GB2155462A

GB2155462A - Heterotricyclic herbicides/fungicides

Info

Publication number: GB2155462A
Application number: GB08406061A
Authority: GB
Inventors: Michael Derek Barker; Peter Roy Woodward; John Ronald Lewis
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1984-03-08
Filing date: 1984-03-08
Publication date: 1985-09-25
Also published as: GB8406061D0

Abstract

Compositions having herbicidal and/or fungicidal activity which comprise a carrier and, as active ingredient, a substituted beta carboline of the formula:- <IMAGE> wherein X represents a hydrogen or halogen atom or alkyl or alkoxy group; R represents a hydrogen atom or an alkyl, alkenyl, or acyl group, and Y represents a halogen atom or an alkoxy or alkylthio group. With the exception of the compound wherein X is hydrogen, R is methyl and Y is chlorine, the compounds are claimed per se, and processes are described for the preparation of such compounds.

Description

SPECIFICATION neterotricyctic herbicides/fungicides T51a present invention relates to a composition for and a method of controlling undesired plant growth and/orfilngi and to compounds for use in such a composition or method.

It has been found that certain carboline derivatives have useful herbicidal and fungicidal properties, and accordingly the present invention provides a herbicidal and/or fungicidal composition which comprises q carrier and, as active ingredient, a substituted beta-carboline of the formula:

wherein X represents a hydrogen or halogen atom or an alkyl or alkoxy group; R represents a hydrogen atom or an alkyl, alkenyl or acyl group; and Y represents a halogen atom or an alkoxy or alkylthio group.

When R represents an acyl group, this is suitably one derived from a carboxylic acid, such as an alkanoic acid.

Preferably X represents a hydrogen or halogen, especially chlorine, atom; R represents an alkyl, alkenyl or alkylcarbonyl group of up to 6 carbon atoms, especially a methyl, ethyl, propyi, allyl or methylcarbonyl group; and Y represents a halogen, especially chlorine or bromine, atom, or an alkoxy or alkylthio group containing up to 6 carbon atoms, especially an ethoxy or methylthio group.

With one exception, the compounds of formula I are novel, and the invention therefore also extends to these novel compounds perse. The novel compounds are the beta-carbolines of formula I wherein X, R and Y are as defined above with the proviso that when Xis hydrogen and Y is chlorine, then R is not methyl.

The invention also provides a process for the preparation of a novel compound of the formula I defined above, which comprises: (a) dehydrogenating a ketocarboline of formula II

(b) halogenating the product to yield a 1-halo beta-carboline cf formula Ill:

wherein Hal represents a halogen atom c) when the desired product is one wherein R is alkyl, alkylating the product to yield the 9-alkyl derivative and d) when the desired product contains an alkoxy or alkylthio group at the 1-position, reacting the 1 -halo compound with the corresponding alcohol or mercaptan.

The starting ketocarboline of formula II can be obtained by synthesis procedures known in the literature, eg by reaction of a piperidone ester with a diazonium salt, followed by cyclization in the presence of formic acid.

The dehydrogenation of step al is conveniently effected by reaction with dicyanodichloroquinone, suitably in a solvent such as dioxan, and the alkylation of step c) suitably effected with an appropriate dialkyl ketal.

When R represents an alkyl group, the novel compounds can be prepared by an alternative process which comprises i) cyclising a compound of formula 1V

in the presence of a strong acid and ii) halogenating the product to yield a 1-halo beta carboline of formula V

The halogenation of step b) or ii) is conveniently effected by reaction with the appropriate phosphorus (oxy)halide.

The compounds of the general formula I have useful herbicidal and fungicidal properties, and accordingly the invention provides also the use as herbicide and/or fungicide of such a compound or a composition containing such a compound. Further, in accordance with the invention, there is provided a method of combating fungi and/or undesired plant growth at a locus by treating the locus with a compound or composition according to the invention. When using the compositions as herbicides the locus will normally be a crop growing area; application to this locus may be pre or post-emergence of the plant crop or weeds.

