WO2024054795A1

WO2024054795A1 - Microencapsulated oxadiazon formulations

Info

Publication number: WO2024054795A1
Application number: PCT/US2023/073466
Authority: WO
Inventors: Aileen SHIEH; Bruce Spesard; Junhua Zhang
Original assignee: Discovery Purchaser Corporation
Priority date: 2022-09-06
Filing date: 2023-09-05
Publication date: 2024-03-14

Abstract

The present invention relates to compositions comprising encapsulated oxadiazon, methods for the preparation of such compositions as well as uses of compositions comprising encapsulated oxadiazon for weed control.

Description

MICROENCAPSULATED OXADIAZON FORMULATIONS

TECHNICAL FIELD OF THE INVENTION

[0001] The present disclosure relates to an herbicidal composition comprising microencapsulated oxadiazon, a method for the manufacture of such herbicidal composition, and a use of a composition comprising microencapsulated oxadiazon for controlling undesirable vegetation.

BACKGROUND OF THE INVENTION

[0002] The herbicide oxadiazon (3-(2,4-dichlor-5-(l-methylethoxy)phenyl)-5-(l,l- dimethylethyl)-l,3,4-oxadiazol-2(3H)-one) is a pre-emergent and early post-emergent oxadiazole herbicide that is used for selective control of grasses and annual weeds, such as crabgrass, annual bluegrass (Poa annua), or goosegrass. Oxadiazon is in particular used on turf grass, e.g. for sports grounds or in park areas. Furthermore, oxadiazon is used for weed control in paddy fields.

[0003] While oxadiazon is an effective weed control agent, it has been observed to have a phytotoxic profile upon application to the foliage, resulting in discolored turf (Johnson, Oxadiazon Treatments on Overseeded Putting-Green Turf, Weed Science, 1982, Volume 30: 335-338). Therefore, all current oxadiazon spray applications are limited to periods when the grass or turf is dormant and, thus, does not suffer from phytotoxic effects; for warm season grasses, the application is, for example, limited to winter time (approx. November to March in the Northern hemisphere). Such a limited application window is, however, not ideal in terms of effectively controlling weeds such as Poa annua. Similar limitations apply to the treatment of other useful plants or crop plants, such as paddy fields, with oxadiazon. Accordingly, there is still a need in the art to provide efficient and safe weed control compositions comprising oxadiazon. SUMMARY

[0004] According to a first aspect of the present disclosure, an aqueous herbicidal composition is provided, comprising microcapsules, the microcapsules comprising a polymer-based shell wall and a core material containing oxadiazon; and further comprising oxadiazon in free form; wherein the weight ratio of the oxadiazon in free form to the oxadiazon within the core material is between 1:50 to 1:5; and wherein the microcapsules have a median particle size (D50) range of between 1 and 10 pm.

[0005] The present disclosure provides for effective weed control while significantly reducing the phytotoxic effects that oxadiazon otherwise has. Oxadiazon is provided in two different forms in the composition, namely encapsulated and free. The encapsulated oxadiazon provides for a reduced phytotoxicity of oxadiazon, such as on turf grass, rice plants, or other crop plants. This allows that the composition can be applied when the respective turf grass, rice or other crop plant is actively growing. Also, the encapsulated oxadiazon provides for a long-term or delayed weed control. On the other hand, the free form of oxadiazon provides for adequate initial weed control, while the concentration of said free form does not exceed the phytotoxic limit.

[0006] Furthermore, the inventors found that, surprisingly, adding small amounts of free oxadiazon also provides for a physical stability to the formulation. Specifically, it was found that in formulations where 100% of the oxadiazon is encapsulated, large and elongated crystal growth is observed after 2-6 months of room temperature storage. Such large crystals would clog the spray nozzle during application and would also drastically increase formulation viscosity. Effectively, by adding nonencapsulated oxadiazon to the composition, no large crystals develop, thereby increasing the shelf-life and usability of the formulation drastically. [0007] In addition, it was found that free oxadiazon saturates the aqueous phase of the composition, thereby preventing encapsulated oxadiazon from diffusing out of the capsules prematurely.

