Effect of single or sequential POST herbicide applications on seed production and viability of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba- and glyphosate-resistant soybean

Abstract Glyphosate-resistant (GR) Palmer amaranth is a troublesome weed that can emerge throughout the soybean growing season in Nebraska and several other regions of the United States. Late-emerging Palmer amaranth plants can produce seeds, thus replenishing the soil seedbank. The objectives of this study were to evaluate single or sequential applications of labeled POST herbicides such as acifluorfen, dicamba, a fomesafen and fluthiacet-methyl premix, glyphosate, and lactofen on GR Palmer amaranth control, density, biomass, seed production, and seed viability, as well as grain yield of dicamba- and glyphosate-resistant (DGR) soybean. Field experiments were conducted in a grower’s field infested with GR Palmer amaranth near Carleton, NE, in 2018 and 2019, with no PRE herbicide applied. Acifluorfen, dicamba, a premix of fomesafen and fluthiacet-methyl, glyphosate, or lactofen were applied POST in single or sequential applications between the V4 and R6 soybean growth stages, with timings based on product labels. Dicamba applied at V4 or in sequential applications at V4 followed by R1 or R3 controlled GR Palmer amaranth 91% to 100% at soybean harvest, reduced Palmer amaranth density to as low as 2 or fewer plants m−2, reduced seed production to 557 to 2,911 seeds per female plant, and resulted in the highest soybean yield during both years of the study. Sequential applications of acifluorfen, fomesafen and fluthiacet premix, or lactofen were not as effective as dicamba for GR Palmer amaranth control; however, they reduced seed production similar to dicamba. On the basis of the results of this study, we conclude that dicamba was effective for controlling GR Palmer amaranth and reduced density, biomass, and seed production without DGR soybean injury. Herbicides evaluated in this study had no effect on Palmer amaranth seed viability.

Download Full-text

Glyphosate Resistance Does Not Affect Palmer Amaranth (Amaranthus palmeri) Seedbank Longevity

Weed Science ◽

10.1614/ws-d-12-00111.1 ◽

2013 ◽

Vol 61 (2) ◽

pp. 283-288 ◽

Cited By ~ 17

Author(s):

Lynn M. Sosnoskie ◽

Theodore M. Webster ◽

A. Stanley Culpepper

Keyword(s):

Seed Viability ◽

Glyphosate Resistance ◽

Early Spring ◽

Palmer Amaranth ◽

Food Sources ◽

Late Winter ◽

Burial Depth ◽

Amaranth Seed ◽

Seed Trap ◽

Soil Seedbank

A greater understanding of the factors that regulate weed seed return to and persistence in the soil seedbank is needed for the management of difficult-to-control herbicide-resistant weeds. Studies were conducted in Tifton, GA to (1) evaluate whether glyphosate resistance, burial depth, and burial duration affect the longevity of Palmer amaranth seeds and (2) estimate the potential postdispersal herbivory of seeds. Palmer amaranth seeds from glyphosate-resistant and glyphosate-susceptible populations were buried in nylon bags at four depths ranging from 1 to 40 cm for intervals ranging between 0 and 36 mo, after which the bags were exhumed and seeds evaluated for viability. There were no detectable differences in seed viability between glyphosate-resistant and glyphosate-susceptible Palmer amaranth seeds, but there was a significant burial time by burial depth interaction. Palmer amaranth seed viability for each of the burial depths declined over time and was described by exponential decay regression models. Seed viability at the initiation of the study was ≥ 96%; after 6 mo of burial, viability declined to 65 to 78%. As burial depth increased, so did Palmer amaranth seed viability. By 36 mo, seed viability ranged from 9% (1-cm depth) to 22% (40-cm depth). To evaluate potential herbivory, seed traps with three levels of exclusion were constructed: (1) no exclusion, (2) rodent exclusion, and (3) rodent and large arthropod exclusion. Each seed trap contained 100 Palmer amaranth seeds and were deployed for 7 d at irregular intervals throughout the year, totaling 27 sample times. There were seasonal differences in seed recovery and differences among type of seed trap exclusion, but no interactions. Seed recovery was lower in the summer and early autumn and higher in the late winter and early spring, which may reflect the seasonal fluctuations in herbivore populations or the availability of other food sources. Seed recovery was greatest (44%) from the most restrictive traps, which only allowed access by small arthropods, such as fire ants. Traps that excluded rodents, but allowed access by small and large arthropods, had 34% seed recovery. In the nonexclusion traps, only 25% of seed were recovered, with evidence of rodent activity around these traps. Despite the physically small seed size, Palmer amaranth is targeted for removal from seed traps by seed herbivores, which could signify a reduction in the overall seed density. To be successful, Palmer amaranth management programs will need to reduce soil seedbank population densities. Future studies need to address factors that enhance the depletion of the soil seedbank and evaluate how these interact with other weed control practices.