Treatment as a fungicide may suitably be to plants, seeds or soil as appropriate. The dosage of active ingredient used may, for example, be from 0.05 to 4kg/ha.

A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, orto facilitate storage, transport or handling. A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in agricultural compositions may be used.Preferably compositions according to the invention contain 0.5 to 95% by weight of active ingredient Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and vermiculites; aluminium silicates, for example kaolinites, montomorillonites and micas; calcium carbonate; calcium sulphate; ammonium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes; and solid fertilisers, for example superphosphates.

Suitable liquid carriers include water; alcohols, for example isopropanol and glycols; ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarbons, for example carbon tetrachloride, perchloroethylene and trichloroethane. Mixtures of different liquids are often suitable.

Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before application. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surface-active agent. For example the composition may contain at least two carriers, at least one of which is a surface-active agent.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide, fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for examplep-octylphenol or p-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, or sulphuric or sulphonic acid esters containing at least 10 carbon atoms in the molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols. Wettable powders usually contain 25, 50 or 75% w of active ingredient and usually contain in addition to solid inert carrier, 3-10% w of a dispersing agent and, where necessary, 0-10% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing 1/2-10% w of active ingredient. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676 - 0.152 mm), and may be manufactured by agglomeration or impregnation techniques. Generally, granules will contain 1/2-75% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-15% w of dispensing agents, 0.1-10% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as antifreeze agents for water.

Aqueous dispersions and emulsions, for example compositions obtained by diluting a wettable powder or a concentrate according to the invention with water, also lie within the scope of the invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick 'mayonnaise'-like consistency.

The composition of the invention may also contain other ingredients, for example other compounds possessing herbicidal, insecticidal or fungicidal properties.

The following Examples illustrate the invention.

Example 1 Preparation of l-chloro-9-methy/beta carboline A) Concentrated sulphuric acid (76 ml) was dissolved in dry ether (400 ml) and N-methyl-N'-(2,2 dimethoxyethyl)indole -2-carboxamide (18.95g) added in portions. The reaction mixture was stirred at ambient temperature and the precipitate filtered off. After removal of solvent, concentrated ammonium hydroxide was added until the solid was completely neutralised. The product was then dried, extracted and recrystallized.

B) The amide product of A) (7g) was mixed with redistilled phosphorus oxychloride (70 ml) under a stream of nitrogen, and heated under reflux with stirring for 6 hours. The reaction mixture was cooled, POCl3 removed in vacuo and then poured onto ice, neturalized and filtered. Chromatographic purification on silica gave the desired product, m.pt.118-120 C Analysis Calc for C12H9N2Cl: C 66.5; H 4.2; N 12.9 Found: C66.3; H 4.2; N 12.9 Example 2 Preparation of 1-chloro beta carboline A) 1-keto-1,2,3,4-tetrahydro beta carboline (14.9g) was mixed with dioxan (300 mali, dicyanodichloro quinone (21.8g) was added and the mixture stirred at ambient temperature overnight.Most of the dioxan was removed, the residue treated with saturated sodium carbonate solution, filtered arid the solid residue recovered and purified by washing and recrystallisation from dioxan and then isopropyl alcohol to yield the 1,2-rlihydro product.

B) The product of A) (5.5g) was added to a mixture of phosphorus pentachloride (3y) and phosphorus oxy chloride (60ml) prepared in situ in a dry fiask. The mixture was vigorously stirred under nitrogen and heated under reflux overnight. The mixture was cooled, poured onto ice, neutralised with saturated sodium bicarbonate solution and the product purified chromatographically on silica to yield the desired product, m.pt. 178-181 C.

Analysis Calc.forC11H7N2CI: C65.2; H3.5; N 13.S Found : C64.8 ; H 3.5 ; N 13.3 Example 3 Preparation of l-chloro-9-ethyl beta carbollne The 1-chloro carboline (prepared as in Example 2) (1g) was mixed with (CH3)2N.CH(OC2H5)2 (5 ml) and stirred under reflux overnight. After cooling and removal of volatiles, the desired product was purified chromatographically over silica.

