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A rapid, simple, precise and accurate high performance liquid chromatographic (HPLC) analytical method was developed and validated for the determination of the active substances (a.s.) azoxystrobin, topramezone, acetamiprid, fluometuron and folpet in their respective commercially available formulations. The method was used for the analysis of samples under the frame of the national quality control program of plant protection products in the Greek market. Chromatographic separation of the active substances from additives and co-formulants is achieved using isocratic elution with acetonitrile and 0.1% phosphoric acid solution (60:40 v/v) at a flow rate of 0.4 mL min

Atrazine offers growers a reliable option to control a broad spectrum of weeds in grain sorghum production systems when applied PRE or POST. However, because of the extensive use of atrazine in grain sorghum and corn, it has been found in groundwater in the United States. Given this issue, field experiments were conducted in 2017 and 2018 in Fayetteville and Marianna, Arkansas, to explore the tolerance of grain sorghum to applications of assorted photosystem II (PSII)-inhibiting herbicides in combination with S-metolachlor (PRE and POST) or mesotrione (POST only) as atrazine replacements. All experiments were designed as a factorial, randomized complete block; the two factors were (1) PSII herbicide and (2) the herbicide added to create the mixture. The PSII herbicides were prometryn, ametryn, simazine, fluometuron, metribuzin, linuron, diuron, atrazine, and propazine. The second factor consisted of either no additional herbicide, S-metolachlor, or mesotrione; however, mesotrione was excluded in the PRE experiments. Crop injury estimates, height, and yield data were collected or calculated in both studies. In the PRE study, injury was less than 10% for all treatments except those containing simazine, which caused 11% injury 28 d after application (DAA). Averaged over PSII herbicide, S-metolachlor–containing treatments caused 7% injury at 14 and 28 DAA. Grain sorghum in atrazine-containing treatments yielded 97% of the nontreated. Grain sorghum receiving other herbicide treatments had significant yield loss due to crop injury, compared with atrazine-containing treatments. In the POST study, ametryn- and prometryn-containing treatments were more injurious than all other treatments 14 DAA. Grain sorghum yield in all POST treatments was comparable to atrazine, except prometryn plus mesotrione, which was 65% of the nontreated. More herbicides should be evaluated to find a comparable fit to atrazine when applied PRE in grain sorghum. However, when applied POST, diuron, fluometuron, linuron, metribuzin, propazine, and simazine have some potential to replace atrazine in terms of crop tolerance and should be further tested as part of a weed control program across a greater range of environments. Nomenclature: Ametryn; atrazine; diuron; fluometuron; linuron; mesotrione; metribuzin; prometryn; propazine; simazine; corn, Zea mays L.; grain sorghum, Sorghum bicolor (L.) Moench. ssp. bicolor

Studies were conducted during 2015 through 2018 in south-central, Coastal Bend, and Southern High Plains areas of Texas to evaluate fluridone herbicide systems for weed control and cotton response. Fluridone alone at 0.17 to 0.23 kg ai ha-1 followed by postemergence (POST) herbicides controlled Amaranthus Palmeri 82 to 100% season-long while Cucumis melo control ranged from 92 to 100%. Control of Urochloa Texana with fluridone alone ranged from 40 to 96% early-season while late-season control ranged from 37 to 96%. Fluridone plus fomesafen systems controlled A. Palmeri, C. Melo, and U. Texana at least 98% early season; however, late-season control of A. Palmeri was less than 70% while C. Melo control was 91% and U. Texana control was 80%. Adding a POST application of glyphosate to fluridone plus fomesafen improved control to at least 98% for all three weed species. Fluridone plus fluometuron combinations provided similar control to fluridone plus fomesafen. Adding glyphosate (POST) improved A. Palmeri control to at least 82% season-long. Cotton yields reflect the level of weed control with significantly better yields from fluridone systems compared with the weedy check. However, in the one year when the untreated was maintained weed-free, no differences in cotton yield were noted between the weed-free and any herbicide treatment.

