WO2000074488A1

WO2000074488A1 - Method of controlling weeds in transgenic crops

Info

Publication number: WO2000074488A1
Application number: PCT/EP2000/005782
Authority: WO
Inventors: Jean-Louis Arnault
Original assignee: Aventis Agriculture Ltd.
Priority date: 1999-06-04
Filing date: 2000-05-30
Publication date: 2000-12-14
Also published as: AU5684900A; GB9913062D0

Abstract

The invention provides a method for securing prolonged, e.g. preferably season-long, control of the growth of weeds at a crop locus, the crop being tolerant to a PPO-inhibiting herbicide, said control starting before the emergence of the crop, said method comprising the pre-crop emergence application of an effective amount of an isoxazole or dione herbicide and optionally a post-crop emergence application of a PPO-inhibiting herbicide or an agriculturally acceptable salt thereof.

Description

Method of controlling weeds in transgenic crops

Background of the invention.

This invention relates to a method for controlling the growth of weeds comprising the application of an isoxazole or dione herbicide and optionally a protoporphyrinogen oxidase inhibiting herbicide, and to their use on transgenic crops, in particular corn (Zea mays).

Discussion of Related Art

Herbicidal isoxazoles and diones are disclosed in the literature for example 4-benzoylisoxazole herbicides (e.g. 5-cyclopropyl-4-(2- methylsulphonyl-4-trifluoromethyl)-benzoylisoxazole, known by the common name isoxaflutole) are described in European applications 418175; 527036; 560482; WO94/14782; US 5,371,063; US 5,371,064;

US 5,489,570; US 5,656,573; 2-benzoylcyclohexane-l,3-diones (e.g. 2- (2-chloro-4-methylsulphonylbenzoyl)-cyclohexane- 1,3 -dione, known by the common name sulcotrione and 2-(2'-nitro-4- methylsulphonylbenzoyl)cyclohexane- 1,3 -dione) are described in US 4,780,127; US 4,806,981;US 4,946,981 ; WO94/04524 and

WO94/08988.

Inhibitors of the enzyme protoporphyrinogen oxidase (PPO) are described in 'Peroxidizing Herbicides' 1999, P.Borger and K.Wakabayashi, ISBN 3-540-64550-0. Examples of PPO-inhibiting herbicides include diphenylether herbicides, (e.g. acifluorfen -Na, bifenox and fomesafen); phenylpyrazole herbicides, (e.g. fluazolate); N-phenylphthalimide herbicides, (e.g. cinidon-ethyl, flumioxazin and flumiclorac); thiadiazole herbicides, (e.g. fluthiacet-methyl and thidiazimin); oxadiazole herbicides, (e.g. oxadiazon and oxadiargyl); triazolinone herbicides,

(e.g. carfentrazone-ethyl and sulfentrazone); triazolopyridinone herbicides, (e.g. azafenidin) and bipyridilium herbicides, e.g. paraquat. Such PPO-inhibiting herbicides are non-selective herbicides which have only been used as a total herbicide or under conditions where there is no growing crop foliage present, (e.g. burndown/no till). To overcome this limitation the PPO-inhibiting herbicides can be used in the presence of crops which have been genetically modified to confer enhanced tolerance to PPO-inhibiting herbicides.

Applications of PPO-inhibiting herbicides for use in burn- down/no-till control are applied to an area when the crop has not emerged and thus selectivity is not a necessary requirement, and further treatments of the field may be needed by the farmer using selective herbicides after sowing the seed to remove the weeds which emerge after application of the herbicide. This requires additional time and expense of the farmer. Moreover, the application of an early post-crop emergence treatment by conventional spraying machinery may physically injure the crop seedlings producing unacceptable damage.

An object of the present invention is to provide a method of growing a genetically modified corn crop which comprises the pre-crop emergence application of an isoxazole or dione herbicide optionally followed by a post-crop emergence application of a PPO-inhibiting herbicide where the pressure of weeds is high.

A further object of the present invention is to provide a method of growing a genetically modified corn crop which is resistant to PPO- inhibiting herbicides which has been planted in an area free of weeds (either by cultivation, by burn down or by treatment with a total herbicide) which comprises the application of an isoxazole or dione, pre- plant or pre-emergence to the crop locus.

A still further object of the invention is to provide a method which may allow the farmer to avoid applying unnecessary further treatments of herbicide after the emergence of the crop, and which allows the farmer maximum flexibility in deciding on a treatment programme. These and other objects which may be achieved in whole or in part by the present invention, will become apparent from the following description.

As a result of research and experimentation it has now been discovered that the application of an isoxazole or dione herbicide to a crop which possesses tolerance to PPO-inhibiting herbicides provides prolonged control of the growth of weeds, starting from before emergence of the crop until canopy closure and all growth stages in between. Summary of the Invention

The present invention provides a method for securing prolonged, e.g. preferably season-long, control of the growth of weeds at a crop locus, the crop being tolerant to a PPO-inhibiting herbicide, said control starting before the emergence of the crop, said method comprising the pre-crop emergence application of an effective amount of an isoxazole or dione herbicide and optionally a post-crop emergence application of a PPO-inhibiting herbicide.

It will be understood that in this specification including the accompanying claims the term pre-crop emergence application embraces pre-plant application.

It will also be understood that herbicides used in the method of the invention may form for example salts or metal complexes, and that the use of such salts or metal complexes is also embraced by the invention.

Description of Preferred Embodiments

It will be understood that the transgenic crop is generally substantially tolerant to PPO-inhibiting herbicides at the doses used.