Analysis Caic for C13H11N2Cl C 67.7 H 4.8 N 12.1 Found C 68.3 H 5.1 N 12.2 N.M.R. (downfield from TMS in ppm) 1.35 (3H triplet for CH3 of ethyl) 4.6 (2H quartet for CH2 of ethyl) 7.0-8.2 (6H, complex aromatic protons) Example 4 Preparation of 1-etnoxy-9-methyl beta cailboline Sodium {0.17g) was dissolved in ethanol (20 ml) and the 1-chloro analogue (prepared as in Ex. 1, 1.5g) was added. The solution was stirred under reflux for 70 hours and the desired product isolated chromatographically over silica with methylene chloride as eluant. m.pt. 62-64 C.

Examples 5-18 Following procedures analogous to those desci ibed in the foregoing Examples, a number of additional compounds were prepared, whose melting points arid chernicai analyses are shown in Table 1 below. In that Table, the compounds are identified by reference to the identity of the substituents in Formula I.

TABLE 1

Elemental Analysis Calc. Found Ex. No. R X Y M.Pt C C H N C H N 5 H 6-Cl Cl 278-280 55.7 2.5 11.8 55.5 2.3 11.5 6 H 8-Cl Cl 165-166 55.7 2.5 11.8 55.6 2.3 11.4 7 H 5-Cl Cl 234-237 55.7 2.5 11.8 55.6 2.8 11.3 8 H 7-Cl Cl 243-246 55.7 2.5 11.8 55.4 2.4 11.6 9 CH3 6-Cl Cl 162-164 57.4 3.2 11.1 56.9 2.9 10.8 10 CH3 8-Cl Cl n.d 57.4 3.2 11.1 57.0 3.2 10.7 11 CH3 5-Cl Cl 177-180 57.4 3.2 11.1 57.5 3.2 11.1 12 CH3 7-Cl Cl 127-129 57.4 3.2 11.1 57.4 3.3 11.1 13 CH3 H Br n.d. 55.2 3.4 10.7 54.6 3.4 10.3 14 CH3 H SCH3 98-102 68.4 5.3 12.3 68.1 5.0 12.5 15 CH(CH3)2 H Cl oil 68.7 5.3 11.5 68.5 5.6 11.4 16 CH2CH=CH2 H Cl oil 69.3 4.5 11.5 70.1 4.9 11.5 17 COCH3 H Cl 70-72 63.8 3.7 11.4 63.9 3.8 11.3 18 COCH3 7-Cl Cl 127-129 52.9 2.7 9.5 56.5 3.2 19.7 n.d. = not determined Example 19 HerbicidalActivity To evaluate their herbicidal activity, compounds according to the invention were tested using as a representative range of plants: maize, Zea mays (Mz); rice, Oryza Sativa (R); barnyard grass, Echinochloa crusgalli (BG); oat, arena sativa (0); linseed, Linum usitatissisum (L); mustard, Sinapsis alba (M); sugar beet, Beta vulgaris (SB) and soya bean, Glycine max (S).

The tests fall into two categories, pre-emergence and post-emergence. The pre-emergence tests involved spraying a liquid formulation of the compound onto the soil in which the seeds of the plant species mentioned above had recently been sown. The post-emergence tests involved two types of test, viz., soil drench and foliar spray tests. In the soil drench tests the soil in which the seedling plants of the above species were growing was drenched with a liquid formulation containing a compound of the invention, and in the foliar spray tests the seedling plants were sprayed with such a formulation.

The soil used in the tests was a prepared horticultural loam.

The formulations used in the tests were prepared from solutions of the test compounds in acetone containing 0.4% by weight of an alkylphenol/ethylene oxide condensate available under the trade mark TRITON X-155. These acetone solutions were diluted with water and the resulting formulations applied at dosage levels corresponding to 5 kg or 1 kg of active material per hectare in a volume equivalent to 600 litres per hectare in the soil spray and foliar spray tests, and at a dosage level equivalent to 10 kilograms of active material per hectare in a volume equivalent to approximately 3,000 litres per hectare in the soil drench tests.

