Leaching of Alachlor from Alginate-Encapsulated Controlled-Release Formulations

The mobility of alachlor from alginate-encapsulated controlled-release (CR) formulations was investigated in two contrasting soil profiles. Two CR formulations of alachlor were prepared with the following components (1) base—sodium alginate+kaolin+‘Tween’ 20 (1+10+0·5 by mass) and (2) base+40 g kg⁻¹ linseed oil. These were compared to technical grade alachlor and to a commercial alachlor EC formulation (‘Lasso’ 4EC). All herbicide treatments were labeled with [¹⁴C]alachlor and were applied to duplicate soil columns that were composed of a surface and a subsoil horizon. Each horizon was packed to a depth of 12·5 cm, giving a total column length of 25 cm. The columns were leached with 21 cm (420 ml) to 30 cm (600 ml) of 0·01M calcium chloride for a period of 7 to 10 days. Alachlor leaching from the EC formulations was the same as that from the technical material in both soils: 33% in the Evesboro and 10% in the Conover soil. The CR-Oil formulation leached 4 and 2% of the applied [¹⁴C]alachlor, compared to 12 and 3% for the CR-N formulation for the Evesboro and Conover soils, respectively. The CR-Oil formulation also increased the amount of [¹⁴C]alachlor retained in the soil surface horizon (105–114%), compared to CR-N (39–45%), technical material (14–23%) and EC (12–17%).     

Release of atrazine and alachlor from clay-oxamide controlled-release formulations

Controlled-release herbicide formulations have been shown to decrease the leaching potential of several herbicides under laboratory and field conditions. The utility and efficacy of these formulations may be improved by combining several herbicides and a fertilizer source in a single formulation. The objective of these studies was to develop granular alginate formulations that were composed of a combination of the herbicides atrazine and alachlor with the slow-release nitrogen source oxamide (ethanediamide). Controlled release of the herbicides was obtained by addition of selected minerals, including calcium bentonite, fine-grind bentonite, montmorillonite K10, kaolinite and iron (III) oxide. A formulation without clay was used as a comparison. The formulations tested had herbicide active ingredient contents ranging from ∽0·02 to 0·54% and a nitrogen content of 21%. Release of the herbicides was studied by equilibrating the formulations with deionized water on a rotary shaker at 200 rev min^-1 and sampling at regular time intervals up to 104 hours. The minerals used in the different formulations influenced the herbicide active ingredient composition, as well as the release properties of the individual formulations. The atrazine content of the formulations decreased in the order calcium bentonite>fine-grind bentonite>kaolinite>montmorillonite=iron oxide>no clay. For alachlor the content decreased in the order of calcium bentonite>fine-grind bentonite>montmorillonite>iron oxide>kaolinite>no clay. Controlled release of atrazine (i.e. reduction in release rate) varied in the order calcium bentonite>iron oxide>montmorillonite>fine-grind bentonite= kaolinite>no clay, and for alachlor fine-grind bentonite>calcium bentonite>montmorillonite>no clay=kaolinite=iron oxide. A certain percentage of the applied active ingredient of both alachlor and atrazine was not recovered. From 5 to 27% of the active ingredient was not released, with the greatest retention by the bentonite formulations. Release of nitrogen was not strongly influenced by mineral type, although a trend indicated greater release with formulations containing kaolinite. © 1998 SCI     

Use of bentonite and humic acid as modifying agents in alginate-based controlled-release formulations of imidacloprid

