information for Sustainable Agriculture

Weed control is important in sweet corn production to reduce weed competition. Sweet corn can be sensitive to new herbicides and crop tolerance needs to be evaluated. These studies evaluated weed control and crop tolerance for BAS 662 and BAS 656 07 H herbicides.

Tolerance and efficacy trials were conducted separately for BAS 662 and BAS 656 07 H herbicides at the Malheur Experiment Station. The soil was Nyssa silt loam with pH 8.1 and 1.2 percent organic matter. The field was fertilized with 140 lb N/acre, 5 lb Zn/acre, 0.5 lb B/acre, and 10 lb Mg/acre as a preplant, sidedressed application. Weeds were controlled in the tolerance trials with a preplant application of EPTC (3.14 lb ai/acre) and atrazine (0.75 lb ai/acre) and by hand weeding. Pioneer sweet corn variety "Jubilee" was planted with a John Deere model 71 Flexi Planter on May 5. Plant population was 29,000 seeds per acre on 30-in rows. Plots were 10 ft wide by 30 ft long and replicated three times in the efficacy trials and four times in the tolerance trials. Plots were organized in a randomized complete block design within each trial. Herbicide treatments were applied with a CO₂-pressurized backpack sprayer delivering 20 gpa at 30 psi. Corn injury and weed control were evaluated throughout the growing season for the efficacy trials. Crop injury was recorded for the tolerance trials. Corn yield was determined August 9 by harvesting and weighing the corn ears from the center two rows of each plot.

Weed Control with BAS 662 in Sweet Corn

BAS 662 was applied alone at three rates (0.088, 0.132, and 0.175 lb ai/acre) and in combination with bentazon, atrazine, bentazon plus atrazine, and quinclorac. BAS 662 also was compared to bentazon alone and bentazon plus atrazine. All treatments included a NIS (0.25 percent v/v) and 32 percent N (1.25 percent v/v). Applications were made June 1 to corn that was 6 in tall. The predominant weeds in the trial were redroot pigweed, common lambsquarters, and hairy hightshade.

Sweet Corn Tolerance to BAS 662

BAS 662 was applied at four rates (0.132, 0.175, 0.263, and 0.350 lb ai/acre) both with and without 32 percent N (1.25 percent v/v). All treatments included NIS (0.25 percent v/v). Herbicides were applied on June 4 to 6-in tall corn. Crop injury was evaluated weekly from June 11 to July 2. A final rating was taken on August 9. After total plot yields were determined, a subsample of 25 ears was taken from each sample, the husks were removed, and the weight recorded. The length and diameter of each ear also was measured.

Weed Control with BAS 656 07 H in Sweet Corn

Treatments in this trial included BAS 656 07 H (0.64 lb ai/acre), Frontier, BAS 656 07 H plus atrazine, Dual II Magnum, and Dual II Magnum plus atrazine. Herbicides were applied 1 day after planting as a postplant, preemerge treatment on May 6. Crop injury and weed control evaluations were recorded throughout the growing season.

Sweet Corn Tolerance to BAS 656 07 H

Sweet corn tolerance was evaluated in response to BAS 656 07 H applied at two rates (0.64 and 1.29 lb ai/acre) and compared to Frontier and Dual II Magnum applied at twice their typical use rates. All treatments were applied 1 day after planting as a preemergence application. Crop injury was evaluated on June 2, 11, 18, July 2, and August 9.

A similar BAS 662 tolerance trial was conducted in 1998 and no crop injury was recorded. However, in the 1999 tolerance trial, crop injury was apparent in all treatments containing BAS 662. When comparing the results for the crop injury ratings between the BAS 662 efficacy trial and the BAS 662 tolerance trial, it is notable that in the efficacy trial, no treatments had a significant amount of crop injury and in the tolerance trial, all treatments showed a significant amount of crop injury on the June 11 date. Further research may be needed to determine the interaction between the preplant applications of EPTC and atrazine that were applied to the tolerance trial, and the post treatments of BAS 662.

Weed Control with BAS 662 in Sweet Corn

There was no significant injury to the crop on the June 11, June 18, and August 9 evaluation dates (Table 1). BAS 662 in combination with atrazine plus Basagran had among the greatest control of redroot pigweed (97 to 98 percent), common lambsquarters (96 to 97 percent), and hairy nightshade (97 to 98 percent) 31 days after treatment (DAT). Prior to harvest, all treatments including BAS 662, except for BAS 662 plus quinclorac, provided greater than 93 percent redroot pigweed control, 89 percent common lambsquarters control, and 85 percent hairy nightshade control. All yields were significantly better than the untreated check, but there were no differences among other treatments.

Sweet Corn Tolerance to BAS 662

Crop injury was apparent with all BAS 662 treatments by 7 DAT (Table 2). The addition of 32 percent N to BAS 662 (0.350 lb ai/acre) caused higher injury than any other treatment. By 14 and 21 DAT, injury decreased for treatments not containing 32 percent N, while injury increased with treatments containing the nitrogen. Injured corn exhibited symptoms similar to drought stress. By 28 DAT, injury was declining for all treatments and symptoms were not apparent as the season progressed. Fresh corn weights were not different among treatments. However, the weight of the 25-ear subsample and the average cob diameter were reduced by all BAS 662 treatments compared to the untreated check (Table 3). BAS 662 at 0.350 lb ai/acre with NIS and 32 percent N also reduced cob length compared to the untreated check. Though not significant, it appeared that both cob length and diameter decreased in response to increasing BAS 662 rates.

