Broadleaf Weed Control Research Articles

Effect of application rate and irrigation on the movement and dissipation of indaziflam

Indaziflam is a new preemergence herbicide for the control of annual grass and broadleaf weeds in various cropping systems including pecan orchards. The objectives of this study were to (1) determine the mobility and dissipation of indaziflam and (2) evaluate herbicide efficacy in a flood-irrigated pecan orchard in southern New Mexico, USA. Indaziflam was applied at 0, 36.5, and 73.1g/ha in areas with (impacted) and without (unimpacted) tree injury symptoms. Soil samples were collected at 0–15, 15–30, and 30–46cm depths 26, 63, 90, and 126days after the first herbicide application. Additional soil samples were collected 4, 30, and 56days after the second application. Indaziflam was detected in soil samples collected at each depth, suggesting movement with irrigation water. Indaziflam concentrations decreased with increasing soil depth and time. Indaziflam mass recoveries were greater in the unimpacted area than in the impacted area after the first and second applications. Dissipation half-lives of indaziflam in the soil ranged from 30 to 86days for total indaziflam recovered from the entire soil profile after the first and second applications in both areas. The percent weed control was similar in the impacted and unimpacted areas for both rates of indaziflam on 26 and 63days after application; however, on 90days after the application, percent weed control was lower in the impacted than unimpacted area.

Selective Broadleaf Weed Control in Turfgrass with the BioherbicidesPhoma macrostomaand Thaxtomin A

Both regulatory and consumer forces have increased the demand for biopesticides, particularly in amenity areas such as turfgrass. Unfortunately, few natural products are available for selective weed control in turfgrass. Two bioherbicides reported to control broadleaf weeds without injuring turfgrass arePhoma macrostomaand thaxtomin A. Field and container experiments were conducted to evaluate PRE and POST efficacy ofP. macrostomaand thaxtomin A on regionally important broadleaf weeds. In container experiments, PRE applications ofP. macrostomaprovided 65 to 100% control of dandelion, marsh yellowcress, and flexuous bittercress, equivalent to that of pendimethalin. Control of yellow woodsorrel, henbit, hairy galinsoga, common chickweed, or annual bluegrass was less than with pendimethalin. In contrast, POST applications did not control any species as well as an industry-standard synthetic auxin herbicide. PRE or POST applications of thaxtomin A controlled six of the eight species tested as well as the industry-standard PRE or POST herbicides. In field tests, overall PRE broadleaf weed control withP. macrostomaand thaxtomin A peaked 4 wk after treatment at 64 and 72%, respectively, and declined afterward, suggesting that these bioherbicides possess short residuals and therefore must be reapplied for season-long control. Overall POST broadleaf weed control usingP. macrostomaand thaxtomin A was only 41 and 25%, respectively. PRE followed by early-POST applications of thaxtomin A provided ≥ 86% henbit control. These results suggest that bothP. macrostomaand thaxtomin A are capable of controlling certain broadleaf weeds in turfgrass. However, both lack efficacy on some important weed species, particularly chickweed. Thaxtomin A efficacy on henbit was improved by increased dose and by PRE followed by early-POST applications.

HERBICIDAL EFFICACY OF ACETIC ACID AND CITRIC ACID BASE ON BROAD LEAF WEEDS OF MEDICINAL CROPS FIELDS

The study aims to determine the effectiveness of acetic acid based formula on broad leaf weeds grown in medicinal crop fields. Two experiments were conducted, i.e. on small plots (2 m x 3 m) of a farmer’s field in Ciapus, Bogor and on a larger plot (2 m x 8 m) at the Cicurug Experimental Station, Sukabumi. The formula consisted of a mixture of acetic acid + NaCl (AG) and acetic acid + citric acid (AC), and formulas of VAC, VACG which were enriched with wood vinegar (V). As control was a commercial synthetic herbicide 2,4 D amine. The acetic acid base formulas applied at two concentrations 10 and 15%, while 2,4-diamine was followed the recommendation (0.3%) using a knapsack sprayer with a flat-fan nozzle tip. Weed vegetations were observed visually before and at 2, 4, 6, and 8 weeks after treatments. Weed severity was recorded using a 0-4 scales (0 = 0-5% mortality ; 1 = 20-50% weeds died ; 3 = 50-75% eradicated and 4 = 75-100% weed were eradicated), as well as re-growth and dry weight of the weeds. The first and second experiment showed that AC, AG, VAC and VACG applied at 10 and 15% were effective in controlling broadleaf weeds. Mechanism of action the formula is a contact poison. Its effectiveness is equivalent to 2,4-D amine treatment dose of 1.5 l ha-1. Repeated application is necessary to prolong the effect of herbicide.

