Effect Of Various Herbicides Research Articles

Chemical weed management in chickpea (Cicer arietinum) under Vertisols of Eastern Plateau Plain zone of India

A field experiment was conducted during the winter seasons of 2020–21 and 2021–22 at Instructional-cumResearch farm of Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh to study the effect of various herbicides and their combinations on weed dynamics and performance of chickpea. A total of 14 treatment combinations including hand weeding and unweeded control were laid out in a randomized block design with three replications. The results revealed that significantly lower weed density and dry matter production, weed index and higher weed control efficiency were observed under two hand weedings at 20 and 40 DAS which was found at par to oxyfluorfen 150 g/ha (PE) fb topramezone 20.6 g/ha (PoE) and metribuzin 350 g/ha (PE) fb topramezone 20.6 g/ ha (PoE). The higher dry matter accumulation, crop growth rate, number of pods/plant, number of seeds/pod, seed index, seed yield (1.78 t/ha) and stover yield (2.70 t/ha) of chickpea were obtained with oxyfluorefen 150 g/ha (PE) fb topramezone 20.6 g/ha (PoE). Application of oxyfluorefen 150 g/ha (PE) fb topramezone 20.6 g/ha (PoE) controlled complex weeds flora effectively and fetched maximum net returns (`63.1 × 103/ha) and benefit-cost ratio (3.02).

Optimizing herbicide types and concentrations: Crucial elements for achieving intensive cultivation of common buckwheat

An appropriate herbicide type and concentration is essential for effective weed management and enhancing crop yield. However, the optimal herbicide type and corresponding application concentration for controlling weeds in common buckwheat on the Loess Plateau region of Northwestern China remain unclear. To address this gap, experiments were conducted to investigate the effects of various herbicides on weed control, dry matter accumulation, and grain yield in common buckwheat, and to analyze the variances in weed control efficacy and grain yields of the optimal herbicides at different concentrations. The results showed that both metolachlor and quizalofop-P-ethyl demonstrated effective weed control with lower phytotoxicity. Dry matter accumulation was lower under metolachlor, with no significant differences observed among the post-emergence herbicide treatments. Importantly, metolachlor and quizalofop-P-ethyl promoted the allocation of dry matter to grains. Remarkably, metolachlor and quizalofop-P-ethyl increased the grain yield by 15.59% and 26.97%, respectively, compared to spraying an equivalent amount of water. Additionally, the m2.25, q0.9, and q1.2 treatments exhibited excellent weed control effectiveness. And the higher grainnumber per plant observed under m2.25, q0.9, and q1.2 contributed to the increase in grain yield. Consequently, m2.25, q0.9 and q1.2 increased the grain yield by 34.42%, 38.86% and 33.16%, respectively. These findings demonstrate that applying metolachlor and quizalofop-P-ethyl at 2.25 L ha−1 and 0.9 or 1.2 L ha−1 respectively, is beneficial for efficient weed management and yield enhancement in common buckwheat cultivation on the Loess Plateau region of Northwestern China. These studies provide important guidance for promoting common buckwheat cultivation in this region.

Effect of various herbicides for weed control in late sown wheat (Triticum aestivum L.)

Effect of various herbicides for weed control in late sown wheat (Triticum aestivum L.)

МЕРЫ БОРЬБЫ С СОРНОЙ РАСТИТЕЛЬНОСТЬЮ НА ПОСЕВАХ СОИ

In the forest-steppe zone of the Republic of North Ossetia-Alania on soybean crops (Iriston varieties), the effect of the soil herbicide Harness and insurance herbicides Galaxy Top, Illoxan, Frontier was studied. The aim of the research was to study the effect of various herbicides on the contamination of crops and the species composition of weed vegetation of promising soybean varieties in the conditions of the forest-steppe zone of the Russian Federation. Scientific novelty of research. The influence of various herbicides on the growth, development and productivity of promising soybean varieties has been studied; the effect of herbicides on the contamination of crops has been shown; The removal of basic nutrients by individual species of weeds has been established. Every year, more and more new herbicides appear on the market, so studying the properties of herbicides and their effect on weeds is an urgent task. The methodology. On the leached chernozems of the forest-steppe zone of the Russian Federation-Alania in 2020-2022, on the experimental fields of the SCNIIGPSH VNC RAS. The sowing method is wide–row (row spacing – 45 cm), with a seeding rate of 400 thousand germinating seeds per 1 hectare. The research area is hot, mostly well-humidified. The sum of temperatures is 3000-3200 °C. The climate of the described territory is continental, the absolute annual amplitude of air temperature fluctuations is 64 ° C. On the territory of the experiment, the soil is represented by medium-sized, heavy-loamy leached chernozem, underlain by pebbles. The soil is mechanically loamy, with a depth that turns into light and medium loamy- rocky. The authors found that chemical protection of crops from weeds in the forest-steppe zone should be carried out with combinations of herbicides Pivot 0.9 + Bazagran 1.1. At the same time, weed death reaches from 79.4 to 92.9%. After harvesting soybeans, the soil is quite suitable for the cultivation of any agricultural crop, since (in specified doses) herbicides do not accumulate in products and are safe for the environment.