[0008] Preferably, the microcapsules have a median particle size (D50) range of below 9 pm, further preferably of below 8 pm.

[0009] It was found that the smaller the diameter of the particles, the better is the efficiency of the composition against weeds.

[0010] Preferably, the microcapsules have a median particle size (D50) range of between 3 and 9 pm, further preferably between 5 and 7 pm.

[0011] Preferably, the weight ratio of the oxadiazon in free form to the oxadiazon within the core material is between 1:30 and 1:5, further preferably between 1:25 and 1:5.

[0012] The ratio between the encapsulated and the free oxadiazon adequately balances phytotoxicity and efficacy; also, the ratio is decisive for the stability of the composition, i.e. the suppression of large crystal growth.

[0013] Preferably, the polymer-based shell wall comprises a polymer selected from polyurea, polyurethane, polyvinylpyrrolidone, cellulose or a lipid.

[0014] Preferably, the polymer-based shell wall is formed in a polymerization reaction between an isocyanate component and an amine component.

[0015] Preferably, the amine component is a polyamine, further preferably triethylenetetramine.

[0016] Alternatively, the polymer-based shell wall is preferably formed in a polymerization reaction between an isocyanate component and an alcohol component. [0017] In a second aspect, the present disclosure provides for a method for preparing an aqueous herbicidal composition as described according to the first aspect, the method comprising the steps of:

Preparing a first phase comprising an aqueous solution of a dispersant, wherein the first phase is heated to a temperature of above 55 °C;

Preparing a second phase comprising oxadiazon, an aromatic solvent and a first polymerization reaction partner, wherein the second phase is heated to a temperature of above 55 °C;

Mixing the first and the second phase at a temperature of above 55 °C;

Adding a second polymerization reaction partner to the mixture and agitate the obtained suspension at a temperature of above 55 °C to allow curing of the polymerization reaction partners;

After curing, combining the mixture with further, nonencapsulated oxadiazon.

[0018] Preferably, the first polymerization reaction partner is an isocyanate component, and the second polymerization reaction partner is an amine or an alcohol component.

[0019] Preferably, in step a. the first phase is heated to a temperature of between 60 and 70 °C; and/or in step b. the second phase is heated to a temperature of between 60 and 70 °C and/or in step c. the mixing is performed at a temperature of between 60 and 70 °C; and/or in step d. the agitating is performed at a temperature of between 60 and 70 °C.

[0020] According to a third aspect, the present disclosure provides for a method for controlling undesirable vegetation which comprises applying to the vegetation or the locus thereof to prevent the emergence or growth of the undesirable vegetation a herbicidally effective amount of an aqueous herbicidal composition; the composition comprising: microcapsules, the microcapsules comprising a polymer-based shell wall and comprising a core material containing oxadiazon, and oxadiazon in free form.

[0021] According to the third aspect, the present disclosure also provides for a use of an aqueous herbicidal composition for controlling undesirable vegetation whereby a herbicidally effective amount of the aqueous herbicidal composition is applied to the vegetation or the locus thereof or to the soil or water to prevent the emergence or growth of the undesirable vegetation; the composition comprising: microcapsules, the microcapsules comprising a polymer-based shell wall and comprising a core material containing oxadiazon, and oxadiazon in free form.

[0022] Preferably, the herbicidally effective amount is applied by means of spraying.

[0023] Spraying proves to be most efficient in terms of weed control, as oxadiazon should form an even layer on the soil surface. Contrary thereto, granular compositions of oxadiazon would not sufficiently and/or evenly reach the soil surface.

[0024] The composition according to the present disclosure allows oxadiazon to be effectively used, e.g., for Poa annua control. Poa annua is known to be resistant to many different modes of action, but not to oxadiazon. Thereby, oxadiazon in accordance with the present disclosure can be used as a further efficient control agent, for example in combination or alternating with other agents, such as indaziflam.

[0025] Preferably, the herbicidally effective amount is applied when the undesirable vegetation is germinating and/or before the undesirable vegetation is germinating (pre-emergent application). Further preferably, the herbicidally effective amount is applied once or several times during a period when the undesirable vegetation is germinating and/or before the undesirable vegetation is germinating.