The isoxazole or dione herbicides are applied pre-emergence of the crop. By the term 'pre-emergence application' is meant application to the soil in which the weed seeds or seedlings are present before emergence of the crop. One example of a pre-emergence application is known as 'pre-plant incorporated' (PPI), where the herbicide is incorporated into the soil before planting the crop. Another is where the herbicide is applied to the soil surface after sowing the crop.

The application of isoxazole or dione herbicides pre-emergence also offers residual activity and consequently can be employed over a long period of crop development, i.e. from pre -weed pre-crop emergence to post-crop emergence (closure of crop canopy) and all growth stages in between. In addition, the pre-emergence application of isoxazole or dione herbicides allows the control of weeds with protracted germinating periods to be accomplished without the need to apply a post-emergence application of a PPO-inhibiting herbicide.

Furthermore the use of a crop possessing tolerance to a PPO- inhibiting herbicide provides the farmer with the flexibility to apply a PPO-inhibiting herbicide post-emergence if the weed pressure becomes too high for the developing crop following a pre-emergence application of an isoxazole or dione herbicide.

Weeds that may be controlled by the method of the invention include grass weeds, broad-leaf weeds and sedges.

Examples of grass weeds include Alopecurus myosuroides. A ena fatua. Digitaria sanguinalis, Echinochloa crus-galli. Sorghum bicolor. Eleusine indica and Setaria spp, e.g. Setaria faberii or Setaria viridis.

Examples of broad-leaf weeds include Abutilon theophrasti. Amaranthus retroflexus, Bidens pilosa. Chenopodium album. Galium aparine, Ipomoea spp. e.g. Ipomoea purpurea. Sesbania exaltata. Sinapis ar ensis, Solanum nigrum and Xanthium strumarium. An example of a sedge includes Cyperus esculentus.

The crop species which may be used in the method of the invention include canola, cotton, maize, rice, sorghum, soybean, sugar beet and wheat. Preferred crops include canola, cotton, maize, soybean and sugar beet. Particularly preferred crop species are maize and soybean, especially maize. The crop has been genetically manipulated to confer enhanced tolerance to PPO-inhibiting herbicides. In general the application rate of the isoxazole or dione herbicide is from 20gha^"' to 500gha^"], preferably from 50gha^"] to 150gha^"' ; the application rate of PPO-inhibiting herbicide is from lg to lOOOOg/ha, preferably from 1 OOg to 7000g/ha. It will be understood that the application rates used will depend on the growth stage of the weeds, the climatic conditions, the time of application, the type of weeds present, the crops and other parameters apparent to the skilled worker.

Preferably the weight ratio of isoxazole or dione : PPO-inhibiting herbicide is from l :500to 500:1, more preferably from 1 :140 to 1.5:1.

The isoxazole or dione herbicides used in the method of the invention generally have the formula (I) (it is to be understood that the term "dione" as used in this specification including the accompanying claims does nor exclude the possible presence of additional C=O groups as in triones):

(I) wherein: A represents a group (A-l) to (A-7):

(A-4) (A-5)

(A-6) (A-7) or a corresponding formula (A-6a) or (A-7a):

(A-6a) (A-7a) in which the position of the carbonyl group and the group Q are reversed and the double bond in the ring is attached to the carbon atom attached to the group Q;

R represents a hydrogen atom or a halogen atom; a straight- or branched chain alkyl, alkenyl or alkynyl group containing from one to six carbon atoms which is optionally substituted by one or more halogen atoms; a cycloalkyl group containing from 3 to 6 carbon atoms optionally substituted by one or more groups R⁵, one or more halogen atoms or a group -CO2 ; or a group selected from -CO2R^J, -COR , cyano, nitro, -CONR³R⁴ and -S(O)kR¹³;

R represents a straight- or branched-chain alkyl, alkenyl or alkynyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; or a cycloalkyl group containing from three to six carbon atoms optionally substituted by one or more groups R or one or more halogen atoms;

7 R represents a halogen atom; a straight- or branched-chain alkyl, alkenyl or alkynyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; a straight- or branched-chain alkyl group containing up to six carbon atoms which is substituted by one or more groups -OR ; or a group selected from nitro, cyano, -CO2R⁵, -S(O)_pR⁶. -O(CH2)_mOR⁵, -COR⁵, -NR^UR¹², -N(R⁸)SO2R⁷, -N(R⁸)CO2R⁷, -OR⁵, -OSO2R⁷, -SO2NR³R⁴, - CONR³R⁴, -CSNR³R⁴, -(CR⁹R¹⁰)_t-S(O)_qR⁷ and -SF5; or two groups R^, on adjacent carbon atoms of the phenyl ring may, together with the carbon atoms to which they are attached, form a 5 to 7 membered saturated or unsaturated heterocyclic ring containing up to three ring heteroatoms selected from nitrogen, oxygen and sulfur, which ring is optionally substituted by one or more groups selected from halogen, nitro, -S(O)_pR^₅ C_]_4 alkyl, C1.4 alkoxy, C1..4 haloalkyl,

Cj_4 haloalkoxy, =O (or a 5- or 6- membered cyclic acetal thereof), and =NO-R-\ it being understood that a sulphur atom, where present in the ring, may be in the form of a group -SO- or -SO2-; n represents an integer from one to five: when n is greater than one

2 the groups R may be the same or different;

R 3 , R 4 and R 22 each independently represent a hydrogen atom, or a straight- or branched chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms;

R 5 and R 23 each independently represent a straight- or branched- chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms or a straight- or branched- chain alkenyl or alkynyl group containing from two to six (preferably from three to six) carbon atoms which is optionally substituted by one or more halogen atoms; R