Effect of Different Weed Management Practices on Growth Characters of Mungbean under Mid-Hills of Himachal Pradesh, India

Weed management in mungbean is one of the most efficient ways to improve its growth, as uncontrolled weed growth causes a significant decrease in crop growth. Effects of various herbicides applied at different rates as pre-emergence or as post-emergence were studied on growth characterstics in mungbean. It is usually infested and its growth parameter is adversely affected by a number of weed species that compete with the crop from germination to harvest, affecting the crop growth adversely. A field experiment titled “Effect of Different Weed Management Practices on Growth Characters of Mungbean under Mid-hills of Himachal Pradesh” was conducted during the kharif season of 2022 at Chamelti Agriculture Farm, MS Swaminathan School of Agriculture, Shoolini University of Biotechnology and Management Sciences, District Solan. The soil of the experimental field was sandy loam in texture, slightly alkaline in reaction with EC in a safer range, medium in organic carbon, available nitrogen, potassium, and high in available phosphorus. The experiment was laid out in randomized block design with three replications comprising ten weed management treatments viz. (T1) Pendimethalin 30 EC @ 1.0 kg a.i. ha-1 PE, (T2) Pendimethalin 30 EC @ 1.0 kg a.i. ha-1 PE fb one HW at 20 DAS, (T3) Pendimethalin 30 EC @ 0.75 kg a.i. ha-1 PE fb Imezathapyr 10% SL @ 70 g ha-1 PoE at 20 DAS, (T4) Pendimethalin 30 EC @ 0.75 kg a.i. ha-1 PE fb Oxyfluoren @ 50 g a.i. ha-1 PoE at 25 DAS, (T5) Pendimethalin @ 0.75 kg a.i. ha-1 PE fb Quizolofop ethyl @ 50 g ha-1 PoE at 20 DAS, (T6) Imazethapyr 10% SL @ 70 g a.i. ha-1 PoE at 20 DAS, (T7) One-hand weeding at 25 DAS, (T8) Two-hand weeding at 20 and 35 DAS, (T9) Weedy check and (T10) Weed free. The recommended dose of fertilizer (20:40:20 kg ha-1) was applied through Urea, SSP, and MOP at the time of sowing. Pusa Baishaki variety of mungbean was used for sowing. Weed management practices were done as per treatment. Other crop management practices were followed as per the recommendation of the area. Data on growth characters revealed that application of (T2) Pendimethalin 30EC @ 1.0 kg a.i. ha-1 PE fb one HW at 20 DAS registered higher growth parameters viz. plant height, number of branches plant-1, dry matter accumulation and trifoliate leaves which was statistically at par with (T3), (T4) and (T5). Thus, study suggest that mungbean can successfully grown under Mid-hills of Himachal Pradesh on (T2) Pendimethalin 30 EC @ 1.0 kg a.i. ha-1 PE fb one HW at 20 DAS.

