Raymond E. Massey

Efficacy and Economics of Weed Management in Glyphosate-Resistant Corn (Zea mays)1

Abstract: Field experiments were conducted in 1997 and 1998 near Columbia and Novelty, MO, and Urbana, IL, to evaluate crop injury, weed control, corn yield, and net economic returns provided by weed control programs in glyphosate-resistant corn. The herbicide programs evaluated included acetochlor preemergence (PRE) followed by (fb) glyphosate with or without atrazine postemergence (POST) and total POST programs consisting of single and sequential applications of glyphosate alone and tank-mixed with actochlor, atrazine, or both. Metolachlor PRE fb dicamba plus atrazine POST and metolachlor plus atrazine PRE were included for comparison. In the total POST treatments, mid-post (MPOST) applications provided better control than early-post (EPOST) applications on weeds that germinated throughout the growing season such as shattercane and common cocklebur, but also resulted in yield reductions of up to 23% caused by early-season weed competition. The addition of atrazine to glyphosate POST generally increased control of common cocklebur, morningglory species, and common waterhemp. EPOST or PRE fb EPOST applications generally provided higher yields than MPOST treatments, although MPOST treatments often provided equal or greater weed control at midseason. Treatments including two herbicide applications tended to provide greater weed control, yield, and profit than those with a single application. Input costs for glyphosate-resistant corn are slightly higher than nontransgenic hybrids. However, net economic returns are similar and the use of glyphosate POST allows greater flexibility in POST weed management decisions. Nomenclature: Acetochlor, 2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)acetamide; atrazine, 6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine; dicamba, 3,6-dichloro-2-methoxybenzoic acid; glyphosate, N-(phosphonomethyl)glycine; metolachlor, 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide; common cocklebur, Xanthium strumarium L.#3 XANST; common waterhemp, Amaranthus rudis Sauer # AMATA; ivyleaf morningglory, Ipomoea hederaceae (L.) Jacq. # IPOHE; pitted morningglory, Ipomoea lacunosa L. # IPOLA; shattercane, Sorghum bicolor (L.) Moench. # SORVU; corn Zea mays L. # ZEAMX ‘MON802’. Additional index words: Corn yield, acetochlor, atrazine, dicamba, economic returns, metolachlor, AMATA, ABUTH, CHEAL, IPOHE, IPOLA, POLPY, SETFA, SORVU, XANST, ZEAMX. Abbreviations: ALS, autolactate synthase; EPOST, early postemergence; fb, followed by; MPOST, mid-postemergence; OM, organic matter; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

Economics of Weed Management in Glufosinate-Resistant Corn (Zea mays L.)'

Abstract: Field experiments were conducted in 1997 and 1998 near Columbia and Novelty, MO, and at Urbana, IL, to evaluate corn injury, weed control, corn yield, and estimated economic returns with weed management programs in glufosinate-resistant corn. Herbicide programs included acetochlor preemergence (PRE) followed by glufosinate alone or with atrazine postemergence (POST) and total POST programs consisting of single and sequential applications of glufosinate alone or tank mixed with acetochlor, atrazine, or acetochlor plus atrazine. Metolachlor PRE followed by dicamba plus atrazine early POST (EPOST) and metolachlor plus atrazine PRE were included for comparison. In the total POST treatments, mid-POST applications controlled shattercane and common cocklebur better than EPOST applications. However, yield reductions as high as 23% occurred because of early-season weed interference, although weeds were controlled later in the season. Applying atrazine with glufosinate generally increased control of giant foxtail, common cocklebur, morningglory species, and common waterhemp compared to glufosinate alone, but did not increase control of common lambsquarters, velvetleaf, or Pennsylvania smartweed. Corn yield was positively correlated with weed control (r = 0.88) and more strongly dependent on grass (r = 0.82) than broadleaf (r = 0.70) weed control. Net incomes were positively correlated to corn yield (r = 0.73). Four of the top six net income-producing treatments included two herbicide applications. Three of the treatments were PRE followed by POST programs, and the fourth was a sequential POST treatment of glufosinate. Nomenclature: Acetochlor; atrazine; dicamba; glufosinate; metolachlor; common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; common waterhemp, Amaranthus rudis Sauer # AMATA; giant foxtail, Setaria faberi (L.) Herrm. # SETFA; morningglory, Ipomoea spp.; Pennsylvania smartweed, Polygonum pensylvanicum L. # POLPY; shattercane, Sorghum bicolor (L.) Moench. # SORVU; velvetleaf, Abutilon theophrasti (L.) Medikus # ABUTH; corn, Zea mays L. # ZEAMX ‘Pioneer 34A55’. Additional index words: Corn yield, economic returns, glufosinate-resistant crop, AMATA, ABUTH, CHEAL, POLPY, SETFA, SORVU, XANST, ZEAMX. Abbreviations: ALS, acetolactate synthase; CV, coefficient of variation; EPOST, early postemergence; MPOST, mid-postemergence; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

