WEED CONTROL AND CROP RESPONSE WITH OPTION^® HERBICIDE

APPLIED IN FIELD CORN

 

 

Corey V. Ransom, Charles A. Rice, and Joey K. Ishida

Malheur Experiment Station

Oregon State University

Ontario, OR, 2004

 

 

Introduction

 

Weed control is important in field corn production to reduce competition with the crop and to prevent the production of weed seed for future crops.  Field trials were conducted to evaluate Option^® (foramsulfuron) herbicide applied alone and in various combinations for weed control and crop tolerance in furrow-irrigated field corn.  Option is a new postemergence sulfonylurea herbicide that controls annual and perennial grass and broadleaf weeds in field corn.  Option contains a safener that is intended to enhance the ability of corn to recover from any yellowing or stunting sometimes associated with the application of sulfonylurea herbicides.

 

Materials and Methods

 

The soil was formed into 22-inch beds on May 10.  Plots were sidedressed with 126 lb nitrogen (N), 14 lb sulfates, 3 lb zinc, 1 lb boron, 1 lb manganese, and 38 lb elemental sulfur/acre on May 11.  Pioneer variety ‘P-36N69’ Roundup Ready^® field corn was planted with a John Deere model 71 Flexi Planter on May 17.  Seed spacing was one seed every 7 inches.  Plots were 7.33 by 30 ft and herbicide treatments were arranged in a randomized complete block with four replicates.  Herbicide treatments were applied with a CO₂-pressurized backpack sprayer calibrated to deliver 20 gal/acre at 30 psi.  Crop response and weed control were evaluated throughout the growing season.  Corn yields were determined by harvesting ears from 26-ft sections of the center 2 rows in each 4-row plot on October 11.  The harvested ears were shelled and grain weight and percent moisture content were recorded.  Grain yields were adjusted to 12 percent moisture content.  Data were analyzed using analysis of variance (ANOVA) and treatment means were separated using Fisher’s protected least significant difference (LSD) at the 5 percent level (P = 0.05).

 

Postemergence treatments of Option, Clarion^®, or Roundup^® were applied alone and in combinations with other herbicides and with or without preemergence (PRE) Dual Magnum^®.  PRE applications were made May 21.  Mid-postemergence (MP) treatments were applied to corn at the V4 growth stage on June 11, and late postemergence treatments (LP) were applied to corn at the V6 growth stage on June 19.  Option was applied with various additives as well as in combination with Distinct^® or Callisto^®.  Option combinations were compared to Clarion applied alone and in combination with Distinct or to Roundup applied alone or following PRE Dual Magnum.  The herbicide rates and combinations are shown in Table 1.

 

Results and Discussion

 

Control of pigweed species (i.e., Powell amaranth and redroot pigweed) ranged from 91 to 100 percent on July 23 and was similar among herbicide treatments. One exception was the treatment with Option, Dyne-Amic^®, and 32 percent N, which provided only 91 percent control (Table 1).  When Option was applied with Dyne-Amic and 32 percent N or Quest^®, common lambsquarters control also was lower than all other treatments.  Clarion alone also provided less common lambsquarters control than all other treatments except for Option applied with Dyne-Amic.  Combinations of Option with Distinct or Callisto, and the combination of Clarion and Distinct provided among the best common lamsquarters control.  Common lambsquarters control was improved when Roundup was applied following PRE Dual Magnum compared to Roundup applied alone.  Clarion alone provided the least hairy nightshade control, and the combination of Clarion and Distinct also provided less hairy nightshade control compared to all other treatments except Option with Dyne-Amic and 32 percent N.  There were no significant differences in kochia and barnyardgrass control among treatments.

 

Injury from herbicide treatments ranged from 0 to 14 percent on June 19 and was 4 percent or less on July 2 (Table 2).  Corn yields ranged from a low of 103 bu/acre with the untreated control to a high of 194 bu/acre with the combination of Option and Callisto (Table 2).  The treatment containing Option with Dyne-Amic and 32 percent N had lower yields than many of the other Option treatments and was likely due to reduced weed control with that treatment. 

 

The selection of additives can significantly affect the efficacy of Option against pigweed species, common lambsquarters, and hairy nightshade.  The addition of Distinct or Callisto to Option can significantly improve common lambsquarters control.

 

Table 1.  Weed control with Option^® herbicide applied in field corn, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.

