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© 2005 Plant Management Network.
Accepted for publication 18 December 2005. Published 24 February 2005.

Broadleaf Weed Control in Field Corn with Postemergence Herbicides

Richard N. Arnold, Associate Professor of Weed Science, Dan Smeal, Associate Professor of Agronomy, and Michael K. O’Neill, Assistant Professor of Agronomy and Superintendent, New Mexico State University, Agricultural Science Center at Farmington 87499

Corresponding author: Richard N. Arnold. riarnold@nmsu.edu

Arnold, R. N., Smeal, D., and O’Neill, M. K. 2005. Broadleaf weed control in field corn with postemergence herbicides. Online. Crop Management doi:10.1094/CM-2005-0224-01-RS.

Abstract

A two-year study was conducted in 2002 and 2003 at the New Mexico State University Agricultural Science Center at Farmington, NM to evaluate postemergence herbicides for control of redroot and prostrate pigweed (Amaranthus retroflexus L. and Amaranthus blitoides S. Wats.), black nightshade (Solanum nigrum L.), common lambsquarters (Chenopodium album L.), and Russian thistle (Salsola iberica Sennen & Pau) and their effect on field corn (Zea mays) injury and yield. Herbicide treatments gave over 95% control of redroot and prostrate pigweed and common lambsquarters through August, in both years. Russian thistle control was 70% or less with DPX 79406, foramsulfuron, and nicosulfuron plus rimsulfuron when applied at 0.0115 plus 0.0115, 0.033, and 0.023 plus 0.012 lb a.i./acre, or in combination with mesotrione at 0.06 lb a.i./acre. Black nightshade control with foramsulfuron applied at 0.033 lb a.i./acre was 30 to 41% better than DPX 79406 or nicosulfuron plus rimsulfuron applied at 0.0115 plus 0.0115 and 0.023 plus 0.012 lb a.i./acre. This research indicates that when nicosulfuron plus rimsulfuron, DPX 79406, and foramsulfuron were applied in combination with diflufenzopyr plus dicamba, dicamba plus atrazine, mesotrione, or dicamba, broadleaf weed control increased significantly without field corn injury or yield reductions.

Introduction

Weeds compete vigorously with corn (Zea mays) for many resources including light, nutrients, and water. When weed populations are left uncontrolled they can substantially reduce corn yields (1,4,5,6,7). Researchers have shown season-long interference from weeds can reduce yields by more than 30% (1,2). Beckett et al. (3) found that common lambsquarters at a plant density of 4.9 plants per meter of row reduced corn yields by approximately 12%. Kenezevic et al. (8) showed that redroot pigweed densities of 0.5 to 8 plants per meter of row caused yield losses in corn ranging from 5 to 34%. To avoid yield loss and reduce herbicide efficacy, weeds that emerge with corn need to be controlled before they exceed six inches in height.

With the increased costs of equipment and herbicide applications, growers strive to reduce weed management programs to a one-pass total postemergence program. The objectives of this research were to determine the efficacy of selected postemergence herbicides applied alone or in combination for control of redroot and prostrate pigweed, common lambsquarters, black nightshade, and Russian thistle, and to determine whether these herbicides caused any significant crop injury or yield reductions.

Field Trials

Field experiments were conducted in 2002 and 2003 at New Mexico State University’s Agricultural Science at Farmington, NM to evaluate the response of field corn and annual broadleaf weeds to postemergence herbicides. Soil was a Doak silt loam (fine-silty, mixed, mesic Typic Haplargid) with a pH of 7.4 and organic matter content of less than 0.5%. Fields were fertilized annually according to New Mexico State University recommendations based on soil tests. The fields were ripped to a depth of 12 inches, fertilized with N at 225 lb/acre, P at 50 lb/acre, and K at 60 lb/acre, disked, and leveled before planting and herbicide application.

Pioneer hybrids 34M95 and 34N44 were planted with a John Deere 71 flex-planter at 35,000 seeds per acre on May 13 and May 14 in 2002 and 2003, respectively. Seeds were planted approximately one inch deep and 5.5 inches apart.

The experiment was arranged as a randomized complete block design with three replications. Individual plots were 30 ft long and consisted of four, 34-inch rows. All treatments were applied with a CO₂ backpack sprayer equipped with XR 11004-VS nozzles and calibrated to deliver 30 gal/acre at 40 psi.

Treatments were applied on June 4 and June 2 in 2002 and 2003 respectively, when field corn was at the 4th leaf stage and weeds were small (less than four inches). All treatments were applied with liquid nitrogen fertilizer (32-0-0) and a crop oil concentrate (COC) at 1 and 0.5% vol/vol, respectively.

Black nightshade, redroot and prostrate pigweed infestations were heavy, averaging 30, 28, and 24 plants per yd². Common lambsquarters infestations were moderate, averaging 20 plants per yd², and Russian thistle infestations were light, averaging 5 plants per yd² throughout the experimental area, in both years.