In order to prepare a formulation to be used for controlled release, imidacloprid was incorporated into alginate granules by using calcium chloride as gellant. The formulation prepared (alginate–imidacloprid–water) was modified by the addition of different sorbents. The effects on release rate of the addition of natural bentonite desiccated at 105 °C, untreated, acid-treated with sulfuric acid solutions over a concentration range between 0.5 mol dm⁻³ and 2.5 mol dm⁻³, and a commercial humic acid, were studied by immersion of the granules in water under static conditions. The time taken for 50% of the active ingredient to be released into water, (T₅₀), was calculated from the data obtained. On the other hand, the sorption–desorption processes of imidacloprid from a 0.01 M aqueous calcium chloride solution at 25 °C, by natural, acid-treated bentonite samples, and humic acid, have been studied by using batch experiments in order to evaluate the potential of these materials for their application in controlled-release formulations of pesticides. The experimental data have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f). K_f values ranged from 1.76 mg kg⁻¹ for the untreated bentonite up to 126.9 mg kg⁻¹ for the humic acid. A correlation study was performed with T₅₀, the surface area (S) and the Freundlich parameter (K_f) of the bentonite samples in order to know the factors that affect release rate of imidacloprid from bentonite granules. A linear correlation of the T₅₀ values and both S and K_f parameters was observed. © 1999 Society of Chemical Industry     

Controlled release of isoproturon from an alginate–bentonite formulation: water release kinetics and soil mobility

The herbicide isoproturon [3‐(4‐isopropylphenyl)‐1,1‐dimethylurea] was incorporated in alginate‐based granules to obtain controlled‐release (CR) properties. The basic formulation (sodium alginate (1.87%)–isoproturon (0.67%) in water) was modified by addition of different sorbents. The effect on isoproturon release rate, modified by the incorporation of natural and acid‐treated bentonite in alginate formulation, was studied by immersion of the granules in water while shaking. The release of isoproturon was diffusion‐controlled. The time taken for 50% of the active ingredient to be released into water, T₅₀, was longer for those formulations containing added bentonite (5.98 and 7.43 days, for natural and acid‐treated (1 M H₂SO₄) bentonite, respectively) than for the preparation without bentonite (3.78 days). The mobilities of non‐formulated technical grade (98%) and formulated isoproturon were compared using soil columns. The use of alginate‐based CR formulations containing bentonite reduced isoproturon movement compared with the technical product. Sorption capacity of the soil for isoproturon was measured using batch experiments (0.29 litre kg⁻¹) and the results obtained here in agreement with those obtained under dynamic conditions. © 2000 Society of Chemical Industry     

Reduced metribuzin pollution with phosphatidylcholine-clay formulations

BACKGROUND: Metribuzin is a widely used herbicide that has been identified as a groundwater contaminant. In this study, slow‐release formulations of metribuzin were designed by encapsulating the active ingredient in phosphatidylcholine (PC) vesicles and adsorbing the vesicles onto montmorillonite. RESULTS: The maximum active ingredient content in the slow‐release formulations was 246 g kg^?1. Infrared spectroscopy results revealed that the hydrophobic interactions between metribuzin and the alkyl chains on PC were necessary for encapsulation. In addition, water bridges connecting the herbicide and the PC headgroup enhanced the solubility of metribuzin in PC. Adsorption experiments in soils were performed to evaluate the relationship between sorption and leaching. Funnel experiments in a sandy soil revealed that the herbicide was not irreversibly retained in the formulation matrix. In soil column experiments, PC–clay formulations enhanced herbicide accumulation and biological activity in the top soil layer relative to a commercial formulation. PC–clay formulations also reduced the dissipation of metribuzin by a factor of 1.6–2.5. CONCLUSIONS: A reduction in the recommended dose of metribuzin can be achieved by employing PC–clay formulations, which reduces the environmental risk associated with herbicide applications. Moreover, PC and montmorillonite are non‐toxic and do not negatively affect the environment. Copyright © 2010 Society of Chemical Industry     