Weed Control with BAS 656 07 H in Sweet Corn

No corn injury was observed throughout the duration of the trial (Table 4). There were no significant differences between BAS 656 07 H, Frontier, or Dual II Magnum when compared to the untreated check for the control of redroot pigweed, common lambsquarters, and hairy nightshade. Weed control ratings with BAS 656 07 H plus atrazine and Dual II Magnum plus atrazine were significantly better than all other treatments for the duration of the trial. Weed control ratings with these treatments were the highest on August 9; 63 percent for redroot pigweed, 73 percent for common lambsquarters, and 83 percent for hairy nightshade. There were no significant differences between Dual II Magnum plus atrazine and BAS 656 07 H plus atrazine for weed control on August 9. Due to variability, there were no significant differences in yield.

Sweet Corn Tolerance to BAS 656 07 H

BAS 656 07 H, Frontier, and Dual II Magnum did not injure sweet corn even when applied at twice their typical use rates (Table 5). Treatments also did not reduce sweet corn yields compared to the untreated check.

Table 1. Weed control and corn yield with BAS 662 in sweet corn, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Corn injury			Weed control‡			Corn yield§
Treatment†	Rate	6-11	8-9		Redroot pigweed	Lambs- quarters	Hairy- nightshade
	lb ai/acre				---------------------%---------------------			cwt/acre
BAS 662	0.088	0	0		85	82	80	241
BAS 662	0.132	3	0		87	83	83	230
BAS 662	0.175	0	0		92	90	82	246
BAS 662 + Basagran	0.088 +0.50	3	0		89	90	93	246
BAS 662 + Basagran	0.088 + 0.75	2	0		92	88	93	226
BAS 662 + Laddok	0.088 + 0.78	5	0		97	97	97	231
BAS 662 + Laddok	0.088 + 1.04	3	0		98	96	98	234
Disinct + Atrazine	0.088 + 0.5	0	0		88	93	95	239
Laddok	1.04	0	0		94	86	93	238
Basagran	0.75	0	0		40	50	53	226
BAS 662 + Quinclorac	0.088 + 0.03	0	0		85	80	57	238
Untreated		0	0		0	0	0	164
LSD (0.05)		5	NS		15	14	23	40

^†NIS (0.25% v/v) and 32% N (1.25% v/v) were added to all treatments.

^‡Weed control was evaluated on July 2.

^§Corn yield was taken on August 9.

Table 2. Sweet corn tolerance to BAS 662, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

^†NIS was applied at 0.25% v/v, and 32% N was applied at 1.25% v/v.

Table 3. BAS 662 effects on a 25-ear sub-sample of sweet corn, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Corn ears
Treatment†	Rate	Deformed	Length	Diameter	Corn yield
	lb ai/acre	# / 25 ears	cm	cm	lb/25 ears
BAS 662 + NIS + 32% UAN	0.132	1.5	20.6	4.6	13.0
BAS 662 + NIS + 32% UAN	0.175	2	20.3	4.6	12.7
BAS 662 + NIS + 32% UAN	0.263	1.8	20.4	4.5	12.6
BAS 662 + NIS + 32% UAN	0.35	3	19.9	4.5	12.6
BAS 662 + NIS	0.132	1	21	4.6	13.2
BAS 662 + NIS	0.175	2.8	21	4.5	12.9
BAS 662 + NIS	0.263	2.3	20.8	4.5	12.8
BAS 662 + NIS	0.35	5	20.5	4.5	12.2
Untreated		1.3	20.8	4.7	14.4
LSD (0.05)		NS	0.6	0.1	0.7

^†NIS was applied at 0.25% v/v, and 32% N was applied at 1.25% v/v.

Table 4. Weed control and corn yield with BAS 656 07 H in sweet corn, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Corn injury			Weed control†			Corn yield‡
Treatment	Rate	6-18	7-2		Pigweed	Lambs- quarters	Hairy nightshade
	lb ai/acre				-----------------%------------------			cwt/acre
Frontier	1.17	0	0		3	3	3	189
BAS 656 07 H	0.64	0	0		0	0	0	175
BAS 656 07 H + Atrazine	0.64 + 1.0	0	0		47	47	40	231
Dual II Magnum + Atrazine	1.3 + 1.0	0	0		52	60	57	230
Dual II Magnum	1.3	0	0		0	0	0	168
Untreated		0	0		0	0	0	188
LSD (0.05)		NS	NS		13	13	12	NS

^†Weed control was evaluated on June 18.

^‡Corn yield was taken on August 9.

Table 5. Sweet corn tolerance to BAS 656 07 H, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Corn injury					Corn yield†
Treatment	Rate	6-2	6-11	6-18	7-2	8-9
	lb ai/acre	-----------------------------%-------------------------------					cwt/acre
Frontier	2.34	0	0	5	0	0	259
BAS 656 07 H	0.64	0	0	3	0	0	256
BAS 656 07 H	1.29	3	0	5	0	0	245
Dual II Magnum	2.60	3	0	1	0	0	250
Untreated		0	0	6	0	0	238
LSD (0.05)		NS	NS	NS	NS	NS	NS
LSD (0.05)

^†Corn yield was taken on August 9.

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Malheur Agricultural Experiment Station

Last updated  Tuesday July 30, 2002 .