Weed Management Practices and Needs in Arkansas and Mississippi Rice

Crop consultants in Arkansas and Mississippi were sent a direct-mail survey in fall of 2011 with questions concerning weed management in rice. The goal of the survey was to document the extent of imidazoline-resistant rice hectares, the herbicides most commonly recommended in rice, the weeds perceived to be most troublesome in rice including those resistant to herbicides, and suggested areas of research and educational focus that would improve weed management in rice. When appropriate, results from this survey were compared to a similar survey conducted in 2006. Completed rice surveys were returned by 43 consultants, accounting for 179,500 ha of scouted rice or 38% of the rice hectarage in Arkansas and Mississippi. Imidazolinone-resistant rice was grown on 64% of the hectares, and this technology was used continually for the past 5 yr on 11% of the rice hectares. Of the area planted to imidazolinone-resistant rice, 42% of this hectarage was treated solely with an acetolactate synthase (ALS)-inhibiting herbicide. Consultants listed improved control options for barnyardgrass and Palmer amaranth as the most important research and educational need in rice. The top five weeds in order of importance were (1) barnyardgrass, (2) sprangletops, (3) red rice, (4) northern jointvetch, and (5) Palmer amaranth. From a predetermined list of research and educational topics, consultants gave the highest ratings of importance to (1) control of herbicide-resistant weeds, (2) strategies to reduce the occurrence and spread of herbicide-resistant weeds, and (3) development of new economical herbicide-resistant rice varieties which was comparable to economical weed control options. Findings from this survey point to the overuse of imidazolinone-resistant rice and a lack of preemptive resistance management strategies such as crop rotation and use of multiple effective herbicide modes of action by some growers, which has likely contributed to selection for the ALS-resistant barnyardgrass and rice flatsedge recently confirmed in Arkansas and Mississippi rice.

Download Full-text

A Midsouthern Consultant’s Survey on Weed Management Practices in Soybean

Weed Technology ◽

10.1017/wet.2017.109 ◽

2017 ◽

Vol 32 (2) ◽

pp. 116-125 ◽

Cited By ~ 9

Author(s):

Lauren M. Schwartz-Lazaro ◽

Jason K. Norsworthy ◽

Lawrence E. Steckel ◽

Daniel O. Stephenson ◽

Mandy D. Bish ◽

...

Keyword(s):

Cover Crops ◽

Weed Management ◽

Management Practices ◽

Palmer Amaranth ◽

Italian Ryegrass ◽

Time Constraints ◽

Primary Concern ◽

Protoporphyrinogen Oxidase ◽

Herbicide Resistant ◽

Southeast Missouri

AbstractSoybean consultants from Arkansas, Louisiana, southeast Missouri, Mississippi, and Tennessee were surveyed in 2016 to assess weed management practices and the prevalence of herbicide-resistant weeds in midsouthern U.S. soybean production. The consultants surveyed represented 13%, 28%, 8%, 16%, and 5% of the total soybean area planted in Arkansas, Louisiana, southeast Missouri, Mississippi, and Tennessee, respectively. Of the total scouted area, 78% of the consultants said their growers planted glyphosate-resistant soybean in 2016, with 18% planting glufosinate-resistant (LibertyLink®), primarily due to familiarity with and cost of the technology. Although 94% of the consultants determined that glufosinate was most effective on killing Palmer amaranth, the primary concern associated with controlling herbicide-resistant weeds was the associated cost, followed by return profit and time constraints. Palmer amaranth, morningglory species, horseweed, barnyardgrass, and Italian ryegrass were the five most problematic weeds in soybean across the five states. Palmer amaranth was the most problematic and important weed in each state individually. The increased concern (77% of consultants) with this species was attributed to the rising concern with and occurrence of protoporphyrinogen oxidase–resistant Palmer amaranth. Consultants were of the opinion that more research was needed on cover crops and the new traited technologies in order to improve weed management in soybean.

