AU2014256380B2

AU2014256380B2 - Herbicidal granular composition

Info

Publication number: AU2014256380B2
Application number: AU2014256380A
Authority: AU
Inventors: Graham Barrett; Miroslava Ognyanova Bratvanova; Abhinetiri Kumari Maharaj; Philip Edward Pentland
Original assignee: Granular Products Assets Pty Ltd
Current assignee: Granular Products Assets Pty Ltd
Priority date: 2013-10-31
Filing date: 2014-10-30
Publication date: 2017-04-13
Anticipated expiration: 2034-10-30
Also published as: AU2014256380A1

Description

1 2014256380 30 Oct 2014

Herbicidal Granular Composition

Technical Field [1 ] The invention relates to a granular composition containing the herbicide tebuthiuron, to a process for preparation of the herbicidal granular composition and to a method of controlling weeds by broadcasting of the granular composition.

Background of Invention [2] Tebuthiuron (1 -(5-fert-Butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) is a non-selective broad spectrum herbicide of the urea class. It is used to control weeds, woody and herbaceous plants, and sugar cane. It is understood to act through absorption by the roots and transportation to the leaves, where it inhibits photosynthesis.

[3] The effective control of weeds by aerial application of herbicidal granular compositions gives rise to different formulation and distribution problems than formulation of herbicidal compositions applied from the ground. In particular, aerial broadcasting of granular material involves very different equipment and considerations than spray application of water dispersed granules or ground application of water dispersed or broadcast granules. The ancillary costs of application of granules, by broadcasting from aircraft, include the cost of aircraft, fuel and equipment which often dominates the economics of weed control. Also the effective use of aerially applied granular herbicides is dependent to a large extent on being able to distribute granules evenly on the ground and to provide a spacing and concentration of herbicidal granules within a range sufficient to control the target weeds without significant off-target distribution and without overloading specific sites within the treatment area.

[4] Ideally granules need the ballistic properties which allow accurate positioning of aerial distribution and a granule size and loading of active which allows good weed control with an economic payload of granules. Good control of weeds may be 2014256380 30 Oct 2014 2 compromised by too sparse a distribution of granules and increasing the loading of herbicide has the potential to either waste the active agent or provide hot spots of herbicide concentration which are too widely spaced to control the target weed population.

[5] Tebuthiuron granules for aerial application have been offered for commercial sale by Dow AgroSciences as “Graslan”™ granules with a loading of tebuthiuron of 200 grams of tebuthiuron per kilogram of granules (200g/Kg). Titan Ag also market granules with 200 g/kg Tebuthiuron. PGR International (an Australian company)has also offered “Tebulan” granules with a loading of 200g/kg of Tebuthiuron for commercial sale. A characteristic of the above commercially available granules is that they are formed by extrusion as short cylindrical or rod like sections, and that throughout the granule sample there is a considerable diversity of cylinder lengths. Prior art granules are typically applied to achieve a spread of from 10 to 20 granules per square meter.

[6] There is a need for a herbicidal granular composition of tebuthiuron which addresses these problems.

[7] 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 each claim of this application.

Summary of Invention [8] In accordance with one aspect we provide a herbicidal granular composition for aerial application of the granules to an area of land on which weeds are to be controlled, comprising: at least 30% w/w (preferably at least 35% w/w) tebuthiuron; 2014256380 30 Oct 2014 3 wherein at least 70% w/w, preferably at least 80% w/w (more preferably at least 90% w/w and more preferably at least 95% w/w) of the granules have an aspect ratio in the range of from 1 to 1.5 preferable from 1 to 1.2 and the weight average particle diameter is in the range of from 1 mm to 4 mm (preferably 1.5 to 3.5 mm).

[9] In a preferred set of embodiments the granular composition comprises 30% to 70%w/w tebuthiuron and from 15% to 70% w/w of filler.

[10] In accordance with one set of embodiments the herbicidal granular composition for application of the granules comprises: from 30% to 60% w/w (preferably 30% to 50%w/w, more preferably 35% to 45% w/w) tebuthiuron; from 30% to 65% w/w filler (preferably kaolinite); wherein at least 70% w/w, preferably at least 80% w/w (more preferably at least 90% w/w and still more preferably at least 95% w/w) of the granules have an aspect ratio in the range of from 1 to 1.5 preferable from 1 to 1.2 and the weight average particle diameter is in the range of from 1 mm to 4 mm (preferably 1.5 to 3.5 mm).