One of the critical components of successful cotton production is effective weed management. Since cotton cannot compete sufficiently with weeds, especially in the first six weeks, a certain number of weeds significantly reduces cotton yield. In addition, weeds can make cotton harvest difficult and contaminate cotton fiber. The main preferred control method for broadleaf weeds in the conventional cotton of Turkey (non-tolerant and non-resistant varieties) is the use of pre-emergence herbicides. However, since there is not much information about the effects of mixtures of different pre-planting herbicides, the aim of this study is to evaluate the efficacy and selectivity of herbicides applied as a pre-emergence mixture in cotton. The randomized complete block design (RCBD) with four replications and eleven treatments was used in the field experiment. The plots were established to 20 square meters (4 m x 5 m). Herbicide applications in the study were carried out in Diyarbakir in 2015, and dual mixtures of clomazone, fluometuron, oxyfluorfen, and pendimethalin were used with different mixtures and doses. Clomazone 0.2 l ha-1 + fluometuron 1,5 l ha-1, clomazone 0.2 l ha-1 + fluometuron 2 l ha-1, clomazone 0.4 l ha-1 + pendimethalin 1.5 l ha-1 and clomazone 0.3 l ha-1 + pendimethalin 2 l ha-1 mixture was found to be complete weed control efficiency. This result shows that mixtures with clomazone active ingredient increase in the efficiency of herbicides pre-planting. Oxyfluorfen mixtures showed the most hazardous damage in terms of product selectivity. The highest cotton yield (> 5 t ha-1) was obtained from the application of mixes of clomazone 0.30 l ha-1 + fluometuron 2 l ha-1 and clomazone 0.2 l ha-1 + fluometuron 1.5 l ha-1, respectively., Başarılı pamuk üretiminin kritik bileşenlerinden biri, etkili yabani ot yönetimidir. Pamuk (Gossypium hirsutum L.), yabani otlarla yeterince rekabet edemediğinden, özellikle ilk altı haftada, bazı yabani ot türleri pamuk verimini önemli ölçüde azaltabilmektedir. Ayrıca yabani otlar pamuk hasadını zorlaştırabilir ve lifini kirletebilir. Türkiye geleneksel pamuk üretiminde (tolerantlı ve dayanıklı olmayan çeşitler) özellikle geniş yapraklı yabancı ot kontrolü için tercih edilen temel yöntem, ekim öncesi veya çıkış öncesi herbisitlerin kullanılmasıdır. Bununla birlikte, farklı çıkış öncesi herbisitlerin karışımlarının etkileri hakkında fazla bilgi bulunmadığından, bu çalışma, pamukta çıkış önceki bir karışım olarak uygulanan herbisitlerin etkinliğini ve seçiciliğini belirlemek için yürütülmüştür. Arazi denemeleri tesadüf blokları deneme desenine göre dört tekerrürlü olarak 11 farklı uygulama olacak şekilde tasarlanmıştır. Parseller 20 metrekare (4 m x 5 m) olarak kurulmuştur. Bu çalışmada herbisit uygulamaları 2015 yılında Diyarbakır'da gerçekleştirilmiş ve çift klomazon aktif maddesinin fluometuron, oksiflorfen ve pendimetalin ile farklı dozlardaki karışımları kullanılmıştır. Clomazone 0.2 l ha-1 + fluometuron 1,5 l ha-1, clomazone 0.2 l ha-1 + fluometuron 2 l ha-1, clomazone 0.4 l ha-1 + pendimethalin 1.5 l ha-1 ve clomazone 0.3 l ha-1 + pendimethalin 2 l ha-1 karışımın yabani ot kontrol etkinliğinin tam olduğu tespit edilmiştir. Bu sonuç, clomazone aktif maddesi ile yapılan herbisit karışımlarının çıkış öncesi uygulandığında yabancı ot control etkinliği arttığını göstermektedir. Oxyfluorfen karışımlarında ürün seçiciliği açısından en tehlikeli hasar gözlenmiştir. En yüksek pamuk verimleri (> 5 t ha-1) sırasıyla clomazone 0.30 l ha-1 + fluometuron 2 l ha-1 ve clomazone 0.2 l ha-1 + fluometuron 1.5 l ha-1 karışımlarının uygulanmasından elde edilmiştir

Weed control in corn traditionally has relied on atrazine as a foundational tool to control problematic weeds. However, the recent discovery of atrazine in aquifers and other water sources increases the likelihood of more strict restrictions on its use. Field-based research trials to find atrazine alternatives were conducted in 2017 and 2018 in Fayetteville, AR, by testing the tolerance of corn to PRE and POST applications of different photosystem II (PSII) inhibitors alone or in combination with mesotrione or S-metolachlor. All experiments were designed as a two-factor factorial, randomized complete block, with the two factors being (1) PSII-inhibiting herbicide and (2) the herbicide added to create the mixture. The PSII-inhibiting herbicides were prometryn, ametryn, simazine, fluometuron, metribuzin, linuron, diuron, atrazine, and propazine. The second factor consisted of either no additional herbicide, S-metolachlor, or mesotrione. Treatments were applied immediately after planting in the PRE experiments and to 30-cm–tall corn for the POST experiments. For the PRE study, low levels of injury (

This study is the first electroanalytical study conducted for the determination of fluometuron herbicide. For this purpose, a new electrode was prepared by combining iron (III) phthalocyanine − 4.4′,4′′,4′′′-tetrasulfonic acid, oxygen monosodium salt hydrated compound (FePc) and multi-walled carbon nanotube powders (MWCNTP). The FePc/MWCNTP composite (hybrid) material prepared in this way was coated on glassy carbon electrode (GCE) and multi-walled carbon nanotube paste electrode (MWCNTPE) using the drop-dry method. Compared to both the bare GCE and MWCNTPE, the modified FePc/MWCNTPE increased the anodic peak current of fluometuron by approximately six fold. Calibration plots of the fluometuron were constructed using the standard addition method with differential puls stripping voltammetry (DPSV) and square wave stripping voltammetry (SWSV) under the optimum conditions. While the working range was determined as 0.4–15.0 mg/L in pH 6.0 Britton Robinson (BR) buffer solution on FePc/MWCNTP electrode with DPSV, this range was found to be 0.4–7.5 mg/L with SWSV. In addition, the limit of detection (LOD) and the limit of quantification (LOQ) values ​​were 69.8 µg/L and 233.0 µg/L, respectively, by DPSV. On the other hand, these two validation values ​​(LOD and LOQ) were 101 µg/L and 337 µg/L by SWSV, respectively. Subsequently, cyclic voltammetric (CV) studies were carried out to elucidate the electrochemical behavior and electrode mechanism of the fluometuron herbicide. In addition, the interference effects of some cations and pesticides in the determination of fluometuron were examined. Finally, studies of recovery of fluometuron herbicide from tap water and determination of fluometuron in Cottonex 500 SC® commercial pesticide formulation using the proposed DPSV method and modified FePc/MWCNTP electrode were performed with very low relative error.