Download Full-text

Effect of row spacing and herbicide programs for control of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba/glyphosate-resistant soybean

Weed Technology ◽

10.1017/wet.2021.36 ◽

2021 ◽

pp. 1-41

Author(s):

Shawn T. McDonald ◽

Adam Striegel ◽

Parminder S. Chahal ◽

Prashant Jha ◽

Jennifer M. Rees ◽

...

Keyword(s):

Field Experiments ◽

Cultural Practices ◽

Integrated Approach ◽

The United States ◽

Palmer Amaranth ◽

Row Spacing ◽

Soybean Field ◽

Narrow Row ◽

Herbicide Programs ◽

Uniform Population

Abstract Glyphosate-resistant (GR) Palmer amaranth is one of the most difficult to control weeds in soybean production fields in Nebraska and the United States. An integrated approach is required for effective management of GR Palmer amaranth. Cultural practices such as narrow row spacing might augment herbicide efficacy for management of GR Palmer amaranth. The objectives of this study were to evaluate the effect of row spacing and herbicide programs for management of GR Palmer amaranth in dicamba/glyphosate-resistant (DGR) soybean. Field experiments were conducted in a grower’s field with a uniform population of GR Palmer amaranth near Carleton, Nebraska in 2018 and 2019. Year-by-herbicide program-by-row spacing interactions were significant for all variables; therefore, data were analyzed by year. Herbicides applied preemergence (PRE) controlled GR Palmer amaranth ≥ 95% in both years 14 d after PRE (DAPRE). Across soybean row-spacing, most PRE fb early-POST (EPOST) herbicide programs provided 84% to 97% control of Palmer amaranth compared with most EPOST fb late-post (LPOST) programs, excluding dicamba in single and sequential applications (82% to 95% control). Mixing microencapsulated acetochlor with a POST herbicide in PRE fb EPOST herbicide programs controlled Palmer amaranth ≥ 93% 14 DAEPOST and ≥ 96% 21 DALPOST with no effect on Palmer amaranth density. Interaction of herbicide program-by-row spacing on Palmer amaranth control was not significant; however, biomass reduction was significant at soybean harvest in 2019. The herbicide programs evaluated in this study caused no soybean injury. Due to drought conditions during a majority of the 2018 growing season, soybean yield in 2018 was reduced compared to 2019.

Download Full-text

Management of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in 2,4-D–, glufosinate-, and glyphosate-resistant soybean

Weed Technology ◽

10.1017/wet.2020.91 ◽

2020 ◽

pp. 1-8

Author(s):

Chandrima Shyam ◽

Parminder S. Chahal ◽

Amit J. Jhala ◽

Mithila Jugulam

Keyword(s):

United States ◽

Field Experiments ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Soybean Yield ◽