Glyphosate-Resistant Waterhemp (Amaranthus Rudis) Control and Economic Returns With Herbicide Programs in Soybean

Abstract Field experiments were conducted in Platte County, Missouri, during 2006 and 2007 to evaluate PRE, POST, and PRE followed by (fb) POST herbicide programs for the control of glyphosate-resistant waterhemp in soybean. All PRE fb POST treatments resulted in at least 66 and 70% control of glyphosate-resistant waterhemp in 2006 and 2007, respectively. Control of glyphosate-resistant waterhemp was less than 23% with lactofen and acifluorfen in 2006, but at least 64% in 2007. Variability in control likely resulted from differences in trial locations and a population of protoporphyrinogen oxidase (PPO)–resistant waterhemp at the Platte County site in 2006 compared with 2007. In both years, glyphosate resulted in less than 23% control of glyphosate-resistant waterhemp and provided the least control of all herbicide programs. Programs containing PRE herbicides resulted in waterhemp densities of less than 5 plants/m2, whereas the POST glyphosate treatment resulted in 38 to 70 plants/m2. Waterhemp seed production was reduced at least 78% in all PRE fb POST programs, from 55 to 71% in POST programs containing lactofen and acifluorfen and by only 21% in the POST glyphosate treatment. Soybean yields corresponded to the level of waterhemp control achieved in both years, with the lowest yields resulting from programs that provided poorest waterhemp control. PRE applications of S-metolachlor plus metribuzin provided one of the highest net incomes in both years and resulted in

Climate forecasts for corn producer decision making

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Use of preplant sulfentrazone in no-till, narrow-row, glyphosate-resistant Glycine max

340/ha greater net income than the glyphosate-only treatment. Collectively, the results from these experiments illustrate the effectiveness of PRE herbicides for the control of glyphosate-resistant waterhemp in glyphosate-resistant soybean and the inconsistency of PPO-inhibiting herbicides or PPO-inhibiting herbicide combinations for the control of waterhemp populations with multiple resistance to glyphosate and PPO-inhibiting herbicides. Nomenclature: Acifluorfen; glyphosate; lactofen; metribuzin; S-metolachlor; common waterhemp, Amaranthus rudis Sauer; soybean Glycine max L

Reduced rates of sulfentrazone plus chlorimuron and glyphosate in no-till, narrow-row, glyphosate-resistant Glycine max

AbstractCorn is the most widely grown crop in the Americas, with annual production in the United States of approximately 332 million metric tons. Improved climate forecasts, together with climate-related decision tools for corn producers based on these improved forecasts, could substantially reduce uncertainty and increase profitability for corn producers. The purpose of this paper is to acquaint climate information developers, climate information users, and climate researchers with an overview of weather conditions throughout the year that affect corn production as well as forecast content and timing needed by producers. The authors provide a graphic depicting the climate-informed decision cycle, which they call the climate forecast–decision cycle calendar for corn.

