AU2007202192B2 - Herbicidal composition - Google Patents

Abstract

The invention relates to a solid particulate herbicidal composition comprising flupropanate, methods for the preparation of a solid particulate herbicidal 5 composition comprising flupropanate and to methods for controlling weeds by using a solid particulate herbicidal composition comprising flupropanate. The solid particulate herbicidal composition may be readily broadcast in an area of treatment.

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: HERBICIDAL COMPOSITION Applicant: Granular Products Pty Ltd The following statement is a full description of this invention, including the best method of performing it known to me: 1 6067 JD 2 HERBICIDAL COMPOSITION This application claims priority from Australian Patent Application No. 2006902847 filed on 26 May 2006, the contents of which are to be taken as 5 incorporated herein by this reference. FIELD OF THE INVENTION The present invention relates to a solid particulate herbicidal composition 10 comprising flupropanate, methods for the preparation of a solid particulate herbicidal composition comprising flupropanate and to methods for controlling weeds by using a solid particulate herbicidal composition comprising flupropanate. In particular, the present invention relates to granular herbicidal compositions comprising flupropanate. 15 BACKGROUND Flupropanate, also known as 2,2,3,3,-tetrafluoropropanoic acid, is an effective herbicide which is generally presented in salt form and is used for the selective control of undesirable perennial grasses in pastures and non-crop applications. 20 The sodium salt form of flupropanate is also known as tetrapion or flupropanate-sodium. Flupropanate-sodium is highly water soluble and many commercially available herbicidal compositions comprising the sodium salt of flupropanate as the 25 active ingredient are formulated as aqueous liquid solutions. An example of a commercial liquid herbicide composition comprising flupropanate is TaskforceTM, an aqueous preparation having a specific gravity of 1.45 and pH 8-10 and containing flupropanate-sodium at a concentration of 745g/litre (acid equivalent basis), which equals 857 g/litre sodium salt basis. 30 While liquid herbicide formulations are convenient, there are a number of problems associated with their use.

3 Aerial sprays are frequently used to deliver liquid flupropanate formulations to a desired treatment area. However, aerial application is problematic due to spray drift and spray capture of the herbicide by off-target foliage. Off-target foliage may comprise woodland having a canopy up to 100 feet up from the 5 ground, or any overhanging or neighboring foliage. Off-target foliage may therefore intercept herbicide spray drops applied aerially under still or windy conditions. As a result, the active herbicide may not reach the targeted foliage. 10 In order to minimize spray drift, large drop sizes having a diameter of approximately 250 microns or more are required. Because of the large drop size, relatively large quantities of water need to be applied with the active ingredient to provide adequate cover. This means that a helicopter load of liquid herbicide (limited to a given liquid volume) can only cover a relatively 15 small spray area, resulting in high application costs. In addition, in order to control weeds in wooded country with prolific seed producing capabilities, complete kill of the weeds under the woodland canopy is highly desirable. Many conventional liquid flupropanate formulations are 20 prone to evaporation when applied as spray droplets. As a result, aerial application of a liquid formulation above the tree canopy may result in up to half the spray volume being lost to evaporation and off-target capture. Consequently, there may be up to 50% variation of herbicide application across the treatment area. Furthermore, the control of weeds in undulating 25 and hilly country is made harder due to the problem of having to follow the terrain, resulting in applications being performed at excessive height. The active ingredient of many commercial formulations, flupropanate-sodium, is commonly supplied as a concentrated aqueous solution. Consequently, the 30 preparation of liquid herbicide formulations is relatively easy and economical while the preparation of solid formulations has been difficult to achieve.

4 It would be desirable to provide a convenient, cost effective and easy-to-use solid herbicidal composition comprising flupropanate which can be readily distributed in a desired treatment area and that does not suffer from the above disadvantages. 5 The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of this application. 10 SUMMARY The present invention relates to a solid particulate herbicidal composition comprising flupropanate for distributing flupropanate over a treatment area. 15 In one aspect, the present invention provides a herbicidal composition. The granules have a particle size range of from about 0.3 - 5 mm, even more preferably about 1 - 3mm. 20 The composition comprises from about 2 to 25% by weight of flupropanate. Here and hereafter, unless otherwise specified, flupropanate content will be described in terms of acid equivalent basis. The flupropanate comprises the sodium salt of flupropanate. The ratio of flupropanate to water in the composition is in the range of from about 4:1 to 1:1. 25 The herbicidal composition comprises a carrier material. Preferably, the herbicidal composition comprises a freely flowing carrier material which remains freely flowing when up to 10% of additional water is loaded into the carrier material.

