Herbicide Solution Research Articles

Amendment of Herbicide Spray Solutions with Adjuvants to Modify Droplet Spreading and Fading Characteristics on Weeds

Abstract.Improving the coverage area and fading time of herbicidal droplets on weeds has the potential to enhance the biological control effectiveness. Droplet spreading and fading behaviors on five different weeds were characterized for spray solutions containing a 1.25% glyphosphate Rodeo herbicide amended with each of three different adjuvants (nonionic surfactant Kinetic, nonionic organosilicone surfactant DyneAmic, and nonionic surfactant and antifoaming agent Preference). The five weeds were ragweed, crabgrass, yellow nutsedge, common purslane, and spurge. Tests were conducted by depositing single 300 and 600 µm herbicidal droplets with different adjuvant concentrations on weed leaves inside an environment control chamber. A droplet at a higher adjuvant concentration had greater coverage area on weed surfaces. Preference-amended herbicidal droplets had the largest coverage area increase for all five weeds, and generally followed by droplets with Kinetic and DyneAmic except for 300 µm droplet on purslane and 600 µm droplet on spurge. In comparison with the herbicidal solution containing Rodeo and water only, with addition of adjuvants the 600 µm droplets increased the coverage area by 2.13 to 5.47, 1.76 to 2.56, 1.84 to 2.07, and 2.40 to 4.49-fold on crabgrass, yellow nutsedge, common purslane, and spurge, respectively, while the 300 µm droplets increased the coverage area on ragweed by 3.88 to 5.86-fold. In contrast, fading times of all 300 µm droplets decreased with the adjuvant addition except for DyneAmic applied on purslane. However, fading times of 600 µm droplets did not have increase or decrease trends with adjuvants, which depended on types of the adjuvant and weed. The overall comparison by integrated index (coverage area × fading time) indicated that a spray droplet at higher adjuvant concentration was likely to have a higher integrated index. In addition, Preference amended droplets had significantly more integrated index increase for crabgrass and nutsedge, while DyneAmic had more increase for purslane. Therefore, appropriate selections of spray adjuvants during herbicide applications could significantly increase droplet deposition effectiveness for controlling specific weeds. Keywords: Spray droplet, Spray additive, Herbicide application, Surfactant, Weed control.

Spectral, luminescent and photochemical properties of humic acids with different genesis of organic raw materials

Spectral-luminescent properties of different samples of humic acids (HAs) are investigated. The samples of HAs fractions were obtained from Fluka Chemical Co, prepared from peat of Western Siberia region, other HAs and lignins were isolated from Arkhangelsk Region. The comparative analysis of these HAs with the sample of humic acids allocated from brown coal is carried out. The presence in the solution of herbicide 2,4-dichlorophenoxyacetic acid the humic acids has a significant effect on the processes of photochemical degradation under the action of light from an excilamp.

Productivity of corn under different systems of protection and permanent growing in Left-Bank Forest-Steppe of Ukraine

Importance of determination of efficiency of herbicides both continuous and selective action is confirmed, for providing selection of necessary preparations on the early and late stages of development of corn plants. It is found out, that application only of the ground herbicides does not guarantee complete defense of sowing against weeds and reduces the productivity of corn, as their action largely depends on hydrothermal factors. The increase of efficiency of complex application of the ground herbicides is set with the additional sprinkling of sowing of corn by insurance herbicides. It is found out, that an important value in the increase of efficiency of chemical preparations has an effect of the repeated bringing of solutions of insurance herbicides on already weak weed vegetation. The greatest productivity of corn at the permanent growing in Left-Bank Forest-Steppe of Ukraine is got for application of the ground herbicide of Harnes and additional bringing of insurance herbicide of Milagro

Ensuring the overall combustion of herbicide metribuzin by electrochemical advanced oxidation processes. Study of operation variables, kinetics and degradation routes