[0026] In particular, the herbicidally effective amount is applied once or several times during a time period ranging from spring to autumn, further preferably between and including April and October (Northern hemisphere), even further preferably between and including August and October (Northern hemisphere).

[0027] The time point of application can be transferred to the respective seasonal equivalent in the Southern hemisphere, i.e. the herbicidally effective amount is preferably applied once or several times during a between and including October and April (southern hemisphere), even further preferably between and including February and April (southern hemisphere).

[0028] The application may be performed while a desired vegetation, in particular turf grass or a crop plant, is actively growing.

[0029] Preferably, the aqueous herbicidal composition according to the method or use of the third aspect is an aqueous herbicidal composition according to the first aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Fig. 1 shows elongated crystals grown in sample TCI:

[0031] Fig. 2 shows mainly small crystals from the addition of free form oxadiazon in sample TC2.

DETAILED DESCRIPTION

[0032] The present disclosure is based on the finding that a combination of encapsulated oxadiazon and oxadiazon in free form provides for adequate weed control while reducing phytotoxic effects that oxadiazon may otherwise impose on the treated plants. Thereby, the composition according to the present disclosure can be applied during active growth of the useful plant, crop plant or turf grass, and for an extended time window. Importantly as well as surprisingly, the presence of oxadiazon in free form stabilizes the composition in that it inhibits large crystal growth. Thereby, the composition can be applied by means of spraying without clogging the nozzles of the respective spray apparatus. Also, applying the composition according to the present disclosure by means of spraying allows for an even coverage of the soil where the weeds are germinating.

[0033] The aqueous herbicidal composition as described herein may comprise a polymer-based shell wall that is formed in a polymerization reaction between an isocyanate component and an amine component, or an alcohol component.

[0034] The amine component can be selected from aliphatic, aromatic, cyclic and alicyclic primary and secondary diamines, and also polyamines. Examples include ethylenediamine (1 ,2), diethylenetriamine, monoisopropylamine, 4-aminopyridine (4- AP), n-propylamine, ethylene- or propylenimine-based polyaziridine, triethylenetetraamine (TETA), tetraethylenepentamine, 2,4,4'-triaminodiphenyl ether, bis(hexamethylene)triamine, ethylenediamine (EDA), trimethylenedipiperidine (TMDP), guanidine carbonate (GUCA), phenylenediamine, toluenediamine, pentamethylenehexamine, 2,4-diamino-6-methyl-l,3,5-triazine, 1,2- diaminocyclohexane, 4,4'-diaminodiphenylmethane, 1,5- diaminonaphthalenisophoronediamine, diaminopropane, diaminobutane, piperazine, aminoethylenepiperazine (AEP), polypropylene glycol) bis(2- aminopropyl ether) or o,o'-bis(2-aminopropyl)polypropylene glycol-block-polyethylene glycol-block- polypropylene glycol, hexamethylenediamine, bis(3-aminopropyl)amine, bis(2- methylaminoethyl)methylamine, 1 ,4-diaminocyclohexane, 3-amino-l- methylaminopropane, N-methylbis(3-aminopropyl)amine, 1,4-diamino-n-butane and

1 ,6-diamino-n-hexane.

[0035] Preference is given to triethylenetetraamine.

[0036] The alcohol component can be selected from primary and secondary, aliphatic and aromatic dialcohols and polyalcohols. Examples include: ethanediol, propanediol (1,2), propanediol (1,3), butanediol (1,4), pentanediol (1,5), hexanediol (1,6), glycerol and diethylene glycol.

[0037] Also amino alcohols can be used for the reaction with the isocyanate component. Examples include triethanolamine, monoethanolamine, triisopropanolamine, diisopropylamine, N-methylethanolamine, N- methyldiethanolamine.

