WO2018011540A1 - Pyrocarbonates, uses thereof and compositions - Google Patents

Abstract

In invention provides the use of pyrocarbonates in a method of killing plants, algae, and/or oomycetes in a treatment area and/or inhibiting photosynthetic electron transport in plants and/or algae in a treatment area, said method comprising applying a pyrocarbonate to said treatment area. The invention further provides a composition comprises a pyrocarbonate, e.g. dimethyl dicarbonate, and a herbicidal adjuvant. The pyrocarbonate may have herbicidal, oomyceticidal, and/or algaecidal activity. The composition may be used as a herbicide, oomyceticide and/or an algaecide.

Description

PYROCARBONATES, USES THEREOF AND COMPOSITIONS

Technical Field of the Invention

The present invention relates to pyrocarbonates and compositions comprising a pyrocarbonate, and uses thereof as a herbicide, algaecide or oomyceticide. The invention further relates to methods of killing or inhibiting the growth or reproduction of plants, algae and oomycetes.

Background to the Invention

Moss poses significant problems in a number of domestic and leisure environments. In domestic environments, moss fouls roofs, paths, lawns, etc. In leisure environments, moss on golf courses is a particular nuisance, and moss on tennis courts is also undesirable.

Moss is surprisingly resistant to existing herbicides such as glyphosates and paraquat (i.e. N,N -dimethyl-4,4 -bipyridinium dichloride). Two common chemicals used for killing moss are alkyl dimethyl benzyl ammonium chloride and didecyl dimethyl ammonium chloride. These highly toxic substances are damaging to the environment (including the aquatic environment), hazardous to humans and they cannot be used where moss comes into contact with other living matter (such as grass), as they kill such associated living matter. Alkyl dimethyl benzyl ammonium chloride and didecyl dimethyl ammonium chloride can therefore only be used on hard surfaces, but such treatment is normally limited to biannual applications owing to their toxicity and risks of associated environmental damage.

Treatment of moss in lawns and golf courses is often undertaken with ferrous sulphate, which has limited efficacy. Treatment can also be undertaken with quinoclamine, but this is limited to one or two applications per year owing to its high toxicity and the environmental damage it causes. In particular, quinoclamine causes serious harm if swallowed and it poses possible risks to unborn children. Quinoclamine is also highly toxic to aquatic organisms, and it may cause long term adverse effects to the aquatic environment.

Similarly, weeds, such as many species of vascular plants, can be difficult to remove, for a number of reasons, including resistance to known herbicides, deep root systems, and the difficulty in using known, often environmentally unfriendly herbicides in many environments or for selectively killing or supressing weeds amongst beneficial plants (such as grass, crops or horticultural plants).

Algae can be a problem in swimming pools, hot tubs, ponds, aquariums, etc. because it is unsightly, it can make surfaces slippery and dangerous, and it can be harmful to human health.

Oomycetes include some of the most destructive plant pathogens including the genus Phytophthora, which includes the causal agents of potato late blight and sudden oak death. Particular species of oomycetes are responsible for root rot.

It would be desirable to find a substance that can rapidly kill bryophytes (including moss, liverworts and hornworts), algae, oomycetes and/or vascular plants. Ideally, such a substance would be suitable for treating areas where moss, algae or vegetative pests are growing amongst other desired plants, such as grass, as well as hard surfaces, without leaving toxic residues or damaging the desired plants. It is also an aim of the invention to develop an environmentally sustainable method of controlling bryophytes, algae, oomycetes and/or vascular plants. Summary of the Invention

According to a first aspect of the invention, there is provided use of a pyrocarbonate as a herbicide, oomyceticide and/or an algaecide.