Growth chamber experiments were conducted to evaluate the response of sesame to PRE and POST applications of soil residual herbicides. PRE applications of acetochlor andS-metolachlor at 1.26 and 1.43 kg ai·ha−1showed little or no sesame injury (0 to 1%) 4 wks after herbicide treatments (WAT). POST treatments of acetochlor and trifluralin made 3 wks after planting (WAP) resulted in greater sesame injury (40%) compared to applications at bloom (18%). Field studies were conducted in Texas and Oklahoma during the 2014 and 2015 growing seasons to determine sesame response to clethodim, diuron, fluometuron, ethalfluralin, quizalofop-P, pendimethalin, pyroxasulfone, trifluralin, and trifloxysulfuron-sodium applied 2, 3, or 4 weeks after planting (WAP). Late-season sesame injury with the dinitroaniline herbicides consisted of a proliferation of primary branching at the upper nodes of the sesame plant (in the shape/form of a broom). Ethalfluralin and trifluralin caused more “brooming” effect than pendimethalin. Some yield reductions were noted with the dinitroaniline herbicides. Trifloxysulfuron-sodium caused the greatest injury (up to 97%) and resulted in yield reductions from the untreated check. Early-season diuron injury (leaf chlorosis and necrosis) decreased as application timing was delayed, and late-season injury was virtually nonexistent with only slight chlorosis (

The herbicide fluridone is a soil-residual herbicide that should provide effective control of several problematic agronomic weeds, but because of herbicide persistence, injury to rotational crops is possible. In this experiment, multiple rates of fluridone were applied PRE to cotton at four irrigated locations across Arkansas to determine the risk of fluridone persisting and injuring subsequently planted wheat, corn, soybean, rice, grain sorghum, and sunflower. The multiple rates of fluridone were compared with fluometuron and evaluated for percentage of crop injury, crop density, and potential yield loss for each crop at the end of the subsequent growing season. Regardless of the location, wheat exhibited the greatest injury with 13 to 26% at Fayetteville (silt loam), 8 to 15% at Pine Tree (silt loam), 2 to 7% at Keiser (silty clay), and 3 to 8% at Rohwer (silty clay). Along with high levels of injury to wheat, fluridone at 900 g ai ha−1caused loss of wheat stands to 29 plants m−1row compared with fluometuron, which had stands of 49 plants m−1row. Although injury occurred in wheat at all locations, no rate of fluridone reduced wheat yields compared with fluometuron. Injury to grain sorghum ranged from 5 to 10% from all rates of fluridone at Pine Tree. Fluridone at 900 g ha−1(11 plants m−1row) also reduced grain sorghum stands at Pine Tree over that of fluometuron (19 plants m−1row). A decrease in grain sorghum yield was also observed from fluridone at 448, 673, and 900 g ha−1compared with fluometuron at Pine Tree. At Keiser, rice exhibited significant levels of injury (1 to 13%) from fluridone 393 d after treatment. In conclusion, injury to a wheat rotational crop is more likely following an application of fluridone in cotton than is injury to other rotational crops, but yield reductions are not expected for most rotational crops when fluridone is applied to cotton at an anticipated labeled rate of 224 g ha−1.

Glyphosate-resistant (GR) weeds, especially GR Palmer amaranth, are very problematic in cotton-producing areas of the midsouthern region of the United States. Growers rely heavily on PRE residual herbicides to control Palmer amaranth since few effective POST options exist. Interest in integrating high-residue cover crops with existing herbicide programs to combat GR weeds has increased. Research was conducted in 2013 and 2014 in Tennessee to evaluate GR Palmer amaranth control when integrating cover crops and PRE residual herbicides. Cereal rye, crimson clover, hairy vetch, winter wheat, and combinations of one grass plus one legume were compared with winter weeds without a cover crop followed by fluometuron or acetochlor applied PRE. Biomass of cover crops was determined prior to termination 3 wk before planting. Combinations of grass and legume cover crops accumulated the most biomass (> 3,500 kg ha−1) but by 28 d after application (DAA) the cereal rye and wheat provided the best Palmer amaranth control. Crimson clover and hairy vetch treatments had the greatest number of Palmer amaranth. These cereal and legume blends reduced Palmer amaranth emergence by half compared to non–cover-treated areas. Fluometuron and acetochlor controlled Palmer amaranth 95 and 89%, respectively, at 14 DAA and 54 and 62%, respectively, at 28 DAA. Cover crops in combination with a PRE herbicide did not adequately control Palmer amaranth.

Johnsongrass populations that are resistant to 5-enolpyruvyl-3-shikimate synthase (EPSPS)–, acetyl coenzyme A carboxylase (ACCase)–, or acetolactate synthase (ALS)–inhibiting herbicides are increasingly common throughout the midsouth. Three trials were conducted in 2012, 2013, and 2014 in Fayetteville, AR and Alexandria, LA to evaluate strategies with and without ALS- and ACCase inhibitors for management of rhizomatous johnsongrass in the absence of glyphosate. Fluometuron or fluometuron plus pyrithiobac applied PRE followed by (fb) EPOST, MPOST, and LAYBY tank mixtures containing multiple effective mechanisms of action (MOA) controlled johnsongrass at least 90%. Simplifying the program by removing a herbicide or eliminating an application timing reduced control, and increased vegetative and sexual reproduction of johnsongrass. To manage severe infestations or escapes glufosinate plus clethodim fb glufosinate plus clethodim or clethodim plus pyrithiobac fb clethodim) effectively controlled 15-cm johnsongrass. However, johnsongrass control was reduced when ALS and ACCase inhibitors were tank mixed, especially for the second POST application, compared to ACCase inhibitors alone. Effective herbicide programs are available to growers to control johnsongrass in the absence of glyphosate, but the use of PRE herbicides followed by multiple applications of POST herbicides is critical for successful management.