Movement of metolachlor in soil: effect of new organo-clay formulations

The use of commercially available formulations of metolachlor has resulted in its leaching and migration to water sources. Formulations of metolachlor designed to reduce its leaching in soil have been prepared by adding the herbicide dissolved in an organic solvent or in water to organo-clay complexes. Best formulations were made when the organo-clay complex was formed by adsorbing the monovalent organic cations benzyltrimethylammonium (BTMA) or benzyltriethylammonium (BTEA) onto sodium montmorillonite (Mont) at 0.5 or 0.8 mole kg⁻¹ clay. Adsorption of metolachlor to organo-clays followed the sequence Mont-BTMA 0.5 > Mont-BTMA 0.8 > Mont-BTEA 0.8 > Mont-BTEA 0.5 > Mont. Fourier transform infrared (FTIR) analysis demonstrated the occurrence of shifts of several peaks of adsorbed metolachlor relative to the free herbicide, indicating the existence of strong interactions between metolachlor molecules and the organo-clay surface. Leaching studies employing organo-clay and commercial formulations were carried out under greenhouse and field conditions. Metolachlor applied as organo-clay formulations leached less than the commercial formulation. Organo-clay formulations prepared by adding the herbicide as a water solution showed less leaching in the soil profile than those made by using organic solvent. Under greenhouse conditions, the herbicidal activity of organo-clay formulations was similar to that of the commercial one. Under field conditions, leaching from Mont-BTMA 0.5-metolachlor was less than that from the commercial formulation, demonstrating the environmental and agricultural advantages of the organo-clay formulations of metolachlor. © 1999 Society of Chemical Industry     

控制释放制剂的组成对异丙甲草胺释放速率的影响

将海藻酸盐与膨润土复合作为载体制备除草剂异丙甲草胺的控制释放制剂,研究了载药量、载体原料配比、膨润土类型等制剂组成因素对异丙甲草胺释放速率的影响。采用Ritger和Peppas方程分析释放动力学过程,计算50%的异丙甲草胺被释放所需时间(t50),并以此表征释放速率。结果表明,采用海藻酸盐/膨润土复合载体时, t50随载药量和载体原料配比不同介于29.4~68.0 h 之间,控制释放效果明显优于单纯以有机改性膨润土作载体(t50=5.9 h)。将有机改性膨润土与海藻酸盐复合作载体时,t50可达110 h。释放动力学方程的n值(0.436~0.496)接近Fickian扩散模型,说明该控制释放制剂中异丙甲草胺的释放过程主要受到扩散控制。     

Bioefficacy and leaching of controlled-release formulations of triazine herbicides

Conventional formulations of atrazine and simazine were compared with controlled-release formulations of these two herbicides for bioefficacy, leaching and crop safety in laboratory and field experiments. Three light-textured soils with a pH range of 5.8–8.5 were used for this work. An oat bioassay (Avena sativa L.) was used to quantify soil concentrations of the herbicides. Comparison of the initial bioefficacy of controlled-release formulations of atrazine and simazine showed their respective relative potencies to conventional formulations to be 0.51–0.85. The results indicated that the controlled-release formulations maintained an entrapped reserve of active ingredient after delivery with a conventional boomsprayer. In laboratory trials, the controlled-release formulations showed a reduction in leaching compared with conventional formulations. A controlled-release formulation and a conventional formulation of atrazine were tested further in a field trial. A higher concentration of atrazine in topsoil from the controlled-release formulation was observed 11 weeks after application after 107 mm of rainfall. It was deduced that this was caused by reduced leaching of the controlled-release formulation, as observed in laboratory trials. EWRC scores for the control of a range of grass and broad-leaved weeds were identical for both formulations. This indicated that, while the controlled-release formulation could inhibit leaching of the active ingredient, it did not hinder the level of potency necessary for early weed control. EWRC crop safety ratings of chickpeas (Cicer arietinum L.) sown at application were higher for the controlled-release formulation 10 weeks after sowing, and subsequent harvest yields were 50% higher. It was inferred that this resulted from a favourable interaction between crop growth and the timing of the release of the active ingredient from the controlled-release formulation. Altogether, the controlled-release formulations displayed the necessary prerequisites for their further development for large-scale use under arable regimes.     

The release of cyanatryn from a controlled-release formulation into flowing water

The problem of maintaining a sufficient concentration of the herbicide cyanatryn in flowing water for a sufficient time to control aquatic weeds has been solved by using a controlled-release pellet formulation. The rate of release of the herbicide depends primarily on the rate of diffusion within the clay matrix and is a function of the formulation ingredients and the degree of compaction achieved during manufacture. Release appears to be independent of water velocity but the concentration produced downstream of the application point depends on the volume of water flowing in unit time and the mass of herbicide used.     