This article reports the electrochemical degradation of the herbicide metribuzin (MTZ) in sulfate medium by advanced oxidation processes like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). A boron-doped diamond (BDD) anode was combined with an air-diffusion cathode with ability to produce H2O2. Unprecedented overall combustion was feasible by all methods at a constant current density (j) ≥100.0 mA cm−2. The total organic carbon (TOC) removal achieved by AO-H2O2 was independent from pH within the range 3.0–9.0, whereas the oscillatory dependence of the pseudo-first-order MTZ decay rate constant with this variable was ascribed to adsorption on the BDD surface. In EF and PEF at pH 3.0, 0.50 mM Fe2+ was determined as optimum catalyst content and the MTZ removal showed two consecutive pseudo-first-order kinetic stages. These were related to the fast reaction of the target molecule with OH formed from Fenton’s reaction, followed by a slower attack of physisorbed BDD(OH) onto Fe(III)-MTZ complexes. The effect of j and MTZ content on decay kinetics and TOC removal was examined. PEF was the best treatment due to the decomposition of photoactive intermediates by UVA radiation, yielding total mineralization of a 0.523 mM herbicide solution after 420 min of electrolysis at 100.0 mA cm−2. A thorough reaction pathway for MTZ degradation is proposed from the sixteen heteroaromatic by-products and three aliphatic molecules identified by GC–MS and LC-MS/MS. Oxalic and oxamic acids were detected as final carboxylic acids by ion-exclusion HPLC.

N-hexanoyl-O-glycol chitosan as a carrier agent for water-insoluble herbicide

The objective of this study was to assess the potential of an amphiphilic chitosan derivative, namely N-hexanoyl-O-glycol chitosan (HGC) as a carrier agent for herbicide atrazine. The physicochemical properties of HGC were characterised using several analytical instruments. The critical micelle concentration (CMC) of HGC was determined using a Fluorescence Spectrometer. A High Performance Liquid Chromatography (HPLC) was used to determine encapsulation efficiency and loading capacity of atrazine in the amphiphilic chitosan derivative. Research findings found that the addition of hexanoyl and glycol groups to the chitosan backbone has improved the thermal stability of chitosan. TEM observation confirmed that HGC can form self-aggregation in the solution with spherical shape. The CMC values determined for HGC was 0.008 mg/mL. HGC also exhibited excellent encapsulation efficiency and loading capacity. The release profiles of atrazine loaded in HGC showed that it has different release behaviour than the pure herbicide in solution. In conclusion, the results from the study suggest that the amphiphilic chitosan derivative is applicable to be utilised as carrier agent for herbicide atrazine in pesticide formulation.

Assessment of the retardation of selected herbicides onto Danube sediment based on small column tests

This study utilizes column tests to investigate the retardation of certain herbicides with different hydrophobicities (atrazine, alachlor and trifluralin) during transport through surface Danube sediment. The influence of water matrix on the retardation factor Rd and Freundlich constant Kf is investigated. The results are compared with batch tests to establish whether different methodologies result in similar or different conclusions. A stainless steel column was filled with natural Danube sediment. Three water matrices were investigated: synthetic, Danube surface, and deep groundwater rich in natural organic matter (NOM). The goal was to examine whether different water matrices would result in changes in the Rd and corresponding Kf values. After a tracer experiment, single herbicide solutions were tested in the three water matrices. Herbicides were analyzed by gas chromatography coupled with electron capture detector (GC/ECD). Retardation factors obtained in the column experiments were calculated using Transmod software (version 2.2). The Kf values calculated were compared with the values obtained in previous batch experiments. A breakthrough curve (BTC) for trifluralin could not be obtained during the experiment. Atrazine Rd values were almost the same in the natural matrices (54 and 55 for the ground and surface waters, respectively), and lower in the synthetic water (40). Alachlor Rd values in the three water matrices were very similar (30–35). The corresponding Kf values for alachlor (8.47–17.4) were lower than those of atrazine (13.5–27.9). These results differ from those obtained by earlier batch tests, which showed similar Kf values for both atrazine (4.4–9.2) and alachlor (4.43–10.35) in all three matrices. In contrast to the results observed during the batch tests, the column tests exhibited higher Kf values in the natural water matrices than the synthetic water, possibly due to the influence of dissolved organic carbon on herbicide sorption. Of the three herbicides investigated, the smallest retardation was observed for alachlor. This was unexpected given the relative hydrophobicities of alachlor and atrazine. The potential risk of transport through the sediment may therefore be greater for alachlor than the other two herbicides. This was indicated neither by the batch tests nor from the Koc–Kow estimations. Both herbicides exhibited similar Kd and Kf values in the batch tests, and lower values in the natural water matrices. In comparison, the column tests showed higher Kf values, with higher values in the natural matrices than in the synthetic water matrix.