[11 ] We further provide a process for preparation of a herbicidal granular composition for aerial application of the granules to an area of land on which weeds are to be controlled, the process comprising: mixing a composition comprising at least 30% w/w (preferably at least 35% w/w) tebuthiuron; with water to form a composition of moist crumb consistency for extrusion; extruding moist crumb composition using an extruder such as a low pressure basket extruder comprising basket orifice diameters in the range of from 1.5 to 4mm to provide an extrudate; spheronising the extrudate to provide granules; and drying the granules to provide a granular composition in which at least 70% w/w granules have an aspect ratio no greater than 1.5 and preferably no greater than 1.2. 4 2014256380 30 Oct 2014 [12] In a preferred set of embodiments the granular composition comprises 30% to 70%w/w tebuthiuron and from 15% to 70% w/w of filler.

[13] The step of mixing preferably involves mixing from 30% to 60% w/w (preferably 30% to 50%w/w, more preferably 35% to 45% w/w) tebuthiuron; from 30% to 65% w/w filler (preferably kaolinite); (each preferably in finely divided form).

[14] In a further aspect we provide a method of controlling weeds in an area of land comprising applying to the area of land by aerial broadcasting the granular composition herein described and preferably prepared according to the process herein described.

[15] In a preferred embodiment the the standard deviation of the distribution of individual particle aspect ratios throughout the sample is less than 0.2 and more preferably less than 0.15.

[16] Throughout the description and the claims of this specification the word “comprise” and variations of the word, such as “comprising” and “comprises” is not intended to exclude other additives, components, integers or steps.

Detailed Description [17] The herbicidal granular composition comprises: at least 30% w/w (preferably 30% to 70% w/w more preferably from 30% to 60% w/w such as 30% to 50%w/w or 35% to 45% w/w) tebuthiuron; optionally a filler (preferably from 15%w/w to 70w/w filler more preferably from 30% to 65% w/w filler which is preferably kaolinite); wherein at least 70% w/w, preferably at least 80% w/w (more preferably at least 90% w/w and still more preferably at least 95% w/w) of the granules have an aspect ratio in the range of from 1 to 1.5 preferable from 1 to 1.2 and the weight average particle diameter is in the range of from 1 mm to 4 mm (preferably 1.5 to 3.5 mm). 5 2014256380 30 Oct 2014 [18] In one embodiment the granules have a weight average particle diameter of about 2 mm. In another embodiment the granules have a weight average particle diameter of about 3 mm.

[19] The granules have an average aspect ratio of from 1 to 1.5. The aspect ratio is the ratio of the largest dimension of a granule divided by the smallest dimension. In one preference the granules have an average aspect ratio of from 1 to 1.3. In a further preference, the standard deviation of the distribution of individual particle aspect ratios throughout the sample is less than 0.4, preferably less than 0.3, more preferably less than 0.2 and most preferably less than 0.15.

[20] The average crush strength (hardness) of the granules is at least 150g and is preferably at least 500g. Granule hardness is lower when more water is retained within the granule, and granule hardness is greater when more water is removed by drying. In one preference the granules contain less than 7% w/w (preferably less than 4% w/w and most preferably less than 2% w/w) water.

[21 ] The granular composition preferably comprises a granule wetting agent. The wetting agent may be a surfactant such as an anionic, cationic, non-ionic, amphoteric surfactant or mixture of two or more thereof. The preferred wetting agent is selected from: sodium alkyl naphthalene sulfonate, sodium napthalene sulfonate, calcium lignosulfonate, sodium lignosulfonate, and ammonium lignosulfonate.