Download Full-text

Assessment of crop and weed management strategies prior to introduction of auxin-resistant crops in Brazil

Weed Technology ◽

10.1017/wet.2020.96 ◽

2020 ◽

pp. 1-11

Author(s):

Maxwel C. Oliveira ◽

Anelise Lencina ◽

André R. Ulguim ◽

Rodrigo Werle

Keyword(s):

Cover Crops ◽

Weed Management ◽

Management Practices ◽

Cropping Systems ◽

Control Strategies ◽

Management Strategies ◽

Acetolactate Synthase ◽

Weed Species ◽

Research Education ◽

No Till

Abstract A stakeholder survey was conducted from April through June of 2018 to understand stakeholders’ perceptions and challenges about cropping systems and weed management in Brazil. The dominant crops managed by survey respondents were soybean (73%) and corn (66%). Approximately 75% of survey respondents have grown or managed annual cropping systems with two to three crops per year cultivated in succession. Eighteen percent of respondents manage only irrigated cropping systems, and over 60% of respondents adopt no-till as a standard practice. According to respondents, the top five troublesome weed species in Brazilian cropping systems are horseweed (asthmaweed, Canadian horseweed, and tall fleabane), sourgrass, morningglory, goosegrass, and dayflower (Asiatic dayflower and Benghal dayflower). Among the nine species documented to have evolved resistance to glyphosate in Brazil, horseweed and sourgrass were reported as the most concerning weeds. Other than glyphosate, 31% and 78% of respondents, respectively, manage weeds resistant to acetyl-CoA carboxylase (ACCase) inhibitors and/or acetolactate synthase (ALS) inhibitors. Besides herbicides, 45% of respondents use mechanical, and 75% use cultural (e.g., no-till, crop rotation/succession) weed control strategies. Sixty-one percent of survey respondents adopt cover crops to some extent to suppress weeds and improve soil chemical and physical properties. Nearly 60% of survey respondents intend to adopt the crops that are resistant to dicamba or 2,4-D when available. Results may help practitioners, academics, industry, and policy makers to better understand the bad and the good of current cropping systems and weed management practices adopted in Brazil, and to adjust research, education, technologies priorities, and needs moving forward.

Download Full-text

A Statewide Survey of Stakeholders to Assess the Problem Weeds and Weed Management Practices in Nebraska

Weed Technology ◽

10.1017/wet.2018.35 ◽

2018 ◽

Vol 32 (5) ◽

pp. 642-655 ◽

Cited By ~ 15

Author(s):

Debalin Sarangi ◽

Amit J. Jhala

Keyword(s):

Weed Management ◽

Crop Production ◽

Management Practices ◽

Acetolactate Synthase ◽

Grain Sorghum ◽

Primary Concern ◽

Weed Species ◽

Common Waterhemp ◽

Herbicide Resistant ◽

Crop Area

AbstractStakeholders were surveyed across Nebraska to identify the problem weeds and assess common weed management practices. A total of 425 responses were returned across four Nebraska extension districts (Northeast, Panhandle, Southeast, and West Central). Collectively, 61.2% of total farmed or scouted areas in Nebraska were under no-till production, and corn and soybean were the major crops (82.3% of total farmed or scouted area). Common waterhemp, horseweed, and kochia were the most problematic weeds statewide. Widespread occurrence of glyphosate-resistant (GR) weeds such as common waterhemp, horseweed, kochia, and Palmer amaranth were a serious problem in GR crop production. Additionally, 60% of growers in Nebraska reported the presence of at least one GR weed species on their farms. The most commonly used preplant burndown herbicides were 2,4-D and glyphosate, followed by saflufenacil and dicamba. In Nebraska, 74% and 59% of corn and soybean growers, respectively, were using PRE herbicides; however, more than 80% of growers were using POST herbicides for in-crop weed management. Atrazine alone or in premix or tank mix with mesotrione,S-metolachlor, or acetochlor were the most widely applied PRE herbicides in corn and grain sorghum, whereas the most commonly used PRE herbicides in soybean were the inhibitors of acetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO). Glyphosate was the most frequent choice of the survey respondents as a POST herbicide in GR corn and soybean; 2,4-D was the most commonly used POST herbicide in grain sorghum and wheat. In Nebraska, only 5.2% of total crop area was planted with glufosinate-resistant crops. Most of the respondents (89%) were aware of the new multiple herbicide–resistant crops, and 80% of them listed physical drift and volatility of the auxinic herbicides as their primary concern. Forty-eight percent of survey respondents identified herbicide-resistant weed management as their primary research and extension priority.