Baseline Sensitivity of Nebraska Waterhemp and Palmer Amaranth to Dicamba and 2,4‐D

The development of dicamba (3,6‐dichloro‐2‐methoxybenzoic acid)‐ and 2,4‐D [(2,4‐dichlorophenoxy) acetic acid]‐resistant soybean [Glycine max (L.) Merr.] will increase the frequency of applying these herbicides to control broadleaf weeds in soybean production systems. We evaluated the sensitivity of randomly selected waterhemp [Amaranthus tuberculatus (Moq.) Sauer var. rudis (Sauer) Costea and Tardif] and Palmer amaranth (Amaranthuspalmeri S. Wats) populations to a single dose of dicamba and 2,4‐D. Selected populations were then used in dicamba and 2,4‐D dose‐response experiments to evaluate: (i) visual injury at 28 d after treatment; and (ii) plant survival, biomass accumulation, and flowering at 84 DAT. Across selected populations, the estimated dicamba dose for 50% visual injury (I50) was below the recommended field rate (560 g ha−1) and ranged between 59 and 117 g ha−1 for waterhemp and 43 and 81 g ha−1 for Palmer amaranth populations. The estimated 2,4‐D dose for I50 was also below the recommended field rate (800 g ha−1) and ranged between 127 and 242 g ha−1 for waterhemp and 127 and 196 g ha−1 for Palmer amaranth. Waterhemp plants flowered with up to 560 g ha−1 dicamba and 2240 g ha−1 2,4‐D, while Palmer amaranth plants flowered with up to 280 g ha−1 dicamba, and 1120 g ha−1 2,4‐D. Individual plants will likely survive and flower following recommended field rates of dicamba (waterhemp) and 2,4‐D (both species). Close monitoring of weed populations are needed for the stewardship of available weed management technologies.Core Ideas We conducted a state‐wide baseline study of auxinic herbicide sensitivity in randomly selected waterhemp and Palmer amaranth populations. Individual plants of both species will likely survive and flower after field rates of dicamba and/or 2,4‐D. Close monitoring of weed populations and continuous update of best management practices are needed for the stewardship of available weed management technologies. This study sets a benchmark to detect shifting in sensitivities to dicamba or 2,4‐D after resistant crops are released.

Green synthesis of functionalized iron nano particles and molecular liquid phase adsorption of ametryn from water

Second generation herbicide ametryn [2-(ethylamino)-4-isopropylamino-6-methyl-thio-s-triazine] is being used to control broadleaf weeds and annual grasses in sugarcane, bananas, maize and pineapple fields; contaminating water resources. The adsorption method of ametryn removal was presented using functionalized iron nano particles as adsorbent. This adsorbent was prepared by green method, functionalized with 1-butyl-3-methylimidazolidium bromide and characterized by FT-IR, SEM and XRD techniques. Residual ametryn in water was analyzed by optimized HPLC. The optimized batch experiment parameters were 30.0μg/L, 30.0min, 7.0, 2.5g/L and 20.0°C as concentration, contact time, adsorbent amount and temperature. Adsorption data followed Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. Thermodynamic parameter such as ΔG°, ΔH° and ΔS° were −6.05, −6.11 and −6.15kJ/mol at 20, 25 and 30°C temperatures; −6.68kJ/mol and −2.45×10−3kJ/molK. These values indicated sorption spontaneous and exothermic. Pseudo-second-order and liquid film diffusion mechanisms of the adsorption were proposed. Developed sorption method was speedy, environmental friendly and inexpensive due to its nature to be used under natural conditions of water resources. The method work at natural water resources pHs with low adsorbent amount and agitating time. The sorption method may be used for the removal of ametryn from any water body at large and economic scale.

