GB2190589A - Herbicidal method comprising the use of bromoxynil or ioxynil and terbuthylazine - Google Patents

Abstract

The present invention relates to a method of controlling the growth of weeds at a maize or sorghum crop locus which comprises applying to the locus (a) bromoxynil, which is 3,5-dibromo-4-hydroxybenzonitrile, or ioxynil, which is 4-hydroxy-3,5-diiodobenzonitrile, an agriculturally acceptable salt or ester thereof or a mixture thereof and (b) terbuthylazine which is 2-t.butylamino-4-chloro-6-ethylamino-1,3,5-triazine.

Description

SPECIFICATION Herbicidal Method Comprising the Use of Bromoxynil or loxynil and Terbuthylazine The present invention relates to new herbicidal compositions comprising bromoxynil and/or ioxynil and to their use in agriculture.

Bromoxynil [3,5-dibromo-4-hydroxybenzonitrile] and ioxynil [4-hydroxy-3,5-diiodobenzonitrile] and mixtures thereof are used on a large scale for post-emergence broad-leaf weed control in maize and sorghum. When used to control weeds at the "seedling" stage, to remove early competition, they are extremely effective, but owing to lack of residual activity in the soil they do not control the weeds which emerge after application. This can necessitate repeated application or delaying spraying until the majority of weeds have emerged by which time the oldest have exerted a considerable competitive effect on the crop. In addition certain broad-leaf weed species such as manyAmaranthus spp. are difficult to control, unless they are very young, with ioxynil and particularly with bromoxynil, without transient crop damage.

Bromoxynil and ioxynil and mixture thereof also have no useful activity against annual grass weeds.

It is to be understood that where in this specification reference is made to a "HBN herbicide" it is intended to refer to bromoxynil [3,5-dibromo-4-hydroxybenzonitrilel or ioxynil [4-hydroxy-3,5-diiodobenzonitrile] in the form of the parent phenol (acid equivalent), an agriculturally acceptable salt or ester thereof, preferably a metal or amine salt or an ester thereof with an alkanoic acid containing from 2 to 10 carbon atoms, or to mixtures, preferably 3:1-1:3 wt/wt mixtures calculated in terms of acid equivalent weights, thereof where the context so permits.

As a result of research and experimentation it has been discovered that the use of the compound 2-t.butylamino-4-chloro-6-ethylamino-1 ,3,5-triazine (hereinafter referred to for convenience as terbuthylazine) in combination with the HBN herbicide: a) adds residual soil activity, allowing early application and removal of weed competition without the necessity of repeated application, b) widens the spectrum of weed control to include weeds such as amaranthus spp. and Portulaca oleracea without loss of crop/weed selectivity, and c) gives control of annual grass weeds such as Echinochloa crus-galli and Digitaria sanguinalis.

Therefore the said combined use represents an important technological advance.

Surprisingly in addition to this, it has been found that the combined herbicidal activity of terbuthylazine with the HBN herbicide against many weed species is much greater than expected when applied post-emergence (e.g. as a post-emergence spray), i.e. the herbicidal activity of terbutylazine with the HBN herbicide showed an unexpected and remarkable degree of synergism in controlling the growth of many broad-leaf weed species, e.g. Datura ferrox, Portulaca oleracea, Chenopodium carinatum, Schkuhria pinnata, Tagetes minuta, Sesamum sp., Commelina benghalensis, Cleome monophylla, Chenopodium album, Argemone mexicana, Alternanthera pungens orAmaranthus spp., as defined by Limpel, L. E., P. H.

Schuldtand D. Lamont, 1962, Proc. NEWCC 16:4F53 using the formula:- XY E=X+Y- 100 where E=the expected percent inhibition of growth by a mixture of two herbicides at defined doses.

X=the percent inhibition of growth by herbicide A at a defined dose, and Y=the percent inhibition of growth by herbicide B at a defined dose (when the observed response is greater than expected the combination is synergistic).

The remarkable synergism gives improved reliability of control of a large number of weed species occurring in agriculture and leads to a considerable reduction in the amount of active ingredient employed for weed control.

More surprisingly it has been found that the synergistic effect does not extend to maize or sorghum. For example, bromoxynil octanoate is used for post-emergence control of broad leaf weeds in maize. In order to obtain greater than 95% control of certain weed species such as many Amaranthus spp. it is necessary to use a dose rate which can cause transient crop damage. It has been found by experiment that associations of bromoxynil octanoate with terbuthylazine act synergistically, giving enhanced herbicidal activity and control of a wide range of weed species.It wou Id be expected that these synergistic associations or bromoxynil octanoate and terbuthylazine would also give the same amount of crop damage as that given by bromoxynil octanoate alone at rates necessary for greater than 95% weed control since enhanced activity on weeds would be expected to be accompanied by enhanced activity on the crop. Unexpectedly, however, it was found that mixtures of bromoxynil octanoate and terbuthylazine caused no crop damage in maize at dose rates giving superior weed control to either bromoxynil octanoate or terbuthylazine used alone.

The remarkable synergistic effect on weeds which does not extend to the crop when the association is applied post-emergence gives improved selectivity for control of a large number of weed species occurring in maize and sorghum crops and permits a reduction in the amount of active ingredients employed.

Accordingly the present invention provides a method for the control of the growth of weeds at a locus which is an area used for growing a crop especially a crop of maize or sorghum which comprises the combined use of (a) ioxynil, which is 4-hydroxy-3,5-diiodobenzonitrile, or preferably bromoxynil, which is 3,5-dibromo-4-hydroxybenzonitrile, and agriculturally acceptable salt or ester thereof, preferably a metal or amine salt or an ester thereof with an alkanoic acid containing from 2 to 10 carbon atoms, or a mixture, preferably a 3:1-1::3 wt/wt mixture calculated in terms of acid equivalent weights, thereof and (b) terbuthylazine which is 2-t.butylamino-4-chloro-6-ethylamino-1,3,5-triazine. Preferably the application rates of (a) and (b) are between 100 and 500 (more preferably between 150 and 350) g acid equivalent (a.e.)/ha and between 200 and 2000 (preferably between 500 and 1000) g/ha respectively, of (a) and (b) in proportions of 5:2 to 1:20 and preferably 1:1 to 1:6 wt/wt of (a) to (b). The method of the invention may be used to control a broad spectrum of weed species in maize and sorghum crops by post-weed emergence pre-crop emergence to post-weed emergence post-crop emergence application and more especially early post-weed emergence post-crop emergence without damage to the crop.The method described above offers both foliar and residual activity and enables the growth of a broad spectrum of weed species to be controlled.