Effects of observability and complexity on farmers’ adoption of environmental practices

Abstract Field studies were conducted in 1998 and 1999 to evaluate crop response, weed control, Glycine max yield, and economic returns with sulfentrazone alone and tank-mixed with glyphosate, cloransulam, or chlorimuron at two preplant application timings in no-till, narrow-row, glyphosate-resistant G. max. No significant crop injury was observed. Setaria faberi and Polygonum pensylvanicum control 5 wk after planting (WAP) was generally greater with sulfentrazone applied early preplant (EPP) than with sulfentrazone applied at planting (AP). When applied AP, glyphosate plus sulfentrazone provided greater S. faberi control than sulfentrazone alone. Control of Amaranthus rudis, Ambrosia artemisiifolia, and Ipomoea hederacea was greater in 1998 than in 1999 because of more timely early-season precipitation. Sulfentrazone-based programs provided 80 to 100% control of A. rudis in 1998, but control in 1999 ranged from 72 to 95% at Columbia and 46 to 83% at Novelty. Cloransulam alone, at either application timing, was the only treatment that provided greater than 80% control of A. artemisiifolia at each site in each year. All sulfentrazone-based treatments provided greater than 80% control of I. hederacea in 1998, but control was less in 1999 and ranged from 54 to 91%. Xanthium strumarium control ranged from 5 to 94% with sulfentrazone alone; however, the addition of cloransulam or chlorimuron provided 75 to 99% control regardless of application timing. A blanket application of glyphosate was made 6 WAP over all preplant herbicide treatments, and weed control 5 wk after this treatment was greater than 79% with all sulfentrazone-based treatments. Sulfentrazone plus cloransulam or chlorimuron plus glyphosate EPP or AP followed by (fb) glyphosate postemergence (POST) generally provided the greatest weed control. Overall weed control was generally greater with the use of residual herbicides vs. glyphosate alone, although yield and net returns were not always greater. A greenhouse study was conducted to determine if altering the preplant application timing reduced sulfentrazone injury to G. max. Treatment variables included herbicide rate, temperature during a preplant incubation period, and application timing. Glycine max, Zea mays, and Sorghum bicolor were used as indicator species. Sulfentrazone caused less injury to G. max, Z. mays, and S. bicolor in soils incubated at 30 C when applied 20 d before planting compared to 0 d before planting. Equivalent amounts of crop injury were noted with sulfentrazone applied 20 or 0 d before planting in soils incubated at 5 C with all indicator species. Nomenclature: Chlorimuron, cloransulam, glyphosate, sulfentrazone; Xanthium strumarium L. XANST, common cocklebur; Ambrosia artemisiifolia L. AMBEL, common ragweed; Amaranthus rudis Sauer AMATA, common waterhemp; Setaria faberi Herrm. SETFA, giant foxtail; Ipomoea hederacea (L.) Jacq. IPOHE, ivyleaf morningglory; Polygonum pensylvanicum L. POLPY, Pennsylvania smartweed; Zea mays L. ‘Pioneer 3394’, corn; Glycine max (L.) Merr. ‘Asgrow 3601’, ‘Pioneer 9362, soybean; Sorghum bicolor (L.) Moench’. ‘Pioneer 8500’, grain sorghum.

Weed Management and Economic Returns in No-Tillage Herbicide-Resistant Corn (Zea mays)1