Download Full-text

Changes in the Prevalence of Weed Species in the Major Agronomic Crops of the Southern United States: 1994/1995 to 2008/2009

Weed Science ◽

10.1614/ws-d-11-00092.1 ◽

2012 ◽

Vol 60 (2) ◽

pp. 145-157 ◽

Cited By ~ 86

Author(s):

Theodore M. Webster ◽

Robert L. Nichols

Keyword(s):

Weed Management ◽

Management Practices ◽

Regional Scale ◽

Palmer Amaranth ◽

Italian Ryegrass ◽

Management Tool ◽

Weed Species ◽

Herbicide Resistant ◽

Resistant Cultivars ◽

Weed Flora

Changes in the weed flora of cropping systems reflect the impacts of factors that create safe sites for weed establishment and facilitate the influx and losses to and from the soil seedbank. This analysis of the annual surveys of the Southern Weed Science Society documents changes in the weed flora of the 14 contiguous southern states since the advent of transgenic, herbicide-resistant crops. In 1994 and 2009, the top five weeds in corn were morningglories, Texas millet, broadleaf signalgrass, johnsongrass, and sicklepod; in this same period Palmer amaranth, smartweeds, and goosegrass had the greatest increases in importance in corn. In cotton, morningglories and nutsedges were among the top five most troublesome weeds in 1995 and 2009. Palmer amaranth, pigweeds, and Florida pusley were also among the five most troublesome species in 2009; the weeds with the largest increases in importance in cotton were common ragweed and two species with tolerance to glyphosate, Benghal dayflower and Florida pusley. In soybean, morningglories, nutsedges, and sicklepod were among the top five weed species in 1995 and 2009. Two species with glyphosate resistance, Palmer amaranth and horseweed, were the second and fourth most troublesome weeds of soybean in 2009. In wheat, the top four weeds in 2008 were the same as those in 1994 and included Italian ryegrass, wild garlic, wild radish, and henbit. Crop production in the southern region is a mosaic of various crop rotations, soil types, and types of tillage. During the interval between the surveys, the predominant change in weed management practices in the region and the nation was the onset and rapid dominance of the use of glyphosate in herbicide-resistant cultivars of corn, cotton, and soybean. Because of the correspondence between the effects of glyphosate on the respective weed species and the observed changes in the weed flora of the crops, it is likely the very broad use of glyphosate was a key component shaping the changes in weed flora. Only eight of the top 15 most troublesome weeds of cotton and soybean, the crops with the greatest use of glyphosate, were the same in 1995 and 2009. In contrast, in corn and wheat where adoption of glyphosate-resistant cultivars lags or is absent, 12 of the 15 most troublesome weeds were the same in 1994 and 2008. These findings show on a regional scale that weeds adapt to recurrent selection from herbicides, currently the predominant weed management tool. Future research should seek methods to hinder the rapid spread of herbicide-tolerant and evolution of herbicide-resistant weed species. As new tools are developed, research should focus on ways to preserve the efficacy of those tools through improved stewardship.

Download Full-text

Managing herbicide resistance in China

Weed Science ◽

10.1017/wsc.2020.68 ◽

2020 ◽

pp. 1-14

Author(s):

Xiangying Liu ◽

Austin Merchant ◽

Shihai Xiang ◽

Tao Zong ◽

Xuguo Zhou ◽

...

Keyword(s):

Herbicide Resistance ◽

Weed Management ◽

Management Practices ◽

Management Strategies ◽

Resistance Management ◽

Acetolactate Synthase ◽

Developed Countries ◽

The United States ◽

Resistance Mechanisms ◽

Future Research

Abstract Since its initial introduction in the late 1950s, chemical control has dominated weed management practices in China. Not surprisingly, the development of herbicide resistance has become the biggest threat to long-term, sustainable weed management in China. Given that China has followed the same laissez-faire approach toward resistance management that has been practiced in developed countries such as the United States, herbicide resistance has evolved rapidly and increased steadily over the years. Previously, we carried out a systematic review to quantitatively assess herbicide-resistance issues in China. In this review, our main objective is to focus on mechanistic studies and management practices to document the (1) history of herbicide application in China; (2) resistance mechanisms governing the eight most resistance-prone herbicide groups, including acetolactate synthase inhibitors, acetyl-CoA carboxylase inhibitors, synthetic auxin herbicides, 5-enolpyruvylshikimate-3-phosphate synthase inhibitors, protoporphyrinogen oxidase inhibitors, photosystem I electron diverters, photosystem II inhibitors, and long-chain fatty-acid inhibitors; and (3) herbicide-resistance management strategies commonly used in China, including chemical, cultural, biological, physical, and integrated approaches. At the end, perspectives and future research are discussed to address the pressing need for the development of integrated herbicide-resistance management in China.

Download Full-text

Sensitivity of imidazolinone-resistant red rice (Oryza sativa L.) to glyphosate and glufosinate

Ciência Rural ◽

10.1590/0103-8478cr20140896 ◽

2015 ◽

Vol 45 (9) ◽

pp. 1557-1563 ◽

Cited By ~ 4

Author(s):

Guilherme Vestena Cassol ◽

Luis Antonio de Avila ◽

Carla Rejane Zemolin ◽

Andrey Piveta ◽

Dirceu Agostinetto ◽

...