Phytoremediation Capacity of Forest Species to Herbicides in Two Types of Soils

Abstract The present study aimed to evaluate the potential of forest species for herbicide phytoremediation. The experiment was conducted in a greenhouse with a randomized block design and a 2x3x3 factorial scheme, using two soils (Red-Yellow Latosol - RYL and Quartzarenic sandy soil - QN), three herbicide solutions (without herbicides/water, 2,4-D and atrazine), and three forest species (Cecropia hololeuca, Eucalyptus grandis x Eucalyptus urophylla and Hymenea coubaril), with four replications. After the experiment, Cucumis sativus was cultivated in order to investigate possible herbicide residues in the soils. The evaluated forest species reduced atrazine and 2,4-D residues in most treatments, except for the Jatoba (Hymenaea coubaril ) cultivated in the RYL soil. Eucalyptus was the species that showed the greatest tolerance to herbicide action, demonstrating the potential for phytoremediation of atrazine and 2,4-D. Cecropia hololeuca and Hymenaea coubaril presented the greatest potential for 2,4-D and atrazine, respectively.

Nanostructured catalysts applied to degrade atrazine in aqueous phase by heterogeneous photo-Fenton process.

SBA-15 and KIT-6 materials have been synthesized and modified with iron salts by the wet impregnation method with different metal loadings. The different mesostructures obtained were characterized by N2 adsorption-desorption at 77K, X-ray diffraction, temperature-programmed reduction, and ultraviolet-visible spectroscopy. These iron-containing mesostructured materials have been successfully tested for the heterogeneous photo-Fenton degradation of aqueous solutions of dangerous herbicides, such as atrazine, using UV-visible light irradiation, at room temperature and close to neutral pH. The results showed that the Fe/SBA-15 (10%) and Fe/KIT-6 (5%) catalysts exhibited the highest activities. However, the Fe/KIT-6 (5%) catalyst with minor Fe loading than Fe/SBA-15 (10%) presented a higher degradation of atrazine (above 98% in a reaction time of 240min). Therefore, the interconnectivity of the cage-like mesopores had an important influence on the catalytic activity, favoring probably mass-transfer effects. Thus, the high performance of these materials indicates that the heterogeneous via of photo-Fenton process can also be efficiently employed to treat wastewaters containing pollutants such as herbicides, in order to reduce them to simplest and less toxic molecules.

Reduction in the spray drift of 2,4-D in tomato using hydraulic nozzles with air induction and LI-700 adjuvant

ABSTRACT The drift of hormonal effect herbicides is a major problem for agriculture, because, even in small amounts, it may cause high losses in crops with plants that are sensitive to their action mechanism. This study aimed to evaluate the efficiency of hydraulic spray nozzles with air induction, as well as the use of the LI-700 adjuvant, in the reduction of the 2,4-D herbicide drift, in tomato crop. A complete randomized split-plot experimental design, with eight replications, was used. Two herbicide solutions were assigned in the plots (with or without the use of adjuvant) [2,4-D (670 g ha-1) and 2,4-D (670 g ha-1) + LI-700 (712.88 g ha-1)], and, in the subplots, five nozzle models [simple fan (JSF11003), simple fan with air induction (AD-IA11003), dual fan with air induction (AD-IA/D11003), simple hammer fan with air induction (TTI11003-VP) and empty cone with air induction (CV-IA10003). The treatments were applied in a wind tunnel, under a pressure of 300 kPa. In a laser analyzer, applying only water, the volumetric median diameter, the relative amplitude and the percentage of drops with diameter lower than 150 µm were measured for all nozzle models. The CV-IA10003 and TTI11003-VP hydraulic nozzles outstand by reducing the 2,4-D herbicide drift and decreasing the damage to tomato plants. The addition of the LI-700 adjuvant to the 2,4-D syrup, independently of the nozzle model, reduces the drift of this herbicide and its effects on the tomato plant root. However, even when adopting these technologies, the application of the 2,4-D herbicide near the tomato crop should be avoided.