Effect of herbicides on pollinator foraging behavior and flower morphology in white clover (Trifolium repens L.)–infested turfgrass

AbstractThe recent decline in pollinator abundance is a cause of concern for sustaining global food production. Several common weeds of managed turfgrass systems attract honeybees and other wild pollinators. As turfgrass often requires treatment with insecticides that harm bees, best practices are needed to prevent bees from visiting weed-infested turf areas that will be treated for insect pests. Weed control tactics can protect pollinator exposure to insecticides by reducing the floral resources afforded to bees from turfgrass weeds. Three field studies were conducted in 2021 and 2022 to evaluate the effect of various herbicides and herbicide formulation constituents on pollinator foraging and white clover floral morphology in managed tall fescue turfgrass. Treatments included a nontreated control; MCPP; 2,4-D; dicamba; Trimec Classic™ (2,4-D, MCPP, dicamba); Speedzone™ (carfentrazone, 2,4-D, MCPP, dicamba); and an herbicide-formulation constituent (inert ingredients of Speedzone™). All response variables were evaluated for 8 d, starting from one day before treatment and ending 6 d after treatment (DAT). The herbicide formulation constituent did not alter white clover flower density, floral discoloration, floral quality, or insect visitation compared to nontreated plots. Herbicides reduced flower density and floral quality to the same extent, but MCPP discolored white clover floral tissue 16% per day and less than all other herbicides except dicamba. Floral quality completely declined in approximately 5 d following any herbicide treatment. Bee visitation to white clover–infested turf increased by 3 bees min–1 for every 100 white clover blooms m–2. Honeybees and other insects vacated herbicide-treated areas in less than 2 d, despite minimal effects on floral quality and density at that time. The data suggest that practitioners could apply insecticides 2 d after auxin herbicide treatment and avoid harm to pollinators, but additional work is needed to directly measure pollinator exposure following such treatments.

Evaluation of Herbicides for the Control of Yellow Nutsedge (Cyperus esculentus L.) and Johnsongrass (Sorghum halepense L.) Under Non-Crop Conditions

Yellow nutsedge (Cyperus esculentus L.) and Johnsongrass (Sorghum halepense (L.) Pers.) are two of the most difficult weeds to control mostly due to their asexual reproduction. Yellow nutsedge reproduces through underground tubers and Johnsongrass through rhizomes. In addition, Johnsongrass is a problematic weed because of its competitive nature due to its C4 carbon fixation pathway metabolism. It typically grows to 1.8 to 2.5 m tall and can severely reduce yields in corn, cotton, soybeans, and other crops. Two separate field studies were conducted in 2020 at the Delta Research and Extension Center in Stoneville, Mississippi to evaluate the effectiveness of various herbicides on yellow nutsedge and Johnsongrass control in a non-crop scenario. The experiments were conducted as randomized complete block designs with 7 and 11 herbicide treatments for yellow nutsedge and Johnsongrass, respectively. All treatments were replicated three times. Research plots were 4-m wide and 6-m long with 3-m alleys between replications. The 7 yellow nutsedge herbicide treatments consisted of trifloxysulfuron, bentazon, halosulfuron, halosulfuron + thifensulfuron, glyphosate, glufosinate, and paraquat. The 11 Johnsongrass herbicide treatments included clethodim, quizalofop, fluazifop, cyhalofop, fenoxaprop, pinoxaden, glufosinate, glyphosate, clethodim + glyphosate, glufosinate + clethodim, and glufosinate + clethodim + glyphosate. Glyphosate and halosulfuron + thifensulfuron provided only 77 and 72% control of yellow nutsedge by five-weeks after application (WAA). On the other hand, glyphosate, clethodim + glyphosate, glufosinate + clethodim, and glufosinate + clethodim + glyphosate provided 99 to 100% Johnsongrass control 4 WAA. Johnsongrass regrowth evaluation was assessed 3-weeks after the experimental area was mowed. Johnsongrass regrew in every herbicide treatment except for glyphosate which was the only treatment that provided 100% Johnsongrass control with no-regrowth.

Confirmation of glufosinate-resistant Palmer amaranth and response to other herbicides

AbstractThe ability of weed populations to evolve resistance to herbicides affects management strategies and the profitability of crop production. The objective of this research was to screen Palmer amaranth accessions from Arkansas for glufosinate resistance. Additional efforts focused on the effectiveness of various herbicides, across multiple sites of action (SOAs), on each putative-resistant accession. The three putative accessions were selected from 60 Palmer amaranth accessions collected in 2019 and 2020 and screened with to 0.5× and 1× rates of glufosinate. A dose-response experiment was conducted for glufosinate on accessions A2019, A2020, and B2020. The effectiveness of various preemergence- and postemergence-applied herbicides were evaluated on each accession. Resistance ratios of A2019, A2020, and B2020 to glufosinate ranged from 5.1 to 27.4 when comparing LD50 values to two susceptible accessions, thus all three accessions were resistant to glufosinate. All three accessions (A2019, A2020, and B2020) were found to have a reduction equal to or greater than 20 percentage points in mortality to at least one herbicide from five different SOAs equal to or greater than five sites of action. Herbicides from nine different SOAs controlled A2019 at least 20 percentage points less than the susceptible accessions, which points to a need for additional research to characterize the response of this accession.