[0038] The isocyanate component is a mono-, di- and/or polyisocyanate mixture, or a reaction product of isocyanate mixtures. Suitable components are, for example, butylene 1 ,4-diisocyanate, hexamethylene 1 ,6-diisocyanate (HDT), isophorone diisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis(4,4'-isocyanatocyclohexyl)methanes (H12-MDI) and mixtures thereof with any isomer content, cyclohexylene 1 ,4-diisocyanate, 4-isocyanatomethyloctane 1,8-diisocyanate (nonane triisocyanate), phenylene 1,4-diisocyanate, tolylene 2,4- and/or 2,6-diisocyanate (TDI), naphthylene 1,5-diisocyanate, diphenylmethane 2,2'- and/or 2,4'- and/or 4, 4'-diisocyanate (MD1), 1,3- and/or l,4-bis(2-isocyanatoprop-2- yl)benzene (TMXDI), l,3-bis(isocyanatomethyl)benzene (XDI), alkyl 2,6- diisocyanatohexanoates (lysine diisocyanates) having alkyl groups having 1 to 8 carbon atoms, and mixtures thereof. Compounds comprising modifications such as allophanate, uretdione, urethane, isocyanurate, biuret, iminooxadiazinedione or oxadiazinetrione structure and based on said diisocyanates are also suitable units for component a2), as also are polycyclic compounds, for example polymeric MDI

(pMDI, for instance PAPI-27 from Dow or Desmodur® 44V20 products from Covestro AG) and combinations of the above.

[0039] Preference is given to a hexamethylene 1,6-diisocyanate (HDI) component.

[0040] The aqueous herbicidal composition as described herein may comprise additives such as emulsifiers, protective colloids, preservatives, defoamers, cold stabilizers, thickeners, pH stabilizers and neutralizing agents.

[0041] Useful emulsifiers include standard surface-active substances present in formulations of active agrochemical ingredients. Examples include ethoxylated nonylphenols, polyethylene glycol ethers of linear alcohols, reaction products of alkylphenols with ethylene oxide and/or propylene oxide, and also fatty acid esters, alkylsulfonates, alkyl sulfates and aryl sulfates.

[0042] Useful protective colloids (dispersants) include all substances typically used for this purpose. Preferred examples include natural and synthetic water-soluble polymers such as gelatin, starch and cellulose derivatives, especially cellulose esters and cellulose ethers, such as methyl cellulose, and also polyvinyl alcohols, partly hydrolysed polyvinyl acetates, lignosulfonates (such as Borresperse® NA, REAX® 88 Kraftsperse® 25 S), modified naphthalenesulfonates (for instance Morwet D-425), polyvinylpyrrolidones and polyacrylamides.

[0043] Useful thickeners include organic thickeners and inorganic thickeners. Useful organic thickeners include organic natural or biotechnologically modified or organic synthetic thickeners. Typical synthetic thickeners are Rheostrux® (Croda) or the Thixin® or Thixatrol® series (Elementis). These are typically based on acrylates. Typical organic thickeners are based on xanthan or cellulose (for instance hydroxyethyl or carboxymethyl cellulose) or a combination thereof. Further typical representatives are based on cellulose or lignin. Preference is given to using natural modified thickeners based on xanthan. Typical representatives are, for example, Rhodopol® (Solvay) and Kelzan® (Kelco Corp.), and also Satiaxane® (Cargill).

[0044] Useful preservatives include all substances typically present for this purpose in crop protection compositions. Examples include Acticide® SPX (Thor) and Proxel® GXL (Lonza).

[0045] Useful defoamers include all substances typically usable for this purpose in crop protection compositions. For example, silane derivatives, such as poly dimethylsiloxanes, and magnesium stearate can be used. Typical products are Silcolapse® 484 (Solvay, Silioxane Emulsion) and SAG 1571 (Momentive).

[0046] Substances that function as cold stabilizers may be all of those typically usable for this purpose in crop protection compositions. Examples include urea, glycerol and propylene glycol.

[0047] Useful neutralizing agents include customary acids and bases. Examples include phosphoric acid, citric acid, sodium hydroxide solution and aqueous ammonia solution.

[0048] The aqueous herbicidal composition as described herein may be applied to turfgrass. Turf species that the described compositions can be used on include different types of grasses on golf courses, sport fields, commercial recreational areas, and sod farms.