Residual herbicides are routinely recommended to aid in control of glyphosate-resistant (GR) Palmer amaranth in cotton. Acetochlor, a chloroacetamide herbicide, applied PRE, controls Palmer amaranth. A microencapsulated (ME) formulation of acetochlor is now registered for PRE application in cotton. Field research was conducted in North Carolina to evaluate cotton tolerance and Palmer amaranth control by acetochlor ME alone and in various combinations. Treatments, applied PRE, consisted of acetochlor ME, pendimethalin, or no herbicide arranged factorially with diuron, fluometuron, fomesafen, diuron plus fomesafen, and no herbicide. The PRE herbicides were followed by glufosinate applied twice POST and diuron plus MSMA directed at layby. Acetochlor ME was less injurious to cotton than pendimethalin. Acetochlor ME alone or in combination with other herbicides reduced early season cotton growth 5 to 8%, whereas pendimethalin alone or in combinations injured cotton 11 to 13%. Early season injury was transitory, and by 65 to 84 d after PRE treatment, injury was no longer noticeable. Before the first POST application of glufosinate, acetochlor ME and pendimethalin controlled Palmer amaranth 84 and 64%, respectively. Control by acetochlor ME was similar to control by diuron plus fomesafen and greater than control by diuron, fluometuron, or fomesafen alone. Greater than 90% control was obtained with acetochlor ME mixed with diuron or fomesafen. Palmer amaranth control was similar with acetochlor ME plus a full or reduced rate of fomesafen. Acetochlor ME controlled large crabgrass and goosegrass at 91 and 100% compared with control at 83 and 91%, respectively, by pendimethalin. Following glufosinate, applied twice POST, and diuron plus MSMA, at layby, 96 to 99% control was obtained late in the season by all treatments, and no differences among herbicide treatments were noted for cotton yield. This research demonstrated that acetochlor ME can be safely and effectively used in cotton weed management programs.

Pesticide contaminated wastewater resulting from leftover mixes, equipment cleaning, and container disposal are problems related to pesticide use. This study reports on the effectiveness of a soil-based bioreactor (SBBR) to dissipate pesticides of differing concentrations and mixtures. In order to accomplish this study, soil columns were used to simulate the SBBR. A mixture of five herbicides and two insecticides from seven different chemical families (atrazine, dicamba, fluometuron, metolachlor, sulfentrazone, chlopyrifus, and λ-cyhalothrin) were added to the SBBR-simulated system as formulated products in three concentrations each: 0 part per million (control), 10 ppm, and 100 ppm. Additionally a 1,000 ppm treatment was added that included just the five herbicides to investigate how the system would respond to heavy loading. The system was run for 90 days with samples taken at day 4 (just prior to loading the columns), then at 30, 60, and 90 days. At low pesticide concentrations (10 and 100 ppm), there was significant dissipation (p < 0.05) of all pesticides in the columns except sulfentrazone. At 1,000 ppm, fluometuron, in addition to sulfentrazone, did not show significant dissipation. Overall, the system performed as expected and could be considered practical for use on farms or nurseries. ©2015 Wiley Periodicals, Inc.

In 2005, the existence of glyphosate-resistance in Palmer amaranth was confirmed at a single 250 ha field site in Macon County, Georgia. Currently, all cotton producing counties in Georgia are infested, to some degree, with glyphosate-resistant Palmer amaranth. In 2010 and 2011, surveys were administered to Georgia growers and extension agents to determine how the development of glyphosate-resistance has affected weed management in cotton. According to respondents, the numbers of cotton acres that were treated with paraquat, glufosinate and residual herbicides effective against Palmer amaranth more than doubled between 2000 to 2005 and 2006 to 2010. Glyphosate use declined between 2000 to 2005 and 2006 to 2010 although, on average, the active ingredient was still applied to a majority of cotton acres. Although grower herbicide input costs have more than doubled following the evolution and spread of glyphosate resistance, chemically-based control of Palmer amaranth is still not adequate. As a consequence, Georgia cotton growers hand weeded 52% of the crop at an average cost of $57 per hand-weeded ha; this represents a cost increase of at least 475% as compared to the years prior to resistance. In addition to increased herbicide use and hand weeding, growers in Georgia are also using mechanical, in-crop cultivation (44% of acres), tillage for the incorporation of preplant herbicides (20% of the acres), and post-harvest deep-turning (19% of the acres every three years) for weed control. Current weed management systems are more diverse, complex and expensive than those employed only a decade ago, but are effective at controlling glyphosate-resistant Palmer amaranth in glyphosate-resistant cotton. The success of these programs may be related to producers improved knowledge about herbicide resistance, and the biological attributes that make Palmer amaranth so challenging, as well as their ability to implement their management programs in a timely manner. Nomenclature: 2,4-D; diuron; fomesafen; flumioxazin; fluometuron; glyphosate; glufosinate; MSMA; paraquat; pendimethalin; pyrithiobac; S-metolachlor; trifluralin; Palmer amaranth

Glyphosate-resistant (GR) weeds, especially GR Palmer amaranth, are very problematic for cotton growers in the Southeast and Midsouth regions of the United States. Glufosinate can control GR Palmer amaranth, and growers are transitioning to glufosinate-based systems. Palmer amaranth must be small for consistently effective control by glufosinate. Because this weed grows rapidly, growers are not always timely with applications. With widespread resistance to acetolactate synthase-inhibiting herbicides, growers have few herbicide options to mix with glufosinate to improve control of larger weeds. In a field study using a WideStrike®cotton cultivar, we evaluated fluometuron at 140 to 1,120 g ai ha−1mixed with the ammonium salt of glufosinate at 485 g ae ha−1for control of GR Palmer amaranth 13 and 26 cm tall. Standard PRE- and POST-directed herbicides were included in the systems. Glufosinate alone injured the WideStrike® cotton less than 10%. Fluometuron increased injury up to 25% but did not adversely affect yield. Glufosinate controlled 13-cm Palmer amaranth at least 90%, and there was no improvement in weed control nor a cotton yield response to fluometuron mixed with glufosinate. Palmer amaranth 26 cm tall was controlled only 59% by glufosinate. Fluometuron mixed with glufosinate increased control of the larger weeds up to 28% and there was a trend for greater yields. However, delaying applications until weeds were 26 cm reduced yield 22% relative to timely application. Our results suggest fluometuron mixed with glufosinate may be of some benefit when attempting to control large Palmer amaranth. However, mixing fluometuron with glufosinate is not a substitute for a timely glufosinate application.