Visual evaluations for crop injury and weed control were made on July 8 and August 8 in 2002 and on July 17 and August 13 in 2003. Field corn was harvested on December 10 in 2002 and December 4 in 2003, by combining the two center rows of each plot using a John Deere 3300 combine equipped with a load cell. The chemical designations for herbicides evaluated in this study are found in Table 1. Only common names will be used in the rest of this text to identify treatments, except for DPX 79406.

Table 1. Chemical designation for herbicides evaluated in this study, including common name, rate, and trade name.

Weed control evaluations were analyzed as a split-plot design with years as main plots and herbicide treatments as the subplots. All data were subjected to analysis of variance and treatment means were separated by the Fisher’s (protected) LSD test at the 5% level of significance.

Weed Control Efficacy

There were no significant year by treatment interactions for weed control evaluations, so data were combined over years. None of the herbicide treatments caused any significant crop injury (data not shown). All treatments except the untreated control resulted in 100% control of redroot and prostrate pigweed and common lambsquarters by July (data not shown). However, DPX 79406, foramsulfuron (Option), and nicosulfuron plus rimsulfuron (Steadfast) applied alone at 0.0115 plus 0.0115, 0.033, and 0.023 plus 0.012 lb a.i./acre or in combination with mesotrione (Callisto) at 0.06 lb a.i./acre only gave from 38 to 70% control of Russian thistle by July (Table 2). Control of black nightshade was 30 to 41% greater with foramsulfuron at 0.033 lb a.i./acre when compared to nicosulfuron plus rimsulfuron at 0.023 plus 0.012 lb a.i./acre and DPX 79406 at 0.0115 plus 0.0115 lb a.i./acre, respectively. DPX 79406 at 0.0115 plus 0.0115 lb a.i./acre and foramsulfuron at 0.033 lb a.i./acre in combination with diflufenzopyr plus dicamba (Distinct) at 0.026 plus 0.064 lb a.i./acre, increased control of black nightshade by 29 and 31%, respectively, when compared to nicosulfuron plus rimsulfuron at 0.023 plus 0.012 lb a.i./acre in combination with diflufenzopyr plus dicamba at 0.026 plus 0.064 lb a.i./acre (Table 2).

Table 2. Averaged control of annual broadleaf weeds with postemergence herbicides in field corn on July 8, 2002 and July17, 2003.

 ^x All treatments were applied with 32-0-0 and a crop oil concentrate at 1.0 and 0.5% vol/vol.

 ^y Based on a visual scale from 0 to 100, where 0 equals no control and 100 equal dead plants.

 ^z Numbers in parentheses indicate the average population of each weed species in the test area, in plants per square yard.

In 2002, Rice et al. (10) reported that postemergence applications of DPX 79406, nicosulfuron plus rimsulfuron, and foramsulfuron at 0.0115 plus 0.0115, 0.023 plus 0.012 and 0.033 lb a.i./acre in combination with mesotrione or diflufenzopyr plus dicamba at 0.06 and 0.026 plus 0.064 lb a.i./acre, resulted in 88 to 100% control of pigweed species (Powell amaranth mixed with some redroot pigweed) and common lambsquarters, approximately 14 days after application. Rice et al. (10) further found that foramsulfuron in combination with diflufenzopyr plus dicamba applied at 0.033 plus 0.026 plus 0.064 lb a.i./acre increased hairy nightshade (Solanaceae family, as is black nightshade) control by 7 and 21%, respectively, when compared to DPX 79406 or nicosulfuron plus rimsulfuron at 0.0115 plus 0.0115 and 0.023 plus 0.012 lb a.i./acre, rated approximately 63 days after application.

In August, all treatments except the untreated control resulted in 95% or better control of redroot, prostrate pigweed, and common lambsquarters, approximately eight weeks after treatment applications (Table 3). Treatments that resulted in poor control of Russian thistle and black nightshade in July (Table 2) remained poor in August (Table 3).

Table 3. Averaged control of annual broadleaf weeds with postemergence herbicides in field corn on August 8, 2002 and August 13, 2003.

 ^x All treatments were applied with 32-0-0 and a crop oil concentrate at 1.0 and 0.5% vol/vol.

 ^y Based on a visual scale from 0 to 100, where 0 equal no control and 100 equal dead plants.

 ^z Numbers in parentheses indicate the average population of each weed species in the test area, in plants per square yard.

CornYields

Corn yields were analyzed statistically for each year. Overall average yields for herbicide treatments in 2002 and 2003 were approximately 244 and 260 bu/acre (Table 4).

Table 4. Effect of herbicide treatments on corn yield, December 10 and 4, 2002-2003.

 ^x All treatments were applied with 32-0-0 and a crop oil concentrate at 1.0 and 0.5% vol/vol.