2,4-D mobility in clay soils: Impact of macrofauna abundance on soil porosity

Pesticides in agriculture are commonly used to meet the growing food demand; however they compromise the quality of water and soil. The pesticide 2,4-D is one of the most widely used herbicides in the world, it belongs to the group of synthetic herbicides that control broadleaf weeds. In this paper the risk of groundwater contamination by 24-D and its major metabolite, 2,4-DCP, is studied in a context of high density of soil worms. We compared the adsorption, desorption, degradation and displacement of 2,4-D in soils from Tabasco Region having different properties: clay, organic matter, iron and aluminum oxides contents. In addition to the classical soil physicochemical characterizations, a 3D analysis of the soil structure and porosity was performed by analyzing images acquired by Computed Tomography. The objective was to evaluate the effect of soil properties and macroporosity produced by the macrofauna activity on solute movement.All the four soils studied sorbed the herbicides, more importantly 2,4-DCP, the metabolite, than 2,4-D itself. The distribution coefficients for 2,4-D sorption were linear and varied between 1 and 4 while those for 2,4-DCP were above 10. The contents of iron and aluminum have an important role in the adsorption of these two compounds. In aerobic conditions, the herbicides half-life was about 2days. Water movement occurred in physical equilibrium in three of the four soils; soil dispersivity ranged from 1.2 to 7cm, clay content being the main factor. After 20 to 60days depending on the soil, no 2,4-D leaching was observed through the soil columns, except for one soil were there was preferential flow. Earthworms burrows were exhibited and quantified in the soils samples through the analysis of Computer Tomography (CT) images, they appeared as small, snail-shaped, rounded volume of 3 to 7mm radius with a higher density with respect to the surrounding soil. They were extracted from the original data using a combination of image processing and mathematical morphology operators. Based on the results obtained, it can be concluded that preferential flow caused by both high clay content and the presence of macrofauna pores significantly reduces the buffering capacity of the soil, increasing the risk of contamination by herbicides of the underlying aquifer.

Transfer of 2,4-D-resistance from Raphanus raphanistrum into Brassica napus: production of F1 hybrids through embryo rescue

Development of 2,4-D-resistant Brassica napus varieties is valuable for conservation tillage and post emergence control of broadleaf weeds. This research documents successful production and transfer of 2,4-D resistance from Raphanus raphanistrum (wild radish) into, Brassica napus via embryo rescue.

Divalent Cations in Spray Water Influence 2,4-D Efficacy on Dandelion (Taraxacum officinale) and Broadleaf Plantain (Plantago major)

2,4-dichlorophenoxyacetic acid (2,4-D) is a common ingredient in POST broadleaf herbicides labeled for use in turf, pastures, rangeland, and grain crops. The herbicide 2,4-D is a weak acid, and when dissociated can bind to cations present in hard-water spray solutions and/or fertilizer solutions. Experiments were conducted with 2,4-D dimethylamine to evaluate the effect of cation solutions on herbicide efficacy on the perennial broadleaf weeds dandelion and broadleaf plantain. The objectives of this research were to (1) determine if 2,4-D efficacy is influenced by the divalent cations, calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) in spray solution; and (2) determine if adding the adjuvant ammonium sulfate (AMS) to the spray solution can overcome antagonism. Broadleaf plantain and dandelion control was reduced and plant size and mass increased when 2,4-D was applied in a Ca solution in comparison to deionized water. However, 2,4-D antagonism was overcome when AMS was added as an adjuvant to the spray solution. Magnesium caused 2,4-D antagonism on both weed species in one run of the experiment similar to Ca solution and AMS was successful at overcoming antagonism when added to the tank mixture. Some 2,4-D antagonism from Mn was noticed even when AMS was in the tank mix, but Zn fertilizer solutions did not antagonize 2,4-D activity on either weed species. Although divalent cations can antagonize 2,4-D dimethylamine and reduce perennial broadleaf weed control, adding AMS can overcome this antagonism when Ca and Mg are the primary cations in spray solution. Applicators should avoid using Mn fertilizers when applying 2,4-D dimethylamine because AMS did not successfully overcome antagonism.