Some physicochemical factors influencing foliar uptake enhancement of glyphosatemono(isopropylammonium) by polyoxyethylene surfactants

Structure-concentration–foliar uptake enhancement relationships between commercial polyoxyethylene primary aliphatic alcohol (A), nonylphenol (NP), primary aliphatic amine (AM) surfactants and the herbicide glyphosatemono(isopropylammonium) were studied in experiments with wheat (Triticum aestivum L.) and field bean (Vicia faba L.) plants growing under controlled-environment conditions. Candidate surfactants had mean molar ethylene oxide (EO) contents ranging from 5 to 20 and were added at concentrations varying from 0·2 to 10 g litre^?-1 to [¹⁴C]glyphosate formulations in acetone–water. Rates and total amounts of herbicide uptake from c. 0·2–μl droplet applications of formulations to leaves were influenced by surfactant EO content, surfactant hydrophobe composition, surfactant concentration, glyphosate concentration and plant species, in a complex manner. Surfactant effects were most pronounced at 0·5 g acid equivalent (a.e.) glyphosate litre^?-1 where, for both target species, surfactants of high EO content (15–20) were most effective at enhancing herbicide uptake: surfactants of lower EO content (5–10) frequently reduced, or failed to improve, glyphosate absorption. Whereas, at optimal EO content, AM surfactants caused greatest uptake enhancement on wheat, A surfactants gave the best overall performance on field bean; NP surfactants were generally the least efficient class of adjuvants on both species. Threshold concentrations of surfactants needed to increase glyphosate uptake were much higher in field bean than wheat (c. 2 g litre^?-1 and < 1 g litre^?-1, respectively); less herbicide was taken up by both species at high AM surfactant concentrations. At 5 and 10 g a.e. glyphosate litre^?-1, there were substantial increases in herbicide absorption and surfactant addition could cause effects on uptake that were different from those observed at lower herbicide doses. In particular, the influence of EO content on glyphosate uptake was now much less marked in both species, especially with AM surfactants. The fundamental importance of glyphosate concentration for its uptake was further emphasised by experiments using formulations with constant a.i./surfactant weight ratios. Any increased foliar penetration resulting from inclusion of surfactants in 0·5 g litre^?-1 [¹⁴C]glyphosate formulations gave concomitant increases in the amounts of radiolabel that were translocated away from the site of application. At these low herbicide doses, translocation of absorbed [¹⁴C]glyphosate in wheat was c. twice that in field bean; surfactant addition to the formulation did not increase the proportion transported in wheat but substantially enhanced it in field bean.     

Optimisation of a semiochemical slow-release alginate formulation attractive towards Aphidius ervi Haliday parasitoids

BACKGROUND: Optimisation of alginate formulations is described in order to develop semiochemical (E-β-farnesene and E-β-caryophyllene) slow-release devices in biological control approaches by attracting predators and parasitoids of aphids. Various formulation criteria were optimised with respect to semiochemical encapsulation capacity. Moreover, the optimised formulation was characterised by texturometry and confocal microscopy. The slow-release rates of semiochemicals were calculated in laboratory controlled conditions. The attractiveness of semiochemical formulations towards Aphidius ervi was demonstrated by olfactometry. RESULTS: Two major parameters were highlighted in encapsulation optimisation: the type of alginate (Sigma L) and the type of crosslinker ion (Ca²⁺). Other formulation parameters were optimised: ionic strength (0.5 M), Ca²⁺ (0.2 M) and alginate (1.5%) concentrations and the maturation time of beads in CaCl₂ solution (48 h). After physical characterisation of beads, semiochemical slow-release measurements showed that alginate formulations were efficient sesquiterpene releasers, with 503 µg of E-β-farnesene and 1791 µg of E-β-caryophyllene totally released in 35 days. The efficiency of semiochemical alginate beads as attractants for female parasitoids was demonstrated, with high percentages of attraction for semiochemical odours (88 and 90% for E-β-farnesene and E-β-caryophyllene respectively) and significant statistical results. CONCLUSION: Semiochemical alginate beads can be considered as efficient slow-release systems in biological control. These formulations could be very useful to attract aphid parasitoids on crop fields. Copyright © 2011 Society of Chemical Industry     