Keyword(s):

Weed Management ◽

Management Practices ◽

Oryza Sativa L ◽

Dry Weight ◽

Integrated Weed Management ◽

Rio Grande Do Sul ◽

Red Rice ◽

Resistance Evolution ◽

Logistic Analysis ◽

Imidazolinone Herbicides

Dose-response experiments were carried out to evaluate the sensitivity of imidazolinone-resistant red rice to nonselective herbicides currently used in rice-soybean rotation in Rio Grande do Sul. Two red rice biotypes previously identified as resistant and susceptible to the imidazolinone herbicides were treated with imazapic plus imazapic, glyphosate and glufosinate under nine herbicide rates. A non-linear log-logistic analysis was used to estimate the herbicide rate that provided 50% red rice control and dry weight reduction (GR50). Imidazolinone-resistant red rice exhibited greater GR50 values than imidazolinone-susceptible biotype for imazapyr plus imazapic. In contrast, both imidazolinone-resistant and susceptible red rice showed similar GR50values for glyphosate and glufosinate. These results indicate that glyphosate and glufosinate effectively control imidazolinone-resistant red rice at similar herbicide rates used to control imidazolinone-susceptible; however, integrated weed management practices must be adopted in rice-soybean rotation to delay resistance evolution of red rice populations to glyphosate and glufosinate

Download Full-text

Effects of Palmer Amaranth (Amaranthus palmeri) Establishment Time and Distance from the Crop Row on Biological and Phenological Characteristics of the Weed: Implications on Soybean Yield

Weed Science ◽

10.1017/wsc.2018.84 ◽

2019 ◽

Vol 67 (1) ◽

pp. 126-135 ◽

Cited By ~ 8

Author(s):

Nicholas E. Korres ◽

Jason K. Norsworthy ◽

Andy Mauromoustakos

Keyword(s):

Seed Production ◽

Weed Management ◽

Cropping Systems ◽

Management Strategies ◽

Palmer Amaranth ◽

Yield Reduction ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Management Measures ◽

Weed Population Dynamics

AbstractInformation about weed biology and weed population dynamics is critical for the development of efficient weed management programs. A field experiment was conducted in Fayetteville, AR, during 2014 and 2015 to examine the effects of Palmer amaranth (Amaranthus palmeriS. Watson) establishment time in relation to soybean [Glycine max(L.) Merr.] emergence and the effects ofA. palmeridistance from the soybean row on the weed’s height, biomass, seed production, and flowering time and on soybean yield. The establishment time factor, in weeks after crop emergence (WAE), was composed of six treatment levels (0, 1, 2, 4, 6, and 8 WAE), whereas the distance from the crop consisted of three treatment levels (0, 24, and 48 cm). Differences inA. palmeribiomass and seed production averaged across distance from the crop were found at 0 and 1 WAE in both years. Establishment time had a significant effect onA. palmeriseed production through greater biomass production and height increases at earlier dates.Amaranthus palmerithat was established with the crop (0 WAE) overtopped soybean at about 7 and 10 WAE in 2014 and 2015, respectively. Distance from the crop affectedA. palmeriheight, biomass, and seed production. The greater the distance from the crop, the higherA. palmeriheight, biomass, and seed production at 0 and 1 WAE compared with other dates (i.e., 2, 4, 6, and 8 WAE).Amaranthus palmeriestablishment time had a significant impact on soybean yield, but distance from the crop did not. The earlierA. palmeriinterfered with soybean (0 and 1 WAE), the greater the crop yield reduction; after that period no significant yield reductions were recorded compared with the rest of the weed establishment times. Knowledge ofA. palmeriresponse, especially at early stages of its life cycle, is important for designing efficient weed management strategies and cropping systems that can enhance crop competitiveness. Control ofA. palmeriwithin the first week after crop emergence or reduced distance between crop and weed are important factors for an effective implementation of weed management measures againstA. palmeriand reduced soybean yield losses due to weed interference.

Download Full-text

Susceptibility of Palmer amaranth (Amaranthus palmeri) to herbicides in accessions collected from the North Carolina Coastal Plain

Weed Science ◽

10.1017/wsc.2020.67 ◽

2020 ◽

Vol 68 (6) ◽

pp. 582-593

Author(s):

Denis J. Mahoney ◽

David L. Jordan ◽

Nilda Roma-Burgos ◽

Katherine M. Jennings ◽

Ramon G. Leon ◽

...