[0049] In an aspect, the aqueous herbicidal composition as described herein may be applied to grass infested with weeds, such as annual grasses and annual broadleaf weeds.

[0050] Annual broadleaf weeds include Bittercress (Cardamine spp.), Bristly Oxtongue (Pieris echioides), Carpetweed (Mollugo verticillata), Cheeseweed (Malva parviflora), Common Groundsel (Senecio vulgaris), Common Purslane (Portulaca oleracea), Evening Primrose (Oenothera spp.), Fiddleneck (Amsinckia intermedia), Fireweed (Epilobium angustifolium), Florida Pusley (Richardia scabia), Galinsoga (Galinsoga spp.), Golden Ragwort (Senecio aureus), Lambsquarters (Chenopodium album), Liverwort (Marchantia spp.), Oxalis (Oxalis spp.), Pennsylvania Smartweed (Polygonum pensylvanicum), Petty Spurge (Euphorbia peplus), Prostrate Spurge (Euphorbia supina), Redroot Pigweed (Amaranthus retroflexus), Shepherdspurse (Capsella bursa-pastoris), Speedwell (Veronica spp.), Sow Thistle (Sonchus oleraceus), Spotted Catsear (Hypochaeris radicata), Swinecress (Coronopus didymus), and Yellow Woodsorrel (Oxalis stricta).

[0051] Annual grasses include Annual Bluegrass (Poa annua), Annual Sedge (Cyprus compressus), Bamyardgrass (Echinochloa crus-galli), Carpetgrass (Axonopus fissifolius), Crabgrass (Digitaria spp.), Fall Panicum (Panicum dichotomiflorum), Goosegrass (Eleusine indica), Green Foxtail (Setaria viridis), Ripgut Bromegrass (Bromus catharticus), and Wild Oats (Avena fatua).

[0052] In particular, the aqueous herbicidal composition as described herein may be applied to grass infested with Poa annua.

[0053] The terms used in the present disclosure are known to those skilled in the art. Otherwise, the following definitions are used:

[0054] The term “dormant” refers to a status of a plant, in which the plant experiences a period of reduced metabolic activity without dying. While being dormant, the plant uses less water and nutrients. Dormancy can be induced by cold weather for warm season turf, or by warm weather for cool season turf. Warm season turf occasionally turns brown while being dormant. [0055] The term “actively growing” refers to a status of a plant, in which the plant is effectively growing, which is typically during late spring and summer for warm season turf, and during fall or spring for cool season turf. This period is also known as “growing season”.

[0056] The term “spring” refers to the season of the year between winter and summer, covering March, April and May in the Northern hemisphere, and September, October and November in the Southern hemisphere, when the weather becomes warmer, leaves and plants start to grow again and flowers appear.

[0057] The term “summer” refers to the season of the year between spring and autumn when the weather is warmest, covering the months June, July and August in the Northern hemisphere, and December, January and February in the Southern hemisphere.

[0058] The term “autumn” refers to the season of the year between summer and winter, covering the months September, October and November in the Northern hemisphere, and March, April and May in the Southern hemisphere.

[0059] The term “winter” refers to the season between autumn and spring, covering December, January and February in the Northern hemisphere, and June, July and August in the Southern hemisphere, when the weather is coldest.

[0060] The abbreviation CS stands for capsule suspension. The abbreviation SC stands for suspension concentrate. The abbreviation ZC stands for a mixed formulation of CS and SC.

[0061] D50 stands for the median particle size distribution. The D50 value disclosed herein is measured by means of laser diffraction, and refers to the volume (also known as Dv50). The particle size parameters are measured using a Beckman Coulter LS Particle Size Analyzer. The analyzer uses the Fraunhofer optical model to measure the distribution of particles using scattered light patterns. Arrays of photodetectors then detect and measure the scattered light.

[0062] The disclosure is further illustrated by the following examples.

