Malheur Experiment Station Information for Sustainable Agriculture

These studies evaluated preemergence and postemergence herbicides for weed control and crop tolerance in furrow-irrigated imidazolinone resistant field corn.

Three trials were conducted comparing registered and experimental herbicides for weed control and crop safety in field corn. 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. Pioneer 3395 IR (Imidazolinone resistant) field corn was planted with a John Deere model 71 Flexi Planter on May 5, 1999. Seed spacing was one seed every 7.2 inches on 30-in rows. Plots were 10 ft wide by 30 ft long and replicated three times in a randomized complete block design. Herbicide treatments were applied with a CO₂-pressurized backpack sprayer delivering 20 gpa at 30 psi. For each trial, corn injury and weed control were evaluated throughout the growing season. Corn yield was determined October 18 by harvesting corn ears from the two center rows of each plot, threshing the ears, and recording the dry weight of the grain. Grain yields were adjusted to 12 percent moisture.

Balance for Weed Control in Field Corn

Balance was evaluated alone and in combination with registered corn herbicides. Registered herbicides applied in combination with Balance were applied at 3/4 of the typical use rate. Herbicide treatments were applied May 6 as a preemergence treatment. On June 18 and July 2, crop injury was rated as a percentage of injured plants, and weed control was rated as a percentage of controlled plants.

Weed Control with Lightning in Field Corn

Lightning was applied preemergence in combination with soil active herbicides and postemergence alone and following the application of preemergence herbicides. Preemergence combinations of Lightning with Balance or Prowl were compared to Prowl plus Dual II Magnum, Prowl plus BAS 656 07 H, Balance, USA 1000, Axiom plus Balance, and Dual II Magnum plus atrazine. Preemergence (PRE) applications were made May 10 and early-postemergence (EPOST) treatments were applied June 1.

Wild Oat Control with Postemergence Herbicides

Tame oats were broadcast to simulate an infestation of wild oats. Basis, Basis Gold, and Accent were applied at several postemergence timings and compared with treatments of Lightning and Atrazine. All treatments included either crop oil concentrate (COC) or non-ionic surfactant (NIS) and 32-0-0 (1 percent v/v). Early treatments of Basis, Lightning, and Atrazine were applied to 3-in tall oats on May 24. Later treatments of Basis Gold, Basis, and Accent were made to 7-in tall oats on June 4.

Results

Because of low natural spring moisture, herbicides that are dependent on moisture for activation were not effective. Activity was greatest in areas that were saturated by furrow irrigation. Soil active herbicides were less effective than in 1998.

Balance for Weed Control in Field Corn

No visible injury to the crop was apparent on June 18 or July 2 (Table 1). Lasso plus atrazine provided the highest control of redroot pigweed, common lambsquarters, and hairy nightshade (98 percent). Balance alone provided significantly less redroot pigweed control compared to Balance tank mixed with Surpass or Harness Extra. Balance plus atrazine and Balance plus Harness Extra, along with the Lasso plus atrazine, provided significantly higher common lambsquarters and hairy nightshade control than all other treatments. Because of variability, differences in corn grain-yields were not significant among treatments.

Weed Control with Lightning in Field Corn

No corn injury was visible throughout the growing season (Table 2). Balance plus Lightning, Prowl plus Lightning with NIS and 32-0-0, and Dual II Magnum plus atrazine all provided 87 to 100 percent control for redroot pigweed, common lambsquarters, and hairy nightshade. Weed control for all three species was significantly less with the Prowl plus Lightning treatment at the preemerge timing compared to Prowl plus Lightning with NIS and 32-0-0 at the early postemergence timing. Corn grain yields were not different among treatments, including the untreated checks.

Wild Oat Control with Postemergence Herbicides

Corn injury was not observed throughout the duration of the trial (Table 3). Basis, Accent, Lightning, and DPX 79406 all had significantly better oats control than atrazine, ranging from 82 to 87 percent. Basis applied to 7-in tall oats provided significantly better control (82 percent) than when applied to 3-in tall oats (30 percent). Corn grain yields were higher than the untreated check for all treatments except Basis applied to 3-in tall oats.