[22] Lignosulfonate wetting agents are particularly preferred. Examples of non-ionic surfactants include ethoxylated sorbitan esters such as EMSORB, TWEEN, and T-MAZE; ethoxylated sorbitan fatty acid esters such as SPAN and ALKAMUL; sucrose and glucose esters and derivatives thereof such as MAZON, RHEOZAN and GLUCOPON; ethoxylated alcohols such as TRYCOL, BRIJ, ARMIX and PLURAFAC; ethoxylated alkylphenols such as IGEPAL, MACOL and TERGITOL; ethoxylated fatty amines such as TRYMEEN and ETHOMEEN; ethoxylated fatty acids such as EMEREST, ALKAMUL and TRYDET; ethoxylated fatty esters and oils such as ALKAMUL and ATLAS G; fatty acids such as ATLAS G-1556; glycerol esters such as MAZOL GMO; glycol esters such as GLYCOL SEG; lanolin-based derivatives such as 2014256380 30 Oct 2014 6 AMERCHOL CAB; methyl esters such as OLEOCAL ME; monoglycerides and derivatives such as ETHOSPERSE G-26; propoxylated and ethoxylated fatty acids such as ANTAROX AA-60; block copolymers of ethylene oxide and propylene oxide such as PLURONIC or SURFONIC; silicone-based surfactants such as SILWET, BREAKTHRU and mixtures of organosilicon surfactant with non- ionic or ionic surfactants; polysaccharides, copolymers of acrylamide and acrylic acid; and acetylenic diol derivatives such as SURFYNOL 104 or tristyrylphenols such as SOPROPFIOR among others. Examples of anionic surfactants include phosphate esters such as EMPFIOS and RFIODAFAC; sulfates and sulfonates of oils and fatty acids such as POLYSTEP; sulfates and sulfonates of ethoxylated alkylphenols such as TRITON X-301; sulfates of dodecyl and fridecylbenzenes such as CALMULSE; sulfonates of condensed naphthalenes such as VULTAMOL; sulfonates of naphthalene and alkyl naphthalene such as MOREWET and sulfuosuccinates and derivatives such as MONAWET, among others.

[23] The wetting agent in one set of embodiments is present in the granular composition in an amount in the range of from 0.5 % to 5% w/w, more preferably about 2% w/w of the composition. The granular composition may further comprise an extrusion aid such as calcium stearate, preferable in an amount in the range of from 0.5 % to 5% w/w, more preferably about 2% w/w of the composition.

[24] The granular composition preferably further comprises a flow agent such as talc, preferable in an amount in the range of from 5 % to 25% w/w, more preferably about 15% w/w of the composition.

[25] The granular composition may comprise a binder. Examples of the binder may comprise one or more selected from the group consisting of polyvinylpyrrolidone, a lignin, a lecithin, a starch, a gluten, a polyethylene glycol, cellulose and cellulose derivatives, disaccharide such as sucrose, lactose and maltose, hydrolyzed starches such as maltodextrin and corn syrup solids, sugar alcohols such as sorbitol and mannitol and other sugars such as glucose and fructose. 2014256380 30 Oct 2014 7 [26] The term broadcast granules refers to granules which are applied directly to an area of ground on which weeds are to be controlled. The broadcast granules are distinguished from water dispersible granules which are prepared and transported in granular form but are dispersed in water prior to application to and area of ground or to soil or weeds. The herbicidal granular composition preferably has a granule crush strength of at least 150 g and more preferably at least 500 g.

[27] The herbicidal granular composition, in a preferred set of embodiments, provides a granule number per unit weight in the range of from 40 to 500 granules per gram. In contrast the TEBULAN and GRASLAN products provide a granule number per unit weight of about 7 to 20 granules per gram. In one preference the average granule size is about 2mm (diameter) and the granule number per unit weight is in the range 150 to 500 per gram. In another preference the average granule size is about 3mm (diameter) and the granule number per unit weight is in the range from 40 to 200 per gram.

[28] In one set of embodiments the herbicidal granular composition is formed by extrusion and spheronisation. The technique generally involves (i) preparation of the wet mass, (ii) shaping the wet mass, (iii) breaking up the extrudate, (iv) rounding off the particles into spheres (spheronisation) and finally (v) drying of the pellets. Hosokawa BEPEX GmbH (http://www.hosokawamicron.com) describes the technique of low-pressure extrusion and spheronisation for the production of cylindrical, rounded and spherical pellets. In a particularly preferred embodiment the extrusion apparatus comprises (i) cylindrical extrusion chamber, (ii) counter-rotating rotors in the upper part of the feed hopper, (iii) a mixing and densification section proximal to the screen baskets, and (iv) screen baskets, which have an array of perforations for forming the extrusions. The dimension of the perforations and the wall thickness of the screen section may be chosen having regard to the desired particle dimensions following spheronisation. Spheronisation typically involves imparting an intense rolling movement to granules. 2014256380 30 Oct 2014 8 [29] In a set of embodiments we provide a process for preparation of a herbicidal granular composition for aerial application of the granules to an area of land on which weeds are to be controlled, the process comprising: mixing a composition comprising at least 30% w/w (preferably 30% to 70% w/w more preferably from 30% to 60% w/w such as 30% to 50%w/w or 35% to 45% w/w) tebuthiuron; optionally a filler (preferably from 15%w/w to 70w/w filler more preferably from 30% to 65% w/w filler which is preferably kaolinite); (the components are preferably in finely divided form) with water to form a composition of moist crumb consistency for extrusion; extruding moist crumb composition using a low pressure basket extruder comprising basket orifice diameters in the range of from 1.5 to 4mm to provide an extrudate; spheronising the extrudate to provide granules; and drying the granules to provide a granular composition in which at least 70% w/w granules, preferably at least 80% w/w granules (preferably at least 90% w/w and more preferably at least 95% w/w) have an aspect ratio no greater than 1.5 and preferably no greater than 1.2. Preferably the standard deviation of the distribution of particle aspect patios throughout the granules is no more than 0.2mm, preferably no more than 0.15mm.