Improving the On-Line Extraction of Polar Compounds by IT-SPME with Silica Nanoparticles Modified Phases

In the present work the extraction efficiency of in-tube solid-phase microextraction (IT-SPME) for polar herbicides has been evaluated using extractive capillaries coated with different polymeric sorbents. For this purpose, aqueous solutions of herbicides with a wide range of polarities, including some highly polar compounds (log Kow < 1), have been directly processed by IT-SPME coupled on-line to capillary liquid chromatography with UV-diode array detection. For extraction, commercially available capillary columns coated with polydimethylsiloxane (PDMS) and polyetilenglicol (PEG)-based phases have been used, and the results have been compared with those obtained with a synthesized tetraethyl orthosilicate (TEOS)-trimethoxyethylsilane (MTEOS) polymer, as well as the same polymer reinforced with silica nanoparticles (SiO2 NPs). The SiO2 NPs functionalized TEOS-MTEOS coating provided the best results for most herbicides, especially for the most polar compounds. On the basis of the results obtained, conditions for the quantification of the herbicides tested are described using a SiO2 NPs reinforced TEOS-MTEOS coated capillary. The proposed method provided satisfactory linearity up to concentrations of 200 μg/L. The precision was also suitable, with relative standard deviations (RSDs) values ≤9% (n = 3), and the limits of detection (LODs) were within the 0.5–7.5 µg/L range. The method has been applied to different water samples and the extract obtained from an agricultural soil.

Seleção de sementes de soja geneticamente modificadas com o gene marcador bar por meio do teste de germinação em solução de glufosinato de amônio

The objective of this work was to identify promising GM events in a fast and practical manner, in replacement of methodologies based in aerial pulverization in greenhouse and conventional PCR. Eight GM events and their respective conventional isolines were used. Germination and seedling length tests were performed on a paper soaked in an herbicide solution and in the control conditions. To compare the method efficiency, greenhouse tests were carried out, in which the herbicide was applied to plants in the V3 stage. Results obtained indicated that events 2Ia4, 2Oa4, 5Ha10, and 1Ea2939 showed resistance phenotype in both germination and seedling length tests, as well as in plants in the V3 developmental stage. Some GM events (2Ha11, 2Ia1, 3Pa4 and 1Ea15), even with the confirmation of gene bar, were sensible to herbicide. The differences observed in the resistance phenotype of the different GM lineages may be associated with variations in the level of expression of the bar gene, which may vary depending on the insertion position in the host genome. It was possible to conclude that the use of germination and seedling length tests in paper was efficient for selecting GM plants with confirmed results in tests performed in greenhouse with adult plants, showing to be a fast, cheap, and practical methodology, applicable in an early stage, accelerating the screening of promising plants in breeding programs.

Fading Activities of Herbicidal Droplets Amended with Emulsifiable Spray Adjuvants on Cucurbitaceous Leaves

Abstract. Understanding reactions of surfactant-amended droplets on difficult-to-wet weed surfaces could help develop application strategies to increase herbicide efficacy. Behaviors of herbicidal droplets containing different emulsifiable anti-evaporation spray adjuvants were investigated by characterizing 250 and 450 µm herbicidal droplet dispersion and fading time on cucurbitaceous leaves placed inside a 20°C chamber at 30% and 60% relative humidity (RH). Droplet maximum coverage area increased with droplet size but not with RH, while droplet fading time increased with both droplet size and RH. Despite 450 µm droplets having greater maximum coverage area than 250 µm droplets, the larger droplets had higher fading rates and lower ratios of maximum coverage area to droplet volume. Droplet maximum coverage area and fading time on leaves were affected by adding spray adjuvants to the herbicide-only solution. The Uptake surfactant was more effective than the other two surfactants (AntiEvap+BS1000 and Enhance) in increasing droplet maximum coverage area and fading time. Compared to the herbicide-only solution, addition of Uptake surfactant to the herbicide solution could increase maximum coverage area by 68% and 52% for 250 and 450 µm droplets, respectively, but addition of AntiEvap+BS1000 or Enhance surfactants did not show significant increase. Similarly, addition of Uptake surfactant to the herbicide-only solution increased droplet fading times by 11.1% and 13.2% at 30% and 60% RH, respectively, for 250 µm droplets and by 34.7% and 2.8% at 30% and 60% RH, respectively, for 450 µm droplets. In contrast, addition of AntiEvap+BS1000 surfactant reduced fading time, and addition of Enhance surfactant did not significantly affect fading time. Therefore, appropriate selection of spray adjuvants for herbicide applications could significantly influence droplet deposit behaviors on cucurbitaceous leaves, leading to improved effectiveness of weed control. Keywords: Herbicide application, Spray deposition, Spray droplet, Surfactant, Weed control.