Amaranthuscontrol in cotton can be difficult with the loss of glyphosate efficacy, especially in conservation-tillage cropping systems. Research was conduction from 2006 to 2008 at EV Smith Research Center, Shorter, AL, to determine the level of glyphosate-susceptibleAmaranthuscontrol provided by four initial tillage and herbicide treatments, including 1) moldboard plowing followed by a single-pass disking and field cultivation plus pendimethalin at 1.2 kg ai ha−1preplant incorporation (PPI), 2) two-pass disking followed by field cultivation plus pendimethalin at 1.2 kg ha−1PPI, 3) no tillage including an application of pendimethalin at 1.2 kg ha−1PRE, or 4) no tillage without pendimethalin in 2006. No further tillage practices or pendimethalin applications were utilized after study initiation. Initial tillage operations, including inversion with disking or disking twice, resulted inAmaranthusdensity of ≤ 4 plants m−2and 47 to 82% control, whereas no-tillage treatments had ≥ 4 plants m−2and 14 to 62% control. Subsequent applications of PRE herbicides included fluometuron at 1.68 kg ai ha−1or prometryn at 1.12 kg ai ha−1and provided 53 to 98% and 55 to 93% control, respectively, and reducedAmaranthusdensity compared to no PRE herbicide to < 2 plants m−2, regardless of tillage treatment. A POST application of glyphosate at 1.0 kg ae ha−1improved control in conjunction with almost all treatments in each year. Results indicate that a one-time tillage operation followed by a return to reduced tillage may aid in the reduction ofAmaranthusdensity when used with PRE-applied herbicides; however, this system will likely not provide adequate control when high population densities of glyphosate-resistantAmaranthusare present, thus highlighting the need for a highly efficacious POST herbicide system.

Simulation models are widely used to assess water contamination risk associated with pesticide use and for evaluating effectiveness of agricultural conservation practices. Currently, the APEX (Agricultural Policy/Environmental eXtender) model is being used for this purpose in the USDA Conservation Effects Assessment Project (CEAP) Cropland National Assessment. In support of the CEAP modeling effort, APEX was calibrated and validated using a nine-year record (1999-2007) of crop yield, surface runoff, and tile outflow and an eight-year record (1999-2006) of soluble pendimethalin and fluometuron herbicide losses from fields in a cotton-peanut rotation located in the Atlantic Coastal Plain region of south-central Georgia. Conventional tillage and strip tillage were directly compared. Monthly surface runoff was calibrated by adjusting three variables: curve number index coefficient (CNIC), a driver of the USDA Natural Resources Conservation Service (NRCS) runoff curve number; runoff curve number for the average soil moisture condition 2 (CN2); and irrigation runoff ratio (IRR). Statistical performance criteria for monthly and annual results were r2 > 0.5, NSE > 0.45, and PBIAS < 20%, based on prior modeling studies. Monthly runoff statistics showed r2 values of 0.62 to 0.82 and met satisfactory criteria between observed and simulated surface runoff for both tillage types, with Nash-Sutcliffe efficiency (NSE) values of 0.62 to 0.80 and PBIAS values within ±19% during the calibration and validation periods. Monthly subsurface lateral flow performance statistics for the strip-tilled plots were satisfactory during the calibration period but weak for the conventional tillage plots. Monthly performance statistics for fluometuron runoff for the conventional tillage plots were below satisfactory criteria. Other monthly statistics for fluometuron and pendimethalin losses were weak. Measured and predicted crop yield and annual runoff for both tillage systems were well aligned and met satisfactory statistical criteria. APEX performance was satisfactory for annual fluometuron soluble runoff for the conventionally tilled plots but not satisfactory for the strip-tilled plot with less runoff. The model’s performance was unsatisfactory for annual subsurface lateral flow and fluometuron transport in subsurface lateral flow for both tillage systems. The percent bias statistical parameter (PBIAS) was within ±20% for all annual mean correlations, indicating that APEX effectively replicated annual means for crop yield, runoff, subsurface lateral flow, and pesticide losses. Measured and simulated results of conservation tillage effects were in close agreement for decreased water and pesticide runoff as well as increased subsurface lateral flow and associated fluometuron losses. Although fluometuron losses in subsurface lateral flow approximately doubled with conservation tillage, loading was still small compared to fluometuron in runoff from the conventionally tilled plots. Results demonstrate APEX’s strength in simulating runoff in this landscape, but less satisfactory results were obtained for pendimethalin runoff, subsurface lateral flow, and fluometuron losses in subsurface lateral flow.

A field study was conducted in 2009, 2010, and 2011 on a grower's field with a known population of glyphosate-resistant giant ragweed to determine potential control options utilizing a WideStrike® cotton variety. Glyphosate-resistant giant ragweed control and cotton response to herbicide applications were both assessed. Few herbicide treatments provided greater than 80% control. Glufosinate followed by glufosinate was the only treatment that provided greater than 90% control at each assessment timing. Other effective treatments were glufosinate alone, glufosinate plus glyphosate, glyphosate plus pyrithiobac, and glufosinate plus fluometuron. Results from this study indicate that few of the studied herbicide treatments provide effective control of glyphosate-resistant giant ragweed without reducing yield in WideStrike cotton. Treatments that had the highest level of giant ragweed control at all ratings and also had the highest yield included glufosinate followed by glufosinate, glufosinate plus pyrithiobac, and glufosinate plus fluometuron at either rate. However, glufosinate followed by glufosinate was the only treatment that resulted in greater than 90% control of giant ragweed without reducing crop yield.