Chlorimuron Ethyl ◽

Density And Biomass ◽

Herbicide Programs ◽

Biomass Reduction

Abstract Glyphosate-resistant (GR) Palmer amaranth is a problematic, annual broadleaf weed in soybean production fields in Nebraska and many other states in the United States. Soybean resistant to 2,4-D, glyphosate, and glufosinate (Enlist E3TM) has been developed and was first grown commercially in 2019. The objectives of this research were to evaluate the effect of herbicide programs applied PRE, PRE followed by (fb) late-POST (LPOST), and early-POST (EPOST) fb LPOST on GR Palmer amaranth control, density, and biomass reduction, soybean injury, and yield. Field experiments were conducted near Carleton, NE, in 2018, and 2019 in a grower’s field infested with GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean. Sulfentrazone + cloransulam-methyl, imazethapyr + saflufenacil + pyroxasulfone, and chlorimuron ethyl + flumioxazin + metribuzin applied PRE provided 84% to 97% control of GR Palmer amaranth compared with the nontreated control 14 d after PRE. Averaged across herbicide programs, PRE fb 2,4-D and/or glufosinate, and sequential application of 2,4-D or glufosinate applied EPOST fb LPOST resulted in 92% and 88% control of GR Palmer amaranth, respectively, compared with 62% control with PRE-only programs 14 d after LPOST. Reductions in Palmer amaranth biomass followed the same trend; however, Palmer amaranth density was reduced 98% in EPOST fb LPOST programs compared with 91% reduction in PRE fb LPOST and 76% reduction in PRE-only programs. PRE fb LPOST and EPOST fb LPOST programs resulted in an average soybean yield of 4,478 and 4,706 kg ha−1, respectively, compared with 3,043 kg ha−1 in PRE-only programs. Herbicide programs evaluated in this study resulted in no soybean injury. The results of this research illustrate that herbicide programs are available for the management of GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean.

Download Full-text

Effects ofEriochloa villosadensity and time of emergence on growth and seed production inZea mays

Weed Science ◽

10.1017/s0043174500091347 ◽

1999 ◽

Vol 47 (6) ◽

pp. 687-692 ◽

Cited By ~ 10

Author(s):

James A. Mickelson ◽

R. Gordon Harvey

Keyword(s):

Seed Production ◽

Field Experiments ◽

Seed Mass ◽

Model Parameters ◽

Growth Stages ◽

Vegetative Biomass ◽

Eriochloa Villosa ◽

Term Management ◽

Weed Emergence

Field experiments were conducted in 1997 and in 1998 to determine the effects of density and time of emergence onEriochloa villosagrowth and seed production inZea mays. E. villosawas transplanted at four densities (3, 9, 27, and 81 plants m−2) to simulate emergence at four Z.maysgrowth stages (VE, V2, V5, and V10). Compared toE. villosaplants that emerged withZ. maysplants, total above-groundE. villosabiomass at maturity of plants grown at 3 plants m−2was reduced by 54, 97, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively, in 1997. In 1998, total abovegroundE. villosabiomass at maturity was reduced by 70, 87, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively.E. villosaaboveground vegetative biomass per plant at maturity was linearly related to seed production per plant in each year.E. villosaseed production m−2decreased nonlinearly as density decreased and time of emergence was delayed. Based on estimated model parameters, maximum seed production was 57,100 and 12,700 seeds m−2in 1997 and 1998, respectively. Within time of emergence,E. villosadensity did not affect seed mass per seed, however, seed mass of late-emerging cohorts was less than that of early-emerging cohorts. Time of weed emergence relative to the crop was a very important factor in determining biomass and seed production. Results suggest that late-emerging plants may not be very important to long-term management ofE. villosa.