, which may be the same or different, each represent

R ; or phenyl optionally substituted by from one to five groups which may be the same or different selected from a halogen atom, a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms, nitro, cyano, - CO2R⁵, -S(O)_pR¹³, -NR^{1 2}NR¹², -OR⁵ and -CONR³R⁴;

R , R and R each represent a hydrogen atom or R ; R and R each represent hydrogen or R ; R 13 and R 21 represent a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms;

Q represents hydroxy, Cl-6 alkoxy, OR²⁰, SR²⁰ or SR²¹ ; L represents oxygen or NR²²;

Rl4, Rl4a _R14b_{? R}15, _R15a, _R15b _R16, Rlόa, _R16b _RH _R17a _R17b _R18_{^ R}18a _R18b_{; R}19_{? R}19a ^d _R19b _represent the same or different groups selected from hydrogen, R ^, -(CH2)_uCO2R , halogen, cyano, Cl-6 alkoxy, -(CH2)_X- [phenyl optionally substituted by from one to five groups R²^ which may be the same or different], and cycloalkyl containing from three to six carbon atoms optionally substituted by Cl-6 alkyl or -S(O)_pR²¹ ;

R *-> represents phenyl optionally substituted by from one to five groups selected from halogen, Cl-6 alkyl, Cl-6 haloalkyl, Cl-6 alkoxy and nitro;

R 4 represents a group selected from halogen, R ^, nitro, cyano, -C0₂R²⁶, -S(O)_pR²¹, -OR²¹ and -NR²⁶R²⁷;

R -> represents a straight- or branched- chain alkyl group containing one to three carbon atoms optionally substituted by one or more halogen atoms;

R²" and R² ' which may be the same or different, each represents hydrogen or R²^; p, q and u independently represent the values zero, one or two; k and m represent one, two or three; x represents zero or one; t represents an integer from one to four; when t is greater than one, the groups R 9 and R 10 may be the same or different; and agriculturally acceptable salts and metal complexes thereof.

Compounds of formula (I) may exist in enolic tautomeric forms that may give rise to geometric isomers around the enolic double bond.

Furthermore in certain cases the above substituents may contribute to optical isomerism and/or stereoisomerism. All such forms and mixtures thereof are embraced by the present invention.

It is to be understood that in this specification compounds comprising a cyclohexane ring corresponding to formula (A-6) or (A-7) or a precursor thereof include the compounds with the corresponding formula (A-6a) or (A-7a) or precursors thereof.

In the definitions of symbols in this specification including the accompanying claims unless otherwise specified the following term is generally defined thus:- 'halogen' means a fluorine, chlorine, bromine or iodine atom; alkyl groups and moieties are straight or branched chain and contain from 1 to 6 carbon atoms.

Preferably A represents a group of formula (A-I), (A-2), (A-3) or (A-4) (compounds of formula (A-l) are most preferred). The benzoyl ring of the compounds of formula (I) is preferably

2,4-disubstituted, 2,3-disubstituted or 2,3,4-trisubstituted.

Preferably in formulae (A-4) to (A-7), the groups R¹⁴, R¹⁵, R¹⁶, Rl7 Rl8, Rl9 _{. R}14a _R15a _R16a _R17a _R14b, _R15b, _R16b _R17b

_R18b _anr\ _R19b represent hydrogen or lower alkyl (preferably hydrogen, methyl or ethyl); L (in A-7a) represents NH; and Q represents hydroxy or -S-phenyl.

Compounds of formula (I) in which A represents (A-l),(A-2) or

(A-3); R represents hydrogen or -CO2R 3 (in A-l or A-2) wherein R 3 represents or a straight- or branched chain alkyl group containing up to three carbon atoms; and R represents cyclopropyl are preferred.

A further preferred class of compounds of formula (I) wherein A represents (A-l) are those wherein:

R is hydrogen or -CO2Et;

R is cyclopropyl; and two groups R², on adjacent carbon atoms of the phenyl ring may, together with the carbon atoms to which they are attached, combine to form a 5 or 6 membered saturated or unsaturated heterocyclic ring which is fused to the 2,3 or 3,4 positions of the benzoyl ring; wherein the heterocyclic ring contains two hetero atoms selected from sulphur and oxygen which are attached to the 2 and 3, or 3 and 4 positions of the benzoyl ring; and in which the 4-substituent of the benzoyl ring is halogen or S(O)pMe, or the 2-substituent of the benzoyl ring is methyl, S(O)pMe or -CH2S(O)qMe respectively; and optionally the heterocyclic ring may be substituted by one or more halogen atoms. A further preferred class of compounds of formula (I) are those wherein A represents (A-l); R is hydrogen or -CO2Et ; R is

2 cyclopropyl; R is a halogen atom or a group selected from -CF3, Me,

Et, -S(O)pMe, -CH2S(O)qMe and optionally halogenated methoxy or ethoxy; and n is two or three.

A further preferred class of compounds of formula (I) wherein A represents (A-4) are those wherein:

R¹⁴-R¹⁵, R¹⁶, R¹⁷, R¹⁸ and R¹⁹ represent hydrogen; and two groups R², on adjacent carbon atoms of the phenyl ring may, together with the carbon atoms to which they are attached, combine to form a 6 membered saturated heterocyclic ring which is fused to the 2,3 or 3,4 positions of the benzoyl ring; wherein the heterocyclic ring contains a sulphur atom attached to the 4 position of the benzoyl ring, optionally in the form of a group -SO- or -SO₂-, and which ring is substituted by a 5- or 6- membered acetal thereof.