Appiication of the HBN herbicide and terbuthylazine may be made simultaneously or sequentially.

By the term 'post-emergence application' is meant application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. By the term 'foliar activity' is meant herbicidal activity produced by application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. By the term 'residual activity' is meant herbicidal activity produced by application to the soil in which weed seeds or seedlings are present before emergence of the weeds above the surface of the soil, whereby seedlings present at the time of application or which germinate subsequent to application from seeds present in the soil, are controlled.

In the method according to the present invention the use of one or more of the esters as hereinbefore defined of the HBN herbicide is preferred. Of the HBN herbicide esters, those with alkanoic acids containing from 4 to 8 carbon atoms, and more particularly the octanoates or heptanoates or mixtures thereof, are preferably used. The use of bromoxynil octanoate or heptanoate or a mixture thereof is especially preferred.

Weeds that may be controlled by the method include broad-leaf weeds such as Datura ferox; Chenopodium spp., e.g. Chenopodium carinatum;Amaranthus spp., e.g.Amaranthus deflexus, Amaranth us hybridus; Argemone subfusiformis; Cleome gynandra; lpomoea spp., e.g. Ipomoea coscinosperma; Tagetes minuta; Schkuhria pinnata; Cftrullus lanatus; Xanthium strumarium, Hibiscus trionum, Portulaca oleracea, Amaranth us spinosus, Sesamum sp., Commelina benghalensis, Cleome monophylla, Chenopodium album, Argemone mexicana and Alternanthera pungens and grass weeds such as Digitaria sanguinalis and Echinochloa crus-galli.

The pattern of persistence of the HBN herbicide and the terbuthylazine aliow the method of the present invention to be practised by the time-separated application of separate formulations.

In accordance with usual practice, a tank mix may be prepared prior to use by combining separate formulations of the individual herbicidal components.

The following Experiments iliustrate the present invention: EXPERIMENT 1 The efficacy ofthese mixtures was demonstrated in the following South African field trials where a bromoxynil ester/terbutylazine tank mix was compared with bromoxynil ester alone.

Bromoxynil octanoate (commercial product) at 675 and 337.5 g a.eJha and tank mixes of bromoxynil octanoate 225 g a.e./ha plus 1000 and 2000 g a.idha of terbuthylazine (commercial wettable powder 8009 a.iSkg) was applied at a volume rate of 187 I/ha to replicate small plots (10 m2) of maize (4-5 leaf stage) using a 2m boom sprayer fitted with 4x8002 T-jet at 200 kPa. Weed control and crop safety are assessed as percentage phytotoxicity compared with untreated plots 11 days post-spray (T+11) and 4 days post-spray for the crop (T+4).

The results are shown in Table I below.

TABLE I

Phytotoxicity Treatments Mean % weed control (T+11 days) (% crop damage) Ipomoea coscino- Datura Hibiscus Schkuhria Tagetes Amaranthus Xanthium Chemicals g. a.i./ha sperma ferox trionum pinnata minuta deflexus strumarium (T+4) (T+11) bromoxynil as octanoate* 675 100 100 97.3 100 100 97.6 100 28 10 bromoxynil as octanoate* 337.5 100 100 94.3 100 100 91.3 100 2 0 bromoxynil*+terbuthylazine 225+1000 100 100 100 100 100 100 100 0 0 bromoxynil*+terbuthylazine 225+1000 100 100 100 100 100 100 100 0 0 The synergistic activity found on Amaranthus spp. was surprisingly not observed on maize thus giving improved weed control and crop safety (improved selectivity).

EXPERIMENT 2 The following South African field trials demonstrate the synergistic activity of the combined use of bromoxynil and terbutylazine in controlling the growth of certain weeds.

Field Trials Showing Nature of Biological Synergism Between Bromoxynil and Terbuthylazine Bromoxynil octanoate (commercial product) at 225 g a.e./ha, terbuthylazine at 500 g a.i./ha and tank mixes of bromoxynil octanoate 225 g a.e./ha plus 500 and 1000 g a.i./ha of terbuthylazine (commercial wettable powder 800 g a.i./kg) was applied at a volume rate of 300 I/ha to replicate small plots (20 m2) of weeds indicated below using a 2m boom sprayer fitted with 5x8002 T-jet at 200 kPa. Weed control is assessed as percentage phytotoxicity compared with untreated plots 14 days post-sqray (T+14).

Growth Stage at Weed Species Application Datura ferox (D.f.) 5-6 leaves Portulaca oleracea (P.o.) 5-6 leaves Chenopodium carinatum (C.c.) 68 leaves Schkuhria pinnata (S.p.) 5--8 leaves Amaranthus spinosus (A.s.) 6-8 leaves Tagetes minuta (T.m.) 6 leaves Sesamum sp. (S.sp) 3-4 leaves Commelina benghalensis (C.b) 3-4 leaves Cleome monophylla (C.m.) 56 leaves Chenopodium album (C.a.) 68 leaves Argemone mexicana (A.m.) 4-5 leaves Alternanthera pungens (A.p.) 5-6 leaves The mean % weed control was observed for each species and tabulated in Table II below for each treatment together with the expected level of weed control anticipated for a combination of the two herbicides using the Limpel formula:- XY E=X+Y- - 100 TABLE II

Treatments Mean percentage weed control (T+14 days) g a.i.