Download Full-text

Integrating Cereals and Deep Tillage with Herbicide Programs in Glyphosate- and Glufosinate-Resistant Soybean for Glyphosate-Resistant Palmer Amaranth Management

Weed Technology ◽

10.1614/wt-d-14-00166 ◽

2016 ◽

Vol 30 (1) ◽

pp. 85-98 ◽

Cited By ~ 5

Author(s):

Holden D. Bell ◽

Jason K. Norsworthy ◽

Robert C. Scott

Keyword(s):

Seed Production ◽

Production Systems ◽

Palmer Amaranth ◽

No Tillage ◽

Tillage Systems ◽

Deep Tillage ◽

Late Season ◽

Amaranth Seed ◽

Herbicide Programs ◽

Moldboard Plow

A field experiment was conducted at Marianna, AR in 2012 and 2013 to test various combinations of (1) soybean production systems: full-season tillage (rye plus deep tillage using a moldboard plow), full season (no rye plus no tillage), late-season tillage (wheat plus deep tillage), and late season (no wheat plus no tillage); (2) soybean cultivars: glufosinate or glyphosate resistant; and (3) four herbicide programs for management of glyphosate-resistant Palmer amaranth. At soybean harvest, Palmer amaranth control was 95 to 100% when flumioxazin plus pyroxasulfone was applied PRE. In both years full-season tillage and late-season tillage systems in combination with flumioxazin plus pyroxasulfone applied PRE increased Palmer amaranth control over the same systems in the absence of flumioxazin plus pyroxasulfone applied PRE. The addition of deep tillage in the form of a moldboard plow to the full-season and late-season systems reduced Palmer amaranth densities at harvest. Similarly, Palmer amaranth seed production was often lower in the full-season tillage and late-season tillage systems compared with the full-season and late-season no-tillage systems, regardless of soybean cultivar and herbicide programs. Overall, the use of deep tillage in the full-season or late-season systems in combination with a PRE application of flumioxazin plus pyroxasulfone provided greater control of Palmer amaranth, decreasing both density and seed production and increasing soybean grain yields.

Download Full-text

Influence of Deep Tillage and a Rye Cover Crop on Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Emergence in Cotton

Weed Technology ◽

10.1614/wt-d-12-00110.1 ◽

2012 ◽

Vol 26 (4) ◽

pp. 832-838 ◽

Cited By ~ 11

Author(s):

Justin D. DeVore ◽

Jason K. Norsworthy ◽

Kristofor R. Brye

Keyword(s):

Cover Crops ◽

Cover Crop ◽

Cultural Practices ◽

Palmer Amaranth ◽

Deep Tillage ◽

Amaranth Seed ◽

Soil Seedbank ◽

Second Year ◽

The Impact ◽

Moldboard Plow

Glyphosate-resistant Palmer amaranth has become a major problem for cotton producers throughout much of the southern United States. With cotton producers relying heavily on glyphosate-resistant cotton, an alternative solution to controlling resistant Palmer amaranth is needed. A field experiment was conducted during 2009 and 2010 at Marianna, AR, in which a rye cover crop and no cover crop were tested in combination with deep tillage with the use of a moldboard plow and no tillage to determine the impact on Palmer amaranth emergence in cotton. To establish a baseline population, 500,000 glyphosate-resistant Palmer amaranth seeds were placed in a 2-m2area in the middle of each plot and incorporated into the soil, and emergence was evaluated five times during the season. In 2009, both tillage and the cover crop reduced Palmer amaranth emergence in cotton, but the combination of the two reduced emergence 85%. In the second year, only the cover crop reduced Palmer amaranth emergence in cotton, a 68% reduction. Cover crops and deep tillage will not eliminate glyphosate-resistant Palmer amaranth; however, use of these tools will likely reduce the risks of failures associated with residual herbicides along with selection pressure placed on both PRE- and POST-applied herbicides. Additional efforts should focus on the integration of the best cultural practices identified in this research with use of residual herbicides and greater focus on limiting Palmer amaranth seed production and reducing the soil seedbank.