5 In one embodiment of the invention, it is preferred that the carrier material loaded with 7% additional water has a crush strength of at least about 500g. More preferably, the carrier material loaded with 10% additional water has a crush strength of at least about 500g. It is further preferred that the carrier material has a bulk density in the 5 range of from 0.5 to 2 grams per cubic centimeter. The carrier material has a particle size in the range of from 0.3 - 5 mm. Accordingly, it is preferred that the carrier material is a solid particulate. 10 It is preferred that the carrier material comprises clay, peat or zeolites. Preferably, the clay is selected from the group consisting of bentonite, attapulgite, kaolin, montmorillonite, smectite and hectonite. When the carrier material comprises zeolite, it is preferred that the zeolite is a natural zeolite. When the carrier material comprises peat, it is preferred that the peat is selected from the group consisting of reed-sedge 15 peat, lignin peat, peat moss, sphagnum peat. In a preferred aspect, the carrier material comprises bentonite, peat, smectite or hectorite. In one preference the carrier material comprises a bentonite clay, more preferably a sodium bentonite clay. A further aspect of the present invention provides a method for the preparation of a 20 solid particulate herbicidal composition comprising flupropanate. In accordance with one aspect, there is provided a process for preparing a solid granular herbicidal composition according to any one of the previous claims comprising providing a particle of carrier material of size in the range of from 0.3 to 25 5mm and absorbing therein an aqueous solution comprising flupropanate-sodium wherein the weight ratio of flupropanate sodium (acid equivalent basisO to water is in the range of from 4:1 to 1:1; to provide a granular herbicidal composition comprising from 2 to 25% by weight of flupropanate-sodium (acid equivalent basis). 30 Yet a further aspect of the invention provides a method of controlling weeds comprising pre-emergent or post-emergent (preferably pre-emergent) application of a solid particulate composition comprising flupropanate to the locus in which control is required. hJ173$ RI JUI 6 In one aspect, there is provided a method of controlling weeds in an area comprising broadcasting in the area a solid granular composition comprising a carrier material and in the range of from 2 to 25% by weight of flupropanate-sodium on an acid equivalent basis and no more than about 20% by weight of water based on the total 5 composition. As used herein, "flupropanate" includes the acid and salt forms of 2,2,3,3 tetrafluoropropanoic acid. 10 DETAILED DESCRIPTION The present invention relates to a solid particulate herbicidal composition comprising flupropanate. In one aspect, the present invention provides a solid particulate herbicidal 15 composition comprising flupropanate and water. The herbicidal composition is the form of granules for broadcasting in a desired treatment area. 20 The herbicidal composition comprise particles of a size that is sufficient to enable the composition to be readily broadcast and spread on the ground to provide adequate coverage to a treatment area, and thereafter to remain on the ground and not be susceptible to dusting or movement by wind, air currents and the like. Removal or movement of the composition may be detrimental to other foliage in the vicinity of the 25 area of treatment which is not the intended target of the herbicide. The granules have an average particle size of from about 0.3 - 5 mm, more preferably an average particle size range of from about 0.5 - 5 mm, even more preferably from about 1 - 3 mm. 30 The herbicidal composition of the invention comprises flupropanate as the main active ingredient. Flupropanate is a compound that selectively targets and kills perennial grasses such as serrated tussock. Flupropanate and in particular, the sodium salt of flupropanate has a high saturation solubility in water. For example, an aqueous solution containing up to 80% (w/v) flupropanate-sodium can be obtained at 20'C.

7 Flupropanate can be present in the composition in any herbicidally effective amount. Preferably, the composition comprises from about 2-25%, more preferably from about 2-15% by weight, even more preferably from about 5-10% by weight of flupropanate 5 (acid equivalent basis). The flupropanate active ingredient preferably comprises the sodium salt of the compound. The herbicidal composition of the invention comprises water. In a preferred aspect of the invention the composition comprises no more than about 20% by weight of water. 10 More preferably, the composition comprises no more than about 15% by weight of water. It is desirable to maintain relatively minor amounts of water in the herbicidal composition as excessive amounts of water can have detrimental effects in terms of loss of active agent concentration in the solid composition and reduced properties such as granule crush strength. The weight ratio of flupropanate (acid equivalent 15 basis) to water is preferably in the range of from about 4:1 to 1:1, more preferably in the range of from about 8:4 to 5:4. The herbicidal composition comprises a carrier material. The carrier material carries the flupropanate active ingredient and assists to add bulk to the composition and 20 provide a solid, flowable and storage-stable form which can be broadcast into the use territory using readily available application equipment. The carrier material is usually present in a significant excess compared with the quantity of flupropanate. For this reason, it is preferred that inexpensive carrier materials are used. 25 The carrier material may comprise any material suitable for agricultural use that is capable of binding to and absorbing liquids. Examples of suitable carrier materials include but are not limited to peat, clay and zeolites. When clay is used in the carrier material, the clay is preferably selected from the 30 group consisting of bentonite, attapulgite, kaolin, montmorillonite, smectite and hectonite. In one preference, the carrier comprises bentonite clay, even more preferably, sodium bentonite clay.

