Early Post Herbicide Research Articles

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

AbstractGlyphosate-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 PRE controlled GR Palmer amaranth ≥95% in both years 14 d after PRE (DAPRE). Across soybean row-spacing, most PRE followed by (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 d after EPOST and ≥96% 21 d after LPOST 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 with 2019.

Evaluation of mesotrione tolerance levels and [14C]mesotrione absorption and translocation in three fine fescue species

AbstractFine fescues (Festucaspp.) are cool-season grasses used in low-maintenance turf areas. Mesotrione is a PRE and early-POST herbicide used during establishment of most cool-season turfgrasses, excluding fine fescues. Currently, efforts are being made to breed for increased tolerance to mesotrione in fine fescues to enhance weed control during establishment. This study was conducted to evaluate the association of foliar and root uptake of [14C]mesotrione with the tolerance of three lines each of Chewings fescue [Festuca rubrassp. commutataGaudin; syn.F. rubrassp.fallax(Thuill.) Nyman], hard fescue [Festuca trachyphylla(Hack.) Hack.], and strong creeping red fescue (Festuca rubraL. ssp.rubra) lines. From a rate-titration experiment, the hierarchical rank of species for mesotrione tolerance from highest to lowest was: hard > Chewings > strong creeping red fescue. The hierarchical rank of species for foliar uptake from highest to lowest was: Chewings > strong creeping red > hard fescue. Translocation of foliar-absorbed14C was not associated with differential tolerance levels of the three species. Root absorption was comparable among species, but differences between lines were detected within the species. The most susceptible lines of Chewings and strong creeping red fescue exhibited greater root uptake than lines with greater tolerance. Hard fescue translocated the least amount of root-absorbed radioactivity to shoots, while Chewings and strong creeping red fescues were comparable.

Efficacy and economics of different herbicides, their weed species selectivity, and the productivity of mechanized dry-seeded rice

A field study was conducted in 2012 and 2013 at the International Rice Research Institute (IRRI) farm in Los Baños, Philippines, to evaluate the economic performance of PRE oxadiazon and pendimethalin, early POST butachlor plus propanil and thiobencarb plus 2,4-D, and late POST herbicides bispyribac-sodium and fenoxaprop plus ethoxysulfuron applied solely or sequentially. All herbicide treatments with PRE or early POST herbicides reduced total weed density by 85–100% and biomass by 80–100%, whereas late POST treatments reduced weed density by 32–50% and biomass by 40–62% compared with the nontreated weedy check. The highest grain yield was achieved in weed-free plots (5.9–6.1 t ha−1) and the lowest in weedy plots (0.2 t ha−1). Among the herbicide treatments, rice treated with oxadiazon, thiobencarb plus 2,4-D, and butachlor plus propanil followed by the late POST herbicides had grain yield increments of 23–25, 20 to 26, and 18 to 23 times that of the yield in weedy plots, respectively. The economic analysis showed that the sole application of oxadiazon provided the highest net profit and benefit-cost ratio in both years, which was similar to the treatments involving oxadiazon or early POST herbicides, followed by the sequential application of late POST herbicides.

Application time and herbicide rate effects on weeds in oilseed rape (Brassica napus var. oleifera)

Field trials were conducted in 2010 and 2011 to evaluate different application time of metazachlor (Butisan 400 SC) and dimethachlor (Teridox-500), and their rate effects on weeds in oilseed rape (OSR). The weed population was consisted of winter and summer annuals, some perennial weeds, and volunteer wheat. Veronica spp., Triticum aestivum, Camelina sativa and Alopecurus myosuroides infestations were heavy throughout the experimental areas in both years. Efficacy of PRE herbicides was lower in comparison with early POST herbicides; it was ranged from 77.8% (Teridox – 2.0 L/ha) in Bitola locality to 86.9% (Butisan – 3.5 L/ha) in Skopje locality. Efficacy of early POST herbicides was ranged from 88.3% (Teridox – 2.0 L/ha) in Bitola locality to 98.6% (Butisan – 3.5 L/ha) in Skopje locality. Control of prevailing weeds was ranged from 53% to 97%, and 66% to 100% with PRE and early POST herbicide treatments, respectively. Particularly high efficacy showed Butisan applied early POST at 2.5 and 3.5 L/ha, respectively which excellent controlled prevailing weeds in both localities. All applied herbicides showed high selectivity to OSR; no visual injuries were determined by any rates in both years. OSR grain yield of herbicides applied PRE was lower in comparison with their early POST application.