A more preferred class of compounds of formula (I) having the formula (la):

(la) are those wherein: R is hydrogen or -CO2Et;

R ,28 i-s selected from -S(O)pMe, Me, Et, a chlorine, bromine or fluorine atom, methoxy, ethoxy and -CH2S(O)qMe; R 29 is selected from a hydrogen atom, a chlorine, bromine or fluorine atom, methoxy, ethoxy and -S(O)pMe; and

R^J is selected from a hydrogen atom, a chlorine, bromine or fluorine atom, methoxy and CF3.

An especially preferred class of compounds of formula (I) have the formula (lb):

(lb) wherein R ,31 : is, chlorine, bromine or trifluoromethyl; and R is hydrogen or -CO2Et.

Preferred diones are those in which a substituted phenyl ring as defined in formula (I); (la); or (lb), is attached to a grouping;

Such diones in which the phenyl ring is substituted by two groups independently selected from halogen, alkyl, S(O)_talkyl (t = 0, 1 or 2) or haloalkyl are also preferred.

Preferred triones are those in which a substituted phenyl ring, as defined above, is attached to a grouping;

The following compounds of formula (I) are among the most preferred for use in the present invention:

5-cyclopropyl-4-[2-chloro-3-ethoxy-4- (ethylsulphonyl)benzoyl]isoxazole;

4-(4-chloro-2-methylsulphonylbenzoyl)-5-cyclopropylisoxazole; 5-cyclopropyl-4-(2-methylsulphonyl-4- trifluoromethylbenzoyl)isoxazole;

4-(4-bromo-2-methylsulphonylbenzoyl)-5-cyclopropylisoxazole; 5-cyclopropyl-4-[4-fluoro-3-methoxy-2-

(methylsulphonyl)benzoyl]isoxazole;

4-(4-bromo-2-methylsulphonylmethylbenzoyl)-5- cyclopropylisoxazole; ethyl 5-cyclopropyl-4-(2-methylsulphonyl-4- trifluoromethylbenzoyl)isoxazole-3-carboxylate;

2- [2-chloro-(4-methylsulphonyl)benzoyl] - 1 ,3 -cyclohexanedione; 2-[2-nitro-(4-methylsulphonyl)benzoyl]-l,3-cyclohexanedione; 2-(2,3-dihydro-5.8-dimethyl-l,l-dioxospiro[4H-l-benzothiin-4,2'- [l,3]dioxolan]-6-ylcarbonyl)cyclohexane-l,3-dione; 5-cyclopropyl-4-(2-methylsulphonyl-4-trifluoromethylbenzoyl)-3- methylthio-isoxazole;

2-cyano-3 -cyclopropyl- 1 -(2-methylsulphonyl-4- trifluoromethylphenyl)propan- 1 ,3-dione.

The most preferred compound is 5-cyclopropyl-4-(2- methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole.

PPO-inhibiting herbicides are preferably chosen from the group consisting of; diphenylethers, phenylpyrazoles, N-phenylphthalimides, thiadiazoles, oxadiazoles, triazolinones, triazolopyridones and bipyridilium herbicides. Specific partner herbicides for use in the present invention include; acifluorfen-Na, which is 5-(2-chloro-α,α,α-trifluoro-/?-tolyloxy)- 2-nitrobenzoic acid, azafenidin, which is 2-(2,4-dichloro-5-prop-2- ynyloxyphenyl)-5,6,7,8-tetrahydro-l,2,4-triazolo[4,3-a]pyridin-3(2H)- one, bifenox, which is methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate, carfentrazone-ethyl, which is ethyl (RS)-2-chloro-3-[2-chloro-5-(4- difluoromethyl-4,5-dihydro-3-methyl-5-oxo-lH-l,2,4-triazol-l-yl)4- fluorophenyl]propionate, chlomethoxyfen, which is 5-(2,4- dichlorophenoxy)-2-nitroanisole, cinidon-ethyl, which is ethyl (Z)-2- chloro-3-[2-chloro-5-(l,3-dioxo-l, 3,4,5, 6,7-hexahydroisoindol-2-yl)- phenyl] -acrylate, fluazolate, which is 5-[4-bromo-l-methyl-5- (trifluoromethyl)-lH-pyrazol-3-yl]-2-chloro-4-fluoro-benzoic acid isopropyl ester, flumiclorac, which is [2-chloro-5-(cyclohex-l-ene-l,2- dicarboximido)-4-fiuorophenoxy]acetic acid, flumioxazin, which is N-

(7-fluoro-3 ,4-dihydro-3 -oxo-4-prop-2-ynyl-2H- 1 ,4-benzoxazin-6- yl)cyclohex-l-ene-l,2-dicarboxamide, fluoroglycofen-ethyl, which is O- [5-(2-chloro-α,α,α-trifluoro-p-tolyloxy)-2-nitrobenzoyl]glycolic acid, fluthiacet-methyl, which is methyl [2-chloro-4-fluoro-5-(5, 6,7,8- tetrahydro-3 -oxo- 1 H,3H- [ 1 ,3 ,4]thiadiazolo [3 ,4-a]pyridazin- 1 - ylideneamino)phenylthio]acetate, fomesafen, which is 5-(2-chloro- α,α,α-trifluoro-/?-tolyloxy)-Ν-methylsulfonyl-2-nitrobenzamide, halosafen, which is 5-(2-chloro-α,α,α-6-tetrafluoro-/ tolyloxy)-N- ethylsulfonyl-2-nitrobenzamide, lactofen, which is ethyl O-[5-(2-chloro- α,α,α-trifluoro- ->-tolyloxy)-2- nitrobenzoyl]-DL-lactate, oxadiargyl, which is 5-tert-butyl-3-[2,4-dichloro-5-(prop-2-ynyloxy)phenyl]-l,3,4- oxadiazol-2(3H)-one, oxadiazon, which is 5-tert-butyl-3-(2,4-dichloro- 5-isopropoxyphenyl)-l,3,4-oxadiazol-2(3H)-one, oxyfluorfen, which is 2-chloro-α,α,α-trifluoro-/j>-tolyl 3-ethoxy-4-nitrophenyl ether, paraquat, which is l,r-dimethyl-4,4'-bipyridinium, pyraflufen-ethyl, which is ethyl 2-chloro-5-(4-chloro-5-difluoromethoxy-l-methylpyrazol-3-yl)-4- fluorophenoxy acetate, sulfentrazone, which is 2',4'-dichloro-5'(4- difluoromethyl-4,5-dihydro-3-methyl-5-oxo-lH-l,2,4-triazol-l- yl)methanesulfonanilide and thidiazimin, which is 6-(6,7-dihydro-6,6- dimethyl-3H,5H-pyrrolo[2,l-c][l,2,4]thiadiazol-3-ylideneamino)-7- fluoro-4-(prop-2-ynyl)-2H-l ,4-benzoxazin-3(4H)-one. The most preferred PPO-inhibiting herbicides are bifenox, oxadiargyl and oxadiazon.