Treatments of nicosulfuron plus rimsulfuron at 0.023 plus 0.012, DPX 79406 at 0.0115 plus 0.0115, and foramsulfuron at 0.033 lb a.i./acre were the lowest yielding treatments, except for the untreated control, ranging from 219 to 234 bu/acre, and was most likely due to poor Russian thistle control (Tables 3 and 4). The addition of dicamba, dicamba plus atrazine, diflufenzopyr plus dicamba, and mesotrione at 0.25, 0.139 plus 0.262, 0.026 plus 0.064, and 0.06 lb a.i./acre to nicosulfuron plus rimsulfuron, DPX 79406 and foramsulfuron at 0.023 plus 0.012, 0.0115 plus 0.0115, and 0.033 lb a.i./acre increased Russian thistle control and corn yield, respectively (Tables 3 and 4). In 2002 and 2003, foramsulfuron in combination with either diflufenzopyr plus dicamba or mesotrione at 0.033 plus 0.026 plus 0.064, or 0.06 lb a.i./acre were among the highest yielding treatments of 258 and 293 bu/acre, respectively (Table 4). In 2002 Rice et al. (10) and Ransom et al. (9) reported foramsulfuron in combination with mesotrione at 0.033 plus 0.06 lb a.i./acre resulted in the highest corn yield of 217 and 189 bu/acre. Rice et al. (10) further indicated that this was an approximate increase of 11 and 27 bu/acre over DPX 79406 or nicosulfuron plus rimsulfuron in combination with mesotrione at 0.0115 plus 0.0115, 0.023 plus 0.012 plus 0.06 lb a.i./acre. The two hybrids grown for this study produced similar results to Rice et al. (10) and Ransom et al. (9) with regard to herbicide response and corn yield. Yields were 109 to 152 and 86 to 150 bu/acre higher in the herbicide treated plots as compared to the untreated controls in 2002 and 2003, respectively (Table 4).

Conclusions

As farm size increases, growers struggle with the number and diversity of tasks. They’re also relying less on cultivation in order to minimize fuel costs and reduce wear and tear on ground and equipment. In New Mexico, corn producers usually apply a preemergence herbicide with costs ranging from $15.00 and $25.00 per acre followed by at least one or two cultivations at approximately $10.00 each per cultivated acre. If cultivation could be eliminated, depending on type of postemergence herbicide used, this could result in an approximate savings of $25.00 to $45.00 per acre (P. Evans, personal communication). Considering current prices, growers can build a good argument for a one-pass weed control system buy saving approximately between $10.00 and $20.00 per acre in cultivation costs.

The results of these tests showed that all the herbicides evaluated did not reduce corn yields as compared to the untreated controls. However, not all were effective for control of weeds which emerged in our study. Nicosulfuron plus rimsulfuron (Steadfast), or foramsulfuron (Option) in combination with dicamba (Clarity), dicamba plus atrazine (Marksman), and diflufenzopyr plus dicamba (Distinct) were the best treatments for weed control and corn yield. Data further indicates that growers could utilize a one-pass total postemergence program in field corn for control of redroot and prostrate pigweed, common lambsquarters, black nightshade, and Russian thistle in field corn.

Literature Cited

1. Arnold, R. N., Murray, M. W., Gregory, E. J., and Smeal, D. 1988. Effects of herbicides on weeds in field corn grown on coarse-textured soils. J. Appl. Agric. Res. 3:121-23.

2. Arnold, R. N. 2003. Broadleaf weed control in field corn with postemergence herbicides. Pages 15-18 in: 2003 Annual Weeds Research Report. Agric. Sci. Center at Farmington, Univ. of New Mex.

3. Becket, T. H., Stoller, E. W., and Wax, L. M. 1988. Interference of four annual weeds in corn (Zea mays). Weed Sci. 36:764-769.

4. Evans, J. O., Hauderlie, P., and Williams, R. W. 2001. Control of common lambsquarters in Roundup ready corn. W. Soc. Weed Sci. 2001 Res. Prog. Rep.

5. Halford, C., Hamill, A. S., Zhang, J., and Doucet, C. 2001. Critical period of weed control in no-till soybean (Glycine max) and corn (Zea mays). Weed Technol. 15:737-744.

6. Hall, M. R., Swanson, C. J., and Anderson, G. W. 1992. The critical period of weed control in grain corn (Zea mays). Weed Sci. 40:441-447.

7. Knezevic, S. Z., Weise, S. F., and Swanson, C. J. 1994. Interference of redroot pigweed (Amaranthus retroflexus) in Corn (Zea Mays). Weed Sci. 42:568-573.

8. Knezevic, S. Z., Evans, S. P., and Mainz, M. 2003. Yield penalty due to delayed weed control in corn and soybean. Crop Management doi:10.1094/CM-2003-0219-01-RS.

9. Ransom, C. V., Rice, C. A., and Ishida, J. K. 2002. Weed control and crop response with herbicides applied in corn. Ann. Pep. Oreg. St. Univ. Malheur Exp. Sta.

10. Rice, C. C., Ransom, C. V., and Ishida, J. K. 2002. Weed control and crop response with herbicides applied in field corn. Ann. Pep. Oreg. St. Univ. Malheur Exp. Sta.