Download Full-text

Evaluation of Herbicide Programs for Use in a 2,4-D–Resistant Soybean Technology for Control of Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri)

Weed Technology ◽

10.1614/wt-d-15-00129.1 ◽

2016 ◽

Vol 30 (2) ◽

pp. 366-376 ◽

Cited By ~ 11

Author(s):

M. Ryan Miller ◽

Jason K. Norsworthy

Keyword(s):

Weed Management ◽

Field Experiments ◽

Palmer Amaranth ◽

Integrated Weed Management ◽

Amaranthus Palmeri ◽

Early Season ◽

Fully Integrated ◽

Soil Seedbank ◽

High Level ◽

Herbicide Programs

Two separate field experiments were conducted over a 2-yr period in Fayetteville, AR, during 2012 and 2013 to (1) evaluate POST herbicide programs utilizing a premixture of dimethylamine (DMA) salt of glyphosate + choline salt of 2,4-D in a soybean line resistant to 2,4-D, glyphosate, and glufosinate and (2) determine efficacy of herbicide programs that begin with PRE residual herbicides followed by POST applications of 2,4-D choline + glyphosate DMA on glyphosate-resistant Palmer amaranth. In the first experiment, POST applications alone that incorporated the use of residual herbicides with the glyphosate + 2,4-D premixture provided 93 to 99% control of Palmer amaranth at the end of the season. In the second experiment, the use of flumioxazin, flumioxazin + chlorimuron methyl, S-metolachlor + fomesafen, or sulfentrazone + chloransulam applied PRE provided 94 to 98% early-season Palmer amaranth control. Early-season control helped maintain a high level of Palmer amaranth control throughout the growing season, in turn resulting in fewer reproductive Palmer amaranth plants present at soybean harvest compared to most other treatments. Although no differences in soybean yield were observed among treated plots, it was evident that herbicide programs should begin with PRE residual herbicides followed by POST applications of glyphosate + 2,4-D mixed with residual herbicides to minimize late-season escapes and reduce the likelihood of contributions to the soil seedbank. Dependent upon management decisions, the best stewardship of this technology will likely rely on the use multiple effective mechanisms of action incorporated into a fully integrated weed management system.

Download Full-text

Germination Ecology of Biennial Wormwood (Artemisia biennis) and Lanceleaf Sage (Salvia reflexa) Seeds

Weed Science ◽

10.1614/ws-09-103.1 ◽

2010 ◽

Vol 58 (1) ◽

pp. 61-66 ◽

Cited By ~ 4

Author(s):

George O. Kegode ◽

Gauri Nazre ◽

Michael J. Christoffers

Keyword(s):

Great Plains ◽

Seed Viability ◽

Field Studies ◽

The United States ◽

Northern Great Plains ◽

Freezing And Thawing ◽

Seed Decay ◽

Soil Seedbank ◽

The Difference ◽

Fluctuating Temperatures

Biennial wormwood and lanceleaf sage have become serious weeds of several crops within the northern Great Plains of the United States and Canada. Both species are prolific seed producers but little is known about their potential for developing persistent seedbanks. Field studies were conducted to determine the influence of duration (7, 8, 11, 19, 20, and 23 mo) and depth of burial (0, 2.5, and 10 cm) on biennial wormwood and lanceleaf sage seed viability and decay. Biennial wormwood and lanceleaf sage seeds were buried in September 2003 (burial 1) and September 2004 (burial 2). In burial 1, biennial wormwood and lanceleaf sage seed viability was 65 and 66%, respectively, after 23 mo of burial. In burial 2, biennial wormwood and lanceleaf sage seed viability was 8 and 3%, respectively, after 23 mo of burial. The difference was likely because of higher soil moisture during burial 2, which promoted seed decay. Controlled-environment studies sought to determine the influence of stratification environments (freezing, chilling, and freeze–thaw) followed by exposure to diurnally fluctuating temperatures on germination of biennial wormwood and lanceleaf sage seeds. Stratified biennial wormwood seed germination was 95% or greater when incubated in fluctuating day/night temperatures of 37/20 or 37/25 C. Stratified lanceleaf sage seeds from freezing and chilling environments did not differ in germination following incubation in fluctuating temperatures and averaged 56 and 55%, respectively. Germination of stratified lanceleaf sage seeds from the freezing and thawing environment was higher than 50% during the thawing cycle, suggesting the possibility of early season emergence of this species. Our study indicates that biennial wormwood and lanceleaf sage have the potential to develop a seedbank that can persist for more than 2 yr. High moisture levels in the soil seedbank can lead to reduced seed survival.