[30] The quantity of water used in the mixing process will depend on the nature of the components and their proportions. In one set of embodiments the amount of water is in the range of from 5% to 20% by weight (preferably 8-15% by weight) addition on dry blend weight. The water used in preparation of the granules may be added in the form of liquid water, steam, an aerosol or fine spray of water.

[31 ] In one set of embodiments the basket extruder comprises a cutting device outside of the basket to reduce the extrudate to a uniform length prior to spheronisation. 2014256380 30 Oct 2014 9 [32] The composition and process use 30% to 65% w/w filler. The filler may comprise a range on inorganic materials such as clays, talc, sodium sulphate, pyrophyllite clay, silica, attapulgus clay, kaolin clay, kieselguhr, chalk, diatomaceous earth, lime, calcium carbonate, bentonite clay, Fuller's earth and the like or organics such as urea. We have found that a filler consisting of clay and more preferably kaolinite, in an amount of from 60% to 100% by weight of the filler component is more preferred. In one embodiment the filler further comprises a relatively minor proportion of silica such as up to 15% (preferably 5% to 10%) by weight of the filler component.

[33] The basket extruder may, and preferably will, comprise a perforated cylinder oriented with a vertical axis.

[34] The basket orifices are preferably about 2 mm in diameter or about 3 mm in diameter.

[35] In one set of embodiments the cylindrical basket is rotated about the vertical axis and a counter rotating stirrer is forces wet crumb through the basket orifices. We have found that the preparation of granules of the desired morphology is enhanced when the basket extruder is provided with at least one stationary cutting blade positioned adjacent the outside of the rotating basket.

[36] In a further set of embodiments there is provided a method of controlling weeds in an area of land comprising applying to the area of land by aerial broadcasting of the granular composition as herein described. The granular composition is typically distributed in dry form from an aircraft such as a fixed wing aeroplane or helicopter.

[37] The method is useful in weed control on land infested with one or more target weeds selected from the group consisting of brigalow, parkinsonia, prickly acacia, mimosa pigra, black tea tree, broadleaf tea tree, cocky apple, paperbark teatree, poplar gum, swamp box, African boxthorn, coolibah, rubbervine, whitewood, belah, currant bush, lime bush, dawson gum, false sandalwood, hollybush, poplar box, yellow wood, silver leaved ironbark, brown box, gidgee, gum-topped box, groundsel bush, lantana, wild rosemary, gorse and parthenium. In a preferred set of 2014256380 30 Oct 2014 10 embodiments the weeds are selected from the group consisting of parkinsonia, prickly acacia, brigalow, mimosa pigra and combinations thereof.

[38] In a preferred set of embodiments the weeds have a confined root system such as those selected from the group consisting of gorse, parthenium, sifton bush/chinese scrub, holly bush, African box thorn, sweet briar, current bush, lime bush, blue heliotrope and combinations thereof.

[39] The composition and method of the invention are particularly useful in control of one or more weeds selected from Brigalow, Parkinsonia, Prickly Acacia and Mimosa Pigra.

[40] We have found that the method is particularly useful in control of weeds of relatively confined root systems such as gorse and parthenium.

[41 ] We have found that the spheronised particles of uniform size and aspect ratio as herein described provide a very significant improvement in weed control, particularly of woody and herbaceous plants and sugar cane, when applied by aerial broadcasting. In particular, the granule composition of the invention provides greater control of granule distribution including more even control of weeds in the area to which the granules are applied and the granules result in fewer “hot spots” with comparatively high concentration of granules than the general area of distribution and fewer areas if inadequate control when compared with known extruded granules of less uniform aspect ratio. Of particular importance is the economy of active application and reduced costs provided by more rapid application in both helicopters and fixed wing aircraft. Without wishing to be bound by theory it is believed that a more rapid application rate can be achieved using a wider swathe of granule application with each pass.