The application rates of the preferred PPO-inhibiting herbicides are from 150 to 2000g, preferably from 200 to 1200g/ha; from 200 to 3000, preferably from 300 to 2000g/ha; and from 600 to 6000g, preferably from 1200 to 4500g/ha; for bifenox, oxadiargyl and oxadiazon respectively.

Preferably the weight ratio of isoxazole or dione : bifenox is from 1 : 100 to 3.3 : 1 , more preferably from 1 :24 to 1 :1.3; the weight ratio of isoxazole or dione : oxadiargyl is from 1 :150 to 2.5:1, more preferably from 1 :40 to 1 :2; and the weight ratio of isoxazole or dione : oxadiazon is from 1 :300 to 1 : 1.2, more preferably from 1 :90 to 1 :8.

The following non-limiting example illustrates the invention.

EXAMPLE 1

Seed of a crop possessing tolerance to a PPO-inhibiting herbicide, various broad-leaf and grass weed species may be sown and 5- cyclopropyl-4-(2-methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole, dissolved in a mixture of acetone and water, applied at a rate of 1 OOg/ha to the soil surface. The said weeds are Amaranthus retroflexus. Abutilon theophrasti and Ambrosia elatior.

Sixty days after treatment the percentage reduction in plant growth, compared to an untreated control, may be assessed to determine whether an application of a PPO-inhibiting herbicide is necessary. Over 90% control in all weed species by 5-cyclopropyl-4-(2- methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole renders an optional treatment with a PPO-inhibiting herbicide unnecessary. In the method of the invention, the isoxazole or dione herbicide and PPO-inhibiting herbicides are normally used in the form of herbicidal compositions (i.e. in association with compatible diluents or carriers and/or surface-active agents suitable for use in herbicidal compositions), for example as hereinafter described.

The compositions used in the invention may be solids (such as wettable powders and water dispersible granules) or comprise at least one liquid phase. It will be understood that in this description the term 'liquid' includes thickened liquids and gels. The compositions are preferably provided in the form of pre-mixed formulations. Preferred liquid formulations are suspension concentrates, emulsifiable concentrates, gels, suspo-emulsions and emulsion concentrates (e.g. either oil-in- water or water-in oil emulsions). Compositions in the form of suspension concentrates are particularly preferred. The herbicidal compositions may contain both a diluent or carrier and surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in the herbicidal compositions may be of the ionic or non-ionic types, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with alkyl and polyaryl phenols, e.g. 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 of sulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sulphonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates and sodium and calcium alkylbenzene sulphonates.

Suitably, the herbicidal compositions may comprise up to 10% by weight, e.g. from 0.05% to 10% by weight, of surface-active agent but, if desired, the herbicidal compositions may comprise higher proportions of surface-active agent, for example up to 15% by weight in liquid emulsifiable or suspension concentrates and up to 25% by weight in liquid water soluble concentrates.

Examples of suitable solid diluents or carriers are aluminium silicate, microfine silicon dioxide, talc, chalk, 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 compounds of formula (I) with solid diluents or by impregnating the solid diluents or carriers with solutions of the compounds of formula (I) in volatile solvents, evaporating the solvents and, if necessary, grinding the products so as to obtain powders. Granular formulations may be prepared by absorbing the compounds of formula (I) (dissolved in suitable solvents, which may, if desired, be volatile) onto the solid diluents or carriers in granular form and, if desired, evaporating the solvents, or by granulating compositions in powder form obtained as described above. Solid herbicidal compositions, particularly wettable powders and granules, 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 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, glycols, glycol ethers, tetrahydrofurfuryl alcohol, acetophenone, cyclohexanone, isophorone, N-alkyl pyrrolidones, toluene, xylene, mineral, animal and vegetable oils, esterified vegetable oils and light aromatic and naphthenic fractions of petroleum (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.

Powders, dispersible granules 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 compound of formula (I) 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 such concentrates to water 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. The herbicidal compositions may also contain, if desired, conventional adjuvants such as adhesives, protective colloids, thickeners, penetrating agents, spreading agents, stabilisers, sequestering agents, anti-caking agents, colouring agents and corrosion inhibitors.

These adjuvants may also serve as carriers or diluents.