8 When the carrier material comprises a zeolite, it is preferred that the zeolite is a natural zeolite. When the carrier material comprises peat, it is preferred that the peat is selected from 5 the group consisting of reed-sedge peat, lignin peat, peat moss, sphagnum peat. The peat will in general comprise organic matter. In a preferred aspect, the carrier material comprises bentonite, peat, smectite, or hectorite. 10 The carrier material is a particulate solid. It is preferable that the solid particulate carrier be capable of binding to or absorbing an aqueous liquid. In this way, the carrier material may be loaded with the aqueous liquor. The carrier material may have an average particle size in the range of about 0.3 mm to 5 mm, preferablyo.5 - 5 15 mm, even more preferably about 1 - 3 mm. Preferably, the carrier material has the capacity to absorb at least 7% aqueous liquor, more preferably at least 10% aqueous liquor (based on pre-loaded weight) without liquor bleeding or seepage and without clumping of the carrier material. Preferably 20 the carrier material, when loaded with said aqueous liquor retains its integrity after packing, storage and transport in a storage format such as a 20 kg (or larger) cardboard container or cloth sack. It is preferred that the carrier material remains freely flowing even if a quantity of at least 7%, preferably at least 10% aqueous liquor has been loaded onto the material. 25 It is further preferred that the loaded carrier material has a crush strength sufficient for the material to its shape and to withstand the weight of the solid particulate herbicidal composition when it is stored in a container such as a bag, and the weight of other bags stacked on top of the bag. The crush strength is an indication of the force 30 required to compress the material. When the carrier material is loaded with up to 1d% liquid, the crush strength of the carrier is preferably at least about 500 grams, more preferably at least about 800 grams. .1735RIXJLB 9 In a preferred embodiment the composition a freely flowing carrier material with an average particle size in the range 0.5-5mm, said carrier material having the characteristic that it remains freely flowing when up to 10% of additional water is loaded into and fully absorbed by the carrier material and is further characterized in 5 that the carrier material when loaded with 7% additional water has a crush strength of at least about 500g. In one embodiment the carrier has a bulk density in the range 0.5-2 grams per cubic centimeters, and further characterized in that the carrier is chosen from the set clay, 10 peat, zeolites, bentonite, attapulgite, kaolin, montmorillonite, smectite, hectonite, reed sedge peat, lignin peat, peat moss, sphagnum peat, sodium bentonite clay, natural zeolites. The carrier material also preferably has a bulk density in the range of from about 0.5 15 to 2 grams per cubic centimeter, more preferably in the range of about 0.7 to 1.5 grams per cubic centimeter. Such relatively high bulk density values are desirable to ensure that fixed-volume applicator systems (e.g. helicopters or fixed wing aircraft) can cover more territory in a given application run. 20 The herbicidal composition of the invention may optionally include additional formulation ingredients if desired, to aid in the processing, appearance or use of the solid particulate composition. Such further optional ingredients would not adversely affect the activity of the flupropanate and would be readily apparent to the person skilled in the art. Examples of additional formulation ingredients include but are not 25 limited to flow agents, surfactants, disintegration aids, preservatives, colors and the like. In one embodiment the herbicidal composition is free of surfactants. 30 The herbicidal composition of the invention may also include other active ingredients such as herbicides or pesticides. .IM7 RIJ2IJ 10 The solid particles of the herbicidal composition of the invention are stable upon storage and are readily handled by the user for application. However, upon wetting the particles after their distribution in an application area with moisture (e.g. rain) the 5 solid particles of the composition are able to release the active flupropanate into the treatment area. The release may be due to disruption or disintegration of the solid particles or by some other mechanism. It is preferred that most if not all of the flupropanate is released from the solid particles after contact with rain. W1735 RilRB 11 Preparation A further aspect of the present invention relates to a method for the preparation of a solid particulate herbicidal composition comprising flupropanate. 5 In one aspect, the present invention provides a method for the preparation of a solid particulate herbicidal composition comprising the steps of: (i) applying a solution comprising fluproponate to a carrier material to provide a bulk composition; and (ii) subjecting the bulk composition to treatment to provide the solid 10 particulate herbicidal composition. In another aspect, the present invention provides a method for the preparation of a solid particulate herbicidal composition comprising the step of applying a solution comprising fluproponate to a solid particulate carrier material. 15 The flupropanate solution may be obtained from commercial sources or may be prepared by mixing a quantity of flupropanate with a solvent. A suitable solvent is water due to the high water solubility of flupropanate and in particular, flupropanate sodium. Non-aqueous solvents may also be used. 20 The flupropanate solution may be applied to the carrier material using any method known in the art. A preferred method for applying the fluproponate solution involves mixing the fluproponate solution with the carrier material for a time sufficient to allow the flupropanate to become absorbed by the carrier. A suitable mixing vessel such as 25 a rotating drum or a ribbon mixer may be used. Other methods of applying the fluproponate solution such as by spraying the flupropanate solution onto the carrier material may also be used. In one embodiment of the invention, when a bulk composition is prepared, the bulk 30 composition may be treated in any manner known in the art to form the desired solid particulate herbicidal composition, for example by incorporation of flow agents. In 1 735 RL.E-JL 12 The solid particulate herbicidal composition may be prepared by applying a flupropanate solution onto a solid particulate carrier of size 0.3 to 5mm prepared without granulation. An advantage of this method that the active ingredient is directly 5 loaded onto the carrier to thereby form the particulate herbicidal composition in a single step process. The resultant composition consequently does not need to undergo subsequent drying or further processing. When a solid particulate carrier material is used, the particulate carrier may be 10 prepared by any suitable method known in the art in order to achieve the desired particle size range. Suitable methods include for example, crushing or screening. The fluproponate solution that is used in the methods of the invention is preferably a concentrated solution, such that only an aliquot of the concentrated solution is 15 required to be applied to the carrier material to obtain the desired final concentration of the active ingredient. Preferably, the final concentration of flupropanate in the herbicidal composition is in the range of 50g/kg to 100 g/kg (acid equivalent basis). If necessary, a diluent may be added during the preparation of the herbicidal composition in order to obtain the desired final concentration of flupropanate. 20 Suitable diluents include for example solvents such as water, or additives that aid in the processing or use of the herbicidal composition.