Effect of Relative Humidity on Sporulation of Fusarium oxysporum in Various Formulations and Effect of Water on Spore Movement Through Soil

ABSTRACT Fusarium oxysporum f. sp. erythroxyli is being investigated as a mycoherbicide for the narcotic plant coca. Sporulation of the fungus in seven formulations containing different organic substrates and movement of its propagules through soil were studied. The formulations were a granular wheat flour/kaolin (pesta); an extruded wheat and rice flour (C-6); and five alginate pellet products containing corn cobs, soybean hull fiber, canola meal, rice flour, or rice flour plus canola oil. Formulations were incubated at 25 degrees C for 6 weeks in desiccators with various salt solutions to provide nine relative humidities (RH), ranging from 100% (pure deionized water) to 0% (anhydrous (CaSO(4)). Hyphae of F. oxysporum f. sp. erythroxyli grew out of alginate pellets with canola meal, rice, and rice plus canola oil as early as 24 h at 100% constant RH. Alginate pellets of rice plus canola oil and granular C-6 and pesta formulations consistently produced more microconidia, macroconidia, and CFU than the other four formulations at all RH tested. The C-6 formulation produced more propagules than the other formulations at low RH (<53%). Canola meal pellets produced more spores than three other formulations when exposed to fluctuating RH (100 to 75%). The effect of percolating water on spore movement through soil was studied using a plant-pathogenic isolate of F. oxysporum f. sp. niveum. To determine the effect of water percolation on propagule movement, formulations were placed on soil columns and artificial rain was applied. In general, 10-fold fewer CFU were recovered at a 8- to 10-cm depth compared with a 0- to 2-cm depth.     

Formulation selection,and investigation of azadirachtin-A persistence in some terrestrial and aquatic components of a forest environment

Five commercial formulations of azadirachtin-A (AZ-A) Margosan-O^®, Azatin-EC^®, Neem-EC^®, RH-9999 and Neemix^® 4.5, were investigated for their volatilization and washoff potential in laboratory studies. Prior to the investigation, RH-9999 (a wettable powder) was mixed with water to provide an end-use formulation containing 35·6 g AZ-A kg^-1, while the remaining four formulations were investigated without dilution. Volatilization and washoff of AZ-A occurred more from white spruce foliage than from wax-coated glass plates. Neem-EC provided the lowest amount of loss, whereas Margosan-O provided the highest. Physical properties and atomization behaviour of the five formulations indicated that Azatin-EC was highly viscous and caused phase separation in droplets collected on glass plates after atomization in a rotary atomizer. RH-9999, despite its low viscosity, caused phase separation in droplets because of the heterogeneity of the wettable powder formulation. Based on the minimum loss of AZ-A due to volatilization and washoff from spruce foliage, and on the minimum potential for phase separation in droplets after atomization in a rotary atomizer, Neem-EC was considered to be the most appropriate choice for use in field studies to investigate environmental persistence and fate of AZ-A in terrestrial and aquatic matrices of a forest ecosystem. The Neem-EC formulation was sprayed at 40 and 80 g AI ha^-1 over single spruce trees and on litter and soil plots selected in a mixed-wood boreal forest in Ontario, Canada. In addition, outdoor aquaria containing stream water and sediment were also fortified with the formulation at 400 and 800 g AI ha^-1. Persistence of AZ-A was evaluated using one-year-old spruce needles, current-year shoots, spruce bark, litter, soil, stream water and sediment. The duration of persistence varied from 3 to 6 days in terrestrial matrices, whereas it ranged from 8 to 13 days in water, and 2 to 3 days in sediment. The half-life (DT₅₀) values ranged from 10·7 h (for soil) to 71·6 h (for spruce bark) at the lower dosage rate, and from 18·8 h (for litter) to 76·2 h (for bark) at the higher dosage rate. The DT₅₀ value for stream water was about 35 h regardless of the dosage rate applied. The data indicated that AZ-A was appreciably labile and short-lived in different forestry matrices, with low DT₅₀ values. © 1997 SCI     