[42] The granules may be applied from the ground by hand or land based vehicle or an aircraft. The method of the invention is particularly advantageous when the granules are applied from an aircraft. One of the significant advantages of the invention is that it allows each aircraft flight to treat a greater surface area and also 11 2014256380 30 Oct 2014 generally improves the rate of treatment (hectares per minute) which is achieved at comparable speeds.

[43] In one set of embodiments the granules are applied using a helicopter having an application speed of greater than 80 Km/hr and a granule carrying capacity of greater than 200Kg.

[44] In one set of embodiments the granules are applied using a fixed wing aircraft having an application speed of greater than 150 Km/hr and a granule carrying capacity of greater than 1500 litres.

[45] In a further set of embodiments the granules are applied from a fixed-wing aircraft wherein the area treated per hopper load is greater than 150 hectares (preferably greater than 200 hectares and more preferably greater than 210 hectares).

[46] In a set of embodiments the granules are applied from a helicopter wherein the area treated per hopper load is greater than 25 hectares (preferably greater than 30 and more preferably greater than 35 hectares).

[47] The invention will now be described with reference to the following examples.

It is to be understood that the examples are provided by way of illustration of the invention and that they are in no way limiting to the scope of the invention.

Brief Description of Drawings [48] Examples of the invention are compared with compositions not of the invention with reference to the drawings. In the drawings:

Figure 1 is a column chart showing the eccentricity values of samples of different commercially available and extruded granules;

Figure 2 is a column chart showing the variation in length (longest dimension) within samples of commercially available and extruded granules;

Figure 3 is a column chart showing the variation in hardness of samples of commercially available and extruded granules; and 2014256380 30 Oct 2014 12 in these Figures, the term “extrudate” refers to shaped granular material of 2mm diameter prior to addition to the spheroniser. EXAMPLES Example 1 [49] A homogeneous dry blend was made of the following finely divided materials by gentle mixing with a spoon followed by use of a food processor with slow planetary mixing action: • Kaolin Clay Q38 (also known as Unimin clay group 3), comprising 65-95% Kaolinite CAS# 1318-74-7, 5-10% quartz (crystalline silica) CAS# 14808-60-7. 43.3 parts were used. • Talc 25B -14 parts were used. • Tebuthiuron 96% technical material - 41.7 parts were used. • Morwet EFW (lignosulfonate) - 2 parts were used.

Example 2 [50] Water was added in small increments to the above dry blend, with further slow mixing to maintain homogeneity. After 5% w/w water had been mixed in, the wet crumb was placed in a small basket (low-pressure) extruder with 2mm diameter holes. The extruded strands were inspected for integrity after extrusion. If the resultant strands were powdery, further small increments of water were added to the wet cake, and a further extrusion process was carried out.

[51 ] If the extruded strands coalesced with each other, this was taken as a sign of water excess.

[52] An adequate quantity of water was typically in the range 8-15% weight addition on dry blend weight, and the exact amount depended on ambient temperature, humidity, and basket extruder size and configuration. 13 2014256380 30 Oct 2014 [53] The extruded strands with adequate water content were mixed by hand to encourage break-up of the strands.

[54] The resultant strands were placed on the plate of a spheroniser with a 50cm diameter plate (having raised pryramidal sections of height approximately 2mm). The spheroniser was set in motion at 600rpm, and with a compressed air stream emerging from the bottom of the spheroniser container, and directed over the side walls. The spheronisation time was 30 seconds.

[55] Spheronised particles were dried, typically to about 2% to 7% w/w water, to provide hard granules that could be packed and stored without dusting.

[56] The granules prepared in accordance with this example are referred to as “Tebuthiuron 2mm” in subsequent examples.

Example 3 [57] This example was carried out in the same way as Example 2; however the holes in the basket extruder were 3mm in diameter.

[58] The granules prepared in accordance with the examples are referred to as “Tebuthiuron 3mm” in subsequent examples.