Unless otherwise specified, the following percentages are by weight. Preferred herbicidal compositions are aqueous suspension concentrates which comprise from 10 to 70% of one or more compounds of formula (I), from 2 to 10% of surface-active agent, from

0.1 to 5% of thickener and from 15 to 87.9% of water; wettable powders which comprise from 10 to 90% of one or more compounds of formula (I), from 2 to 10% of surface-active agent and from 8 to 88% of solid diluent or carrier; water soluble or water dispersible powders which comprise from

10 to 90%) of one or more compounds of formula (I), from 2 to 40% of sodium carbonate and from 0 to 88% of solid diluent; liquid water soluble concentrates which comprise from 5 to 50%, e.g. 10 to 30%, of one or more compounds of formula (I), from 0 to 25%) of surface-active agent and from 10 to 90%, e.g. 45 to 85%, of water miscible solvent, e.g. tri ethylene glycol, or a mixture of water-miscible solvent and water; liquid emulsifiable suspension concentrates which comprise from 10 to 70% of one or more compounds of formula (I), from 5 to 15% of surface-active agent, from 0.1 to 5% of thickener and from 10 to 84.9% of organic solvent, e.g. mineral oil; water dispersible granules which comprise from 1 to 90%, e.g. 25 to 75% of one or more compounds of formula (I), from 1 to 15%, e.g. 2 to 10%, of surface-active agent and from 5 to 95%, e.g. 20 to 60%>, of solid diluent, e.g. clay, granulated with the addition of water to form a paste and then dried and, emulsifiable concentrates which comprise 0.05 to 90%, and preferably from 1 to 60% of one or more compounds of formula (I), from 0.01 to 10%, and preferably from 1 to 10%, of surface-active agent and from 9.99 to 99.94%, and preferably from 39 to 98.99%, of organic solvent. The herbicidal compositions may also comprise the compounds of formula (I) 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 include herbicides, for example,

2,4-D, which is (2,4-dichlorophenoxy)acetic acid, acetochlor, which is, 2-chloro-N-ethoxymethyl-6'-ethylaceto-ø-toluidide, atrazine, which is 6-chloro-N²-ethyl-N⁴-isopropyl-l,3,5-triazine-2,4-diamine, bromoxynil, which is 3,5-dibromo-4-hydroxybenzonitrile, dicamba, which is 3,6-dichloro-ø-anisic acid, glufosinate, which is 4- [hydroxy (methyl)phosphinoyl] -DL-homoalanine, glufosinate- ammonium, which is ammonium 4-[hydroxy(methyl)phosphinoyl]-DL- homoalaninate, glyphosate, which is N-(phosphonomethyl)glycine, the glyphosate-trimesium salt, imazamox, which is (RS)-2-(4-isopropyl-4- methyl-5-oxo-2-imidazolin-2-yl)-5-methoxymethylnicotinic acid, imazapyr, which is 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2- yl)nicotinic acid, imazethapyr, which is (RS)-5-ethyl-2-(4-isopropyl-4- methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid, metolachlor, which is 2- chloro-6'-ethyl-N-(2-methoxy- 1 -methylethyl)aceto-o-toluidide, metribuzin, which is 4-amino-6-tert-butyl-4,5-dihydro-3-methylthio- l,2,4-triazin-5-one, nicosulfuron, which is 2-(4,6-dimethoxypyrimidin- 2-ylcarbamoylsulfamoyl)-N,N-dimethylnicotinamide, pendimethalin, which is N-(l-ethylpropyl)-2,6-dinitro-3,4-xylidine, rimsulfuron, which is 1 -(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2- pyridylsulfonyl)urea, and trifluralin, which is α,α,α-trifluoro 2,6-dinitro-N,N-dipropyl- j9-toluidine.

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

The compositions may also contain safeners which may be useful to reduce the phytotoxicity of one or more of the pesticidally active compounds on a crop (generally where the partner pesticide is a herbicide).

According to a further feature of the present invention there is provided an article of manufacture comprising at least one of the isoxazole or dione derivatives of formula (I) and/or a PPO-inhibiting herbicide or, as is preferred, a herbicidal composition as hereinbefore described, and preferably a herbicidal concentrate which must be diluted before use, comprising at least one of the isoxazole or dione derivatives of formula (I) and/or a PPO-inhibiting herbicide within a container for the aforesaid derivative or derivatives of formula (I) and/or a PPO- inhibiting herbicide, or a said herbicidal composition, and instructions physically associated with the aforesaid container setting out the manner in which the aforesaid derivative or derivatives of formula (I) and/or a PPO-inhibiting herbicide 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 solid at normal ambient temperatures and herbicidal compositions particularly in the form of concentrates, for example cans and drums of metal, which may be internally lacquered, and plastics materials, bottles or 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 isoxazole or dione derivative 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 0.01kg and 20kg of active material per hectare in the manner and for the purposes hereinbefore described.

The following is an example of a composition suitable for use in the method of the invention. In the description that follows the following are trade marks: REAX, Sellogen, Barden, Aerosil. The Active Ingredient listed in the following example refers to compounds of general formula (I). Example Cl

The following composition was prepared as a wettable dispersible granule (the percentages that follow are by weight): Active Ingredient: 75.0 %

REAX 88 A (Surfactant): 10.0 %

Sellogen HR (Surfactant): 3.0 % Barden AG- 1 (Clay): 11.0 %

Aerosil R972 (Silica filler) 1.0 %

The invention also provides a product comprising an isoxazole or dione derivative as defined in general formula (I) or an agriculturally acceptable salt or metal complex thereof and a PPO-inhibiting herbicide or agriculturally acceptable salt thereof, for separate or sequential application in securing the prolonged control of the growth of weeds at a crop locus, the crop being tolerant to the PPO-inhibiting herbicide and the isoxazole or dione derivative or agriculturally acceptable salt or complex thereof, being applied pre-emergence of the crop.