Keyword(s):

North Carolina ◽

Dose Response ◽

Coastal Plain ◽

Weed Management ◽

Acetolactate Synthase ◽

Fold Increase ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Sites Of Action ◽

Two Populations

AbstractPalmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.

Download Full-text

Modeling the Population Dynamics and Economics of Velvetleaf (Abutilon theophrasti) Control in a Corn (Zea mays)-Soybean (Glycine max) Rotation

Weed Science ◽

10.1017/s0043174500081169 ◽

1995 ◽

Vol 43 (2) ◽

pp. 269-275 ◽

Cited By ~ 17

Author(s):

John L. Lindquist ◽

Bruce D. Maxwell ◽

Douglas D. Buhler ◽

Jeffrey L. Gunsolus

Keyword(s):

Population Dynamics ◽

Weed Management ◽

Management Practices ◽

Seedling Emergence ◽

Management Strategies ◽

Parameter Estimates ◽

Economic Returns ◽

Net Return ◽

Herbicide Use ◽

Optimum Threshold

A simulation model was developed to predict the population dynamics and economics of velvetleaf control in a corn-soybean rotation. Data compiled from the literature were used to parameterize the model for two situations, one in which velvetleaf was infected by aVerticilliumspp. wilt and one without infection.Verticilliumwas assumed to have no effect on corn or soybean yield. In the absence of control, simulated seedbank densities of aVerticillium-infected velvetleaf population were 5 to 50 times lower than for an uninfected velvetleaf population. The model was used to evaluate a threshold weed management strategy under the assumption that velvetleaf was the only weed and bentazon the only herbicide available for its control. In the absence ofVerticillium, an economic optimum threshold of 2.5 seedlings 100 m−2afforded the highest economic returns after 20 yr of simulation. Simulations in which velvetleaf was infected in 8 out of 20 randomly assigned years indicated a 6% increase in annualized net return and an 11 % reduction in the number of years that control was necessary. Sensitivity analysis indicated the parameter estimates having the greatest impact on economic optimum threshold were seedling emergence and survival, maximum seed production, and herbicide efficacy. Under an economic optimum threshold of 2.5 seedlings 100 m−2, management practices that manipulate the most sensitive demographic processes increased annualized net return by up to 13% and reduced long-term herbicide use by up to 26%. Results demonstrate that combining an economic optimum threshold with alternative weed management strategies may increase economic return and reduce herbicide use.

Download Full-text

Herbicide Timing and Rate Effects on Weed Management in Three Herbicide-Resistant Canola Systems

Weed Technology ◽

10.1614/wt-03-188r1 ◽

2004 ◽

Vol 18 (4) ◽

pp. 1006-1012 ◽

Cited By ~ 7

Author(s):

K. Neil Harker ◽

George W. Clayton ◽

John T. O'Donovan ◽

Robert E. Blackshaw ◽

F. Craig Stevenson

Keyword(s):

Weed Control ◽

Weed Management ◽

Management Practices ◽

Integrated Weed Management ◽

Weed Biomass ◽

Herbicide Resistant ◽

Leaf Stage ◽

Rate Effects ◽

Herbicide Timing ◽

Weed Removal

Herbicide-resistant canola dominates the canola market in Canada. A multiyear field experiment was conducted at three locations to investigate the effect of time of weed removal (two-, four-, or six-leaf canola) and herbicide rate (50 or 100% recommended) in three herbicide-resistant canola systems. Weeds were controlled in glufosinate-resistant canola (GLU) with glufosinate, in glyphosate-resistant canola (GLY) with glyphosate, and in imidazolinone-resistant canola (IMI) with a 50:50 mixture of imazamox and imazethapyr. Canola yields were similar among the three canola cultivar–herbicide systems. Yields were not influenced by 50 vs. 100% herbicide rates. Timing of weed removal had the greatest effect on canola yield, with weed removal at the four-leaf stage giving the highest yields in most cases. Percent dockage was often greater for GLU and IMI than for GLY. In comparison with the other treatments, dockage levels doubled for GLU after application at 50% herbicide rates. The consistency of monocot weed control was usually greater for GLY than for GLU or IMI systems. However, weed biomass data revealed no differences in dicot weed control consistency between IMI and GLY systems. Greater dockage and weed biomass variability after weed removal at the six-leaf stage or after low herbicide rates suggests higher weed seed production, which could constrain the adoption of integrated weed management practices in subsequent years.

Download Full-text