Table 1. Weed control and corn yield with preemergence Balance combinations, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

		Corn injury			Weed control†			Corn yield‡
Treatment	Rate	6-18	7-2		Redroot pigweed	Lambs- quarters	Hairy- nightshade
	lb ai/acre				---------------------%---------------------			bu/acre
Balance	0.047	0	0		30	43	33	281
Balance	0.059	0	0		30	33	30	294
Balance + Dual II Magnum	0.059 + 0.83	0	0		27	17	17	285
Balance + Surpass	0.059 + 1.0	0	0		75	47	37	298
Balance +  Harness Extra	0.059 + 1.5	0	0		89	78	74	300
Balance + Lasso	0.059 + 1.0	0	0		53	42	45	279
Balance +  BAS 656 07 H	0.059 +  0.48	0	0		27	13	13	291
Balance + Axiom	0.059 + 0.32	0	0		50	37	33	295
Balance + Atrazine	0.059 + 1.0	0	0		73	89	74	283
Lasso + Atrazine	2.0 + 1.0	0	0		98	98	98	289
Balance + Frontier	0.059 + 0.88	0	0		53	43	33	292
Balance	0.070	0	0		10	10	10	295
Untreated		0	0		0	0	0	281
LSD (0.05)		NS	NS		34	25	30	NS

^†Weed control was evaluated July 2.

^‡Corn yield was taken October 18 and adjusted to 12 percent moisture.

Table 2. Weed control and corn yield with Lightning in imidazolinone resistant field corn, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

			Corn injury			Weed control§			Corn yield¶
Treatment†	Rate	Timing‡	6-18	7-6		Pigweed	Lambs- quarters	Hairy nightshade
	lb ai/acre					----------------%--------------			bu/acre
Prowl + Dual II Magnum	1.0 + 1.3	PRE	0	0		73	55	63	262
Prowl + BAS 656 07 H	1.0 + 0.64	PRE	0	0		63	60	62	303
Balance + Lightning	0.063 + 0.080	PRE	0	0		100	99	100	286
Prowl + Lightning	1.0 + 0.080	PRE	3	0		68	68	52	278
Prowl +  Lightning + NIS + 32-0-0	1.0 +  0.080	PRE + EPOST	0	0		100	95	100	287
Lightning	0.080	EPOST	0	0		100	93	100	285
Prowl + Lightning + NIS+ 32-0-0	1.0 + 0.080	EPOST	0	0		99	95	100	270
Untreated			0	0		0	0	0	280
USA 1000	0.399	PRE	0	0		82	65	83	278
USA 1000	0.544	PRE	0	0		70	50	58	278
Axiom + Balance	0.32 + 0.063	PRE	0	0		68	48	47	292
Dual II Magnum + Atrazine	1.3 + 1.215	PRE	0	0		88	100	97	281
Balance	0.063	PRE	0	0		40	30	33	279
LSD (0.05)			NS	NS		14	15	22	NS

^†NIS was applied at 0.25% v/v, and 32-0-0 was applied at 1.5 qt/acre.

^‡Preemergence (PRE) treatments were applied May 10. Early postemergence (EPOST) treatments were applied June 1.

^§Weed control was evaluated July 6.

^¶Corn yield was taken October 18 and adjusted to 12 percent moisture.

Table 3. Tame oat control and corn yield with postemergence herbicides, Malheur Experiment Station, Oregon State University, Ontario, Oregon, 1999.

			Corn injury‡	Oat control‡			Corn yield§
Treatment†	Rate	Timing		6-18	7-2	8-5
	lb ai/acre	oats	--------------------%----------------------				bu/acre
Basis + COC + 32-0-0	0.016	3"	0	53	43	30	229
Basis Gold + COC + 32-0-0	0.788	7"	0	72	73	77	274
Basis + COC + 32-0-0	0.016	7"	0	71	63	82	278
Accent + COC + 32-0-0	0.031	3"	0	76	88	87	298
Untreated			0	0	0	0	205
Lightning + NIS + 32-0-0	0.080	3"	0	83	80	85	288
Atrazine + COC + 32-0-0	1.0	3"	0	65	57	57	277
DPX 79406 + NIS + 32-0-0	0.023	3"	0	77	85	87	300
LSD (0.05)			NS	9	9	21	38
LSD (0.05)

^†COC was applied at 1% v/v; 32-0-0 was applied at 4 qt/acre; NIS was applied at 0.25% v/v.

^‡Corn injury was evaluated June 18.

^§Corn yields were taken October 18 and adjusted to 12% moisture.

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Malheur Agricultural Experiment Station

Last updated  Tuesday June 28, 2011.