Example 4 [59] This example was carried out using the same component ratios as in Example 1, however with a total of 30 kg of dry blend material. The dry blend components were added to a hopper containing a slowly rotating screw (vertical Nauta mixer configuration). A further 2% by weight of calcium stearate (on total dry blend weight) was mixed in as a processing aid. Water was added in multiple small increments with intermittent extrusion testing of wet crumb. Wet crumb was added to a basket extruder with the following features: Rotating vertical cylindrical basket with 2mm or 3mm holes, counter-rotating feed agitator designed to force wet crumb at low pressure through the holes in the basket, stationary cutting blades positioned on the outside of the rotating basket to cut the extruded strands so that relatively uniform strand segments were formed and added to the spheroniser. 2014256380 30 Oct 2014 14

Examples 5 and 6 [60] These examples compare the eccentricity, length and hardness of granule compositions of Examples 2 and 3 with commercially available Tebulan™ granules, Graslan™ granules and simple extrudates (2mm diameter) without spheronisation.

Example 5 [61] Eccentricities were calculated as ratio of long granule dimension to short granule dimension. Eccentricity values close to 1 were found to be desirable, and correspond to spherical or semi-spherical granule morphology. Length measurement is for the long granule dimension (the two short dimensions are uniform, and are determined by the hole dimension in the basket of the basket extruder). Hardness measurement is in terms of individual granule crush test where the granules are compressed under a flat surface on top of a scale, and the weight at granule crush is determined. The eccentricity of the granule compositions and variation within compositions is shown in Figure 1. The standard deviation in eccentricity of each granule composition was determined and is reported in Table 1.

Table 1: Eccentricity - Standard deviation

Tebuthiuron 3mm 0.065877 Tebuthiuron 2mm 0.118713 Tebulan™ 0.55021 Graslan™ 0.667592 Tebuthiuron Extrudates 0.501649 [62] The length measurement (length in mm) and variation for each of the granule compositions is shown in Figure 2.

[63] The average length measurement for each granule composition is shown in Table 2.

Table 2: Average length 15

Tebuthiuron 3mm 3.123 mm Tebuthiuron 2mm 2.1665 mm Tebulan 5.64 mm Graslan 5.84 mm Tebuthiuron Extrudates 5.265 mm 2014256380 30 Oct 2014 [64] The hardness (individual crush strength) of each of the compositions, including variation in crush strength, is shown in Figure 3 where the vertical axis relates to grams of weight required for crushing. The average hardness for each granule composition is reported in Table 3.

Table 3: Average hardness (crush strength)

Tebuthiuron 3mm-average hardness 634.0075g Tebuthiuron 2mm-average hardness 285.0905g Tebulan™-average hardness 3201.65g Graslan™ -average hardness 1224.18g

Example 6 [65] A composition in accordance with the invention comprising 60% w/w tebuthiuron active was prepared by blending the components in Table 4 in accordance with the general procedure of Example 2. The water content in the extruded crumb was approx. 11% w/w which was dried to approx. 2%w/w.

Table 4

Constituent name CAS No. 600g/kg Purpose in formulation Tebuthiuron (96%) 34014-18-1 625 Active Kaolin Clay 318-74-7 188 Carrier Talc T25B 14807-96-6 41.7 Carrier 16

Sodium alkyl naphthalene sulfonate (Morwet EFW) Proprietary 92 Wetter Calcium Stearate 1592-23-0 83.3 Processing aid Total weight/weight (nonaqueous) 1000 g/kg Formulation type: Granular 2014256380 30 Oct 2014

Example 7 [66] This example relates to the method of controlling weeds in accordance with the invention using fixed wing aircraft and helicopters for aerial broadcasting of the granules of the invention.

[67] The known products Graslan 200 and Tebulan 200 and Invention Example 2 and Invention Example 3 are distributed on weed infested areas of land using helicopters or fixed wing aircraft such as those specified in Table 5. Where helicopters are used it was preferred that the application speed was at least about 80 Km/hr and the granule carrying capacity (*weight) is typically at least 200Kg. Where fixed wing aircraft were used the preferred application speed was 150 Km/hr and preferred granule capacity (volume) was at least 1500L.