Impact of different herbicides on weed control in grape (Vitis vinifera L.) cv. ‘2A clone’

A field experiment on “Impact of different herbicides on weed control in grape (Vitis vinifera L.) cv. 2A Clone” was carried out during October 2019 to March 2020 at fruit orchard, Main Horticultural Research and Extension Center (MHREC) Sector no 70, University of Horticultural Sciences, Udyanagiri, Bagalkote, to test the effect of various herbicides for controlling weeds in the vineyards under dry zone climate of north Karnataka. The trial was laid out in randomized complete block design (RCBD), having ten treatments with three replications. Lower number of total weeds/m2 4.67, 9.00, 16.00 and 23.00/m2 at 30, 60, 90 and 120 days after spraying was recorded with T6-tank mix post-emergent application of oxyfluorfen 23.5% @ 1.0 lit/ha + glyphosate 41% SL @ 2.62 lit/ha. Among different herbicides, the higher yield per hectare (32.31 t/ha) and the lower weed index (5.76 %) were recorded with tank mix post-emergent application of oxyfluorfen 23.5% @ 1.0 lit/ha + glyphosate 41% SL @ 2.62 lit/ha. No phyto-toxicity symptoms viz. leaf tip/surface injury, wilting, vein clearing, necrosis, epinasty and/ or hyponasty were observed.

Blood biomarkers of herbicide, insecticide, and fungicide toxicity to fish-a review.

Pesticides are widely used in the world agriculture, and they may adversely affect non-target organisms, including fish. The present 2000-2019 literature review summarizes hematological and blood biochemical effects of various herbicides, insecticides, and fungicides in fish. The observed changes usually indicate anemia and inflammation, as well as hyperglycemia, hypoproteinemia, increase in cortisol concentration and activities of hepatic aminotransferases that are typical for intoxication and stress. Other changes that are also sometimes observed such as increase in red blood parameters indicate compensatory response. The often-noted symptoms of immunosuppression show an adverse effect of pesticides on immune system and possible immunosuppression. Pathophysiological changes in fish induced by pesticides depend on many factors, such as active compound and its concentration, exposure duration, fish species, environmental conditions, etc. Hematological and blood biochemical parameters appear to be useful biomarkers for evaluation of physiological state of fish exposed to pesticides; however, they are not specific markers of intoxication.

Influence of herbicides on symbiotic parameters, growth, yield and nutrient uptake in mungbean [Vigna radiata (L.) Wilczek

ABSTRACT Effects of various herbicides applied at different rates as pre-emergence or as post-emergence were studied on symbiotic parameters, growth, productivity and nutrient accumulation in mungbean. Pre-emergence application of pendimethalin 30 EC at 0.75 kg ha−1, pendimethalin 30 EC at 0.45 kg ha−1 + hand weeding (HW) at 4 weeks after sowing (WAS) and pendimethalin 30 EC + imazethapyr 2 SL (pre-mix) at 0.45 kg ha−1 + HW at 4 WAS had no/little inhibitory effect on symbiotic parameters (nodule number, nodule dry weight and leghaemoglobin content). Among herbicide treatments, pendimethalin 30 EC at 0.45 kg ha−1 + HW proved to be the best in influencing grain yield (1574 and 1246 kg ha−1 in 2016 and 2017, respectively) and nutrient uptake by crop (130.0–150.9 kg nitrogen, 13.6–16.4 kg phosphorus and 75.9–87.9 kg potassium ha−1) followed by pendimethalin 30 EC + imazethapyr 2 SL (pre-mix) at 0.45 kg ha−1 + HW (1528 and 1177 kg ha−1 grain yield, 123.9–140.9 kg nitrogen, 12.8–15.2 kg phosphorus and 71.5–81.5 kg potassium ha−1). Application of imazethapyr at 50 or 75 g ha−1 at 15 or 25 DAS had adverse effect on symbiotic parameters, grain yield and nutrient uptake.