Download Full-text

Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Morphology, Growth, and Seed Production in Georgia

Weed Science ◽

10.1614/ws-d-14-00051.1 ◽

2015 ◽

Vol 63 (1) ◽

pp. 264-272 ◽

Cited By ~ 24

Author(s):

Theodore M. Webster ◽

Timothy L. Grey

Keyword(s):

United States ◽

Seed Production ◽

Growing Season ◽

Palmer Amaranth ◽

Competitive Balance ◽

Potential Growth ◽

Southeast United States ◽

Alternative Means ◽

Soil Seedbank ◽

Crop Competition

Herbicide-resistant Palmer amaranth has become the most economically detrimental weed of cotton in the southeast United States. With the continual marginalization of potential herbicide tools, research has expanded to include alternative means of affecting future Palmer amaranth populations by altering safe sites and reducing inputs to the seedbank population. The influence of delayed Palmer amaranth establishment on seed production potential has not been investigated in the southeast United States. Studies were conducted to evaluate the influence of time of Palmer amaranth establishment on morphology, growth, and seed production. The experiment was a factorial, with five levels of Palmer amaranth transplanting (0 to 12 wk after cotton planting) and two levels of crop type (cotton and noncrop). In the absence of crop competition, the first cohort of Palmer amaranth produced 446,000 seeds per plant. This potential seed production was reduced 50% when Palmer amaranth plants were established nearly 6 wk later. In contrast, the first Palmer amaranth cohort growing in competition with cotton produced 312,000 seeds, 30% less than was produced in the absence of competition. Interference from cotton shifted time to 50% seed production to nearly 4 wk earlier in the growing season, relative to plants without crop competition. Delayed establishment of Palmer amaranth simulates premature loss of herbicide efficacy and alters the competitive balance between cotton and Palmer amaranth. Although the planting time that resulted in 50% reduction in Palmer amaranth plant height at the end of the season was not affected by the presence of cotton, 50% reduction in plant width and biomass occurred within the first 3.8 wk of the growing season when growing with cotton, more than 4 wk earlier than Palmer amaranth growing without a crop. This suggests that early season weed control programs will have a large effect on Palmer amaranth potential growth and seed production, as well as crop yield. To implement soil seedbank reduction strategies effectively, information on mechanisms that regulate Palmer amaranth persistence in the soil seedbank is needed.

Download Full-text

Import of Palmer amaranth (Amaranthus palmeri S. Wats.) seed with sweet potato (Ipomea batatas (L.) Lam) slips

Canadian Journal of Plant Science ◽

10.1139/cjps-2020-0321 ◽

2021 ◽

Author(s):

Eric Robert Page ◽

Robert E. Nurse ◽

Sydney Meloche ◽

Kerry Bosveld ◽

Christopher Grainger ◽

...

Keyword(s):

Sweet Potato ◽

Arable Land ◽

The United States ◽

Palmer Amaranth ◽

Amaranthus Palmeri ◽

Nucleotide Polymorphisms ◽

Single Nucleotide ◽

Ipomea Batatas ◽

Amaranth Seed ◽

Species Specific

Palmer amaranth is one of the most economically important and widespread weeds of arable land in the United States. Although no populations are currently known to exist in Canada, its distribution has expanded northward such that it is present in many of the States bordering Canada and multiple pathways exist for its introduction. In this short communication we report on the transport of viable Palmer amaranth seed on imported sweet potato slips. A reproductive pair of Palmer amaranth seedlings were identified from soil accompanying imported sweet potato slips in 2018. Identification was confirmed using species specific single nucleotide polymorphisms.

Download Full-text