Economics of herbicide weed management in wheat in Ethiopia

Effective use of herbicides for the control of annual grass and broadleaf weeds in wheat ( Triticum aestivum L.) was not a reality in Ethiopia, until in recent years. This study aimed at evaluating different post-emergence herbicides against annual grasses and broadleaf weeds in wheat for selection and incorporation into an integrated weed management (IWM) system. The study was conducted at Kulumsa Agricultural Research Centre main station, Bekoji and Lole farm fields. Treatments included herbicides, namely, Mesosulfron methyl+Idosulfuron methyl sodium (liquid) 1 lit ha -1 a.i. Pyroxsulam (liquid) 0.5 l ha -1 a.i. hand weeding twice (30-35 and 55-60 days after emergence (DAE)); and a weedy check. Among the annual grass weeds, Snowdenia polystachya, Avena fatua, Bromus pectinatus, Phalaris paradoxa and Setaria pumila ; and most broad leaf weeds like Polygonum nepalense, Guizotia scabra, Galinsoga parviflora and Gallium spurium were controlled with herbicide efficacy ranging from 75 to 100%. Mesosulfron methyl +Idosulfron methyl sodium, Pyroxulam and hand weeded twice plots outyielded the weedy check by 63, 58 and 53%, respectively. Maximum wheat grain yield (5,184 kg ha -1 ), biomass (12,808 kg ha -1 ), thousand kernel weight (48.55) and hectoliter weight (74.2) were obtained due to the application of Mesosulfron methyl+Idosulfuron methyl sodium. In addition, the herbicide had a yield advantage over Pyroxsulam, two hand weedings and the weedy check by 12, 21 and 63%, respectively. Application of Mesosulfron methyl + Idosulfuron methyl sodium (US$1,596.31 ha -1 ) had the highest net field benefit compared to Pyroxsulam (US$1,379.21 ha -1 ), two hand weeding (US$1,126.7 ha -1 ) and weedy check (US$574.1 ha -1 ) by 13.6, 29 and 64%, respectively. Moreover, the herbicide was also economically profitable to farmers, providing a marginal rate of return (MRR) of 1,737%. Sensitivity analysis (aMRR) also remained the most profitable even when the price of herbicide increased by 20%. Hence, Mesosulfron methyl +Idosulfuron methyl sodium at a rate of 1 lit ha -1 is thebest herbicide for the effective control of annual grasses and broad leaf weeds in wheat and can be used as one of the component in Integrated Weed Management Program (IWM) in wheat fields. Key Words : Idosulfuron methyl sodium, Mesosulfron methyl, Triticum aestivum

Strip Tillage and Early-Season Broadleaf Weed Control in Seeded Onion (Allium cepa)

Field experiments were conducted in 2007 and 2008 near Oakes, North Dakota (ND), USA, to evaluate if strip tillage could be incorporated into a production system of seeded onion (Allium cepa) to eliminate the standard use of a barley (Hordeum vulgare) companion crop with conventional, full width tillage, yet support common early-season weed control programs. A split-factor design was used with tillage (conventional and strip tillage) as the main plot and herbicide treatments (bromoxynil, DCPA, oxyfluorfen, and pendimethalin) as sub-plots. Neither tillage nor herbicide treatments affected onion stand counts. Common lambsquarters (Chenopodium album) densities were lower in strip tillage compared to conventional tillage up to three weeks after the post-emergence applied herbicides. In general, micro-rate post-emergence herbicide treatments provided greater early-season broadleaf weed control than pre-emergence herbicide treatments. Onion yield and grade did not differ among herbicide treatments because the mid-season herbicide application provided sufficient control/suppression of the early-season weed escapes that these initial weed escapes did not impact onion yield or bulb diameter. In 2007, onion in the strip tillage treatment were larger in diameter resulting in greater total and marketable yields compared to conventional tillage. Marketable onion yield was 82.1 Mg ha−1 in strip tillage and 64.9 Mg ha−1 in conventional tillage. Results indicate that strip tillage use in direct-seeded onion production was beneficial, especially when growing conditions were conducive to higher yields and that the use of strip tillage in onion may provide an alternative to using a companion crop as it did not interfere with either early-season weed management system.

Tolerance of Processing Tomato (Solanum lycopersicum L.) Varieties to Thifensulfuron-Methyl

Field experiments were conducted at the Ohio Agricultural Research and Development Center in Wooster, OH, in 2005, 2006, and 2007 to evaluate the tolerance of eight tomato varieties to thifensulfuron-methyl and POST control of broadleaf weeds. Herbicide treatments included thifensulfuron-methyl at 0, 6, and 12 g ai ha−1. In 2005, significant injury was observed in variety TR122244 at 1 and 3 wk after treatment (WAT). The highest crop injury in 2005 was 38% at 1 WAT for variety TR122244. However, this variety experienced a conflicting effect on crop marketable yield when treated with the low and high rates of thifensulfuron-methyl in 2005. Variety TR122244 had the highest crop injury, yet produced the highest marketable yield when treated with either rate of thifensulfuron-methyl. At 3 WAT in 2005, significant injury occurred in variety 11111120, with 13% injury recorded for both the high and low rates of thifensulfuron-methyl. No significant injury resulted from either rate of thifensulfuron-methyl at 1, 3, or 6 WAT in 2006 or 2007. However, in 2006 a significant marketable yield reduction was observed for variety 97045116 when treated with the high rate of thifensulfuron-methyl. No varieties experienced significant marketable yield effects or injury when treated with either rate of thifensulfuron-methyl in 2007. Registration of thifensulfuron-methyl herbicide is not recommended at this time because of the potential for crop stunting and yield reduction in certain tomato varieties.