Chemicals /ha D.f. P.o. C.c. S.p. A.s. T.m. S.sp. C.b. C.m. C.a. A.m. A.p.

Bromoxynil 225 92.5 0 50 60 20 57.5 62.5 50 20 75 52.5 55 as octanoate* Terbuthylazine 500 42.5 20 10 25 15 10 20 15 15 22.5 10 15 Bromoxynil* 225 + + Terbuthylazine 500 O 99 94.5 95 96.5 94.5 100 99 94.5 95.5 100 100 95.5 E 95.7 20 55 70 32 61.8 70 57.5 32 80.6 57.3 61.8 Bromoxynil* 225 + + 100 97 98 98 96 100 100 97 97 100 100 98 Terbuthylazine 1000 E=Expected from Limpel formula O=Observed These results show clearly that the combination is synergistic as the observed weed control for the combination of the two herbicides was much greater than expected.

EXPERIMENT 3 The following South African field trials demonstrate the activity of the combined use of bromoxynil and terbuthylazine on sorghum crops.

Two formulations of bromoxynil (as octanoate/heptanoate mix) and terbuthylazine containing per litre 150 g bromoxynil and 333 g terbuthylazine, and 90 g bromoxynil and 400 g terbuthylazine, respectively (prepared as hereinafter described in Examples 10 and 11 respectively) were diluted to give three doses.

Trials 1 and 2 Bromoxynil octanoate and heptanoate plus terbuthylazine was applied at a volume rate of 245 I/ha to replicate small plots (10 mx4 m) of sorghum (2--4 leaf stage) cultivar SSK 52 (trial 1) or cultivar NK 304 (trial 2).

Trial 3 Bromoxynil octanoate and heptanoate plus terbuthylazine was applied at a volume rate of 300 I/ha to replicate small plots (9 m x2.25 m) of sorghum (67 leaf stage cm to 45 cm tall) cultivar NK 222.

Crop safety is assessed as percentage phytotoxicity compared with untreated plots 7 days (T+7), 14 days (T+14) and 21 days post-spray (T+21) in Trials 1 and 2, and 12 days post-spray (T+12) in Trial 3.

The results are shown in Table Ill below.

TABLE III Treatment Phytotoxicity (% crop damage) bromoxynil + terbuthylazine Trial 1 Trial 2 Trial 3 g. a.e./ha g. a.i./ha (T+7) (T+14) (T+21) (T+7) (T+14) (T+21) (T+12) 300 + 666 5 7 5 5 8 5 1 375 + 832.5 - - - - - - 1 600 + 1332 10 10 10 10 10 8 9 180 + 800 - - - - - - 0 225 + 1000 2 0 0 2 0 0 0 450 + 2000 5 3 2 5 2 2 6 It will be appreciated that for the preferred ranges of rates of use the crop damage is acceptable in practice.

Selectivity of treatment of weeds in sorghum crops, using the mixtures of the invention is more than satisfactory.

According to a further feature of the present invention, there is provided a product comprising (a) 4-hydroxy-3,5-diodobenzonitrile or preferably 3,5-dibromo-4-hydroxy-benzonitrile, an agriculturally acceptable salt or ester thereof, preferably a metal or amine salt or an ester thereof with an alkanoic acid containing from 2 to 10 carbon atoms, or a mixture, preferably a 3:1-1:3 wt/wt mixture calculated in terms of acid equivalent weights, thereof and (b) terbuthylazine as a combined preparation for simultaneous, separate or sequential use in controlling the growth of weeds at a crop, especially a maize or sorghumicrop, locus.

According to a further feature of the present invention, there are provided compositions suitable for herbicidal use comprising (a) 4-hydroxy-3,5-diidobenzonitrile or preferably 3,5-dibromo-4-hydroxy-benzo- nitrile, an agriculturaily acceptable salt or ester thereof, preferably a metal or amine salt or an ester thereof with an alkanoic acid containing from 2 to 10 carbon atoms, or a mixture, preferably a 3:1-1:3 wt,wt mixture calculated in terms of acid equivalent weights, thereof and (b) terbuthyiazine in proportions of preferably 5:2 to 1:20 wt/wt of (a) to (b) [preferably 1:1 to 1::6 wfwt of (a) to (b)] in association with, and preferably homogeneously dispersed in, one or more compatible herbicidally-acceptable diluents or carriers and/or surface-active agents (i.e. diluents or carriers or surface-active agents of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with the HBN herbicide and terbuthylazine). The term "homogeneously dispersed" is used to include compositions in which the HBN herbicide and terbuthlazine are dissolved in the other components. The term "herbicidal compositions" is used in a broad sense to include not only compositions which are ready for use as herbicides but also concentrates which must be diluted before use. Preferably, the compositions contain from 0.05 to 90% by weight of the HBN herbicide and terbuthylazine.

The herbicidal compositions may contain both a diluent or carrier and a surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in herbicidal compositions of the present invention may be of the ionic or non-ionic types, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with nonyl- or octyl-phenols, or carboxylic acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxy groups by condensation with ethylene oxide, alkali and alkaline earth metal salts or sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sulphono-succinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates.Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, adsorbent carbon black and clays such as kaolin and bentonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding the HBN herbicide and terbuthylazine with solid diluents or by impregnating the solid diluents or carriers with solutions of the HBN herbicide and terbuthylazine in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obtain powders.

Granularformulations may be prepared by absorbing the HBN herbicide and terbuthylazine (dissolved in volatile solvents) onto the solid diluents or carriers in granular form and evaporating the solvents, or by granulating compositions in powder from obtained as described above. Solid herbicidal compositions, particularly wettable powders, may contain wetting or dispersing agents (for example of the types described above), which may also, when solid, serve as diluents or carriers.

Liquid compositions according to the invention may take the form of aqueous, organic or aqueous-organic solutions, suspensions and emulsions which may incorporate a surface-active agent.