[0063] The terms used in the examples below have the following meaning:

Oxadiazon tech 5-tert-butyl-3-(2,4-dichloro-5-propan-2-yloxyphenyl)-l,3,4- oxadiazol-2-one with purity of 99.7 %

Reax® 105 M highly sulfonated, low molecular weight kraft lignosulfonate dispersant with a low free electrolyte content (Ingevity)

Aromatic 200 liquid aromatic solvent (Exxon Mobile)

Desmodur N 3200 aliphatic polyisocyanate, HDI Biuret (Covestro AG) antifoam agent Agnique DFM 11 IS (BASF)

TETA Triethylenetetramine, Sigma- Aldrich

Biocide Acticide B20

Kelzan CC thickener, xanthan gum (CP Kelco)

Preparation of microencapsulated oxadiazon

Example 1: Preparation of sample TC5

[0064] Preparation of external phase: In a large beaker, 133 g water were added together with 51.6 g Reax 105 M (40 % solution), the solution was well mixed. The beaker containing the liquid was put into a 65 °C oven until the beaker and its content reached equilibrium with the oven temperature.

[0065] Preparation of internal phase: 80g of Oxadiazon tech (99.7%) was dissolved with 93g of Aromatic 200 in a separate beaker. The mixture was heated to 65 °C under continuous agitation for 30 minutes. The result was a clear solution. The temperature was maintained at 65 °C and 5.6g Desmodur N 3200 were added under continuous agitation before proceeding with the emulsification process.

[0066] Emulsification and curing process: 0.5g antifoam agent was added to the external phase and the external phase beaker was placed under the Silverson. High shear was turned on, and the content of the internal phase was poured into the external phase beaker. The mixture was allowed to shear for 2 -3 minutes and did not exceed 70 °C during the process. An emulsion with milky brown appearance was formed. The beaker was transferred from the Silverson to an overhead agitator with a regular mixing blade. The beaker was placed in a water bath set at 65 °C and the overhead agitator was turned on. 13.1g 10% TETA were added to the emulsion. The water bath temperature was maintained between 65 °C to 70 °C and continued to agitate the emulsion for 4 hours.

[0067] Stabilization: The water bath heat was turned off and the mixture was allowed to cool down to ~30°C. 0.4g Biocide and 23g of 2% Kelzan CC gel were added to the cured mixture, and continuous agitation for 20 minutes was maintained.

[0068] The median particle size D50 was 6 pm, measured by means of laser diffraction using a Beckman Coulter LS Particle Size Analyzer using a method based on CIPAC Method MT 187.

[0069] The final concentration was 20% ODZ.

Example 2: Preparation of sample TC2

[0070] 17.6 g of 34.1% ODZ SC (which is the commercial product Ronstar Flo) 2.4g water, and 80g of TC5 were combined to make a ZC sample with a final concentration of 22% ODZ. [0071] A sample TC2 was stored at room temperature over approx. 1 year and microscopic pictures were made afterwards as shown in Fig. 2. The sample mainly contained small crystals. In comparison, a sample TCI comprising only encapsulated oxadiazon (see below table 1) was stored over a similar time period and microscopic pictures were likewise generated (Fig. 1). Here, large crystal growth could be observed.

Example 3: Preparation of sample TC6

[0072] TC6 was prepared as TC5, except that 8.4 g Desmodur N 3200 and 19.6 g TETA were used. The median particle size D50 was 7 pm, measured by means of laser diffraction.

[0073] The final concentration was 20% ODZ.

Example 4: Preparation of sample TC3

[0074] 17.6 g of 34.1% ODZ SC, 2.4g water, and 80g of TC6 were combined to make a ZC sample with a final concentration of 22% ODZ.

[0075] Further test compounds were prepared according to the methods described above and summarized in the following table.

Table 1. ODZ formulations used in field and greenhouse trials

Greenhouse trials:

[0076] Greenhouse trials were conducted to test ODZ CS efficacy against problematic grass weeds including Poa annua (annual bluegrass) and Digitaria sanguinalis (large crabgrass).

[0077] The trials were arranged as a randomized complete block design with six replications of each treatment applied to 75 x 120 mm fiber flats. Flats were filled with a sand based potting mix soil (35% sand, 65% OM, pH 6.5) and seeded with Digitaria sanguinalis immediately prior to ODZ application.