Claims

1. A method for securing prolonged control of the growth of weeds at a crop locus, the crop being tolerant to a PPO-inhibiting herbicide, said control starting before the emergence of the crop, said method comprising the pre-crop emergence application of an effective amount of an isoxazole or dione herbicide and optionally a post-crop emergence application of a PPO-inhibiting herbicide.

2. A method according to claim 1 in which the crop is selected from canola, cotton, maize, soybean and sugar beet.

3. A method according to claim 2 in which the crop is maize or soybean.

4. A method according to claim 1, 2 or 3 in which the application rate of the isoxazole or dione herbicide is from 20gha^"1 to 500gha^"', preferably from 50gha^"' to 150ghaJ

5. A method according to any one of the preceding claims in which the application rate of the PPO-inhibiting herbicide is from lg to lOOOOg/ha, preferably from lOOg to 7000g /ha.

6. A method according to any one of the preceding claims in which the weight ratio of isoxazole or dione herbicide to PPO-inhibiting herbicide is from 1 :500 to 500:1, more preferably from 1 :140 to 1.5:1.

7. A method according to any one of the preceding claims in which the isoxazole or dione herbicide has the general formula (I):

(I) wherein:

A represents a group (A-l) to (A-7):

(A-4) (A-5)

(A-6) (A-7) or a corresponding formula (A-6a) or (A-7a):

R represents a hydrogen atom or a halogen atom; a straight- or branched chain alkyl, alkenyl or alkynyl group containing from one to six carbon atoms which is optionally substituted by one or more halogen atoms; a cycloalkyl group containing from 3 to 6 carbon atoms optionally substituted by one or more groups R\ one or more halogen atoms or a group -CO2R 3 ; or a group selected from -CO2R 3 , -COR 5 , cyano, nitro, -CONR³R⁴ and -S(O)kR¹³;

2 R represents a halogen atom; a straight- or branched-chain alkyl, alkenyl or alkynyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; a straight- or branched-chain alkyl group containing up to six carbon atoms which is substituted by one or more groups -OR ; or a group selected from nitro, cyano, -CO2R⁵, -S(O)_pR⁶, -O(CH2)_mOR⁵, -COR⁵, -NR^{1 1}R¹²,

-N(R⁸)SO2R⁷, -N(R⁸)CO2R⁷, -OR⁵, -OSO2R⁷, -SO2NR³R⁴, - CONR³R⁴, -CSNR³R⁴, -(CR⁹R¹⁰)_t-S(O)_qR⁷ and -SF5; or two groups R², on adjacent carbon atoms of the phenyl ring may, together with the carbon atoms to which they are attached, form a

5 to 7 membered saturated or unsaturated heterocyclic ring containing up to three ring heteroatoms selected from nitrogen, oxygen and sulfur, which ring is optionally substituted by one or more groups selected from halogen, nitro, -S(O)pRl3, C1.4 alkyl, Cμ4 alkoxy, Ci .4 haloalkyl,

C _4 haloalkoxy, =O (or a 5- or 6- membered cyclic acetal thereof), and

=N0-R3, it being understood that a sulphur atom, where present in the ring, may be in the form of a group -SO- or -SO2-; n represents an integer from one to five: when n is greater than one

2 the groups R may be the same or different;

R 3 , R 4 and R 22 each independently represent a hydrogen atom, or a straight- or branched chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; R 5 and R 23 each independently represent a straight- or branched- chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms or a straight- or branched- chain alkenyl or alkynyl group containing from two to six (preferably from three to six) carbon atoms which is optionally substituted by one or more halogen atoms;

R

, which may be the same or different, each represent R ; or phenyl optionally substituted by from one to five groups which may be the same or different selected from a halogen atom, a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms, nitro, cyano, - CO2R⁵, -S(O)_pR¹³, -NR^πNR¹², -OR⁵ and -CONR³R⁴; R , R and R each represent a hydrogen atom or R ;

R and R each represent hydrogen or R ; R ^J and R represent a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; Q represents hydroxy, C 1 -6 alkoxy, OR²⁰, SR²⁰ or SR²¹ ;

L represents oxygen or NR²²; _R14 _R14a _R14b_{; R}15, _R15a _R15b _R16_{3 R}16a _R16b_{5 R}H

_R17a _R17b_{; R}18_{3 R}18a _R18b_{5 R}19_{? R}19a ^d _R19b represent the same or different groups selected from hydrogen, R²^, -(CH2)_uCO2R²², halogen, cyano, Cl-6 alkoxy, -(CH2)_X- [phenyl optionally substituted by from one to five groups R²⁴ which may be the same or different], and cycloalkyl containing from three to six carbon atoms optionally substituted by Cl-6 alkyl or -S(O)_pR²¹ ;

R²0 represents phenyl optionally substituted by from one to five groups selected from halogen, Cl-6 alkyl, Cl-6 haloalkyl, Cl-6 alkoxy and nitro;

R²⁴ represents a group selected from halogen, R²^, nitro, cyano, -CO₂R²⁶, -S(O)_pR²¹, -OR²¹ and -NR 6R²⁷;

R²^ represents a straight- or branched- chain alkyl group containing one to three carbon atoms optionally substituted by one or more halogen atoms; R²6 and R²⁷ which may be the same or different, each represents hydrogen or R^2j; p, q and u independently represent the values zero, one or two; k and m represent one, two or three; x represents zero or one; t represents an integer from one to four; when t is greater than one, the groups R 9 and R 10 may be the same or different; or an agriculturally acceptable salt or metal complex thereof.