Influence of Broadcast Spray Nozzle on the Deposition, Absorption, and Efficacy of Dicamba plus Glyphosate on Four Glyphosate-Resistant Dicot Weed Species

AbstractDicamba-resistant soybean technology provides an additional site of action for POST control of herbicide-resistant broadleaf weeds in soybean but also raises concern of off-site movement and damage to sensitive crops in adjacent fields. Dicamba formulations approved for use on dicamba-resistant soybean require applicators to use nozzles producing large droplets to reduce the risk of spray-particle drift. The use of nozzles with relatively larger droplet spectra can reduce herbicide deposition on target weeds, especially if a filtering effect from the crop canopy occurs. Experiments were conducted to evaluate the influence of broadcast nozzle design on the deposition and efficacy of 280 g ha−1glyphosate plus 140 g ha−1dicamba applied POST to four herbicide-resistant weed species. The TTI11004 nozzle, the original nozzle labeled for dicamba applications on dicamba-resistant soybean, reduced deposition coverage and density on spray cards compared with the TT11004 and XR11004 nozzle. The AIXR11004 nozzle produces a very coarse droplet spectrum and did not reduce coverage on spray cards, though it did reduce deposition density. Herbicide solution deposition onto Palmer amaranth, tall waterhemp, giant ragweed, and horseweed ranged from 0.41 to 0.52, 0.55 to 0.87, 0.49 to 0.58, and 0.38 to 0.41 µl cm−2, respectively. Nozzle design and droplet spectrum did not influence the deposition of herbicide solution onto the target weed, as all nozzles were equivalent for all species and site-years. Herbicide efficacy was not influenced by nozzle design, as weed control and plant height reduction were similar for all species. The results of this experiment show that the use of the TTI11004 nozzle for dicamba applications to dicamba-resistant soybean will provide acceptable herbicide deposition and efficacy when applied under the label requirements of weed height and carrier volume.

Glyphosate plus 2,4-D Deposition, Absorption, and Efficacy on Glyphosate-Resistant Weed Species as Influenced by Broadcast Spray Nozzle

AbstractThe introduction of 2,4-D–resistant soybean will provide an additional POST herbicide site of action for control of herbicide-resistant broadleaf weeds. The introduction of this technology also brings concern of off-site movement of 2,4-D onto susceptible crops such as sensitive soybean and tomato. The 2,4-D formulation approved for use in 2,4-D–resistant soybean restricts application of the herbicide to nozzles that produce very coarse to ultra-coarse droplet spectrums. The use of larger droplet spectrums for broadcast applications can reduce herbicide deposition onto target weeds and thus influence herbicide efficacy. Field experiments were conducted to evaluate the influence of nozzle design on herbicide deposition onto target plants and the resulting efficacy of a POST application of 280 g ha−1glyphosate plus 280 g ha−12,4-D. The TTI11004 nozzle produced an ultra-coarse droplet spectrum and reduced coverage and deposition density on spray cards as compared with the XR11004 and TT11004 nozzles that produced medium droplet spectrums. The AIXR11004 nozzle also reduced deposition density on spray cards but did not reduce coverage. Herbicide solution deposition onto glyphosate-resistant Palmer amaranth, tall waterhemp, giant ragweed, and horseweed ranged from 0.28 to 0.72 µl cm−2and was not influenced by nozzle design. Herbicide efficacy was reduced by the TTI11004 nozzle on Palmer amaranth and horseweed compared with the AIXR11004, TT11004, and XR11004 nozzles when applications were made to either high densities of plants or plants exceeding the labeled height. The use of the AIXR11004 and TTI11004 nozzles that are listed as approved nozzles for glyphosate plus 2,4-D applications on 2,4-D–resistant soybean did not reduce herbicide deposition onto four of the most troublesome broadleaves and did not reduce herbicide efficacy when applied in conjunction with lower weed densities and smaller weeds.