[0078] Treatments were made as a spray application using a single-track spray chamber calibrated to deliver 387 L/ha carrier volume at 32 psi. Across all formulations, ODZ was applied at a rate of 2240 g ODZ/ha (2 Ibs/A), the lowest labeled rate applicable for screening. [0079] Plant count and density data were collected weekly for four weeks after application. Percent control was determined using the Abbott function by calculating the percent difference in plant count between treatments and the untreated control.

[0080] The CS formulation demonstrated excellent efficacy against the annual grass weed large crabgrass (Digitaria sanguinalis), with TCs 2 and 3 resulting in nearly 100% control from 7 to 28 days after application (Table 2). This level of control was equal to that observed with applications of Ronstar FLO, the positive control. As can be derived from Table 2, control was highest in TCs with encapsulated and free ODZ

Table 2. Efficacy of ODZ CS test compounds on large crabgrass (Digitaria sanguinalis) applied preemergence at a rate of 2240 g ODZ/ha (2 Ibs/A) in a greenhouse.

Treatment Percent control

7 DAA^y 14 DAA 21 DAA 28 DAA

Untreated 0 c⁵ 0 c O d 0 c

Ronstar FLO 99 a 100 a 100 a 100 a

TCI 40 b 53 b 73 b 62 b

TC2 97 a 98 a 100 a 99 a

TC3 96 a 97 a 99 a 98 a

TC5 50 b 87 a 95 a 95 a

TC6 0 c 10 c 11 c 9 c ^y DAA = days after application A.

Means with the same letter within a column are not significantly different at P < 0.05. Field trials 1:

[0081] Field trials were conducted to assess turfgrass tolerance to CS ODZ.

[0082] The trials were arranged as a randomized complete block design with four replications of each treatment applied to 1 x 2 m plots. The experimental area was bermudagrass (Cynodon dactylon) maintained as a golf course fairway.

[0083] Treatments were made to actively growing turfgrass during autumn (October) in Clayton, NC, a timing typical for Poa annua control, as a spray application using a hand boom calibrated to deliver 387 L/ha. Across all formulations, ODZ was applied at a rate of 3366 g ODZ/ha (3 lbs/ A), the highest labeled rate applicable for screening.

[0084] Turfgrass quality and phytotoxicity data were visually rated 4, 7, 14, and 28 days after application.

[0085] The CS formulation resulted in a > 50% reduction in phytotoxicity compared to Ronstar FLO (Table 3). Phytotoxicity was most reduced in TCs without free ODZ (TC5 and 6). However, the TCs with the greatest demonstrated efficacy on weeds (TCs 2 and 3) still limited phytotoxicity to approximately 10%.

Table 3. Tolerance of actively growing bermudagrass (Cynodon dactylon L. Pers.) to ODZ

CS test compounds applied at a 3366 g ODZ/ha (3 lb/ A) rate in the field.

Treatment Percent phytotoxicity

4 DAA^y 7 DAA 14 DAA 28 DAA

Untreated 0 c^x 0 c 0 d 0

Ronstar FLO 20 a 24 a 28 a 0

TC2 10 b 11 b 13 b 0

TC3 10 b 10 b 11 b 0

TC7 10 b 10 b 10 b 0

TC8 10 b 10 b 8 be 0

TC5 0 c 0 c 6 bed 0

TC6 0 c 0 c l ed 0 ^y DAA = days after application A. ^x Means with the same letter within a column are not significantly different at P < 0.05.

Field trials 2:

[0086] A further series of field trials was performed as described above for Field trials

1, with samples TC7, TC9 and TC10, but in a different season, namely spring (May) in Clayton, NC.

[0087] Turfgrass quality and phytotoxicity data were visually rated 5, 8, 15, and 27 days after application and compared to Ronstar Flo (Table 4).

[0088] The CS formulations TC7, TC8 and TC10 resulted in a significant reduction in phytotoxicity compared to Ronstar FLO for at least 15 days after application (Table

4). Table 4. Tolerance of actively growing bermudagrass (Cynodon dactylon L. Pers.) to ODZ

CS test compounds applied at a 3366 g ODZ/ha (3 lb/ A) rate in the field.