Table 5

Aircraft Type Graslan 200 Tebulan 200 Example 2 2mm Example 3 3mm *Ayres Turbo Thrush / Air Tractor (PT6) (TPE331) Area per minute 10.3 Ha/min 10.3 Ha/min 12.6 Ha/min 13.3 Ha/min Ha treated / hopper load 100 Ha 100 Ha 240 Ha 213 Ha #Bell 205/206 (110 KPH) Area rep minute 2.2 Ha/min 2.2 Ha/min 2.9 Ha/min 3 Ha/min 17 2014256380 30 Oct 2014

Ha treated / hopper load 20 Ha 20 Ha 40 Ha 40 Ha #Bell 47 (80 KPH) Area per minute 1.5 Ha/min 1.5 Ha/min 1.8 Ha/min 1.8 Ha/min Ha treated / hopper load 20 Ha 20 Ha 40 Ha 40 Ha #R 44 / 66 Area per minute 2.2 Ha/min 2.2 Ha/min 2.9 Ha/min 3 Ha/min Ha treated / hopper load 20 Ha 20 Ha 40 Ha 40 Ha *Fixed wing aircraft # helicopter

Example 8 [68] The granules of Example 3 were prepared with 11% moisture content (predrying) and were then dried to (a) 8.2% and (b) 1.8% moisture content. The hardness (crush strength) was determined and was as shown in Table 6.

Table 6

Moisture Content Hardness 8.2% 620 - 805 g 1.8% >2.4 kg [69] Drying increased granule hardness - the drier granules were difficult to crush. Example 9

Methodology and data For Gorse weed Trial (Gorse = Ulex europaeus) [70] Trial site was quarantined from cultivation, herbicide application, grazing stock, flood and other cultural practices (e.g. trimming, fire burn-off). 2014256380 30 Oct 2014 18 [71] Trial design was: Randomised complete block design, plot size was 1 plant (preferably isolated single plants to allow accurate application and assessment. 3 replicates. Granules were applied by hand at label rates around the base of the plant.

[72] Assessments: At 9 months after treatment. Herbicidal effects noted as % brown-out. The treatments need rainfall to activate the product.

Untreated Control: 3% brown-out

Tebuthiuron 400 (3mm), 7.5 kg/ha 70-75% brown-out

Tebulan 200, 1.5 kg/ha, 70-75% brownout

Example 10

Bioefficacy Example (Teb 400) [73] Aerial application of granules performed at Moura, Queensland, Australia (Parthenium weed infestation).

[74] Granules made according to the method of Example 2 (2 mm diameter) were applied by a fixed wing “402 Air Tractor” agricultural aircraft, with a Meter-rate precision metering device. The runs were flown in a race-track, with all applications of all treatment rates flown in the same direction. Each individual application run had 26m swathes. Each treatment was 3 runs wide or 78m wide and each separating control strip is 2 runs wide 52m. The following treatments compared: 1. zero-granule control 2. Tebulan 200 granules at 200g/kg tebuthiuron loading (commercially available from PGR International P/L Australia) and applied at 15 kg/ha 3. Granules at 400 g/kg Tebuthiuron loading (as described in example 2) and applied at 7.5 kg/ha [75] At 6 months after treatment the estimated % biomass reduction (parthenium biomass) for the above treatments was as follows: (1) zero, (2) 72.5 and (3) 75 (not significantly different from 72.5).