Suitable liquid diluents for incorporation in the liquid compositions include water, acetophenone, cyclohexanone, isophorone, toluene, xylene and mineral, animal and vegetable oils (and mixtures of these diluents). Surface-active agents, which may be present in the liquid compositions, may be ionic or non-ionic (for example of the types described above) and may, when liquid, also serve as diluents or carriers.

Wettable powders and liquid compositions in the form of concentrates may be diluted with water or other suitable diluents, for example mineral or vegetable oils, particularly in the case of liquid concentrates in which the diluent or carrier is an oil, to give compositions ready for use. When desired, liquid compositions of the HBN herbicide and terbuthylazine may be used in the form of self-emulsifying concentrates containing the active substances dissolved in the emulsifying agents or in solvents containing emulsifying agents compatible with the active substances, the simple addition of water to such concentrates producing compositions ready for use.

Liquid concentrates in which the diluent or carrier is an oil may be used without further dilution using the electrostatic spray technique.

Herbicidal compositions according to the present invention may also contain, if desired, conventional adjuvants such as adhesives, protective colloids, thickeners, penetrating agents, stabilisers, sequestering agents, anti-caking agents, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Preferred herbicidal compositions according to the present invention are aqueous, organic or aqueous-organic suspension concentrates which comprise from 10 to 80% w/v of the HBN herbicide and terbuthylazone, from 2 to 13% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 2 to 87.9% by volume of water and/or organic solvent; wettable powders which comprise from 10 to 90% wlw of the HBN herbicide and terbuthylazine, from 2 to 10% w/w of surface-active agent and from 8 to 88% w/w of solid diluent or carrier; liquid emulsifiable suspension concentrates which comprise 10 to 70% w/v of the HBN herbicide and terbuthylazine, from 5 to 15% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 10 to 84.9% by volume of organic solvent; granules which comprise from 1 to 90% w/w of the HBN herbicide and terbuthylazine, from 0.5 to 2% wlw of surface-active agent and from 8 to 98.5% w/w of granular carrier and emulsifiable concentrates which comprise from 0.05 to 90% w/v, and preferably from 1 to 60% w/v, of the HBN herbicide and terbuthylazine, from 0.01 to 10% w/v, and preferably from 1 to 10% w/v, of surface-active agent and from 9.99 to 99.94%, and preferably from 39 to 98.99%, by volume of organic solvent.

An especially preferred herbicidal composition according to the present invention is a formulation which comprises one or more of the esters as hereinbefore defined of the HBN herbicide, an organic water immiscible solvent therefor, preferably an aromatic hydrocarbon, and in which terbuthylazine is substantially insoluble (less than 1% w/v), terbuthylazine and optionally water in which terbuthylazine is substantially insoluble (less than 0.5% w/v); from 2.0% to 5.0% w/v of water-insoluble nonionic surfactant; from 3.0% to 6.0% w/v of water-soluble wetting agents; from 0.2% to 2.0% w/v of water-soluble dispersion agent; from 0.01 to 0.5% w/v of antifoaming agent and from 0.5 to 2.0- w/v of mineral gelling agent.In the especially preferred herbicidal composition above the ratio of HBN ester(s) to terbuthylazine is from 5:2 to 1:20 and preferably from 1:1 to 1:6 wt'wt with the total amount of active ingredients comprising from 50% to 80% w/v of the formulation.

This formulation has flowable characteristics and is stable on storage both physically and chemically without separation of the two herbicidal components nor instability as a result of hydrolysis.

Any other pesticide soluble in the organic solvent may also be present. Also any other solid pesticide which is substantially insoluble in both water (less than 0.5% w/v) and the organic solvent (less than 1% w/v) may be present.

The especially preferred pesticidal compositions of this invention may be prepared by separately preparing a solvent based portion and a terbuthylazine portion and then combining the two.

First considering the terbuthylazine portion, the solid terbuthylazine is preferably ground in water using a conventional bead mill to give a particle size in the desired range to achieve optimum suspension stability.

The water-soluble surfactants together with the gelling agent are previously dispersed in the terbuthylazine and water before milling. This yields a sly wry of the terbuthylazine. The terbuthylazine and the surfactants and the gelling agent may be ground dry but this does not give the same desirable properties of long term stability as is achieved by grinding in water.

The solvent based portion may be prepared by dissolving the nonionic surfactant and the HBN herbicide ester in the solvent. Any convenient vessel fitted with a stirrer may be used. If required, heating may be used to aid solution.

The final formulation is prepared by simply pouring the solvent portion into the terbuthylazine portion in conventional equipment.

Simple stirring is sufficient to yield a homogeneous mixture.

Herbicidal compositions according to the present invention may also comprise the HBN herbicide and terbuthylazine in association with, and preferably homogeneously dispersed in, one or more other pesticidally active compounds and, if desired, one or more compatible pesticidally acceptable diluents or carriers, surface-active agents and conventional adjuvants as hereinbefore described.Examples of other pesticidally active compounds which may be included in, or used in conjunction with, the herbicidal compositions of the present invention include herbicides, for example to increase the range of weed species controlled, for example alachlor [a-chloro-2,6-diethyl-N-(methoxymethyl)acetanilidej, molinate [S-ethyl N,N-hexamethylene(thiocarbamate)], and oxadiazon [3-(2,4-dichloro-5-isopropoxy- phenyl)-5-t-butyl-1,3,4-oxadiazolin-2-onej; insecticides, e.g. carbaryl [naphth-1-yl N-methylcarbamate]; synthetic pyrethroids, e.g. permethrin and cypermethrin; and fungicides, e.g. 2,6-dimethyl-4-tridecylmorpholine, methyl N-( 1 -butylcarbamoylbenzimidazol-2-yl)carbamate, 1 ,2-bis-(3-methoxy- carbonyl-2-thioureido)benzene, isopropyl 1-carbamoyl-3-(3,5-dichlorophenyl)hydantoin and 1-(4-chloro- phenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)-butan-2-one. Other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention are plant growth regulators, e.g. succinamic acid, (2-chloroethyl)trimethylammonium chloride and 2-chioroethane- phosphonic acid; or fertilizers, e.g. containing nitrogen, potassium and phosphorus and trace elements known to be essential to successful plant life, e.g. iron, magnesium, zinc, manganese, cobalt and copper.