13 Application A further aspect of the invention provides a method of controlling weeds using a solid particulate herbicidal composition comprising flupropanate. The method preferably comprises the application of the herbicidal composition to 5 the locus of the weed in which control is required. In use, the herbicidal composition is broadcast by the user and distributed onto the area to be treated by the herbicide. The composition may be broadcast at any suitable application rate that provides adequate cover to an area of land 10 and achieves the advantages of controlling weed growth. Preferred application rates are from about 0.5 - 3.0 kg flupropanate (acid equivalent basis) per hectare and more preferably from about 0.7 -1.5 kg flupropanate per hectare. Such application rates are known and may be readily ascertained by the person skilled in the art. 15 The herbicidal composition may be broadcast and spread with the aid of suitable equipment known for use in spreading solid particulate materials. Such equipment would be known to the skilled addressee. Examples of suitable broadcasting and spreading equipment are detailed in the Examples. 20 The solid particulate material is spread onto the treatment zone by broadcasting, for example broadcasting from a helicopter or fixed wing aircraft. The herbicidal composition of the invention once applied, can be readily 25 disrupted by water, such as rain, so that the flupropanate active ingredient is then released from the composition into the treatment area. The solid particulate herbicidal composition of the invention advantageously allows easy and controlled distribution of the herbicide to be achieved in the 30 desired area of application. Because of the use of a solid form of the herbicide composition, more consistent application can be achieved with less wastage of the flupropanate active.