The current invention proposes the use of pyrocarbonates as the key active ingredient in a range of herbicides, algaecides and/or oomyceticides for agricultural and horticultural use. This use may relate to one, two, three or four of the following uses: as a herbicide against vascular plants, as a bryophytocide, as an algaecide, as an oomyceticide. For example, there is provided use of a pyrocarbonate-containing composition as herbicide against vascular plants or as a bryophytocide or as an oomyceticide or as an algaecide. There is also provided use of a pyrocarbonate or a pyrocarbonate-containing composition as a herbicide against vascular plants and as a bryophytocide and optionally as an algaecide. There is also provided use of a pyrocarbonate-containing composition as a bryophytocide and/or as an algaecide. The pyrocarbonate-containing composition may optionally comprise an adjuvant. In one aspect, the invention provides use of a pyrocarbonate as a herbicide against vascular plants, in which the pyrocarbonate has the general formula Ri-O-CO- O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group.

The term "herbicide" used herein, refers to a biocidal substance which kills, suppresses, inhibits the growth of, or inhibits photosynthesis of plants. Herbicides include plant/crop protection products, which protect plants from damaging influences such as moss, weeds, etc. The herbicide may be a selective herbicide, e.g. which kills a specific class of unwanted organism, such as moss and/or algae. Such selective herbicides may leave other classes of organisms, such as grass, unharmed.

The term "plants" includes vascular plants and non-vascular plants. Nonvascular plants include bryophytes (which include moss, liverworts and hornworts). "Herbicidal" as used herein means the ability of a substance to: inhibit the growth of plants; suppress photosynthesis in plants; and/or kill plants.

"Bryophytocidal" as used herein means the ability of a substance to: inhibit the growth of bryophytes; suppress photosynthesis in bryophytes; and/or kill bryophytes.

"Algaecidal" as used herein means the ability of a substance to: inhibit the growth of algae; suppress photosynthesis in algae; and/or kill algae.

"Oomyceticidal" as used herein means the ability of a substance to: inhibit the growth of oomycetes; and/or kill oomycetes.

The pyrocarbonate may comprise general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group. The alkyl group is a functional group that consists of single-bonded carbon and hydrogen atoms connected acyclically, such as methyl or ethyl groups. Alkyl groups have the general formula CnH2n+l, where n is an integer, for example, n = 1 for a methyl group (CH3).

According to some embodiments, n may be 0-20, 0-10, 0-5, 1-4, 0-3, 1-3, 1-2 or 1. In some embodiments both of Ri and R₂ comprise the same alkyl group. Ri and R₂ may be independently selected from methyl, ethyl, propyl, isopropyl or butyl, preferably methyl or ethyl.

Examples of pyrocarbonates having the general formula Ri-0-CO-0-CO-0-R₂, wherein Ri and/or R₂ is an alkyl group, include dimethyl dicarbonate (DMDC) and diethyl dicarbonate (DEDC). Thus, in some embodiments, the pyrocarbonate may be DMDC. The structure of DMDC and DEDC are shown below:

Dimethyl dicarbonate (DMDC)

Diethyl dicarbonate (DEDC)

DMDC is otherwise known as methoxycarbonyl methyl carbonate, dicarbonic acid dimethyl ester and dimethyl pyrocarbonate. Velcorin® is a trade name for DMDC, which is sold by LANXESS®. DMDC is primarily used as a beverage preservative, processing aid, or sterilization agent, e.g. for cold microbial treatment of beverages including but not limited to wines, fruit juices and soft drinks. DMDC is approved in the EU, where it is listed under E number E242, as well as Australia and New Zealand. In addition, the US FDA and the JECFA of the WHO have confirmed the safe use of DMDC in beverages. Fruit juices, beer and white wine to which DMDC was added at a concentration of 4000 mg/L did not induce any adverse effects in short-term or subchronic toxicity studies in rats and dogs. The available data (in vitro and in vivo) did not report a genotoxic potential and no reproductive or developmental toxic effects were reported in rats drinking orange juice treated with DMDC at 4000 mg/L.