			Weed control§
Treatment	Rate*	Timing†	Pigweed spp‡		C. lambs- quarters		H. night- shade		Kochia		Barnyard- grass
	lb ai/acre pt/acre % v/v		------------------------------------- % --------------------------------------
Option + MSO + 32% N	0.033 + 1.5 + 3.0	MP	100		79		92		96		97
Option + MSO + AMS	0.033 + 1.5 + 3.0	MP	100		88		99		97		100
Option + DYNE-AMIC + 32% N	0.033 + 0.25% + 3.0	MP	91		45		76		95		94
Option + MSO + QUEST	0.033 + 1.5 +2.5%	MP	98		89		98		100		97
Clarion + MSO + 32% N	0.023 + 1.5 +4	MP	98		61		52		98		99
Option + MSO + 32% N	0.033 + 1.5 +3.0	MP	99		89		94		100		97
Option + Distinct + MSO + 32% N	0.033 + 0.088 + 1.5 + 3.0	MP	100		100		96		100		96
Option + Distinct + MSO + 32% N	0.33 + 0.175 + 1.5 + 3.0	MP	100		100		99		100		97
Clarion + Distinct + NIS + 32% N	0.023 + 0.088 + 0.5% + 4.0	MP	100		97		73		100		100
Option + Callisto + MSO + 32% N	0.033 + 0.0625 + 1.5 + 3.0	MP	99		100		97		100		98
Dual II Magnum Option + MSO + 32% N	1.6 0.033 + 1.5 + 3.0	PRE LP	97		90		85		100		100
Option + MSO + AMS	0.033 + 1.5 +3	MP	99		88		97		99		96
Option + DYNE-AMIC + Quest	0.033 + 0.25 % + 0.25%	MP	97		48		88		99		100
Roundup Ultramax	0.58	MP	99		81		95		100		97
Dual II Magnum Roundup Ultramax + AMS	1.6 0.58 + 3.0	PRE LP	100		92		90		100		99
LSD (0.05)			3		6		11		NS		NS

*Herbicide rates are in lb ai/acre.  Additive rates are in pt/acre or percent v/v.

^†Application timings were preemergence (PRE) on May 21, mid-postemergence (MP) applied to corn at the V4 growth stage on June 11, and late postemergence (LP) to corn at the V6 growth stage on June 19.

^‡Pigweed species  were a mixture of Powell amaranth and redroot pigweed.

^§Weed control was evaluated July 23.  The untreated control was not included in the ANOVA for weed control.

 

Table 2.  Injury and yield with Option^® herbicide applied in field corn, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.

			Field corn
			Injury‡					Yield§
Treatment	Rate*	Timing†	6-19	7-2
	lb ai/acre pt/acre % v/v		------------------- % -----------------					bu/acre
Untreated control	--	--	--	--				103
Option + MSO + 32% N	0.033 + 1.5 + 3.0	MP	8	0				179
Option + MSO + AMS	0.033 + 1.5 + 3.0	MP	9	0				187
Option + DYNE-AMIC + 32% N	0.033 + 0.25% + 3.0	MP	5	0				157
Option + MSO + QUEST	0.033 + 1.5 +2.5%	MP	10	0				192
Clarion + MSO + 32% N	0.023 + 1.5 +4	MP	3	0				178
Option + MSO + 32% N	0.033 + 1.5 +3.0	MP	9	3				174
Option + Distinct + MSO + 32% N	0.033 + 0.088 + 1.5 + 3.0	MP	11	0				183
Option + Distinct + MSO + 32% N	0.33 + 0.175 + 1.5 + 3.0	MP	14	4				178
Clarion + Distinct + NIS + 32% N	0.023 + 0.088 + 0.5% + 4.0	MP	6	1				189
Option + Callisto + MSO + 32% N	0.033 + 0.0625 + 1.5 + 3.0	MP	5	0				194
Dual II Magnum Option + MSO + 32% N	1.6 0.033 + 1.5 + 3.0	PRE LP	9	3				184
Option + MSO + AMS dry	0.033 + 1.5 +3	MP	9	0				178
Option + DYNE-AMIC + Quest	0.033 + 0.25 % + 0.25%	MP	1	0				178
Roundup Ultramax	0.58	MP	0	0				189
Dual II Magnum Roundup Ultramax + AMS	1.6 0.58 + 3.0	PRE LP	0	0				173
LSD (0.05)	--	--	4.5	2				21

*Herbicide rates are in lb ai/acre.  Additive rates are in pt/acre or percent v/v.

^†Application timings were preemergence (PRE) on May 21, mid-postemergence (MP) applied to corn at the V4 growth stage on June 11, and late postemergence (LP) to corn at the V6 growth stage on June 19.

^‡The untreated control was not included in the ANOVA for percent injury.

^§Corn was harvested October 11 and yields were adjusted to 12 percent moisture content.