14 The solid particulate herbicidal composition of the invention may be used to control the growth and spread of various weeds. The herbicidal composition of the invention is particularly advantageous for controlling the growth of perennial grasses such as giant rats tail grass, parramatta grass, serrated 5 tussock, African lovegrass and Chilean needle grass. The herbicidal composition of the invention is preferably for post-emergent application to weeds. 10 EXAMPLES Example 1 - Preparation of Flupropanate Granules This example describes the synthesis of granules of a flupropanate composition according to the invention. The granules in this example will be 15 designated as M10, M5, L10 and L5. The designations relate to the following properties: M10: medium size 10% active, M5: medium size, 5% active, L10: large size, 10% active and L5: large size, 5% active. 20 Preparation of MIO Granules M10 granules were made by taking Trufeed granular sodium bentonite (Particle size - Dry Screen (retained 5mm) 2%, Dry Screen (passing 1.5mm) 5%, Water absorption 750%, Bulk Density 1.0, pH 7), sold by Unimin, 25 Melbourne Australia. The granules were crushed using a rolling crushing mill (Kustner Switzerland Model No. 28888), and passed through a 2 mm sieve. The particles which passed through a 2mm sieve and were retained on a 1 mm sieve were used for further treatment. 30 To check for carrier suitability, sieved particles were loaded with 7% water and 10% water, to check that no water bleeding occurred when the granules were loaded with water, and that the granules remained freely flowing after the 15 absorption of significant quantities of aqueous liquor (these wet samples then discarded). The sieved particles (20 kg batch) were added to a mixing vessel (Minimix 150 5 Belie Group Sheen UK) and flupropanate concentrate liquor (60% flupropanate, acid equivalent basis) was slowly poured onto the mixing granules over a 10 minute period. Sufficient flupropanate liquor was added to provide a loading of 10% flupropanate (acid equivalent basis) on final granule weight. The mixing was continued for a further 20 minutes after the pouring 10 was complete. A flow agent (precipitated silica, Hisil 257 Fernz Corporation) was added until a concentration of 1 -2% of final product weight was achieved. Preparation of M5 Granules M5 granules were following the procedure detailed above for the M10 15 granules, except that the granules were loaded with 5% flupropanate (acid equivalent basis). Preparation of L10 Granules L10 granules were made following the procedure detailed above for the M10 20 granules, except that particles which passed through a 3mm sieve and were retained on a 2mm sieve were retained for treatment. Preparation of L5 Granules L5 granules were made in the same way as L10 granules, except that the 25 granules were loaded with 5% flupropanate (acid equivalent basis). None of the granules prepared in this example required drying prior to packing and application. 30 Properties of M10, M5, L10 and L5 Granules: The packing density and crush strength of the M10, M5, L10, L5 granules respectively are shown in Table 1: 16 Table 1 Granule Packing Density Crush Strength M10 1.02g/kg 500-600g M5 1.01g/kg 550-700g L10 1.05g/kg 500-600g L5 1.03g/kg 550-700g 5 Example 2 - Aerial application of Liquid Flupropanate Composition (Comparative Example) This example describes the aerial application of flupropanate liquid formulation in Rockhamton, Queensland, Australia. The application aircraft was an Air Tractor 502 (made by Air Tractor, USA), and the volume of the hopper was 10 1800 litres. The hopper was filled with a liquor comprising 1728 parts water and 72 parts flupropanate liquid concentrate (2 litres of concentrate contains 1.49 kg flupropanate , acid equivalent basis). The Air Tractor was used to treat rats tail grass using 50 litres/hectare of spray liquor (i.e. 1.49kg flupropanate per ha application rate, acid equivalent basis). The Air Tractor was equipped 15 with a nozzle arrangement configured for large droplets (VMD 336 micron). The Air Tractor flew at 120 knots during spray application, and the spray was delivered through a flat fan 4020 nozzle oriented at 10 degrees to air flow (zero degrees corresponds to straight backwards orientation). The application pressure was 40 psi, and the application height was 30 metres. 20 The flupropanate spray was applied over open woodland with 15 - 20% canopy cover, and the canopy height varied up to 30 metres. Standard methods (WRK string system with fluorescent marker dye in liquor, water sensitive paper, comparison with application over unwooded area etc) were 25 used to establish that (a) 25% of liquor (volume) discharged from the Air Tractor did not reach the ground because of interception by the canopy, (b) 40% of liquor (volume) discharged from the Air Tractor did not reach the ground because of evaporation, (c) the area covered using the 1800 litre 17 hopper load of application liquor was 36 hectares - this corresponds to an aerial application cost of approx $50 per hectare and (d) the coefficient of variation of liquor reaching the ground across the application area was 35%. 5 Example 3 - Aerial application of M10 Granules This example describes the aerial application of flupropanate granules according to this invention. Granules designated M10 as prepared in Example 1 contained 10% flupropanate (acid equivalent basis) by weight. The 1800 litre hopper on the Air Tractor 502 was filled with M1 0 granules, and was fitted 10 at the base with a Transland model meterate precision applicator (Transland Inc, USA). Granules dispensed by the applicator were fed into a Transland model Venturi spreader (Transland Model 23539, 10 vane slimline spreader). The meterate applicator was calibrated to deliver 15 kg of granules per hectare (based on a 120 knot application velocity). This corresponds to an application 15 rate of 1.5 kg flupropanate (acid equivalent basis) per hectare. Other application conditions were as per Example 2. Standard methods (including the use of the WRK granular system for granule distribution) were used to establish that (a) less than 5% of the granules were 20 intercepted by the canopy, (b) less than 5% of the granules did not reach the ground for any reason, (c) the area covered using the 1800 litre hopper load of the applicator was 120 hectares - this corresponds to an application cost of $15 per hectare and (d) the coefficient of variation of granules reaching the ground across the application area was 8%. 25 Example 4 - Herbicidal Efficacy This example describes and compares the relative efficacy of granular and liquid formulations of flupropanate on giant rats tail grass devoid of canopy cover. Hand application was used in both cases. The example also describes 30 the relative efficacy for various granules designated M10, M5, L10 and L5, prepared in accordance with Example 1.