DMDC is unstable in aqueous solution and breaks down almost immediately after addition to aqueous solutions. The principal breakdown products in aqueous liquids are methanol and carbon dioxide. Other minor hydrolysis products may include dimethyl carbonate (DMC), methyl ethyl carbonate (MEC) and methyl carbamate (MC). As the boiling point of methanol is 64.7°C, this primary residue would quickly evaporate off plants in normal ambient spraying conditions. Assuming a spray concentration of 4000ppm of DMDC at a rate of 300L/hec this implies deposition of 72g/hec of methanol, which would in normal circumstances rapidly evaporate.

The pyrocarbonate DMDC for example at 5000ppm concentration (in the presence of water alone or a herbicidal adjuvant), is unexpectedly toxic to moss but not to grass. DMDC in the presence of various herbicidal adjuvants shows higher levels of toxicity to mint and basil leaves than similar proportions of paraquat. Thus, pyrocarbonates such as DMDC may be used as a key active ingredient in herbicides. Pyrocarbonates such as DMDC offer the potential for a non-toxic sustainable product for both the agricultural and horticultural industries. Advantages of DMDC include its unexpected plant protection qualities in relation to many classes of plants important to agriculture (such as grasses including cereal crops) and horticulture (such as flowering plants sold for their aesthetic qualities), as well as its ability to hydrolyse quickly into non-toxic substances. At 20°C, DMDC has a half-life of 17 minutes, at 10°C it has a half-life of 40 minutes, and at 4°C it has a half-life of 70 minutes.

By avoiding the production of toxic residues, DMDC provides a more sustainable solution for controlling plants, algae, and/or oomycetes.

Such a pyrocarbonate may be capable of: inhibiting photo synthetic electron transport in plants and/or algae; and/or inhibiting the growth of or killing: plants, algae and/or oomycetes. Thus, the pyrocarbonate may have herbicidal (such as bryophytocidal, for example), oomyceticidal, and/or algaecidal activity.

It is believed that the herbicidal, algaecidal and oomyceticidal properties of pyrocarbonates as described and defined hereinabove may result from the ability of the pyrocarbonate to react with amino acid chemical groups, including imidazoles, amines and thiols, and alter protein structure and function. For example, the pyrocarbonate may facilitate the carbonylation of imidazole rings, e.g. imidazole rings of histidine amino acids located in enzyme active sites. The compound functions by carbonylation (e.g. methoxycarbonylation) of enzymes and/or produces methanol and C0₂ as by-products. The pyrocarbonate may react with amino acid chemical groups, including imidazoles, amines and thiols, and alter protein structure and function. For example, the compound may facilitate the carbonylation of imidazole rings, e.g. imidazole rings of histidine amino acids located in enzyme active sites. According to a second aspect of the invention, there is provided a composition comprising a pyrocarbonate and a herbicidal adjuvant, said pyrocarbonate having the general formula R1-0-CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group. The pyrocarbonate may be as defined hereinabove for the first aspect of the invention, and may be dimethyl dicarbonate or diethyl dicarbonate. In one aspect, the invention provides use of a composition as a herbicide against vascular plants, in which the composition comprises a pyrocarbonate and an adjuvant, the pyrocarbonate having the general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group.

The composition may comprise other components. Alternatively the composition may consist of the pyrocarbonate and a herbicidal adjuvant.

The pH of the composition may be at least pH 1, at least pH 1.5 or at least pH 2. The pH of the composition may be no more than pH 10, no more than pH 9 or no more than pH 8. A Suitable pH range is pH 2-8 or pH 2-7.

The composition may have an acidic pH. An advantage of maintaining pyrocarbonates having the general formula Rl -O-

CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group at low pH is that the un- dissociated form of the pyrocarbonate predominates at low pH, and this form can penetrate cell membranes more rapidly than dissociated ionic forms. Once inside the cell where the pH is close to neutral, a large proportion of the pyrocarbonate dissociates into membrane-impermeable ions, which become trapped inside the cell membrane. This is especially advantageous for dimethyldicarbonate and diethyldicarbonate in which the un-dissociated form the pyrocarbonate predominates at low pH. The concentration of the pyrocarbonate in the composition may be > 25 ppm,

>250 ppm, >500 ppm, or >1000 ppm.