In the pre-emergence tests untreated sown soil and in the post-emergence tests untreated soil bearing seedling plants were used as controls.

The herbicidal effects of the test compounds were assessed visually twelve days after spraying the foliage and the soil, and thirteen days after drenching the soil and were recorded on a 0-9 scale. A rating 0 indicates growth as untreated control, a rating 9 indicates death. An increase of 1 unit on the linear scale approximates to a 10% increase in the level of effect.

The results of the tests are set out in Table II below.

Table II

Compound of Example Soil Drench 10 kg/ha Dosage Foliar Spray Pre-emergence Number Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 6 0 0 0 0 0 0 0 0 5 3 0 6 3 5 7 8 6 0 0 0 0 0 0 0 0 1 2 0 4 2 3 5 5 4 0 0 0 0 0 0 0 0 1 0 2 6 0 0 3 0 0 5 4 5 6 5 9 7 9 9 4 3 5 2 3 2 6 2 1 2 3 4 2 8 5 6 8 0 0 0 0 0 0 0 0 11 0 0 0 0 0 0 0 0 5 3 3 7 2 6 6 9 6 0 0 0 0 0 0 0 0 1 2 2 5 1 5 6 8 4 0 0 0 0 0 0 0 0 12 0 0 3 0 0 0 4 2 5 2 3 7 5 5 8 9 7 0 0 4 0 0 0 0 0 1 2 2 7 4 4 7 9 5 0 0 2 0 0 0 0 0 3 0 0 0 0 0 0 0 0 5 2 0 7 4 6 8 9 4 0 0 6 3 4 5 6 4 1 0 0 5 2 4 7 5 3 0 0 4 3 4 4 4 0 Table II (continued)

Compound of Example Soil Drench 10 kg/ha Dosage Foliar Spray Pre-emergence Number Mz R BG O L M SB S kg/ha Mz R BG O L M SB S Mz R BG O L M SB S 17 0 0 0 0 0 0 0 0 5 4 4 8 5 6 8 9 8 0 0 0 0 0 0 0 0 1 2 1 7 2 3 8 8 6 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 5 4 2 6 3 6 7 9 6 0 0 0 0 0 0 0 0 1 0 0 2 0 2 4 3 4 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 5 0 0 7 0 6 9 7 5 0 0 0 0 0 0 0 0 1 0 0 2 0 3 5 3 3 0 0 0 0 0 0 0 0 13 0 0 5 0 0 4 3 0 5 5 3 8 6 8 9 9 8 0 0 5 2 3 4 4 0 1 2 0 6 4 7 7 7 7 0 0 2 0 2 0 0 0 Example 20 (a) Activity against vine downy mildew {Plasmopara viticola; P. v.a.) The test is a direct antisporulant one using a foliar spray. The lower surfaces of leaves of whole vine plants are inoculated by spraying with an aqueous suspension containing 105zoosporangia/ml 2 days prior to treatment with the test compound.The inoculated plants are kept for 24 hours in a high humidity compartment, and then 24 hours at glasshouse ambient temperature and humidity. The plants are then dried and infected leaves detached and sprayed on the lower surfaces with a solution of active material in 1:1 water/acetone containing 0.04% Triton X-155 (Trade Mark). The spraying is carried out with a moving track sprayer which delivers 620 1/ha, and the concentration of active material is calculated to give an application rate of 1 kg/ha. After drying, the petioles of the sprayed leaves are dipped in water and the leaves returned to high humidity for a further 96 hours incubation, followed by assessment. Assessment is based on the percentage of the leaf area covered by sporulation compared with that on control leaves.

(b) Activity against vine downy mildew (Plasmopara viticola; Pv.t) The test is a translaminar protectant one using a foliar spray. The upper surfaces of leaves of whole vine plants are sprayed at a dosage of 1 kilogram of active material per hectare using a track sprayer. The lower surfaces of the leaves are then inoculated, up to 6 hours after treatment with the test compound, by spraying with an aqueous suspension containing 1 zoosporangia/ml. The inoculated plants are kept for 24 hours in a high humidity compartment, 4 days at glasshouse ambient temperature and humidity and then returned for a further 24 hours to high humidity. Assessment is based on the percentage of leaf area covered by sporulation compared with than an control leaves.