Claims

Claims

1. A herbicidal granular composition for aerial application of the granules to an area of land on which weeds are to be controlled, comprising at least 30%w/w tebuthiuron wherein at least 70% w/w of the granules have an aspect ratio in the range of from 1 to 1.5 and the weight average particle diameter is in the range of from 1 mm to 4 mm.
2. A granular herbicidal composition according to claim 1 comprising: from 30% to 60% w/w tebuthiuron; and from 30% to 65% w/w filler.
3. A herbicidal granular composition according to claim 1 or claim 2, wherein at least 90% w/w of the granules have an aspect ratio of from 1 to 1.2.
4. A herbicidal granular composition according to any one of the previous claims, wherein the standard deviation of aspect ratio distribution of the granules is less than 0.2.
5. A herbicidal granular composition according to any one of the previous claims further comprising a granule wetting agent in an amount in the range of from 0.5 % to 5% w/w of the composition.
6. A herbicidal granular composition according to any one of the previous claims further comprising an extrusion aid such as calcium stearate, preferable in an amount in the range of from 0.5 % to 5% w/w of the composition.
7. A herbicidal granular composition according to any one of the previous claims further comprising a flow agent in an amount in the range of from 5 % to 25% w/w.
8. A herbicidal granular composition according to any one of the previous claims, wherein the granule crush strength is at least 150 g.
9. A herbicidal granular composition according to claim 7, wherein the granule crush strengths is at least 500g.
10. A herbicidal granular composition according to any one on the previous claims, wherein the granule number per unit weight is in the range of from 40 to 500 granules per gram.
11. A herbicidal granular composition according to any one of the previous claims formed by extrusion and spheronisation.
12. A herbicidal granular composition according to any one of the previous claims, comprising: from 30% to 50% w/w tebuthiuron, from 30% to 65% w/w kaolinite filler, wherein 90% of the granules have an aspect ratio in the range of from 1 to 1.2, the weight average particle diameter is in the range of from 1.5mm to 3.5mm and the granules comprise less than 7% w/w water.
13. A herbicidal granular composition according to any one of the previous claims, wherein the water content is less than 2% w/w.
14. A process for preparation of a herbicidal granular composition for aerial application of the granules to an area of land on which weeds are to be controlled, the process comprising: mixing a composition comprising at least 30% w/w tebuthiuron with water to form a composition of moist crumb consistency for extrusion; extruding moist crumb composition using a low pressure basket extruder comprising basket orifice diameters in the range of from 1.5 to 4mm to provide an extrudate; spheronising the extrudate to provide granules; and drying the granules to provide a granular composition in which at least 70% w/w granules have an aspect ratio no greater than 1.5.
15. A process according to claim 14, wherein the step of mixing the composition comprises mixing from 30% to 60% w/w tebuthiuron; and from 30% to 65% w/w filler.
16. A process according to claim 14 or claim 15, wherein the drying of the granules provides a water content of less than 7% w/w.
17. A process according to claim 14 or claim 15, wherein the drying of the granules provides a water content of less than 2% w/w.
18. A process according to any one of claims 14 to 16, wherein the basket extruder comprises a cutting device outside of the basket to reduce the extrudate length prior to spheronisation.
19. A process according to claim 14, wherein the basket extruder comprises a perforated cylinder oriented with a vertical axis.
20. A process according to any one of claims 14 to 19, wherein the average standard deviation of the granule aspect ratio is less than 0.2.
21. A process according to claim 19, wherein the cylindrical basket is rotated about the vertical axis and a counter rotating stirrer is forces wet crumb through the basket orifices.
22. A process according to claim 18, wherein the basket extruder is provided with at least one stationary cutting blade positioned adjacent the outside of the rotating basket.
23. A method of controlling weeds in an area of land comprising applying to the area of land by aerial broadcasting of the granular composition according to any one of claims 1 to 13.
24. A method according to claim 23, wherein the granular composition is distributed in dry form from an aircraft such as a fixed wing aeroplane or helicopter.
25. A method according to any one of claims 23 or claim 24, wherein the land is infested with weeds selected from , brigalow, parkinsonia, prickly acacia, mimosa pigra, black tea tree, broadleaf tea tree, cocky apple, paperbark teatree, poplar gum, swamp box, African boxthorn, coolibah, parkensonia, prickly acacia, rubbervine, whitewood, mimosa pigra, belah, brigalow, currant bush, lime bush, dawson gum, false sandalwood, hollybush, lime bush, poplar box, whitewood, yellow wood, silver leaved ironbark, brown box, gidgee, gum-topped box, groundsel bush, lantana, wild rosemary, current bush, gorse and parthenium. In a preferred set of embodiments the weeds are selected from the group consisting of parkinsonia, prickly acacia, brigalow, mimosa pigra and combinations thereof.
26. A method according to any one of claims 23 to 25, wherein the weeds include at least one selected from the group consisting of Gorse, Parthenium, Sifton bush/Chinese scrub,Holly bush, African box thorn, Sweet briar, Current bush, Lime bush, Blue heliotrope and combinations thereof.
27. A method according to claim 25, wherein the weeds include at least one selected from Brigalow, Parkinsonia, Prickly Acacia and Mimosa Pigra.
28. A method according to any one of claims 23 to 27, wherein the granules are applied using a helicopter having an application speed of greater than 80 Km/hr and a granule capacity of greater than 200Kg.
29. A method according to any one of claims 23 to 26, wherein the granules are applied using a fixed wing aircraft having an application speed of greater than 150 Km/hr and a granule capacity of greater than 1500 litres.
30. A method according to any one of claims 23 to 27, wherein the granules are applied from a fixed-wing aircraft wherein the area treated per hopper load is greater than 150 hectares.
31. A method according to any one of claim 23 to 28, wherein the granules are applied from a helicopter wherein the area treated per hopper load is greater than 25 hectares.