Pesticidally active compounds and other biologically active materials which may be included in, or used in conjunction with, the herbicidal compositions of the present invention, for example those hereinbefore mentioned, and which are acids, may, if desired, bs utilized in the form of conventional derivatives, for example alkali metal and amine salts and esters.

The compositions of the invention may be made up as an article of manufacture comprising the HBN herbicide and terbuthylazine and optionally other pesticidally active compounds as hereinbefore described or, as is preferred, a herbicidal composition as hereinbefore described, and preferably a herbicidal concentrate which must be diluted before use, comprising the HBN herbicide and terbuthylazine within a container for the aforesaid HBN herbicide and terbuthylazine or a said herbicidal composition, and instructions physically associated with the aforesaid container setting out the manner in which the aforesaid HBN herbicide and terbuthylazine or herbicidal composition contained therein is to be used to control the growth of weeds.The containers will normally be of the types conventionally used for the storage of chemical substances which are solids at normal ambient temperatures and herbicidal compositions, particularly in the form of liquid concentrates, for example cans and drums of metal, which may be internally-lacquered, and plastics materials, bottles of glass and plastics materials and, when the contents of the container is a solid, for example granular herbicidal compositions, boxes, for example of cardboard, plastics materials and metal, or sacks. The containers will normally be of sufficient capacity to contain amounts of the active ingredients or herbicidal compositions sufficient to treat at least one acre of ground to control the growth of weeds therein but will not exceed a size which is convenient for conventional methods of handling.The instructions will be physically associated with the container, for example by being printed directly thereon or on a label or tag affixed thereto. The directions will normally indicate that the contents of the container, after dilution if necessary, are to be applied to control the growth of weeds at rates of application between 100 g and 500 g a.e. of the HBN herbicide and between 200 g and 2000 g of terbuthylazine per hectare in the manner and for the purposes hereinbefore described.

The following Examples illustrate herbicidal compositions according to the present invention and herbicidal compositions suitable for use in the method for controlling the growth of weeds according to the present invention.

EXAMPLE 1 A water-miscible composition containing bromoxynil triethylamine salt was prepared from: bromoxynil 34% w/v triethylamine 15% w/v Soprophor BSU (tristyryl phenol ethylene oxide condensate containing 18 moles of ethylene oxide) 1.5% w/v diethylene glycol 25% w/v water to 100% by volume by mixing together a portion of the water, the diethylene glycol, the bromoxynil and the triethylamine (15% w/v of triethylamine represents a 2.6% by weight excess of triethylamine over the stoichiometric amount required to form bromoxynil triethylamine salt) with heating and stirring. The tristyryl phenol/ethylene oxide condensate was then added and the volume was made up to 100% by the addition of water.

EXAMPLE 2 A wettable powder was formed from: Terbuthylazine 80% w/w Arylan S (sodium dodecyl benzene sulphonate) 2% w/w Darvan No.2 (sodium lignosulphonate 5% w/w Aerosil (silicon dioxide of microfine particle size) 5% w/w Celite PF (synthetic magnesium silicate carrier) 8% w/w EXAMPLE 3 A water-miscible composition containing bromoxynil potassium salt was prepared from: bromoxynil 25% w/v potassium hydroxide 5.1% w/v tetrahydrofurfuryl alcohol 25% w/v water to 100% by volume by mixing together a portion of the water, the tetrahydrofurfuryl alcohol, the bromoxynii and the potassium hydroxide with heating and stirring and then the volume was made up to 100% by the addition of water.

EXAMPLE 4 An emulsifiable composition containing bromoxynil octanoate was prepared from: bromoxynil octanoate containing 63.9% w/w phenol acid equivalent 35.2% w/v Atlox 4855 (a mixture of anionic and nonionic surfactants) 3.75% w/v Agrilan A (a mixture of anionic and nonionic surfactants) 3.75% w/v Solvesso 150 (aromatic C10 petroleum fraction) to 100% by volume by mixing together a portion of the aromatic C10 petroleum fraction, the Atlox 4855, the Agrilan A and the bromoxynil octanoate with heating and stirring and then the volume was made up to 100% by the addition of aromatic C10 petroleum fraction.

EXAMPLE 5 An aqueous suspension concentrate containing bromoxynil phenol was prepared from: bromoxynil 56.25% w/v Soprophor FL (phosphate ester of aryl phenol ethoxylate) 3.5 w/v Sopropon T36 (sodium salt of polycarboxylic acid) 0.3% w/v Ethylan BCP (nonyl phenoi/ethylene oxide condensate containing 9 moles of ethylene oxide) 0.5% w/v Antifoam FD (silicone antifoam) 0.1%w/v Attagel 50 (swellable attapulgite clay) 2.0% w/v propylene glycol 5.0% w/v water to 100% by volume by intimately mixing the ingredients and grinding by pumping under pressure through a bead-charged mill.