Treatment Percent phytotoxicity

5 DAA' 8 DAA 15 DAA 27 DAA

Untreated 0 d^x O e O d O b

Ronstar FLO 44 a 61 a 60 a 18 a

TC7 23 b 35 b 36 b 18 a

TC9 10 c 25 c 29 be 0 a

TC10 6 c 21 d 25 c 10 a ^y DAA = days after application A. ^x Means with the same letter within a column are not significantly different at P < 0.05.

Claims

Claims:

1. Aqueous herbicidal composition comprising microcapsules, the microcapsules comprising a polymer-based shell wall and a core material containing oxadiazon; and oxadiazon in free form; wherein the weight ratio of the oxadiazon in free form to the oxadiazon within the core material is between 1:50 to 1:5; and wherein the microcapsules have a median particle size (D50) range of between 1 and 10 pm.

2. The aqueous herbicidal composition of claim 1 , wherein the ratio of the oxadiazon in free form to the oxadiazon within the core material is between 1:30 and 1:5, further preferably between 1:25 and 1:5.

3. The aqueous herbicidal composition of claim 1 or 2, wherein the microcapsules have a median particle size range of below 9 pm, preferably of below 8 pm, further preferably a median particle size range of between 5 and 7 pm.

4. The aqueous herbicidal composition of any one of the preceding claims, wherein the polymer-based shell wall comprises a polymer selected from polyurea, polyurethane, polyvinylpyrrolidone, cellulose or a lipid. The aqueous herbicidal composition of any one of the preceding claims, wherein the polymer-based shell wall is formed in a polymerization reaction between an isocyanate component and an amine component. The aqueous herbicidal composition of claim 5, wherein the amine component comprises triethylenetetramine. The aqueous herbicidal composition of any one of claims 1 to 4, wherein the polymer- based shell wall is formed in a polymerization reaction between an isocyanate component and an alcohol component. Method for preparing an aqueous herbicidal composition according to any one of the preceding claims, comprising the steps of: a. preparing a first phase comprising an aqueous solution of a dispersant, wherein the first phase is heated to a temperature of above 55 °C; b. preparing a second phase comprising oxadiazon, an aromatic solvent and a first polymerization reaction partner, wherein the second phase is heated to a temperature of above 55 °C; c. mixing the first and the second phase at a temperature of above 55 °C; d. adding a second polymerization reaction partner to the mixture and agitate the obtained suspension at a temperature of above 55 °C to allow curing of the polymerization reaction partners; e. After curing, combining the mixture with further, nonencapsulated oxadiazon. The method of claim 8, wherein the first polymerization reaction partner is an isocyanate component, and wherein the second polymerization reaction partner is an amine or an alcohol component. The method of claim 8 or 9, wherein in step a. the first phase is heated to a temperature of between 60 and 70 °C; and/or wherein in step b. the second phase is heated to a temperature of between 60 and 70 °C and/or wherein in step c. the mixing is performed at a temperature of between 60 and 70 °C; and/or wherein in step d. the agitating is performed at a temperature of between 60 and 70 °C. Use of an aqueous herbicidal composition for controlling undesirable vegetation which comprises applying to the vegetation or the locus thereof to prevent the emergence or growth of the undesirable vegetation a herbicidally effective amount of the aqueous herbicidal composition; the composition comprising: microcapsules, the microcapsules comprising a polymer-based shell wall and comprising a core material containing oxadiazon, and oxadiazon in free form. The use of claim 11, wherein the herbicidally effective amount is applied by means of spraying. The use of any one of claims 11 or 12, wherein the herbicidally effective amount is applied onto turf grass. The use of any one of claims 11 to 13, wherein the herbicidally effective amount is applied when the undesirable vegetation is germinating, and/or wherein the herbicidally effective amount is applied in a time period including summer and autumn, preferably between and including the months August and November in the Northern hemisphere. The use of any one of claims 11 to 14, wherein the aqueous herbicidal composition is an aqueous herbicidal composition according to any one of claims 1 to 7.