Adsorptive removal of 2,4-dichlorophenoxyacetic acid from aqueous solution using bagasse fly ash as adsorbent in batch and packed-bed techniques

Among the several synthetic herbicides available currently, 2,4-D is a commonly used herbicide to control broadleaf weeds in agriculture and forestry. However, its increasing use in agricultural and nonagricultural activities has resulted in increasing concentrations of 2,4-D being detected in water bodies. Thus, there is a need to identify methods to remove 2,4-D to protect the environment. Among the various methods used for 2,4-D removal, adsorption is found to be effective, and several adsorbents have been studied to remove 2,4-D from aqueous solutions. In this study, we used bagasse fly ash (BFA), a common industrial waste generated in large amount worldwide, for 2,4-D removal from aqueous solution using batch and continuous packed-bed adsorption. In the batch adsorption process, the effects of initial concentration, contact time, temperature, pH, and particle size of BFA were studied. The packed-bed performance of BFA was investigated by varying the influent concentration (50–150 mg/L), flow rate (1.2–4 mL/min), and bed height (4.5–9 cm). Isotherm and thermodynamic parameters are determined for batch adsorption, whereas the performance of continuous adsorption is evaluated by different packed-bed models. The particle-size effect indicated the higher removal of 2,4-D on the bigger particles of BFA due to greater BET surface area and carbon-to-silica ratio than smaller particles. The maximum percentage removal (37.04) is achieved for an influent concentration of 50 mg/L, flow rate of 1.2 mL/min, and bed height of 6.5 cm. For the first time ever, the deactivation kinetic model was applied for the solid–liquid adsorption system and it showed the best fit among the selected models. The bed capacity (m2/g) of BFA is three times greater than synthetic activated carbon for adsorption of 2,4-D. This informs that the BFA can be used as an adsorbent for 2,4-D removal from aqueous solution.

MODIFICATION OF TITANIUM DIOXIDE NANOPARTICLES WITH COPPER OXIDE CO-CATALYST FOR PHOTOCATALYTIC DEGRADATION OF 2,4-DICHLOROPHENOXYACETIC ACID

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common herbicide that has been used in control of broadleaf weeds, wheat, corn, pastureland, lawn, recreational lakes, turf; and roadsides. Due to it excessive usage, these herbicides that contained 2,4-D can cause contamination over agricultural land and water bodies. Photocatalytic removal environmental pollutants such as herbicides has been a topic of great interest over the years 1. One of the most widely used materials for photocatalytic degradation of environmental pollutants is TiO,. A number of strategies have been developed in order to improve the catalytic activity of TiO, photocatalyst. In particular, it has been shown that transition metal oxides, such as copper oxide, are potential to enhance the photocatalytic activity of TiOl. In the present work:, a simple impregnation method was used to modify the commercial P25 TiD, nanoparticles with the copper oxide. The prepared samples were characterized by XRD, reflectance UVvisible and fluorescence spectroscopies. It was observed that the incorporation of copper oxide did not significantly affect the crystal structure of TiD,. On the other hand, the presence of copper oxide was confirmed by reflectance UV-visible and fluorescence spectroscopies. Figure I shows the photocatalytic removal of 2,4-D on bare TiD, and modified TiO,nanoparticles. It can be clearly shown that after I hour reaction, the photocatalytic activity of TiD, increased from 48 to 54% with the increase of copper oxide loading up to 0.5 mol%. Unfortunately, the higher loading amount of copper oxide resulted in the lower photocatalytic activity. When the loading amount was 5 mol%, the activity decreased to 26%. This result clearly suggested that the small amount of copper oxide, which was 0.5 mol%, was the optimum amount in this study to give the highest activity for the copper oxide supported on TiD, series. The higher photocatalytic activity would be originated from the lower electron-hole recombination.