Effect of herbicides in weed management of wheat-chickpea intercropping system

The review paper is based on the effect of various herbicides in weed management of wheat (Triticum aestivum L.)- Chickpea (Cicer arietinum L.) intercropping system. Weeds are considered most harmful to the crops. They interfere with crops during the different growth stages and reduce the growth and yield of the crop drastically. Therefore, different weed management practices have been taken to decrease the crop-weed competition, especially by using herbicidal treatments. So in reference to the weeds found in the wheat-chickpea intercropping and their control, various herbicidal treatments are used to check the weed competition with crops. The chemical weed control method is the most effective and time saving. The herbicides should be selected properly on the basis of selectivity, so they do not harm the main crop. Pre-emergence like Pendimethalin are translocated herbicide, they are applied in the soil and inhibit the cell division in the weed seeds. Post-emergence herbicides like Isoproturon, clodinafop-propargyl, pinoxaden etc are contact herbicide, they enter through aerial parts like leaves and affect the photosynthesis (photosystem-I, II). All these herbicides were proven to be efficient in reducing weed density, dry matter accumulation of weeds and increased the yield and net returns of main crop grown in the field.

Influence of Nitrogen Rate, Seeding Rate, and Weed Removal Timing on Weed Interference in Barley and Effect of Nitrogen on Weed Response to Herbicides

Field experiments were conducted at the Montana State University Southern Agricultural Research Center, Huntley, MT, in 2011 through 2013 to determine the effect of nitrogen (N) rate, seeding rate, and weed removal timing on weed interference in barley. A delay in weed removal timing from the 3- to 4-leaf (LF) stage to the 8- to 10-LF stage of barley resulted in up to 3.5-fold increase in total weed biomass and 10% reduction in barley biomass, and this was unaffected by a N rate that ranged from 56 (low) to 168 (high) kg ha−1. The effect of N rate on barley biomass was more pronounced when weed removal was delayed from the 3- to 4-LF stage to the 8- to 10-LF stage of barley and in nontreated plots. Increasing the barley seeding rate from 38 to 152 kg ha−1increased the barley plant density by 50%, biomass by 13%, and grain yield by 29%, averaged over N rates and weed removal timing. On the basis of 5 and 10% levels of acceptable yield loss, the addition of ≥112 kg N ha−1delayed the critical timing of weed removal by at least 1.3 wk in barley, compared with the 56 kg N ha−1rate. A medium or high N rate prevented reduction in barley grain quality (plumpness and test weight) observed when the seeding rate was increased from 38 to 76 or 152 kg ha−1at the low N rate. In a separate greenhouse study, the effect of N rate on the effectiveness of various herbicides for controlling wild oat, green foxtail, kochia, or Russian thistle was investigated. Results highlighted that wild oat or green foxtail grown under 56 kg N ha−1(low N) soil required 1.4 to 2.6 times higher doses of clodinafop, fenoxaprop, flucarbazone, glyphosate, glufosinate, pinoxaden, or tralkoxydim for 50% reduction in shoot dry weights (GR50) compared with plants grown under 168 kg N ha−1(high N). Similarly, a reduced efficacy of thifensulfuron methyl + tribenuron methyl, metsulfuron methyl, or bromoxynil+pyrasulfotole was observed (evident from the GR50values) for kochia or Russian thistle grown under low- vs. high-N soil. Information gained from this research will aid in developing cost-effective, integrated weed management (IWM) strategies in cereals and in educating growers on the importance of fertilizer N management as a component of IWM programs.

English

Chemical application is a viable and popular method for weed control, but the effectiveness of various herbicides depends on the target weed. The objectives of this study were to determine the appropriate herbicide for three tall fescue varieties that either do or do not contain endophytic fungi. Plants were split into six herbicide treatments and an untreated control for 7, 14, 21, and 28 days in a randomized complete block design experiment with four replicates. Herbicides evaluated were 2,4-D, aminopyralid, 2,4-D plus dicamba, metsulfuron plus chlorsulfuron, aminocyclopyrachlor, and metsulfuron plus aminopyralid. In all three tall fescue varieties, the application of 2,4-D, aminopyralid, 2,4-D plus dicamba, or aminocyclopyrachlor failed to reduce phytotoxicity, height, tiller number, and dry matter when compared with the untreated control. However, metsulfuron-containing treatments reduced all variables in every variety. We thus conclude that herbicides containing metsulfuron are the most phytotoxic to tall fescue.   Key words: Endophytic fungi, grass, weed control.