Research was conducted at experimental research stations near Keiser and Marianna (Marianna-A), AR, in 2007, and in a grower's field near Marianna (Marianna-B), AR, in 2008, to compare herbicide programs, including POST application(s) of glyphosate/glufosinate alone or in combination with residual herbicides applied as PRE, mid-POST (MPOST), or layby POST-directed (PD) in enhanced glyphosate- and glufosinate-resistant cotton. Weed species evaluated included Palmer amaranth, pitted morningglory, hemp sesbania, barnyardgrass, and a mixture of large crabgrass and goosegrass. At Marianna-B, AR, the Palmer amaranth population was a mixture of glyphosate-resistant and -susceptible plants. For both cotton cultivars and at all locations, inclusion ofS-metolachlor plus fluometuron PRE increased weed control and/or decreased the number of glufosinate or glyphosate applications needed in-season. At Marianna-B, AR, PRE residual herbicides and/or glufosinate were required to control glyphosate-resistant Palmer amaranth. Addition of pyrithiobac to glufosinate or glyphosate did not increase weed control. A layby PD application of flumioxazin plus MSMA was required to increase late-season control of all weed species in POST glufosinate-only programs, but not in POST glyphosate-only programs. None of the programs caused > 5% injury to either cotton cultivar. Seed-cotton yield was similar in all herbicide programs at Keiser, AR, and Marianna-A, AR, except for the POST glyphosate-only program, which yielded less than the PRE followed by POST programs in glyphosate-resistant cotton at Keiser, AR. In general, PRE herbicides did not increase cotton yield but did improve early and late-season control of glyphosate-susceptible and -resistant weeds in both cotton cultivars.

Biochar, the solid residual remaining after the thermochemical transformation of biomass for carbon sequestration, has been proposed to be used as a soil amendment, because of its agronomic benefits. The effect of amending soil with six biochars made from different feedstocks on the sorption and leaching of fluometuron and 4-chloro-2-methylphenoxyacetic acid (MCPA) was compared to the effect of other sorbents: an activated carbon, a Ca-rich Arizona montmorillonite modified with hexadecyltrimethylammonium organic cation (SA-HDTMA), and an agricultural organic residue from olive oil production (OOW). Soil was amended at 2% (w/w), and studies were performed following a batch equilibration procedure. Sorption of both herbicides increased in all amended soils, but decreased in soil amended with a biochar produced from macadamia nut shells made with fast pyrolysis. Lower leaching of the herbicides was observed in the soils amended with the biochars with higher surface areas BC5 and BC6 and the organoclay (OCl). Despite the increase in herbicide sorption in soils amended with two hardwood biochars (BC1 and BC3) and OOW, leaching of fluometuron and MCPA was enhanced with the addition of these amendments as compared to the unamended soil. The increased leaching is due to some amendments' soluble organic compounds, which compete or associate with herbicide molecules, enhancing their soil mobility. Thus, the results indicate that not all biochar amendments will increase sorption and decrease leaching of fluometuron and MCPA. Furthermore, the amount and composition of the organic carbon (OC) content of the amendment, especially the soluble part (DOC), can play an important role in the sorption and leaching of these herbicides.

A 2-yr field study was conducted during 2007 and 2008 at Stoneville, MS, to determine the effect of twin-row (two rows 38 cm apart on 102-cm beds) and single-row (on 102-cm beds) patterns and glyphosate POST applications with and without fluometuron + S-metolachlor PRE on cotton canopy closure, weed control, and lint yield in two cultivars (‘DP117B2RF’, early maturity, hairy leaf; ‘DP164B2RF’, mid to full maturity, smooth leaf) under an irrigated environment. The experiment was conducted in a split–split plot arrangement of treatments in a randomized complete block design with row pattern as the main plot, cultivars as the subplot, and herbicide programs as the subsubplot. Cotton canopy closed 2 wk earlier in the twin-row pattern compared to the single-row pattern. Canopy closure was unaffected by cultivars and herbicide programs. Control of nine predominant weeds was sufficient (≥ 95%) to support cotton production. Total weed dry biomass was reduced by 35% in twin rows compared to the single-row pattern, 15% in DP117B2RF compared to DP164B2RF cultivar, and ≥ 97% with glyphosate early POST (EPOST), EPOST followed by (fb) mid-season POST (MPOST), EPOST fb MPOST fb late POST (LPOST) following PRE herbicides or three applications of glyphosate POST only without PRE herbicides compared to no herbicide. Cotton grown in twin-row pattern produced 6% higher lint yield than single-row cotton. Cultivar DP117B2RF produced 23% higher lint yield than cultivar DP164B2RF. Lint yields were higher with glyphosate EPOST fb MPOST, EPOST fb MPOST fb LPOST following PRE herbicides or three applications of glyphosate POST only without PRE herbicides (1,210 to 1,230 kg/ha) compared to glyphosate EPOST following PRE herbicides (1,130 kg/ha). These results demonstrated that cotton grown in twin-rows closed canopy early and produced higher lint yields than cotton grown in single-rows.