Spray Drift from Dicamba and Glyphosate Applications in a Wind Tunnel

With the recent introductions of glyphosate- and dicamba-tolerant crops, such as soybean and cotton, there will be an increase in POST-applied tank-mixtures of these two herbicides. However, few studies have been conducted to evaluate drift from dicamba applications. This study aimed to evaluate the effects of dicamba with and without glyphosate sprayed through standard and air induction flat-fan nozzles on droplet spectrum and drift potential in a low-speed wind tunnel. Two standard (XR and TT) and two air induction (AIXR and TTI) 110015 nozzles were used. The applications were made at 276 kPa pressure in a 2.2 ms−1 wind speed. Herbicide treatments evaluated included dicamba alone at 560 gaeha−1 and dicamba+glyphosate at 560+1,260 gaeha−1. The droplet spectrum was measured using a laser diffraction system. Artificial targets were used as drift collectors, positioned in a wind tunnel from 2 to 12 m downwind from the nozzle. Drift potential was determined using a fluorescent tracer added to solutions, quantified by fluorimetry. Dicamba droplet spectrum and drift depended on the association between herbicide solution and nozzle type. Dicamba alone produced coarser droplets than dicamba+glyphosate when sprayed through air induction nozzles. Drift decreased exponentially as downwind distance increased and it was reduced using air induction nozzles for both herbicide solutions.

Techno-optimism as a barrier to overcoming herbicide resistance: Comparing farmer perceptions of the future potential of herbicides

The purpose of this analysis is to explore how U.S. grower perceptions of the future potential of different weed management approaches is conditioned by faith in technological fixes and how the latter is influenced by the rate and persistence of herbicide resistant weeds (HRW). We ground our analysis in rural studies literature on location and environmental sociological evaluations of techno-optimism. Using a coding typology of techno-optimism, -skepticism, and -dissonance, focus group data show that farmers in Southern states responded with more skepticism and dissonance to the potential of chemical herbicides as a solution to HRW while farmers in Northern states, where there have historically been fewer HRW, have greater optimism in the potential of chemicals to solve the problem. We conclude that (1) the presence of HRWs provides an important context for farmer ideology and (2) those working with farmers in areas with high HRW rates may be able to tap into the skepticism and dissonance farmers feel toward the future potential of chemical herbicide solutions by providing integrated weed management alternatives.

Shoreline Drizzle Applications for Control of Incipient Patches of Yellowflag Iris (Iris pseudacorus)

Yellowflag iris, native to Europe, is a rhizomatous, emergent, invasive plant found in pond margins, ditches, and other wetland sites in much of the United States. In water depths up to approximately 50 cm, it forms dense stands, which displace native sedges and rushes, reducing waterfowl habitat and water flow. The rhizomes can reach 6 m in lateral spread, making it very difficult to control by mechanical methods. In addition, conventional boom-sprayer applications are often impractical in most aquatic systems. Drizzle application is a technique for directed treatment of hard-to-reach invasive plants. It uses low volumes (26 to 104 L ha—1) of concentrated herbicide solution, applied using a spray gun emitting a thin stream of solution with an effective range of 6 m. In this study, conducted along the margins of two ponds at the University of California, Davis, we compared drizzle applications of glyphosate, imazapyr, and triclopyr to applications using a conventional boom sprayer. Although both glyphosate and imazapyr provided excellent control (> 96 %) of yellowflag iris with either treatment technique, only the drizzle treatments of imazapyr at 2.26 and 4.52% ae (10 and 20% product) at spray volumes of 52 and 26 L ha—1, respectively, were below the maximum labeled rate and still gave > 98 % control. Furthermore, a cost analysis indicated that the most economical application for effective control of yellowflag iris was a drizzle application of imazapyr at 4.52 % ae (20 % product) at 26 L ha—1. This study demonstrates that drizzle application with imazapyr can be a practical application method for yellowflag iris control in aquatic systems in which broadcast treatments with conventional boom sprayers may be difficult.

Removal of aqueous metazachlor, tembotrione, tritosulfuron and ethofumesate by heterogeneous monopersulfate decomposition on lanthanum-cobalt perovskites

This study reports LaCoO3 perovskite oxide activity in the removal of aqueous herbicides (metazachlor, tembotrione, tritosufuron and ethofumesate) by means of potassium monopersulfate (MPS) decomposition. The influence of initial MPS concentration and catalyst load have been assessed. MPS is instantaneously absorbed onto the perovskite surface where this species decomposes. Thus, MPS breakage leads to the formation of powerful oxidizing radicals which react with herbicides in solution. Tritosulfuron was the most recalcitrant compound towards this technology. Catalyst stability was tested by means of consecutive reuse cycles. No appreciable loss of activity was experienced. Experiments in the presence of tert-butyl alcohol, methanol and carbonate outlined the importance of radicals in herbicides degradation. Finally, synthetized LaCoO3 was characterized. Scanning and transmission electron microscopy showed the presence of nanosized material, mostly spherical shaped, with 15.20m2g−1 of BET area. LaCoO3 perovskite structure was corroborated by diverse techniques such as X-ray fluorescence (La:Co atomic ratio of 1:1), X-ray photoelectron spectroscopy (surface Co(III) and La(III)), and X-ray diffraction (rhombohedral LaCoO3 phase).