A Potential New Herbicide for Invasive Annual Grass Control on Rangeland

Downy brome (Bromus tectorum L.), a winter annual grass, is considered one of the most invasive non-native rangeland species in the United States. Although glyphosate, imazapic, and rimsulfuron are herbicides commonly recommended to control invasive, annual grasses, their performance is inconsistent and they can injure desirable perennial grasses. Indaziflam is a recently registered cellulose biosynthesis inhibiting herbicide, providing broad-spectrum control of annual grass and broadleaf weeds. Indaziflam is labeled for winter annual grass control in citrus, grape, and tree nut crops and could represent a new mode of action for selective winter annual grass control on rangeland. Three field experiments were conducted to compare indaziflam with imazapic, rimsulfuron, and glyphosate, three herbicides commonly used for downy brome control. Multiple herbicide application timings were evaluated. At all three sites, glyphosate and rimsulfuron provided less downy brome control than indaziflam 1 year after treatment (YAT). Percent downy brome control with imazapic decreased significantly 2 YAT (45−64%) and 3 YAT (10−32%). Across all sites and application timings, indaziflam provided the greatest downy brome control 2 YAT (89−100%) and 3 YAT (83−100%). Indaziflam did not significantly reduce species richness. This study demonstrates that indaziflam can provide extended downy brome control compared with currently used herbicides.

Response of conventional and imidazolinone-resistant chickpea (Cicer arietinum L.) cultivars to imazamox and/or imazethapyr applied post-emergence

Chickpea (Cicer arietinum L.) production in the Northern Great Plains is limited by very few broadleaf weed control options. Field experiments were conducted at two locations in 2012 and at three locations in 2013 in Saskatchewan, Canada, to examine the performance of the conventional and the imidazolinone (IMI) resistant chickpea cultivars to post-emergence application of imazamox or imazethapyr applied alone or in tank-mix. Treatments included imazamox (20 and 40 g a.i. ha−1), imazethapyr (50 and 100 g a.i. ha−1), and a tank-mixture of imazamox (35%) + imazethapyr (35%) (30 and 60 g a.i. ha−1). Conventional cultivars, CDC Luna and CDC Corinne, showed moderate to severe injury compared with resistant cultivars, CDC Alma and CDC Cory, which showed minimal to no injury. Plant height was arrested and node development slowed for conventional cultivars treated with IMI herbicides. This susceptibility to IMI herbicides was also noted with a delay in flowering and maturity. Despite a significant negative response, CDC Luna and CDC Corinne were able to recover throughout the growing season resulting in no yield loss from IMI treatments at all locations, except one. Resistant cultivars, CDC Alma and CDC Cory, demonstrated no significant injury from IMI herbicide compared with the untreated controls. These results show the potential to use IMI herbicides in the resistant chickpea cultivars, expanding the currently limited options for broadleaf weed control in chickpea cultivation.

Control of broadleaf weeds and sedges in direct seeded rice with carfentrazone-ethyl

Control of broadleaf weeds and sedges in direct seeded rice with carfentrazone-ethyl

Response of Four Dry Bean Market Classes to Pre-Emergence Applications of Pyroxasulfone, Sulfentrazone and Pyroxasulfone plus Sulfentrazone

Only one herbicide mode of action (ALS inhibitor) is currently available to Ontario dry bean producers for soil-applied broadleaf weed control. Four field studies were conducted over two years (2014, 2015) to examine the tolerance of four market classes of dry beans to sulfentrazone (210 and 420 g·ai·ha-1) and pyroxasulfone (100 and 200 g·ai·ha-1) applied alone and in combination. The registration of these two herbicides would provide Ontario dry bean producers with two additional modes of action for broadleaf weed control. Pyroxasulfone caused up to 23%, 6%, 7% and 10% injury in adzuki, kidney, small red Mexican and white bean, respectively; sulfentrazone caused up to 51%, 12%, 15% and 44% injury and the combination caused up to 90%, 23%, 29% and 62% injury, respectively. Kidney and small red Mexican bean density, height, seed moisture content and yield were not affected. Pyroxasulfone (200 g·ai·ha-1) + sulfentrazone (420 g·ai·ha-1) reduced adzuki and white bean density, shoot dry weight, height and yield. This study concludes that pyroxasulfone (100 g·ai·ha-1) + sulfentrazone (210 g·ai·ha-1) applied PRE can be safely used to control weeds in Ontario kidney and small red Mexican bean production.