The adjuvant may enhance the herbcidal, oomyceticidal and/or algaecidal activity of said pyrocarbonate, for example by increasing permeability of cuticles and/or cell membranes. The adjuvant may enhance the herbicidal and/or algaecidal activity of said pyrocarbonate, for example by increasing permeability of plant cuticles and/or cell membranes. The adjuvant may reduce pH and/or bicarbonate levels in spray solutions.

The adjuvant may be an additive for crop protectant sprays, such as a surfactant; a non-ionic spreading and a penetration aid; and/or act to reduce surface tension of the composition, for example.

The adjuvant may comprise an activator adjuvant or a utility adjuvant.

Activator adjuvants are compounds that when added to the composition comprising the pyrocarbonate, enhance the herbicidal, algaecidal and/or oomyceticidal activity thereof. Activator adjuvants include surfactants, oil carriers such as phytobland (not harmful to plants) oils, crop oils, crop oil concentrates (COCs), vegetable oils, methylated seed oils (MSOs), petroleum oils, and silicone derivatives, as well as nitrogen fertilizers, for example. Utility adjuvants, which are sometimes called spray modifiers, alter the physical or chemical characteristics of the composition mixture making it easier to apply, such as by increasing its adherence to plant surface so that it is less likely to roll off, or increasing its persistence in the environment. One or more oils may be used as an adjuvant carrier or diluent for the pyrocarbonate.

Salts may also be used as activator adjuvants, such as to increase the uptake and effect of the pyrocarbonate in a target plant over time.

One or more surfactant adjuvants may be present in the composition to facilitate or enhance the emulsifying, dispersing, spreading, sticking or wetting properties of the composition. Surfactants reduce surface tension in the spray droplets of the composition, when the composition is applied to the plant, algae or oomycetes, which aids the composition to spread out and cover the target plant, algae or oomycetes with a thin film, leading to more effective or quicker absorption of the composition into the plant, algae or oomycetes. Surfactants may also affect the absorption of the composition when sprayed on stems or leaves of a plant, by changing the viscosity and crystalline structure of waxes on leaf and stem surfaces, so that they are more easily penetrated by the pyrocarbonate of the composition.

The surfactant may be chosen to enhance the herbicidal, algaecidal and/or oomyceticidal properties of the composition, through any one or more of: a) making the composition spread more uniformly on the plant; b) increasing retention (or 'sticking') of the composition on the plant, algae or oomycetes; c) increasing penetration of the composition through hairs, scales, or other leaf surface structures of a plant; d) preventing crystallization of the composition; and/or e) slowing the drying of the composition.

The or each surfactant may be selected from a non-ionic surfactant, an ionic surfactant, an amphoteric surfactant or a zwitterionic surfactant, or any combination thereof.

Non-ionic surfactants are generally biodegradable and are compatible with many fertilizers and so may be preferable in compositions of the invention. Some nonionic surfactants are waxy solids and require the addition of a co-solvent (such as alcohol or glycol) to solubilize into liquids. Glycol co-solvents are generally preferred over alcohols, as the latter are flammable, evaporate quickly, and may increase the number of fine spray droplets (making the formulation likely to drift when sprayed).

The non-ionic surfactant may comprise an organosilicone or silicone surfactant (including siloxanes and organosiloxanes). Organosilicone surfactants significantly reduce surface tension of the composition, enabling the composition, in use, to form a thin layer on a leaf or stem surface of a plant. Silicone surfactants also decrease surface tension and may allow the composition to penetrate the stomates of a plant leaf. Silicone surfactants also provide a protective effect to the compositions of the invention by making the compositions very difficult to wash off after they are applied. Silicone surfactants can also influence the amount/rate of herbicide that is absorbed through the cuticle of a leaf.