Field studies were conducted during the 2004 and 2005 growing seasons in the south Texas and the High Plains of Texas sesame growing areas to evaluate sesame tolerance and weed control following various preemergence herbicides. All herbicides controlled Amaranthus tuberculatus at least 89%, while diuron, flumioxazin at 0.14 kg ai/ha, and S-metolachlor controlled Brachiaria platyphylla greater than 90%. Flufenacet controlled B. platyphylla 78% and all other herbicides controlled this weed less than 70%. Cloransulam, diclosulam, flufenacet, and flumioxazin-treated plots had few sesame plants emerge and resulted in little or no yield. S-metolachlor alone caused no sesame stand reduction in south Texas, but S-metolachlor plus metribuzin caused at least 49% stand reduction in both years. Fluometuron, prometryn, and S-metolachlor-treated plots produced the greatest sesame yield.

A simple dispersive liquid-liquid microextraction method combined with HPLC-photodiode array detection has been developed for the determination of phenylurea herbicides in water samples. The herbicides studied included tebuthiuron, diuron, propanil, fluometuron, siduron, linuron, thidiazuron, and diflubenzuron. Several factors influencing the extraction efficiency of the studied compounds, such as extraction and disperser solvent type and their volumes, co-solvent type and its fraction, and ionic strength were investigated and optimized. Under the optimum extraction conditions, the calibration graphs were linear in the range of 0.2-200 mug/L for target analytes. The enrichment factors were between 11 and 118. The LOD were in the range of 0.01-0.5 mug/L (S/N=3). The relative standard deviations obtained ranged from 3.0 to 7.8% (n=5).

Two field experiments were conducted at the Agronomy Research Station near Stillwater, OK in 2004 and 2005 to identify and evaluate herbicides applied preplant incorporated, preemergence, early postemergence, or late postemergence for the control of seedling sericea lespedeza. Trifluralin, applied preplant incorporated, controlled seedlings 77 (15 wk after emergence [WAE]) and 63% (16 WAE) in 2004 and 2005, respectively. Flumioxazin, imazapic, fluometuron, diuron, sulfentrazone, atrazine, metribuzin, and metolachlor applied preemergence all provided greater than 86% seedling control at 15 and 16 WAE in both years. Diclosulam, applied preemergent, controlled seedlings 47% at 15 WAE in 2004 and 91% control at 16 WAE in 2005. In 2004, triclopyr, metsulfuron-methyl, glyphosate, picloram, dicamba, and 2,4-D amine plus picloram (tank-mix) applied early postemergence controlled 90 to 100% of the sericea lespedeza seedlings at 15 WAE. However, in 2005, only triclopyr, metsulfuron-methyl, glyphosate, and 2,4-D amine plus picloram (tank-mix) showed greater than 80% control at 16 WAE. Triclopyr, applied late postemergence, controlled seedlings 100% at 15 and 16 WAE, in both years. In 2004, dicamba plus 2,4-D (premix) and glyphosate were the only other herbicides which provided greater than 75% control at 15 WAE. These data suggest that there were preemergence-applied herbicides that were effective for the control of seedling sericea lespedeza. These data also suggest that triclopyr was the most effective postemergence-applied herbicide for the control of seedling sericea lespedeza. The data also showed that the overall level of control of seedling sericea lespedeza decreased as the season progressed and the plant matured.

The metabolism and biotransformation of the (14)C-labeled phenylurea herbicide fluometuron was examined using tobacco cell suspension cultures transformed separately with human cyp1a1, cyp1a2 and cyp3a4, and corresponding non-transformed cultures in order to screen and predict metabolic patterns. Experimental parameters modified were concentration of (14)C-fluometuron, incubation period, and additional application of inhibitor carbaryl. Media and cell extracts were analyzed by radio-TLC and radio-HPLC, isolated metabolites by LC-MS, and non-extractable residues by combustion. During 48 hours, the CYP1A1 expressing cultures metabolized 90.0 % of applied fluometuron, while the non-transgenic controls transformed 67.0 %. The CYP1A2 expressing cultures exhibited highest rates (95.1 %), CYP3A4 expressing cultures lowest rates (43.0 %). The primary metabolites identified were mono-demethyl (main metabolite in controls) and di-demethyl fluometuron (mainly in CYP1A2 cultures), besides a non-identified primary product (mainly in CYP1A1 cultures); metabolic profiles differed distinctly among cultures. After addition of carbaryl, rates of fluometuron decreased noticeably in controls and not in CYP3A4 expressing cultures. This may indicate inhibition of endogenous tobacco P450s involved in fluometuron metabolism but not of CYP3A4. Additionally, the P450-transgenic cultures proved to be valuable tools to produce large amounts of metabolites for thorough identification.

Glyphosate-resistant Conyza canadensis emerging in autumn and spring in the southern USA must be controlled prior to establishment of spring-seeded glyphosate-resistant crops. Research was conducted to evaluate C. canadensis control with residual herbicides labeled for pre-emergence use in cotton and to determine the length of residual activity of each herbicide. Additionally, glufosinate and dicamba-based pre-plant burndown programs were evaluated for control and reduction in C. canadensis emergence at three locations in 2007 in Arkansas, USA, with two of these sites containing glyphosate-resistant C. canadensis. Fluometuron, oxyfluorfen, and norflurazon were the most consistent and efficacious herbicides evaluated, providing at least 80% residual control of glyphosate-resistant C. canadensis through 8 weeks after treatment. Glufosinate alone applied in early and late March (8 and 10 weeks before cotton sowing) usually provided less than complete control, resulting in C. canadensis regrowth and subsequent seedling emergence. Addition of dicamba in a tank-mix with glufosinate generally improved C. canadensis control in addition to providing some residual suppression of further emergence. No C. canadensis emerged over a 10- to 12-week period in plots treated with glufosinate plus dicamba plus flumioxazin. Although dicamba does provide short-lived residual C. canadensis control, this research confirms that additional residual herbicides are needed with pre-plant burndown programs to prevent subsequent emergence when conditions are conducive for C. canadensis germination.