(c) Activity against vine grey mould {Botrytis cinerea; B. c.) The test is a direct eradicant one using a foliar spray. The under-surface of the detached vine leaves are inoculated by pipetting ten large drops of an aqueous suspension containing 5x105 conidia/ml on to them.

The inoculated leaves are kept uncovered overnight during which time the fungus has penetrated the leaf and a visible necrotic lesion may be apparent where the drop was made. The infected regions are sprayed directly with a dosage of 1 kg of active material per hectare using a track sprayer as described under (a).

When the spray has dried the leaves are covered with a petri dish and the disease allowed to develop under these humid conditions. The extent of the necrotic lesion beyond the original drop together with the degree of sporulation is compared with on control leaves.

(d) Activity against potato late blight (Phytophtora in fes tans; P. i. p.) The test measures the direct protectant activity of compounds applied as a foliar spray. Tomato plants, cultivarAilsa Craig, 1-15 cms high, in monopots are used. The whole plant is sprayed at a dosage of 1 kilogram of active material per hectare using a track sprayer. The plant is then inoculated up to 6 hours after treatment with the test compound, by spraying with an aqueous suspension containing 5 x 103 zoosporangia/ml. The inoculated plants are kept in high humidity for 3 days. Assessment is based on comparison between the levels of disease on the treated and control plants.

(e) Activity against barley powdery mildew {Erysiphe graminis; E.g.) The test measures the direct antisporulant activity of compounds applied as a foliar spray. For each compound about 40 barley seedlings are grown to the one-leaf stage in a plastic pot of sterile potting compost. Inoculation is effected by dusting the leaves with conidia of Erysiphe graminis, spp. hordei. 24 hours after inoculation the seedlings are sprayed with a solution of the compound in a mixture of acetone (50%), surfactant (0.04%) and water using a track sprayer as described under (a). The rate of application is equivalent to 1 kg of active material per hectare. First assessment of disease is made 5 days after treatment, when the overall level of sporulation on the treated plants is compared with that on control plants.

(f) Activity against apple powdery mildew (Podsophaera leucotrica; P. l.) The test is a direct anti-sporulant one using a foliar spray. The upper surfaces of leaves of whole apple seedlings are inoculated by spraying with an aqueous suspension containing 105 conidia/ml 2 days prior to treatment with the test compound. The inoculated plants are immediately dried and kept at glasshouse ambient temperatures and humidity prior to treatment. The plants are sprayed at a dosage of 1 kilogram of active material per hectare using a track sprayer. After drying the plants are returned to a compartment at ambient temperature and humidity for up to 9 days, followed by assessment. Assessment is based on the percentage of the leaf area covered by sporulation compared with that on leaves of control plants.

(g) Activity against peanut leaf spot fCercospora arachidicola; Ca) The test is a direct eradicant one using a foliar spray. The upper surfaces of the leaves of peanut plants (12-20 cms high, monopots) are inoculated by spraying with an aqueous suspension containing 105 conidia/ml 4 hours prior to treatment with the test compound. The inoculated plants are kept at high humidity and then allowed to dry during the interval between inoculation and treatment by spraying at a dosage of 1 kg of active material per hectare using a track sprayer. After spraying the plants are moved to a humid compartment at 25-28"C for a further period of up to 10 days. Assessment is based on a comparison between the levels of disease on the treated and control plants.

(h) Activity against broad bean rust (Uromyces fabae; Uf) This test measures the translaminar antisporulant activity of compounds applied as a foliar spray. For each compound, seedling broad bean plants with two pairs of leaves were inoculated with an aqueous suspension containing 104 spores/ml. After 24 hours, the plants were sprayed with the test compound at a rate equivalent to 1 kg/ha. Assessment, after about 12 days, is by comparing the relative density of sporalating pustules compared with controls.