18 Materials and Methods The experimental site was located at Kunwarara approximately 70km north of Rockhampton in Central Queensland. The site had been fenced to exclude stock for a number of years. The plots were located on areas of dense giant 5 rats tail grass (Sporobolus pyramidalis) to ensure there were plenty of weed plants to evaluate. There were minimal numbers of other plant species in the plots, therefore herbicide selectivity was not tested. Experimental design 10 The experimental design was a randomised block design with 4 blocks, 10 treatments and a square plot size of 5 x 5m. Sampling consisted of running a measuring tape diagonally across the plot. Starting approximately 1.5 m along the tape (-1 m from the sides of the plot) plants were individually located (distance along tape, left or right of tape, distance out from tape). The basal 15 diameter of located plants was measured in two directions. Plant basal area was calculated from the diameter measurements using the formula for an oval. Measurements were taken prior to the application of herbicide (15 December 2004) and 14 months later (9 February 2006). Approximately 20 plants were individually identified and measured per plot. 20 Ten treatments were combined in the same experimental design, with two groups of treatments available for comparison (Table 2 and 3). The first group of treatments assessed the effect of different herbicide active 25 ingredient application rates using granular formulation M10 (Table 2). The second group of treatments assessed the effect of four different granular formulations (two granule sizes and two herbicide concentrations) at the same herbicide active ingredient application rate (Table 3). 30 Treatment 3 (medium sized granule and 10% herbicide concentration, 100% rate) was common to both treatment groups. All treatments with the granular herbicide composition were compared with weeds treated with liquid herbicide 19 composition (currently available herbicide formulation - 100% recommended rate) and untreated control. All treatments were statistically analysed together. Table 2. Assessment of the efficacy of varying application rates of 5 flupropanate granular herbicide compared to the recommended liquid formulation rate (100%). The M10 granule was used for all the granule treatments. Treatment Herbicide Rate Granule Number Treatment Name Number (g active per ha) per m 2 1 Granules 50% rate 745 44.7 2 Granules 80% rate 1192 71.5 3 Granules 100% rate 1490 89.4 4 Granules 150% rate 2235 134.1 5 Granules 200% rate 2980 178.8 9 Liquid Control 100% rate 1490 10 Untreated control 0 20 Table 3. Assessment of the efficacy of different flupropanate granule formulations at the same application rate. Two granule sizes and two herbicide concentrations (4 combinations) that modified the granule number 5 per area were tested. All granule treatments and the liquid control were applied at the recommended 100% rate. reatment THerbicide Rate Granule Number Treatment Name Number (g active per ha) per M2 Granules, Medium 3 size, 10% conc. 1490 89.40 (M10) 6 Granules, Large 1490 119.20 size, 5% conc. (L5) Granules, Large 7 size, 10% conc. 1490 59.60 (L1O) Granule, Medium 8 1490 178.80 size, 5% conc. (M5) Liquid Control 9 1490 Untreated control 10 0 Herbicide application 10 Each granular herbicide composition was weighed for each plot and mixed with approximately 2.5 L of sand. The mixture was hand-spread across the plot, crossing the plot in two directions. A 'dummy' plot was erected prior to herbicide application to practice hand-spreading the sand. The liquid herbicide was applied with a backpack sprayer and 0.9 m boom. The rate of application 15 was calibrated by measuring the spray volume required to spray a 'dummy' plot in two directions. Prior to herbicide application, the plots were clearly outlined by running tape along the plot borders.