Three strains of bacteria (designated as YBL1, YBL2, YBL3 respectively) capable of degrading isoproturon, 3-(4-isopropylphenyl)-1, 1-dimethylurea, were isolated from the soils of two herbicide plants. Based on the comparative analysis of the 16S rRNA gene, and phenotypic and biochemical characterization, these strains were identified as Sphingobium sp. The optimum conditions for isoproturon degradation by these strains were pH 7.0, and temperature 30°C. Mg2+ (1 mM) enhanced the isoproturon degradation rate, while Ni2+ and Cu2+ (1 mmol l−1) inhibited isoproturon degradation significantly. These three strains also showed the ability to remove the residues of other phenylurea herbicides such as chlorotoluron, diuron and fluometuron in mineral salt culture medium. The N-demethylation was the first step of degradation of dimethylurea-substituted herbicides. Strain YBL1 was found capable of degrading both dimethylurea-substituted herbicides and methoxymethylphenyl-urea herbicides i.e. linuron (3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea). Using the PCR method, partial sequences of the catechol 1,2-dioxygenase gene were obtained from these strains.

Field experiments were conducted during 2003 and 2004 at four locations in northern Greece to evaluate the effects of tillage implements and herbicide treatments on the weed control and yield of cotton grown under a mobile sprinkler or drip irrigation system. The tillage implements consisted of three seedbed preparation tillage implements: a field cultivator with a double rolling basket, a disk harrow or a rotary harrow. The herbicide treatments consisted of a broadcast preplant-incorporated (PPI) application of trifluralin or S-metolachlor followed by pre-emergence (PRE)-applied prometryn, a PRE 38 cm band application of S-metolachlor plus fluometuron or a broadcast PPI application of S-metolachlor followed by early postemergence-applied trifloxysulfuron-sodium. In most cases, the PPI applications followed by the PRE application of prometryn resulted in the greatest control of black nightshade (Solanum nigrum L.), redroot pigweed (Amaranthus retroflexus L.), and common lambsquarters (Chenopodium album L.). The control of black nightshade and common lambsquarters was slightly reduced when the herbicides were incorporated by rotary harrow. The cotton yield was not affected in most cases by the tillage implements, while the drip irrigation system provided a greater or similar cotton yield as compared with the sprinklers. The PPI application of trifluralin followed by the PRE-applied prometryn in the cotton grown under drip irrigation provided the greatest lint yield in most cases. Therefore, a drip irrigation system and disk harrow or field cultivator implement could be used as the first choice of cotton growers in integrated crop management production systems.

Field experiments were conducted to evaluate weed control provided by glyphosate, glufosinate, and MSMA applied alone or in mixture with residual and nonresidual last application (LAYBY) herbicides. Herbicide treatments included glyphosate early postemergence (EPOST) alone or followed by glyphosate, glufosinate, or MSMA late-postemergence (LPOST) alone or tank-mixed with one of the following LAYBY herbicides: carfentrazone-ethyl at 0.3 kg ai/ha, diuron at 1.12 kg ai/ha, flumioxazin at 0.07 kg ai/ha, fluometuron at 1.12 kg ai/ha, lactofen at 0.84 kg ai/ha, linuron at 0.56 kg ai/ha, oxyfluorfen at 1.12 kg ai/ha, prometryn at 1.12 kg ai/ha, or prometryn + trifloxysulfuron at 1.12 kg ai/ha + 10 g ai/ha. Residual herbicides were also applied alone LPOST. Weeds evaluated included barnyardgrass, broadleaf signalgrass, coffee senna, entireleaf morningglory, hemp sesbania, ivyleaf morningglory, johnsongrass, large crabgrass, Palmer amaranth, pitted morningglory, prickly sida, redroot pigweed, sicklepod, smooth pigweed, spiny amaranth, and velvetleaf. Treatments containing MSMA provided lower average weed control compared to those containing glyphosate or glufosinate, and residual herbicides applied alone provided inadequate weed control compared to mixtures containing a nonresidual herbicide. Across 315 of 567 comparisons (55%), when a LAYBY herbicide was added, weed control increased. The most difficult to control weed species at all locations was pitted morningglory. Barnyardgrass and hemp sesbania at the Mississippi location and hemp sesbania at the Louisiana location were collectively difficult to control across all treatments as well. Nomenclature: carfentrazone-ethyl; diuron; flumioxazin; fluometuron; glufosinate; glyphosate; lactofen; linuron; MSMA; oxyfluorfen; prometryn; trifloxysulfuron; barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash BRAPP; coffee senna, Cassia occidentalis L. CASOB; entireleaf morningglory, Ipomoea hederacea var. integruiscula Grey IPOHG; hemp sesbania, Sesbania exaltata (Raf.) Rydb.ex A. W. Hill SEBEX; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq IPOHE; johnsongrass, Sorghum halepense L. Pers. SORHA; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; Palmer amaranth, Amaranthus palmeri L. AMAPA; pitted morningglory, Ipomoea lacunosa L. IPOLA; prickly sida, Sida spinosa L. SIDSP; redroot pigweed, Amaranthus retroflexus L. AMARE; sicklepod, Senna obtusifolia (L.) Irwin & Barnaby CASOB; smooth pigweed, Amaranthus hybridus L. AMACH; spiny amaranth, Amaranthus spinosus L. AMASP; velvetleaf, Abutilon theophrasti Medik. ABUTH; cotton, Gossypium hirsutum L.