EXAMPLE 6 An aqueous-organic suspension concentrate containing bromoxynil octanoate and terbuthylazine (1:4.5) was prepared from: bromoxynil octanoate containing 63.9% w/w phenol acid equivalent 10.0% w/v terbuthylazine 45.0% w/v Arylan CA (calcium dodecyl benzene sulphonate 70% solution in butanol) 2.0% w/v Synperonic NPE 1800 (nonyl phenol ethylene oxide/propylene oxide block copolymer) 3.0% w/v Solvesso 200 (aromatic C10/C13 petroleum fraction) 6.0% w/v Soprophor 3D33 (ethoxylated polyaryl phenol phosphate neutralised with triethanol amine) 0.16% w/v Olin 10G (nonyl phenol/glycidol condensate containing 10 moles of glycidol) 0.08% w/v Antifoam FD (silicone antifoam) 0.2% w/v Attagel 50 (swellable attapulgite clay) 2.0% w/v ammonium chloride 5.0% w/v water to 100% by volume by mixing together the calcium dodecyl benzene sulphonate solution, the nonyl phenol ethylene oxide/propylene oxide block copolymer, the aromatic C10/C13 petroleum fraction and the bromoxynil octanoate with heating and stirring. An aqueous suspension concentrate was then prepared by intimately mixing 25% by volume of water with terbuthylazine the ethoxylated polyaryl phenol phosphate neutralised with triethanolamine, the nonyl phenol/glycidol condensate, the silicone antifoam, the attapulgite clay and the ammonium chloride and then grinding by pumping under pressure through a bead-charged mill. The previously prepared bromoxynil octanoate solution was then added to this suspension concentrate with stirring and the volume was made up to 100% by the addition of water.

2.5 litres of the resulting formulation was diluted in 200 litres of water and sprayed post-emergence to control Amaranthus spp., lpomoea spp., Tagetes minuta and Xanthium strumarium in one hectare of maize.

EXAMPLE 7 An organic suspension concentrate containing bromoxynil octanoate and terbuthylazine (1:4.5) was prepared from: bromoxynil octanoate containing 63.9% w/w phenol acid equivalent 10.0% w/v terbuthylazine 45.0% w/v Agrilan A8 (a mixture of anionic and nonionic surfactants) 7.5% w/v Bentone 38 (an organic derivative of special magnesium montmorillonitethickener) 1.0% w/v Shellsol R (aromatic petroleum fraction) to 100% by volume by dissolving the bromoxynil octanoate in the aromatic petroleum fraction containing the mixture of anionic and nonionic surfactants. The terbuthylazine was dispersed in the resulting solution and then ground to the required particle size by pumping under pressure through a bead-charged mill.

2.5 litres of the resulting formulation was diluted in 200 litres of water and sprayed post-emergence to control Amaranthus spp., Ipomoea spp., Tagetes minuta and Xanthium strumarium in one hectare of maize.

EXAMPLE 8 A 1:1 mixture was formed by tank mixing 888 ml of the composition of Example 5 with 525 g of the composition of Example 2 in a volume of 100 litres of water. The resulting spray fluid was applied to one hectare of emerged maize to control Amaranth us retroflexus.

EXAMPLE 9 A 1:20 mixture was formed by tank mixing 444 ml of formulation of Example 4 with 2500 g of formulation of Example 2 in 300 litres of water. The resulting spray fluid was applied to one hectare of maize soon after emergence to control emerged and germinating Amaranthus retroflexus.

EXAMPLE 10 An aqueous-organic suspension concentrate containing bromoxynil as octanoate and heptanoate and terbuthylazine (0.45:1) was prepared from: bromoxynil as octanoate and heptanoate (1:1) 15.0% w/v terbuthylazine 33.3% w/v Ethylan NP1 (nonyl phenol/ethylene oxide condensate containing 1.5 moles of ethylene oxide) 3.0% w/v Solvesso 200 (aromatic C10/C13 petroleum fraction) 6.0% w/v Soprophor FL (ethoxylated polyaryl phenol phosphate neutralised with triethanolamine) 1.4% w/v Arylan PWS (amine salt of dodecyl benzenesulphonate) 0.35% w/v Ethylan BCP (nonyl phenol/ethylene oxide condensate containing 9 moles of ethylene oxide) 2.8% w/v Antifoam 426R (silicone antifoam) 0.21%w/v Attagel 50 (swellable attapulgite clay) 1.4% w/v propylene glycol 4.0% w/v water to 100% by volume By mixing together some attapulgite clay, the nonyl phenol/ethylene oxide condensate containing 1.5 moles of ethylene oxide, the aromatic C10/C13 petroleum fraction and the bromoxynil octanoate/ heptanoate with heating and stirring. An aqueous suspension concentrate was then prepared by intimately mixing 25% by volume of water with the terbuthylazine, the ethoxylated polyaryl phenol phosphate neutralised with triethanolamine, amine salt of dodecyl benzenesulphonate, the nonyl phenol/ethylene oxide condensate containing 9 moles of ethylene oxide, the silicone antifoam, the remaining attapulgite clay and the propylene glycol and then grinding by pumping under pressure through a bead-charged mill.

The previously prepared bromoxynil octanoate/heptanoate solution was then added to this suspension concentrate with stirring and the volume was made up to 100% by the addition of water.

1.5 litres of the resulting formulation was diluted in 200 litres of water and sprayed post-emergence to control Amaranthus spp., Ipomoea spp., Tagetes minuta and Xanthium strumarium in one hectare of sorghum.

EXAMPLE 11 An aqueous-organic suspension concentrate containing bromoxynil as octanoate and heptanoate and terbuthylazine (1:4.5) was prepared from: bromoxynil as octanoate and heptanoate (1:1) 9.0% w/v terbuthylazine 40.0% w/v Ethylan NP1 (nonyl phenol/ethylene oxide condensate containing 1.5 moles of ethylene oxide) 1.8% w/v Solvesso 200 (aromatic C10/C13 petroleum fraction) 3.5% w/v Soprophor FL (ethoxylated polyaryl phenol phosphate neutralised with triethanolamine) 1.7% w/v Arylan PWS (amine salt of dodecyl benzenesulphonate) 0.42% w/v Ethylan BCP (nonyl phenol/ethylene oxide condensate containing 9 moles of ethylene oxide) 3.4% w/v Antifoam 426R (silicone antifoam) 0.25% w/v Attagel 50 (swellable attapulgite clay) 1.26% w/v propylene glycol 4.8% w/v water to 100% by volume by mixing together some attapulgite clay, the nonyl phenol/ethylene oxide condensate containing 1.5 moles of ethylene oxide, the aromatic C10/C13 petroleum fraction and the bromoxynol octanoatel heptanoate with heating and stirring. An aqueous suspension concentrate was then prepared by intimately mixing 25% by volume of water with the terbuthylazine, the ethoxylated polyaryl phenol phosphate neutralised with triethanolamine, amirie salt of dodecyl benzenesulphonate, the nonyl phenol/ethylene oxide condensate containing 9 moles of ethylene oxide, the silicone antifoam, the remaining attapulgite clay and the propylene glycol and then grinding by pumping under pressure through a bead-charged mill.