Response of Forage Chicory to Various Herbicides

Chicory (Cichorium intybus L.) is a short‐lived perennial warm‐season forb in the Asteraceae family. Although its use is predominantly as a wildlife food plot component in the Unites States, it is widely used in countries such as New Zealand as alternative forage for livestock. There is potential for utilizing chicory in mixtures with perennial pasture species such as tall fescue {Festuca arundinacea Schreb. [syn. Schedonorus arundinaceus (Schreb.) Dumort]} and alfalfa (Medicago sativa L.). The objectives of these field experiments were to determine the effects of various herbicides on the percent injury and forage yield of (i) established chicory treated in the spring and (ii) newly‐planted chicory treated in autumn. Pendimethalin, imazethapyr, and flumetsulam alone or with 0.5% methylated seed oil (MSO) were safe to apply regardless of season. Bromoxynil and flumioxazin alone or with 2,4‐DB were most injurious to chicory regardless of season. In all instances, chicory sufficiently recovered from injury and there were no differences in forage yield among herbicide treatments compared to the untreated controls. Even though chicory injury responses to herbicides were no longer apparent at forage harvest, it is recommended that herbicides that are least injurious to chicory that also provide greatest weed control be used to reduce the risk of chicory stand failure.

Effect of Various Herbicides on Warm‐season Grass Weeds and Switchgrass Establishment

ABSTRACTSwitchgrass (Panicum virgatum L.) is typically slow and difficult to establish. Field experiments evaluated switchgrass establishment and the response of warm‐season grass weeds (large crabgrass [Digitaria sanguinalis (L.) Scop.], broadleaf signalgrass [Urochloa platyphylla (Munro ex C. Wright) R.D. Webster], Johnsongrass [Sorghum halepense (L.) Pers.], and Texas panicum [Urochloa texana (Buckley) R.D. Webster]) to a preemergence (cloransulam) or postemergence (foramsulfuron, pendimethalin, quinclorac, foramsulfuron + pendimethalin + quinclorac, nicosulfuron, nicosulfuron + pendimethalin + quinclorac, nicosulfuron + quinclorac + atrazine, and monosodium methanearsonate [MSMA]) herbicides. Experimental design was a split‐split‐plot design with presence/absence of preemergence herbicide cloransulam as main plot, weed species as subplot treatment, and postemergence herbicides as sub‐subplot treatments. Herbicides foramsulfuron + pendimethalin + quinclorac was applied at the 1‐ to 2‐ and 2‐ to 3‐leaf stage, whereas nicosulfuron was applied at 2‐ to 3‐leaf stage and nicosulfuron combinations and MSMA were applied at 3‐ to 4‐leaf stage. Using cloransulam as a preemergence herbicide resulted in lower switchgrass seedling numbers and generally did not improve establishment. Interseeding Johnsongrass allowed for the greatest number of switchgrass seedlings and was the least competitive weed, whereas interseeding large crabgrass resulted in the least amount of switchgrass and proved to be the most competitive weed. Foramsulfuron + pendimethalin + quinclorac resulted in effective weed control (>70%) for all four species evaluated and improved switchgrass establishment (13–26%) compared to the untreated control (0–3%); however, greater improvement in stand establishment is needed.

Evaluation of herbicides to manage herbicide-resistant corn poppy ( Papaver rhoeas) in winter cereals

Corn poppy is the most important broad-leaved weed in winter cereals in southern Europe. It is an increasing problem due to the appearance of herbicide-resistant biotypes. Experiments were conducted in north-eastern Spain with three corn poppy populations to determine the level of resistance to 2,4-D and tribenuron using seed-germination tests. Field experiments were conducted at sites from where the tested populations had been collected to test the effectiveness of various herbicides applied pre-emergence (PRE) or post-emergence (POST) in winter cereals. In the seed-germination tests, two populations were found to be 2,4-D-resistant and one resistant to both 2,4-D and tribenuron. In field trials, the efficacy of 2,4-D at 900 g a.i. ha −1 ranged from 25 to 76% of reduction of plant densities, depending on season and population, indicating that all populations were 2,4-D-resistant in field conditions. Moreover, at 15 g a.i. ha −1 tribenuron, one of the three populations (CU2) was only reduced by 65% in two seasons, indicating also the presence of resistance to tribenuron in this population in addition to 2,4-D. Florasulam at 6.25 g a.i. ha −1 + 2,4-D at 300 g a.i. ha −1 resulted in poor control (75–85%) in CU2 suggesting possible cross-resistance to this triazolopyrimidine. On average, all the other herbicides provided 90–100% control of corn poppy. Only PRE herbicides and the mixture 150 g a.i. ha −1 bromoxynil + 150 g a.i. ha −1 ioxynil + 450 g a.i. ha −1 mecoprop in POST performed consistently well (>90% control). The results of this study indicate that 2,4-D and tribenuron-resistant corn poppy populations in winter cereals can be controlled by application of PRE or POST herbicides with alternative modes of action.