Relation between volatility rating and composition of phenoxy herbicide ester formulations

A CIPAC/AOAC test with tomato plants is used to specify the volatility ratings of herbicide ester formulations. This work compares the tomato plant test with an alternative chemical one. The concentrations of esters and the effective molecular weight and density of each formulation were used with the ester vapour pressures to calculate its herbicide vapour pressure as complete, and evaporated formulations. The range was from 28.8 mPa (at 257deg;C) for a mixture of 2,4–D esters to 0–07 mPa (at 25°C) for a 2,4,5–T-(iso-octyl) formulation, as complete formulations, and 35-5 and 0–16 mPa (at 25°C) as evaporated ones. A value of 0–6 mPa (at 25°C) was selected on the basis of the tomato plant test as the cut-off area for low-volatile esters and is recommended to be included in specifications for herbicide esters. Formulations with a herbicide vapour pressure above 3.3 mPa (at 25°C) are high-volatile ones according to the tomato plant test, while between 0–6–3.3 mPa (at 25°C) is a borderline region where the test gives mixed results. Levels of 2,4–D-ethyl and methyl were added to pure 2–ethylhexyl esters of 2,4–D and a 2,4,5–T-(iso-octyl) formulation to find what level of contamination would change the rating of these esters from low to high volatile. Formulations of 2,4–D-(iso-octyl) should not contain more than 11 g litre^?1 2,4–D as methyl ester or 2.0 g litre^?1 2,4–D as ethyl ester. Formulations of 2,4,5–T-(iso-octyl) should not contain more than 26 g litre^?1 2,4–D as methyl ester or 4.7g litre^?1 2,4–D as ethyl ester.     

Formulation affecting alachlor efficacy and persistence in sandy soils

BACKGROUND: The development of controlled‐release formulations of alachlor to extend the period of weed control was studied. This extended duration reduces the need for high herbicide application rates that could lead to environmental contamination. For this purpose, the influence of formulation, as well as the influence of soil characteristics, on alachlor efficacy and persistence in soil of a commercial formulation (CF) and different ethylcellulose microencapsulated formulations (MEFs) was evaluated. RESULTS: Higher alachlor rates yielded an enhanced initial herbicidal activity. The prolonged release of alachlor provided by the MEFs resulted in a higher herbicidal efficacy and a longer period of weed control compared with the effects of CF in the two soils tested (at 40 days after treatment, oat growth inhibition for CF and MEFs was 1.96% and 93.5% respectively). Soil characteristics strongly influenced alachlor efficacy and weed control by MEFs. The highest alachlor efficacy and persistence were observed in the soil with lowest microbial activity and clay and organic matter content. CONCLUSIONS: The use of MEFs can be advantageous because they permit the maintenance of the desired concentration of the herbicide in the soil for longer periods of weed control. Copyright © 2009 Society of Chemical Industry     

Green nanoemulsion‐laden glyphosate isopropylamine formulation in suppressing creeping foxglove (A. gangetica), slender button weed (D. ocimifolia) and buffalo grass (P. conjugatum)

BACKGROUND: Pesticides are developed with carriers to improve their physicochemical properties and, accordingly, the bioefficacy of the applied formulation. For foliar‐applied herbicide, generally less than 0.1% of the active ingredient reaching the target site could reduce pesticide performance. Recently, a carrier of nanoemulsion consisting of oil, surfactant and water, with a particle size of less than 200 nm, has been shown to enhance drug permeability for skin penetration in pharmaceutical delivery systems. In the present work, the aim was to formulate a water‐soluble herbicide, glyphosate isopropylamine (IPA), using a green nanoemulsion system for a biological activity study against the weeds creeping foxglove, slender button weed and buffalo grass. RESULTS: The nanoemulsion formulations displayed a significantly lower spray deposition on creeping foxglove (2.9–3.5 ng cm^?2), slender button weed (2.6–2.9 ng cm^?2) and buffalo grass (1.8–2.4 ng cm^?2) than Roundup^® (3.7–5.1 ng cm^?2). The visible injury rates of weeds treated with the nanoemulsion formulations were statistically equivalent to those relating to Roundup^® at 14 days after treatment, with a control range of 86.67–96.67%. CONCLUSION: It was hypothesised that the significant difference in spray deposition with equal injury rates can be attributed to enhanced bioactivity of the nanoemulsion formulations. This initial discovery could be the platform for developing better penetration of agrochemical formulations in the future. Copyright © 2012 Society of Chemical Industry     