21 Weather conditions at time of application were hot (38 0 C) and humid. The 14 months following herbicide application was generally dry for the region. 5 Results and Discussion Treatment Group 1: Efficacy of varying rates of granular flupropanate herbicide compared to liquid flupropanate herbicide 10 Plant death increased with flupropanate herbicide application rate. There was no significant difference between the 100% rate granular flupropanate formulation (medium size, 10% concentration) on plant death (73.3%) compared to the liquid flupropanate formulation (79.8%). Increasing the granular herbicide application rate to 150% increased plant death to 92.5%, 15 which suggests the efficacy may be slightly improved at a rate greater than 100% rate. Few plants died when no herbicide treatment was applied. There was also no significant difference on the alive basal area remaining after 14 months between the 100% rate granular formulation (5.7%) compared to the liquid formulation (14.3%). 20 Treatment Group 2: Efficacy of different granular flupropanate herbicide formulations There was no significant difference between the different flupropanate granular 25 formulations on plant death and the alive basal area remaining after 14 months, however the medium size 10% concentration (M10) formulation and the large size 5% concentration (L5) formulation had the greatest plant death and least alive basal area remaining after 14 months. 30 Impact of different granular flupropanate formulations (using the same active ingredient application rate) on a) Plant death (LSD 5% is 29.1), and b) Alive basal area (LSD 5% is 11.8), 14 months after herbicide application: 22 There appeared to be no consistent link between granule number and plant death, although the treatment with the least granule number (large granule, 10% concentration treatment - 60 granules per M 2 ) had the lowest plant death. 5 In this experiment, there was no significant difference between the granular and the liquid flupropanate herbicide formulations in efficacy for giant rats tail grass (Sporobolus pyramidalis) control when applied at the recommended active ingredient rate (1490 g active per ha). 10 Example 5 - Assessment of Carrier Materials This example describes tests performed on a range of potential carrier materials to establish the suitability of these materials for the preparation of granular flupropanate compositions in accordance with this invention. 15 Test 1 - Water absorption The first test involved stirring the potential carrier granules with a spatula in a beaker with 10% added water (drop-wise water addition to the beaker), and checking that the treated granules remained freely flowing at the end of the 20 treatment. If the potential carrier granules were not freely flowing at the end of this treatment (or if they could not hold the water without seepage, run-off or bleeding), the granules were allocated a failed status, and discarded. Test 2 - Crush strength 25 The second test involved taking granules of the carrier material loaded with 10% added water, and subjecting these granules to a crush test. A single granule was placed on a balance and a flat surface was pressed down on the single granule until it collapsed or was significantly distorted. The weight recorded by the balance at collapse was noted (20 replicates performed and 30 results averaged). The potential carrier material was accorded a pass status if the crush weight was over 500g. The following potential carrier granules were tested for crush strength: Zeolite, calcined flint clay, Doen grey clay, peat, 23 vermiculite, sand, perlite, bentonite. The details of the potential carrier materials are shown in Table 4. Table 4 Compound Brand Packing Density Zeolite Escott Natural Zeolite 1.6 g/ml Calcined Flint Clay Small Mountain 2.5 g/ml Montmorillonite Doen Grey Clay 1.16g/ml Fibrous Peat Biogreen Fibrous Peat 0.6 - 1.0 g/ml Vermiculite Packing Vermiculite 0.16 g/ml Sand Garfield washed sand 1.4 g/ml Perlite Exfoliators Perlite 0.32 g/ml Bentonite Trufeed Granular bentonite 1.0 g/ml 5 The results of the crush strength tests are as follows: Zeolite (failed), calcined flint clay (failed), Doen grey clay (200 -300 g crush strength not a pass), peat (800 - 1000 g crush strength - pass), vermiculite (50 - 100 g crush strength - not a pass), sand (failed), perlite (100 - 250 g crush strength - not a pass), 10 bentonite (500 - 700g crush strength - pass).

Claims (33)

1. A herbicidal composition for broadcasting in an area to be treated with flupropanate herbicide, the composition being in the form of granules of particle size in the range of from 0.3 mm to 5 mm and comprising: particles of carrier material; an aqueous liquor comprising from 2% to 25% by weight of the granule composition of flupropanate-sodium (on an acid equivalent basis) and a weight ratio of flupropanate to water of from 4:1 to 1:1; and wherein the aqueous liquor has been absorbed into the particles of carrier material and said particles of carrier material are of size in the range of from 0.3mm to 5mm.