The previously prepared bromoxynil octanoate/heptanoate solution was then added to this suspension concentrate with stirring and the volume was made up to 100% by the addition of water.

2.5 litres of the resulting formulation was diluted in 300 litres of water and sprayed post-emergence to control Amaranthus spp., Ipomoea spp., Tagetes minuta and Xanthium strumarium in one hectare of sorghum.

In the mixed formulations in the Examples hereinbefore, the HBN herbicide may be replaced by one other or a mixture of the HBN herbicides.

Claims (55)

1. A method of controlling the growth of weeds at a crop locus which comprises applying to the locus (a) bromoxynil, which is 3,5-dibromo-4-hydroxybenzonitrile, or ioxynil, which is 4-hydroxy-3,5-diidobenzonitrile, an agriculturally acceptable salt or ester thereof or a mixture thereof and (b) terbuthylazine which is 2-t.butylamino-4-chloro-6-ethylamino-l ,3,S4riazine.

2. A method according to claim 1 in which the crop is a maize or sorghum crop.

3. A method according to claim 1 or 2 in which (a) comprises bromoxynil, an agriculturally acceptable salt or ester thereof.

4. A method according to claim 1,2 or 3 in which the acid equivalent weight ratio of (a) to (b) is from 5:2 to 1:20 and in which (a) is applied to the locus at a rate of from 100 to 500 g acid equivalent/ha and (b) at a rate of from 200 to 2000 g/ha.

5. A method according to claim 1,2 or 3 in which the acid equivalent weight ratio of (a) to (b) is from 1:1 to 1:6 and in which (a) is applied to the locus at a rate of from 150 to 350 g acid equivalent/ha and (b) at a rate of from 500 to 1000 g/ha.

6. A method according to claim 1, 2,3,4 or 5 in which (a) comprising a metal or amine salt of bromoxynil or oxynil.

7. A method according to claim 1,2,3,4 or 5 in which (a) comprises the ester of bromoxynil or ioxynil with an alkanoic acid of from 2 to 10 carbon atoms.

8. A method according to claim 7 in which (a) comprises the ester of bromoxynil or ioxynil with an alkanoic acid of from 4 to 8 carbon atoms.

9. A method according to claim 7 or 8 in which (a) comprises the ester of bromoxynil or ioxynil with octanoic or heptanoic acid.

10. A method according to claim 9 in which (a) comprises bromoxynil octanoate or bromoxynil heptanoate.

11. A method according to claim 1,2,3,7,8,9 or 10 in which (a) comprises the ester of bromoxynil or ioxynil with a mixture of acids.

12. A method according to any one of claims 1 to 11 in which the application is early post-weed emergence post-crop emergence.

13. A method according to any one of claims 1, 2 and 4 to 14 in which the mixture of bromoxynil and ioxynil is in a ratio of 3:1-1:3 wt/wt calculated in terms of acid equivalent weights.

14. A method according to claim 1 substantially as hereinbefore described with reference to any one of Experiments 1 to 3 and Examples 6 to 11.

15. A product comprising (a) bromoxynil, which is 3,5-dibromo-4-hydroxybenzonitrile, or ioxynil, which is 4-hydroxy-3,5-diiodobenzonitrile, or an agriculturally acceptable salt or ester thereof, or a mixture thereof, and (b) terbuthylazine which is 2-t.butylamino-4-chloro-6-ethylamino-1,3,5-triazine, as a combined preparation for simultaneous, separate or sequential use in controlling the growth of weeds at a crop locus.

16. A product according to claim 15 in which the crop is a maize or sorghum crop.

17. A product according to claim 15 or 16 in which (a) comprises bromoxynil, an agriculturally acceptable salt or ester thereof.

18. A product according to claim 15, 16 or 17 in which (a) comprises a metal or amine salt of bromoxynil or ioxynil.

19. A product according to claim 15, 16 or 17 in which (a) comprises the ester of bromoxynil or ioxynil with an alkanoic acid of from 2 to 10 carbon atoms.

20. A product according to claim 19 in which (a) comprises the ester of bromoxynil or ioxynil with an alkanoic acid of from 4 to 8 carbon atoms.

21. A product according to claim 19 or 20 in which (a) comprises the ester of bromoxynil or ioxynil with octanoic or heptanoic acid.

22. A product according to claim 21 in which (a) comprises bromoxynil octanoate or bromoxynil heptanoate.

23. A product according to claim 15, 16, 17, 19, 20, 21 or 22 in which (a) comprises the ester of bromoxynil or ioxynil with a mixture of acids.

24. A product according to claim 15, 16, 17, 19, 20, 21 or 22 which comprises the two separate formulations one comprising the ester of bromoxynil or ioxynil in an organic water immiscible solvent for the ester of bromoxynil or ioxynil and in which terbuthylazine is substantially insoluble and a formulation comprising solid terbuthylazine optionally in the presence of water.

25. A product according to any one of claims 15, 16 and 18 to 24 in which the mixture of bromoxynil and ioxynil is in a ratio of 3:1-1:3 wt/wt calculated in terms of acid equivalent weights.

26. A product according to claim 15 substantially as herein before described.

27. A herbicidai composition which comprises (a) bromoxynil or ioxynil or an agriculturally acceptable salt or ester thereof, or a mixture thereof, and (b) terbuthylazine which is 2-t.butylamino-4-chloro-6 ethylamino-1 ,3,5-triazine in association with a herbicidally acceptable diluent or carrier and/or surface active agent.