Evaluation of two controlled-release 2,4-D formulations for control of Myviophyllum spicatum L.*

The controlled release herbicide delivery system 2,4-dichlorophenoxy-acetic acid/poly(glycidyl methacrylate) was evaluated for control of Myriophyllum spicatum L. Release profiles were constructed for the release of 2,4-dichlorophenoxy-acetic acid (2,4-D) from two polymer formulations into a reconstituted fresh water (pH 8). Herbicide was released with rates averaging 1.2 and 4.0 mg 2,4-D g-1polymer day-1 over the 112-day experiment, depending on the molecular weight of the glycidyl methacrylate precursors used in the preparation of the formulation. A formulation evaluated in a flowing water apparatus was effective for control of M. spicatum when treatment of the polymer was made with amounts calculated to maintain a herbicide concentration in the water of 0.08 mg 1^?1 or higher. The same 2,4-D polymer treated at 88 kg ae ha^?1 provided extended control of M. spicatum in a 5-month study in replicated outdoor pools with water flow adjusted to provide one volume change every 24 h. Evaluation de 2 formulations de 2,4-D à libération progressive pour la lutte contre Myriophyllum spicatum L. Le mécanisme de libération progressive du poly-(glycidyl methacrylate) acide 2,4-dichlorophen-oxyacétique a étéévalué dans le cadre de la lutte contre‘Myriophyllum spicatum L'. Des profils de libération ont étéétablis à partir de la libération de l'acide 2,4-dichlorophenoxyacétique (2,4-D) à partir de deux formulations polymerisées en suspension aqueuse (pH 8). L'herbicide était libéré avec des taux atteignant 1,2 et 4 mg de 2,4-D/gramme de polymère/jour pendant les 112 jours de l'expérimentation, en relation avec le poids moléculaire des précurseurs du glycidyl methacrylate utilisé pour la préparation de la formulation. Une formulation testée avec un appareil à courant d'eau s'est révélée efficace pour détruire M. spicatum quand le traitement était fait avec des quantités telles que soit maintenue une concentration d'au moins 0,08 mg/d'herbicide/litre d'eau. Le même 2,4-D polymérisé, appliquéà 88 kg/ha a permis une destruction prolongée de M. spicatum pendant les 5 mois de l'étude dans des bassins extérieurs avec un courant d'eau ajusté pour assurer un changement de volume par 24 heures. Untersuchung von zwei 2,4-D-Formulierungen mit kontrollierter Wirkstofffreisetzung zur Bekämpfung von Ähren-Tausendblatt (Myriophyllum spicalum L.) Die kontrollierte Wirkstofffreisetzung von 2,4-Dichlorphenoxyessigsäure aus Polyglycid-meth-acrylsäureester-Formulierungen wurde bei der Bekämpfung von Myriophyllum spicatum untersucht. Der Wirkstoff wurde dabei aus 2 Formulierungen mit unterschiedlichen Polymeren in Frischwasser (pH = 8) mit 1,2 und 4,0 mg 2,4-D g^?1 Polymer pro Tag während der Versuchsdauer von 112 Tagen freigesetzt. Die jeweilige Menge hing vom Molekulargewicht des in den Formulierungen eingesetzten Methacrylsäureesters ab, um in dem Durchfluss-System eine Herbizidkonzentration von mindestens 0,08 mg 1^?1 zur Bekämpfung der Pflanzen zu gewährleisten. Mit denselben 2,4-D-Formulierungen konnte in Freilandbecken (mit einmaligem Wasseraustausch innerhalb 24 Stunden) Myriophyllum spicatum mit 88 kg AS ha-1 bekämpft werden (Versuchsdauer: 5 Monate: mit Wiederholung).     