2. A herbicidal composition according to claim 1 wherein the granules and particles of carrier material are each of size in the range of from 1 mm to 3 mm.

3. A herbicidal composition according to any one of the previous claims wherein the granular herbicidal composition comprises no more than 15% by weight of water.

4. A herbicidal composition according to any one of the previous claims wherein the granular herbicidal composition comprises no more than 10% by weight of water.

5. A herbicidal composition according to claim 4 wherein the weight ratio of flupropanate-sodium (acid equivalent base) to water is 8:4 to 5:4.

6. A herbicidal composition according to any one of the previous claims wherein the carrier material is selected from the group consisting of peat, clay and zeolites.

7. A herbicidal composition according to claim 6 wherein the carrier material is a clay material selected from the group consisting of bentonite, attapulgite, kaolin, montmorillonite, smectite and hectonite. 25

8. A herbicidal composition according to claim 7, wherein the clay is sodium bentonite clay.

9. A herbicidal composition according to any one of the previous claims wherein the particles of carrier material have a crush strength of at least about 500g when loaded with 10% added water.

10. A herbicidal composition according to any one of the previous claims which is free of surfactant.

11. A process for preparing a herbicidal composition according to any one of the previous claims comprising providing particles of carrier material of size in the range of from 0.3 to 5mm and absorbing therein an aqueous solution comprising flupropanate-sodium wherein the weight ratio of flupropanate sodium (acid equivalent basis) to water is in the range of from 4:1 to 1:1; to provide a granular herbicidal composition comprising from 2 to 25% by weight of flupropanate-sodium (acid equivalent basis).

12. A process according to claim 11 wherein the weight ratio is from 8:5 to 5:4.

13. A process according to claim 11 or claim 12 wherein the particles of carrier material are prepared by crushing carrier material and dry screening.

14. A process according to any one of claims 11 to 13 wherein the granule composition is free of surfactant.

15. A method of controlling weeds in an area comprising broadcasting in the area a solid granular composition of granular size in the range of 0.3mm to 5mm comprising a carrier material and in the range of from 2 to 25% by weight of flupropanate-sodium on an acid equivalent basis and no more than about 20% by weight of water based on the total composition. 26

16. A method according to claim 15 wherein the granular composition comprises particles of carrier material of size in the range of from 0.3 to 5mm.

17. A method according to claim 15 wherein the granular composition comprises granules and particles of carrier material are each of size in the range of from 1 to 3mm.

18. A method according to any one of claims 15 to 17 wherein the flupropanate is released from the granular composition on being wet by rain following broadcasting.

19. A method according to any one of claims 15 to 18 further comprising a freely flowing carrier material wherein the granules remain freely flowing when up to 10% of additional water is loaded into and fully absorbed by the particles of carrier material.

20. A method according to claim 19 wherein the particles of carrier material loaded with 10% additional water have a crush strength of at least about 500g.

21. A method according to claim 19 wherein the particles of carrier material has a bulk density in the range of from 0.5 to 2 grams per cubic centimetre.

22. A method according to any one of claims 15 to 21 wherein the granular composition is broadcast at a rate of from 0.5 to 3.0 kg flupropanate-sodium on an acid equivalent basis per hectare.

23. A method according to claim 15 wherein the carrier material comprises clay, peat or zeolites.

24. A method according to claim 23 wherein the clay is selected from the group consisting of bentonite, attapulgite, kaolin, montmorillonite, smectite and hectonite. 27

25. A method according to claim 23 wherein the peat is selected from the group consisting of reed-sedge peat, lignin peat, peat moss, sphagnum peat.

26. A method according to claim 23 wherein the zeolite is a natural zeolite.

27. A method according to claim 23 wherein the carrier material comprises a bentonite clay.

28. A method according to claim 24 wherein the carrier material is attapulgite.

29. A method according to any one of claims 15 to 28 wherein the granular composition is broadcast from a helicopter or fixed wing aircraft.

30. A method according to any one of claims 15 to 29 substantially as herein described with reference to any one of the examples.

31. A solid granular herbicidal composition according to any one of claims 1 to 10 substantially as hereinbefore described with reference to any one of the Examples.

32. A process according to claim 13 wherein dry screening comprises collecting particles which pass through 2mm sieve and are retained on a 1mm sieve.

33. A herbicidal composition according to any one of claims 1 to 10 substantially as herein described with reference to any one of the Examples.