Herbicide Options for Rice Cutgrass (Leersia oryzoides) Control

Rice cutgrass is encroaching into rice fields from ditch banks and canals, especially into continuous rice fields where tillage is limited in the Mississippi Delta region of Arkansas. Experiments were conducted to evaluate the effectiveness of various herbicides applied alone on rice cutgrass and to determine if the effectiveness of bispyribac on rice cutgrass is influenced by number of applications, adjuvant type, and adjuvant rate. Glyphosate, glufosinate, and clethodim were the most effective herbicides when applied alone; however, none of these are labeled for over-the-top application in rice. Of those herbicides that can be applied over the top of rice, imazethapyr and bispyribac were the most effective, providing 52 to 62% rice cutgrass control, albeit imazethapyr can be used only in imidazolinone-resistant rice. The addition of an adjuvant to bispyribac improved rice cutgrass control, and sequential bispyribac applications were generally superior to a single application. Methylated seed oil/organosilicone/urea ammonium nitrate adjuvant increased rice cutgrass control with bispyribac, especially when bispyribac was applied as a single application. A single application of imazethapyr, bispyribac, halosulfuron, penoxsulam, clomazone, thiobencarb, cyhalofop, propanil, quinclorac, and fenoxaprop provided less-than-acceptable control, which partially explains the difficulty that growers are experiencing in controlling rice cutgrass, especially in continuous rice production.

Control of Smellmelon (Cucumis Melo) in Soybean with Herbicides

Field studies were conducted during the 2004 and 2005 growing seasons to evaluate the effects of various herbicides on smellmelon control and soybean yield response. Pendimethalin applied pre-emergence (PRE) alone controlled smellmelon no better than 70%, whereas pendimethalin plus imazethapyr, flumioxazin, or cloransulam applied PRE provided almost complete smellmelon control (99%). Pendimethalin applied PRE followed by acifluorfen applied early postemergence (EPOST) provided similar control. Glyphosate alone applied late postemergence (LPOST) provided complete control (100%), and pendimethalin followed by glyphosate applied EPOST controlled smellmelon at least 95%. Most herbicides increased soybean yield over the nontreated check.Nomenclature: Acifluorfen, cloransulam, flumioxazin, glyphosate, imazethapyr, pendimethalin, smellmelon, Cucumis melo L. var. Dudaim Naud. CUMME, soybean, ‘HBK 5123’

Influence of Selected Pasture Herbicides and Application Timings on Sericea Lespedeza Control

Field trials were conducted in 2004 and 2005 to determine the effect of various herbicides alone or in pre-mix formulations applied in the summer and autumn on sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] control and density one year after treatment (YAT). In both years, triclopyr plus fluroxypyr, picloram plus fluroxypyr, and metsulfuron were applied at five application timings. In 2005, triclopyr was also applied at each of these timings. In both years, all treatments provided greater than 90% late-season sericea lespedeza control when applied at the early- or mid-vegetative stage of growth. All treatments except metsulfuron also provided greater than 80% late-season sericea control when applied at the late-vegetative or pre-bloom stage. There was no effect of application timing on sericea lespedeza stem density 1 YAT. Herbicide treatments reduced sericea lespedeza stem density from 53 to 86% when compared to non-treated control plots 1 YAT. Triclopyr, triclopyr plus fluroxypyr and metsulfuron provided similar reductions in sericea lespedeza stem density 1 YAT. These results indicate that, regardless of the application timing, similar sericea lespedeza control will be achieved 1 YAT with triclopyr, triclopyr plus fluroxypyr, and metsulfuron, which is contrary to current recommendations for this species.