A scanning electron microscope study of glyphosate deposits in relation to foliar uptake

The effects of several formulations on foliar uptake of glyphosate, and on the morphology of glyphosate deposits on leaves, were examined in Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.). [¹⁴C]glyphosate, in the form of the free acid or the isopropylamine salt (IPAS), was applied to foliage alone or with various adjuvants. Uptake of all glyphosate IPAS formulations was greater than that of the corresponding acid formulation. Addition of ‘Tween 20’ enhanced the uptake of glyphosate IPAS compared to glyphosate alone, but had no effect on the uptake of glyphosate acid. Ammonium sulfate and the ‘Roundup’ formulation blank increased the uptake of glyphosate acid and IPAS to 2-3 times that of herbicide alone. Surface deposits, as observed by scanning electron microscopy, varied with the formulation of the herbicide, although there were no differences between the acid and IPAS formulations. Glyphosate alone initially formed a deposit with both crystalline and smooth, amorphous areas. Later in the treatment period (48 and 72 h after application), the deposit was almost entirely crystalline. The addition of ‘Tween 20’ or of formulation blank resulted in the formation of a more amorphous, non-crystalline deposit. Herbicide solutions containing ammonium sulfate dried to form a highly crystalline deposit. However, crystals similar to those of glyphosate alone were not visible in these deposits. The ability of these adjuvants to prevent or delay crystal formation may play a role in their enhancement of herbicide uptake.     

Surfactant and salt affect glyphosate retention and absorption

The influence of nonylphenoxy surfactants and glyphosate salt formulation on spray retention, phytotoxicity and [¹⁴C]glyphosate uptake was investigated in wheat (Triticum aestivum L). and Kochia scoparia L. The amount of spray retained, and uptake of [¹⁴C]glyphosate increased with increasing hydrophilic-lipophilic balance (HLB) value of surfactants. The volume of spray delivered to the plant treatment area and retained by wheat and K. scoparia plants increased with increasing surfactant HLB values, but this only partly accounted for the higher spray retention. Spray retention by leaves of plants was not affected by calcium chloride, either alone or with ammonium sulphate in the glyphosate spray solution. [¹⁴C]Glyphosate absorption by wheat and K. scoparia was reduced by calcium chloride alone, but not in mixtures with ammonium sulphate, regardless of surfactant. Phytotoxicity and uptake of glyphosate salt formulations for wheat was: isopropylamine > ammonium > sodium > calcium; these results indicate that the surfactant selected is important to maintain glyphosate efficacy and that sodium and calcium cations antagonize glyphosate by forming salts that are absorbed less than commercial isopropylamine formulations.     

Green nano-emulsion intervention for water-soluble glyphosate isopropylamine (IPA) formulations in controlling Eleusine indica (E. indica)

This article describes the development of environmentally friendly nano-emulsion system for water-soluble herbicide application. Pseudoternary phase diagrams were established in the emulsion system of fatty acid methyl esters (FAMEs)/alkylpolyglucosides (APG) and/or 3-(3-hydroxypropyl)-heptamethyltrisiloxane (organosilicone)/water encompassed with 41% (w/w) glyphosate isopropylamine (IPA) as herbicide active. Pre-formulations were selected from isotropic (L) region in the phase diagrams and their emulsion system characteristics were determined. The microemulsion systems were chosen and then dispersed into water using low-energy stirring method (200 rpm for 5 min). Oil-in-water (O/W) nano-emulsions were formed with particle sizes of diameter less than 200 nm. The nano-emulsion systems showed significantly lower surface tension than a commercial formulation (Roundup®). In the biological application study, treatments of nano-emulsion formulations and Roundup® were applied on narrow-leaved weed Eleusine indica. Multiple doses of glyphosate IPA of the treatments were applied for the construction of dose-response curves for determination of effective dose (ED₅₀). The nano-emulsion formulation showed lower ED₅₀ was 0.40 kg a.e./ha in controlling the weed than Roundup® was 0.48 kg a.e./ha. This finding suggested that the possibility of using nano-emulsion system to increase penetration and uptake of glyphosate IPA.