Mesotrione plus Prodiamine for Smooth Crabgrass (Digitaria ischaemum) Control in Established Bermudagrass Turf

Crabgrass species are problematic weeds in bermudagrass turf that can be controlled by PRE herbicide applications. Because of the difficulty in predicting crabgrass emergence and other prevailing management constraints, PRE herbicide applications are not always properly timed. Mesotrione controls crabgrass both PRE and POST; however, relatively short soil-residual activity limits its use as a PRE herbicide. Two experiments were conducted to evaluate smooth crabgrass control with PRE applications of mesotrione plus prodiamine. The first experiment evaluated the influence of application timing on the efficacy of mesotrione-plus-prodiamine combinations. Applications were made every 2 wk from March 15 to May 24. Mesotrione plus prodiamine controlled smooth crabgrass more consistently across all application dates than either mesotrione or prodiamine applied alone. The second experiment evaluated mesotrione along with current PRE and early POST herbicide treatments used for control of crabgrass. When applied at one to two tillers growth stage, mesotrione plus prodiamine controlled smooth crabgrass 99% when rated on August 31. Bermudagrass injury from mesotrione ranged from 9 to 44%, but did not result in any reduction in turf plant density. Mesotrione plus prodiamine is an effective tank mixture when prodiamine alone is not applied in a timely fashion; however, variable and excessive turf injury is a potential impediment to mesotrione use on bermudagrass turf.Nomenclature: Mesotrione, prodiamine, smooth crabgrass, Digitaria ischaemum (Schreb) Schreb. ex Muhl Schreb. DIGIS, bermudagrass, Cynodon dactylon L. CYNDA

Weed Control Programs in Drill-Seeded Imidazolinone-Resistant Rice (Oryza sativa)

A study was conducted to evaluate weed control with imazethapyr applied at different timings or a combination of timings with or without an early POST application of bensulfuron, bentazon plus aciflurofen, bispyribac, carfentrazone, halosulfuron, propanil plus molinate, or triclopyr in drill-seeded imidazolinone-resistant rice. Control of barnyardgrass, red rice, and alligatorweed was insufficient with imazethapyr at 87 g/ha PRE or at 53 g/ha late POST alone. Imazethapyr at 87 g/ha PRE followed by imazethapyr at 53 g/ha late POST controlled red rice 86% or greater but did not control hemp sesbania. The imazethapyr PRE followed by late POST combination was also weak on barnyardgrass and alligatorweed early in the season. The addition of an early POST application of the other herbicides to the imazethapyr combination improved overall weed control, especially hemp sesbania control. Among the early POST herbicides, bispyribac, carfentrazone, or propanil plus molinate were more effective in helping improve the overall weed control, resulting in better rice grain yield.

Weed Management in No-Tillage Bromoxynil-Tolerant Cotton (Gossypium hirsutum)

An experiment was conducted at four locations in North Carolina during 1994 and 1995 to evaluate weed control, cotton yield, fiber quality, and net returns in no-tillage bromoxynil-tolerant cotton. The experiment focused on using bromoxynil or pyrithiobac sodium applied early POST over-the-top as alternatives to fluometuron plus MSMA applied early POST directed. Fluometuron plus MSMA was more effective than bromoxynil or pyrithiobac sodium on tall morningglory, large crabgrass, goosegrass, and broadleaf signalgrass. Bromoxynil and fluometuron plus MSMA were similarly effective on common lambsquarters, common ragweed, and eclipta and more effective than pyrithiobac sodium. Pyrithiobac sodium and fluometuron plus MSMA were similarly effective on smooth pigweed and Palmer amaranth and more effective than bromoxynil. Prickly sida control by bromoxynil and pyrithiobac sodium was equal to or greater than control by fluometuron plus MSMA. All early POST herbicides controlled pitted morningglory similarly. Regardless of the early POST herbicides used, fluometuron applied PRE and cyanazine plus MSMA applied late POST directed increased control of most weeds and increased cotton yield and net returns. Bromoxynil and pyrithiobac sodium effectively substituted for fluometuron plus MSMA only in systems that included fluometuron applied PRE and cyanazine plus MSMA applied late POST directed. Effects of herbicide systems on cotton fiber quality were minor.

Sicklepod (Senna obtusifolia) Management in an ALS-Modified Soybean (Glycine max)

Herbicide systems consisting of PRE, early POST, and late POST options arranged factorially were compared for control of sicklepod in narrow-row soybean with modified acetolactate synthase (ALS) (E.C.4.1.3.18). Other weeds present included common cocklebur and mixed infestations of entireleaf, ivyleaf, pitted, and tall morningglories. PRE options were alachlor or alachlor plus metribuzin plus chlorimuron. Early POST options included chlorimuron, chlorimuron plus thifensulfuron, and no herbicide applied 3 wk after planting. Late POST options were chlorimuron and no herbicide applied 5 wk after planting. POST herbicides were more effective than PRE herbicides on all weeds. Chlorimuron and chlorimuron plus thifensulfuron applied early POST were equally effective on these weeds and usually more effective than chlorimuron applied late POST. There was no advantage of two POST applications compared with a single early POST application. Greatest net returns were obtained in systems using only early POST herbicides. There was no economic advantage from using metribuzin plus chlorimuron PRE in systems that included an early POST herbicide.