Abstract Field studies were conducted in 1998 and 1999 to evaluate crop response, weed control, Glycine max yield, and economic returns of labeled (1×) and one-half labeled (½×) rates of early preplant (EPP) sulfentrazone plus chlorimuron and postemergence glyphosate, compared to glyphosate-alone systems in no-till, narrow-row, glyphosate-resistant G. max. Treatments containing a 1× or ½× rate of EPP sulfentrazone plus chlorimuron with glyphosate followed by (fb) a postemergence treatment of glyphosate provided 80 to 100% control of Xanthium strumarium, Ambrosia artemisiifolia, and Polygonum pensylvanicum and 82 to 100% control of Setaria faberi and Amaranthus rudis if glyphosate was applied mid-postemergence (MPOST) or late postemergence (LPOST). Glyphosate alone EPP fb glyphosate postemergence or sequential postemergence treatments of glyphosate provided 77 to 100% control of S. faberi, A. artemisiifolia, and P. pensylvanicum. Glycine max yield did not significantly differ between treatments that contained 1× or ½× rates of sulfentrazone plus chlorimuron EPP with postemergence glyphosate or sequential glyphosate. Residual herbicides fb glyphosate reduced overall weed control variability but did not reduce the overall yield variability compared to glyphosate alone. Greater weed control, G. max yield, net incomes, and lower coefficient of variation (CV) of net incomes were generally associated with treatments that included both EPP and postemergence treatments vs. single herbicide applications. A greenhouse study was conducted to determine the optimal spray additive to maximize the foliar activity of sulfentrazone on three annual weeds. Sulfentrazone alone and in combination with a nonionic surfactant (NIS), methylated seed oil (MSO), crop oil concentrate (COC), and a silicone-based surfactant (SBS), with and without ammonium sulfate (AMS), were applied on two sizes of Abutilon theophrasti, P. pensylvanicum, and S. faberi. AMS provided little additional efficacy of sulfentrazone on S. faberi, but improved efficacy on A. theophrasti and P. pensylvanicum. SBS or MSO plus AMS with sulfentrazone generally provided the greatest efficacy on all species. Nomenclature: Chlorimuron; glyphosate; sulfentrazone; Xanthium strumarium L. XANST, common cocklebur; Ambrosia artemisiifolia L. AMBEL, common ragweed; Amaranthus rudis AMATA, common waterhemp; Setaria faberi Herrm. SETFA, giant foxtail; Polygonum pensylvanicum L. POLPY, Pennsylvania smartweed; Abutilon theophrasti (L.) Medik. ABUTH, velvetleaf; Glycine max (L.) Merr. ‘Asgrow 3601’, soybean.

Management of Acetolactate Synthase (ALS)-Resistant Common Sunflower (Helianthus annuus L.) in Soybean (Glycine max)1

The ability of both regulators and farmers themselves to monitor the impact of environmental practices may be an issue with nonpoint source pollution. Effects that can be perceived via direct sensory evidence provide information at low cost. Results from a survey of livestock farmers suggest that a practice that has more obvious effects on water quality, manure application setbacks, is more likely to be adopted than a more complicated one with less visible effects, manure testing. Farmers’ perceptions of the profitability of the two practices were similar. The importance of observability and complexity has implications for educational programs.

Comparison of Weed Control, Yield, and Net Income in Conventional, Glyphosate-Resistant, and Glufosinate-Resistant Soybean

Field studies were conducted to evaluate corn vigor reduction, weed control, corn yield, and economic returns in a no-till system with various herbicide strategies using full and reduced rates of acetochlor and atrazine with glyphosate, glufosinate, or imazethapyr + imazapyr in their respective type of herbicide-resistant, no-tillage corn. Crop vigor reduction due to herbicide injury was 10% or less with all treatments. A burndown plus a full label rate of a residual herbicide applied early preplant (EPP) generally provided less than 80% control of giant foxtail, common waterhemp, and common cocklebur but usually greater than 85% control of common ragweed and common lambsquarters. Two-pass strategies generally provided greater than 85% control of all species evaluated. Early postemergence, mid-postemergence (MPOST), and late postemergence strategies generally provided inconsistent and poor overall weed control. EPP–MPOST strategies generally provided lower weed control than strategies using acetochlor or atrazine EPP followed by a postemergence application. Corn yield and net economic returns followed a similar trend as weed control, with strategies that provided greater than 80% weed control showing minimal crop vigor reduction and high grain yields. Two-pass strategies with residual herbicides generally provided the highest yields, economic returns, and low coefficients of variation (CV) of net income. Although EPP strategies provided similar economic returns as some of the two-pass strategies, they had higher CVs, implying greater risk to economic return. Nomenclature: Acetochlor; atrazine; glufosinate; glyphosate; imazapyr; imazethapyr; common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; common waterhemp, Amaranthus rudis Sauer. # AMATA; giant foxtail, Setaria faberi Herrm. # SETFA; corn, Zea mays L. ‘Dekalb 626’, ‘Pioneer 3395’, ‘Pioneer 34T14’. Additional index words: Application strategies, application timing, tank mixes. Abbreviations: ac/at+, acetochlor EPP followed by atrazine plus; ALS, acetolactate synthase; CEC, cation-exchange capacity; CV, coefficients of variation; EPOST, early postemergence; EPP, early preplant; MPOST, mid-postemergence; LPOST, late postemergence; OM, organic matter.