28. A herbicidal composition according to claim 27 in which (a) comprises bromoxynil, an agriculturally acceptable salt or ester thereof.

29. A herbicidal composition according to claim 27 or 28 in which the acid equivalent weight ratio of (a) to (b) is between 5:2 and 1:20.

30. A herbicidal composition according to claim 27 or 28 in which the acid equivalent weight ratio of (a) to (b) is between 1:1 and 1:6.

31. A herbicidal composition according to claim 27, 28,29 or 30 in which (a) comprises a metal or amine salt of bromoxynil or ioxynil.

32. A herbicidal composition according to claim 27, 28, 29 or 30 in which (a) comprises the ester of bromoxynil or ioxynil with an alkanoic acid of from 2 to 10 carbon atoms.

33. A herbicidal composition according to claim 32 in which (a) comprises the ester of bromoxynil or ioxynii with an alkanoic acid of from 4 to 8 carbon atoms.

34. A herbicidal composition according to claim 32 or 33 in which (a) comprises the ester of bromoxynil or ioxynil with octanoic or heptanoic acid.

35. A herbicidal composition according to claim 34 in which (a) comprises bromoxynil octanoate or bromoxynil heptanoate.

36. A herbicidal composition according to claim 27, 28, 32, 33, 34 or 35 in which (a) comprises the ester of bromoxynii or ioxynil with a mixture of acids.

37. A herbicidal composition according to any one of claims 27 to 36 which comprises from 0.05 to 90% by weight of terbuthylazine and bromoxynil or ioxynil.

38. A herbicidal composition according to any one of claims 27 to 37 which contains from 0.05 to 25% of surface-active agent.

39. A herbicidal composition according to any one of claims 27 to 37 which contains from 0.05 to 10% of surface-active agent.

40. A herbicidal composition according to any one of claims 27 to 39 in the form of dusts, granules or wettable powders.

41. A herbicidal composition according to any one of claims 27 to 39 in the form of aqueous, organic or aqueous-organic solutions, suspensions or emulsions.

42. A herbicidal composition according to any one of claims 27 to 39 and 41 in which the herbicidally-acceptable diluent is water.

43. A herbicidal composition according to claim 41 or 42 in the form of an aqueous, organic or aqueous-organic suspension concentrate comprising from 10% to 80% w/v of terbuthylazine and bromoxynil or ioxynil, from 2 to 13% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 2 to 87.9% by volume of water and/or organic solvent.

44. A herbicidal composition according to claim 40 in the form of a wettable powder which comprises from 10 to 90% w/w of terbuthylazine and bromoxynil or ioxynil, from 2 to 10% w/w of surface-active agent and from 8 to 88% w/w of solid diluent or carrier.

45. A herbicidal composition according to claim 41 in the form of a liquid emulsifiable suspension concentrate which comprises from 10 to 70% w/v of terbuthylazine and bromoxynil or ioxynil, from 5 to 15% w/v of surface-active agent, from 0.1 to 5% w/v of thickener and from 10 to 84.9% by volume of organic solvent.

46. A herbicide composition according to claim 40 in the form of granules comprising from 1 to 90% w/w of terbuthylazine and bromoxynil or ioxynil, from 0.5 to 2% w/w of surface-active agent and from 8 to 98.5% of granular carrier.

47. A herbicidal composition according to claim 41 in the form of an emulsifiable concentrate which comprises from 0.05 to 90% w/v of terbuthylazine and bromoxynil or ioxynil, from 0.01 to 10% w/v of surface-active agent and from 9.99% to 99.94% by volume of organic solvent.

48. A herbicidal composition according to claim 27, 28, 29, 30 or 32 which comprises the ester of bromoxynil or ioxynil, an organic water immiscible solvent therefor and in which terbuthylazine is substantially insoluble, terbuthylazine and optionally water; from 2.0% to 5.0% w/v of water-insoluble nonionic surfactant; from 3.0% to 6.0% w/v of water-soluble wetting agents; from 0.2% to 2.0% w/v of water-soluble dispersing agent; from 0.01 to 0.5% w/v of antifoaming agent and from 0.5 to 2.0% w/v of mineral gelling agent.

49. A herbicidal composition according to claim 48 in which the organic water immiscible solvent for the ester of bromoxynil or ioxynil and in which terbuthylazine is substantially insoluble is an aromatic hydrocarbon.

50. A herbicidal composition according to claim 48 in which the total amount of terbuthylazine and bromoxynil or ioxynil ester comprises from 50% to 80% w/v of the composition.

51. A herbicidal composition according to any one of claims 27 to 50 which contains one or more other pesticidally-active (including herbicidally-active) compounds.

52. A herbicidal composition according to claim 51 in which the pesticidally-active compound is soluble in the organic water immiscible solvent for the ester of bromoxynil or ioxynil or is substantially insoluble in both water and the organic solvent.

53. A herbicidal composition according to any one of claims 27 to 52 in which the mixture of bromoxynil and ioxynil is in a ratio of 3:1-1:3 wt/wt calculated in terms of acid equivalent weights.

54. A herbicidal composition according to claim 27 substantially as hereinbefore described with reference to any one of Experiments 1 to 3 and Examples 6 to 11.

55. A process for the preparing of a product according to claim 24 or a composition according to claim 48 which comprises the following steps: the solid terbuthylazine is ground optionally in water to give a particle size in the desired range to achieve optimum suspension stability, the water-soluble surfactants together with the gelling agent having been previously dispersed in the terbuthylazine and water before milling, to yield a slurry of the terbutylazine; the solvent based portion is prepared by dissolving the nonionic surfactant and the ester of bromoxynil or ioxynil in the solvent optionally heating to aid solution; optionally followed by pouring the solvent portion into the terbuthylazine portion.