The extent of disease control achieved in these tests is expressed as a control rating in Table Ill below; greater than 80% disease control is given the rating 2 after the test; control of between 50% and 80% is given the rating 1 after the test.

Table III

Compound of Tests in which disease control is greater Example No. than 50% 1 Pva (1); Eg (2); Pl (2) 2 Pip (1); Pg (1); Pl (2); Ca (1) 3 Eg (2); Pl (2); Ca (l) 4 Eg (1); 6 Bc (2); Pip (2); Pg (1) 9 Pvt (1); Pip (1); Pg (2); Pl (2) 10 Eg (2); Pl (2) 11 Pvt (1); Pg (2); Pl (2) 12 Pvt (1); Pip (1); Pl (2) 13 Eg (2) 14 Eg (1); Ca (2) 15 Pi (2) 16 Ca (1) 18 Uf (2); Pl (2)

Claims

1. A herbicidal and/orfungicidal composition which comprises a carrier and, as active ingredient, a substituted beta-carboline of the formula:

2. A composition as claimed in claim 1 in which the active ingredient is a carboline of formula I wherein X represents a hydrogen or halogen atom; R represents a hydrogen atom or an alkyl, alkenyl or alkyl carbonyl group containing up to 6 carbon atoms; and Y represents a halogen atom or an alkoxy or alkylthio group containing up to 6 carbon atoms.

3. A composition as claimed in claim 2 wherein X represents a hydrogen or chlorine atom; R represents a hydrogen atom or a methyl, ethyl, propyl, allyl, or methylcarbonyl group; and Y represents a chlorine or bromine atom or an ethoxy or methylthio group.

4. A composition as claimed in any one of claims 1-3 wherein the carboline of formula I is any one of those named in Examples 1-18 herein.

5. A composition as claimed in any one of Claims 1-4 which comprises at least two carriers, at least one of which is a surface-active agent.

6. A composition as defined in Claim 1 substantially as hereinbefore described.

7. A substituted beta-carboline of the formula I as shown in Claim 1 wherein X, Y and R are as defined in Claim 1 with the proviso that when Xis hydrogen and Y is chlorine, then R is not methyl.

8. A substituted beta-carboline as claimed in Claim 7 wherein X represents a hydrogen or halogen atom; R represents a hydrogen atom or an alkyl, alkenyl or alkylcarbonyl group containing up to 6 carbon atoms; and Y represents a halogen atom or an alkoxy or alkylthio group containing up to 6 carbon atoms.

9. A substituted beta-carboline as defined in Claim 7 specifically named in any one of Examples 1-18 herein.

10. A process for the preparation of a compound as claimed in Claim 7, which comprises: a) dehydrogenating a ketocarboline of formula II

b) halogenating the product to yield a 1 -halo beta carboline of formula Ill

wherein Hal represents a halogen atom.

c) when the desired product is one wherein R is alkyl, alkylating the product to yield the 9-alkyl derivative and d) when the desired product contains an alkoxy or alkylthio group at the l-position, reacting the 1 -halo compound with the corresponding alcohol or mercaptan.

11. Process as claimed in Claim 10 wherein the dehydrogenation of step a) is effected by reaction with dicyanodichloro quinone, and the alkylation of step c) is effected with the appropriate dialkyl ketal.

12. Process for the preparation of a compound as claimed in Claim 7 wherein R is alkyl, which comprises; i) cyclising a compound of formula IV

13. Process as claimed in Claim 10 or 12 wherein the halogenation step b) or ii) is effected by reaction with phosphorus (oxy) halide.

14. Process as claimed in Claim 10 or 12 carried out substantially as hereinbefore described with particular reference to Examples 1 to 4.

15. A compound as claimed in Claim 7 whenever prepared by a process as claimed in any one of Claims lotto 14.

16. Method of combating undesired plant growth and/or fungi at a locus, which comprises treating the locus with a composition as claimed in any one of Claims 1-6 or a compound as claimed in any one of Claims 7-9or15.

17. Use as a herbicide and/or fungicide of a substituted beta-carboline as defined in any one of Claims 1-9 or15.