Coverage Area and Fading Time of Surfactant-Amended Herbicidal Droplets on Cucurbitaceous Leaves

Proper use of appropriate surfactants to control droplet behavior on leaf surfaces is critical to improving herbicide application efficacy for controlling paddy melons (). An esterified seed oil surfactant and a petroleum oil surfactant were investigated to modify spread areas and fading times of water and herbicidal droplets on watermelon leaves, which were used to simulate paddy melon leaves. A combination of two systemic herbicides (triclopyr and glyphosate) was also used to form a water-based spray solution for comparisons. The glyphosate herbicide was pre-formulated with a non-ionic surfactant. Tests were conducted with 250 and 450 I¼m sessile droplets at 30% and 60% relative humidity (RH) inside a controlled environmental chamber. The sessile droplets were produced with a single-droplet generator. Droplet fading times significantly increased with both droplet size and RH. Droplet maximal coverage areas increased only with droplet size but not RH. For the water-only solution, addition of seed oil surfactant increased the droplet coverage area by over 2.3 times, but addition of the petroleum oil surfactant did not increase the droplet coverage area. For the spray solution containing two herbicides, addition of the seed oil surfactant increased droplet coverage areas on leaves from 0.146 ±0.012 mm 2 to 0.201 ±0.014 mm 2 for 250 I¼m droplets and from 0.348 ±0.017 mm 2 to 0.537 ±0.024 mm 2 for 450 I¼m droplets. In addition, their fading times increased from 36 ±7 s to 43 ±6 s at 30% RH and from 53 ±10 s to 62 ±3 s at 60% RH for 250 I¼m droplets, and from 98 ±6 s to 107 ±5 s at 30% RH and from 145 ±5 s to 151 ±8 s at 60% RH for 450 I¼m droplets. In comparison, addition of the petroleum oil surfactant to the herbicide solution reduced the maximal coverage areas and shortened the droplet fading times but increased droplet penetration rates. Therefore, to improve spray coverage area and reduce droplet evaporation, herbicide spray solutions that already contain a surfactant could be amended with the seed oil surfactant. The petroleum oil surfactant could be used when enhancement of droplet penetration into leaf tissues is necessary.

Influence of Spray-Solution Temperature and Holding Duration on Weed Control with Premixed Glyphosate and Dicamba Formulation

Water is the primary carrier for herbicide application, and carrier-water–related factors can influence herbicide performance. In a greenhouse study, premixed formulation of glyphosate plus dicamba was mixed in deionized (DI) water at 5, 18, 31, 44, or 57 C and applied immediately. In a companion study, glyphosate and dicamba formulation was mixed in DI water at temperatures of 5, 22, 39, or 56 C and sprayed after the herbicide solution was left at the respective temperatures for 0, 6, or 24 h. In both studies, glyphosate plus dicamba was applied at 0.275 plus 0.137 kg ae ha−1(low rate), and 0.55 plus 0.275 kg ha−1(high rate), respectively, to giant ragweed, horseweed, Palmer amaranth, and pitted morningglory. Glyphosate plus dicamba applied at a low rate with solution temperature of 31 C provided 14% and 26% greater control of giant ragweed and pitted morningglory, respectively, compared to application at solution temperature of 5 C. At both rates of glyphosate and dicamba formulation, giant ragweed and pitted morningglory control was 15% or greater at solution temperature of 44 C compared to 5 C. Weed control was not affected with premixture of glyphosate and dicamba applied ≤ 24 h after mixing herbicide. When considering solution temperature, glyphosate and dicamba applied at low rate provided 13 and 6% greater control of Palmer amaranth and pitted morningglory, respectively, with solution temperature of 22 C compared to 5 C. Similarly, giant ragweed control was 8% greater with solution temperature of 39 C compared to 5 C. Glyphosate and dicamba applied at high rate provided 8% greater control of giant ragweed at solution temperature of 22 or 39 C compared to 5 C. Therefore, activity of premixed glyphosate and dicamba could be reduced with spray solution at lower temperature; however, the result is dependent on weed species.