Management of complex weed flora in maize with post-emergence herbicides

Some weed species are not controlled by atrazine where the farmers are using this herbicide year after year and different flushes of weeds in rainy season are among the major problems in maize growing areas of India. A field experiment was conducted during the crop growing seasons of 2012 and 2013 at Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana to evaluate the efficacy of glyphosate 41% SL against complex weed flora in maize. The treatments included glyphosate 41% SL 900, 1800 and 3600 g/ha applied as post-emergence at 2–4 leaf stage of weeds, atrazine 750 g/ha as preemergence, paraquat 24 SL 500 g/ha as post-emergence at 2–4 leaf stage of weeds, 2,4-D sodium salt 1000 g/ha as post-emergence at 2–4 leaf stage of weeds, weed free and unweeded control. The results revealed that non-selective herbicides paraquat at 500 g/ha and glyphosate at 900 and 1800 g/ha as a directed spray in maize as post-emergence at 2–4 leaf stage of weeds recorded effective control of grass and broad-leaf weeds during both the years and recorded grain yield at par with atrazine.

Weed Control with Sulfentrazone plus a Low Rate of Imazethapyr in White Bean

Ontario dry bean (Phaseolus vulgaris L.) growers have few options for broadleaf weed control. Sulfentrazone is a group 14 herbicide that provides good control of several common Ontario weed species, and would provide another mode of action for broadleaf weed control if registered for use in Ontario dry beans. Five field studies were conducted during 2014 and 2015 to determine if a low dose of imazethapyr added to a tank mix of sulfentrazone + s-metolachlor would improve broadleaf control in white bean. Sulfentrazone (140 and 210 g·ai·ha-1) was mixed with imazethapyr and s-metolachlor and evaluated at 2 and 4 weeks after crop emergence for crop injury. Weed control was assessed visually at 4 and 8 weeks after herbicide application (WAA), and weed stand counts and biomass were determined at 8 WAA. Seed moisture and yield were determined at harvest. At 8 WAA, sulfentrazone (140 g·ai·ha-1) controlled pigweed species, common ragweed, common lambsquarters, wild mustard, barnyard grass and green foxtail 100%, 4%, 100%, 2%, 86% and 62%, respectively. The addition of imazethapyr (37.5 g·ai·ha-1) to sulfentrazone (140 g·ai·ha-1) improved the control of common ragweed, wild mustard and green foxtail by 19%, 98% and 33%, respectively. The three-way tank mix of sulfentrazone (140 g·ai·ha-1) plus s-metolachlor (1050 g·ai·ha-1) plus imazethapyr (37.5 g·ai·ha-1) controlled pigweed species, common ragweed, common lambsquarters, wild mustard, barnyard grass and green foxtail 100%, 35%, 100%, 100%, 96% and 100%, respectively. The tank mixes evaluated caused unacceptably high levels of crop injury; this study does not support the registration of sulfentrazone plus s-metolachlor + imazethapyr for use in Ontario white bean.

Tolerance of Four Dry Bean Market Classes to Pre-Emergence Applications of Sulfentrazone

Ontario dry bean growers are currently limited to ALS inhibitor herbicides for soilapplied broadleaf weed control; therefore another mode of action is needed. Sulfentrazone is a PPO inhibitor herbicide that has activity on some annual grass and broadleaf weed species. Four field trials were conducted over two years (2014, 2015) to determine the tolerance of four commonly grown dry bean market classes (adzuki, kidney, small red Mexican and white bean) to PRE applications of sulfentrazone at 140, 210, 280 and 420 g·ai·ha-1. Crop injury, plant height, plant density, shoot biomass, seed moisture content and yield were examined. Sulfentrazone (420 g·ai·ha-1) caused up to 74%, 22%, 30%, and 57% injury in adzuki, kidney, small red Mexican and white bean, respectively. Plant density, height and yield were not reduced for kidney or small red Mexican bean. Sulfentrazone (420 g·ai·ha-1) reduced white bean plant density, height and yield by 28%, 29% and 29%, respectively; and reduced adzuki bean plant density, height and yield by 51%, 34% and 57%, respectively. Overall, kidney and small red Mexican bean were the most tolerant to sulfentrazone, followed by white bean, and then adzuki. This study determined sulfentrazone applied PRE is safe for Ontario kidney bean and small red Mexican bean crops.