8. A method according to any one of the preceding claims in which the isoxazole or dione herbicide has the general formula (la):

(la)

wherein:

R is hydrogen or -CO2Et; R 28 is selected from -S(O)pMe, Me, Et, a chlorine, bromine or fluorine atom, methoxy, ethoxy and -CH2S(O)qMe; R 29 is selected from a hydrogen atom, a chlorine, bromine or fluorine atom, methoxy, ethoxy and -S(O)pMe; R 30 is selected from a hydrogen atom, a chlorine, bromine or fluorine atom, methoxy and trifluoromethyl; and p and q independently represent the values zero, one or two.

9. A method according to any one of the preceding claims in which the isoxazole or dione herbicide has the general formula (lb):

(lb) wherein R ,31 is chlorine, bromine or trifluoromethyl; and

R is hydrogen or -CO2Et.

10. A method according to any one of the preceding claims in which a substituted phenyl ring as defined in formulae (I); (la); or (lb) as depicted in claim 7,8 or 9 is attached to a grouping;

11. A method according to claim 10 in which the phenyl ring is substituted by two groups independently selected from halogen, alkyl, S(O)_talkyl (t = 0, 1 or 2) or haloalkyl.

12. A method according to claim 7, 8 or 9 in which a substituted phenyl ring as defined above in formula (I); (la); or (lb) is attached to a grouping;

13. A method according to claim 7 wherein the compound of formula (I) is:

5 -cyclopropy 1-4- [2-chloro-3 -ethoxy-4- (ethylsulphonyl)benzoyl]isoxazole;

4-(4-bromo-2-methylsulphonylbenzoyl)-5-cyclopropylisoxazole; 5 -cyclopropy 1-4- [4-fluoro-3 -methoxy-2- (methy lsulphonyl)benzoyl] isoxazole ;

4-(4-bromo-2-methylsulphonylmethylbenzoyl)-5- cyclopropylisoxazole; ethyl 5-cyclopropyl-4-(2-methylsulphonyl-4- trifluoromethylbenzoyl) isoxazole-3-carboxylate; 2- [2-chloro-(4-methylsulphonyl)benzoyl]- 1 ,3 -cyclohexanedione;

2- [2-nitro-(4-methylsulphonyl)benzoyl]- 1 ,3 -cyclohexanedione; 2-(2,3-dihydro-5,8-dimethyl-l,l-dioxospiro[4H-l-benzothiin-4,2' [1,3] dioxolan] -6-ylcarbonyl)cyclohexane- 1 ,3 -dione; 5 -cy clopropyl-4-(2-methylsulphonyl-4-trifluoromethy lbenzoyl)-3 - methylthio-isoxazole;

2-cyano-3-cyclopropyl- 1 -(2-methylsulphonyl-4- trifluoromethylphenyl) propan- 1 ,3-dione.

14. A method according to claim 13 in which the compound is 5- cyclopropyl-4-(2-methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole.

15. A method according to any one of the preceding claims in which the PPO-inhibiting herbicide is selected from aciflurofen-Na, azafenidin, bifenox, carfentrazone-ethyl, chlomethoxyfen, cinidon-ethyl, fluazolate, flumiclorac, flumioxazin, fluoroglycofen-ethyl, fluthiacet- methyl, fomesafen, halosafen, lactofen, oxadiargyl, oxadiazon, oxyfluorfen, paraquat, pyraflufen-ethyl, sulfentrazone and thidiazimin.

16. A method according to claim 15 in which the PPO-inhibiting herbicide is bifenox, oxadiargyl or oxadiazon.

17. A method according to claim 15 or 16 in which the application rate of bifenox is from 150 to 2000g/ha, preferably from 200 to 1200g/ha.

18. A method according to claim 15 or 16 in which the application rate of oxadiargyl is from 200 to 3000g/ha, preferably from 300 to 2000g/ha.

19. A method according to claim 15 or 16 in which the application rate of oxadiazon is from 600 to 6000g ha, preferably from 1200 to

4500g/ha.

20. A method according to any one of the preceding claims in which the weight ratio of isoxazole or dione herbicide to bifenox is from 1 : 100 to 3.3 : 1 , more preferably from 1 :24 to 1 :1.3

21. A method according to any one of the preceding claims in which the weight ratio of isoxazole or dione herbicide to oxadiargyl is from 1:150 to 2.5:1, more preferably from 1 :40 to 1 :2

22. A method according to any one of the preceding claims in which the weight ratio of isoxazole or dione herbicide to oxadiazon is from 1 :300 to 1 :1.2, more preferably from 1 :90 to 1 :8.

23. A method for the control of weeds at a maize or soybean crop locus, said method comprising the pre-crop emergence application to said crop of an effective amount of 5-cyclopropyl-4-(2- methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole, and optionally a post-crop emergence application of a PPO-inhibiting herbicide: wherein the crop is tolerant to the PPO-inhibiting herbicide.

24. A method for the control of weeds at a maize or soybean crop locus, said method comprising the pre-crop emergence application to said crop of an effective amount of 5-cyclopropyl-4-(2- methylsulphonyl-4-trifluoromethylbenzoyl)isoxazole: wherein the crop is tolerant to PPO-inhibiting herbicides.

25. A product comprising an isoxazole or dione derivative as defined in claim 1 , or an agriculturally acceptable salt or metal complex thereof and a PPO-inhibiting herbicide or agriculturally acceptable salt thereof, for separate or sequential application in securing the prolonged control of the growth of weeds at a crop locus, the crop being tolerant to the PPO-inhibiting herbicide and the isoxazole or dione derivative or agriculturally acceptable salt or complex thereof, being applied pre- emergence of the crop.

26. A method according to claim 1 substantially as hereinbefore described.

27. A product according to claim 25 substantially as hereinbefore described.