In other embodiments the non-ionic surfactant may comprise a carbamide surfactant (also known as a urea surfactant). The carbamide surfactant may comprise monocarbamide dihydrogen sulphate, for example. Suitable ionic surfactants include cationic surfactants and anionic surfactants. Suitable cationic surfactants include tallow amine ethoxylates. Suitable anionic surfactants include sulphates, carboxylates, and phosphates attached to lipophilic hydrocarbons, including linear alkylbenzene sulphonates, for example. Amphoteric surfactants contain both a positive and negative charge and typically function similarly to nonionic surfactants. Suitable amphoteric surfactants include lecithin (phosphatidylcholine) and amidopropylamines, for example.

Utility adjuvants, which are sometimes called spray modifiers, alter the physical or chemical characteristics of the compositions of the invention making the composition easier to apply, which may increase its adherence to a plant surface or surface of algae or oomycetes so that the compositions having a reduced risk of being removed from said surface; or increasing the persistence of the composition in the environment or treatment area in which the composition is present.

Examples of different functional categories of utility adjuvants suitable for use in the compositions and uses of the invention include wetting agents, spreading agents, drift control agents, foaming agents, dyes, thickening agents, deposition agents (stickers), water conditioning agents, humectants, pH buffers, de-foaming agents, anti- foaming agents and UV absorbents. Some utility adjuvants may function in more than one of the aforesaid functional categories. Some activator adjuvants are also utility adjuvants.

Wetting agents or spreading agents lower surface tension in the compositions, and allow the compositions to form a large, thin layer on the leaves and stems of a target plant. Since these agents are typically non-ionic surfactants diluted with water, alcohol, or glycols they may also function as activator adjuvants (surfactants). However, some wetting or spreading agents affect only the physical properties of the composition, and do not affect the behaviour of the composition once it is in contact with plants.

Drift control agents may be used to reduce spray drift of the composition, for example when the composition is sprayed onto a plant, algae or oomycetes, which most often results when fine (< 150 μηι diameter) spray droplets are carried away from the target area by air currents,. Drift control agents alter the viscoelastic properties of the spray solution, yielding a coarser spray with greater mean droplet sizes and weights, and minimizing the number of small, easily-airborne droplets. Suitable drift control agents may comprise large polymers such as polyacrylamides, polysaccharides and certain types of gums.

Suitable deposition agents (stickers) include film-forming vegetable gels, emulsifiable resins, emulsifiable mineral oils, vegetable oils, waxes, and water-soluble polymers, for example. Deposition agents may be used to reduce losses of composition from the target plant, algae or oomycetes due to the evaporation of the composition from the target surface, or beading-up and falling off of the composition. Deposition agents are particularly suitable for compositions of the invention in the form of dry (wettable) powder and granule formulations.

De-foaming and antifoam agents reduce or suppress the formation of foam in containers in which the compositions of the invention may be contained. Suitable de- foaming agents include oils, polydimethylsiloxanes and other silicones, alcohols, stearates and glycols, for example. The adjuvant or adjuvants may comprise BREAK-THRU® S 240, BREAK- THRU® SP 131, BREAK-THRU® SP 133, BREAK-THRU® S 233, BREAK- THRU® OE 446, Aduro (RTM) and/or Transport Ultra (RTM) . BREAK-THRU® S 240 is a polyether trisiloxane that imparts super spreading and dramatically reduces surface tension. BREAK-THRU SP131 is composed of polyglycerol fatty esters and polyglycols, and it improves the performance of herbicides.

BREAK- THRU® SP 133 is based on polyglycerol esters and fatty acid esters. BREAK- THRU® S 233 is a non-ionic trisiloxane surfactant, which increases the deposition of agrichemical sprays and improves the penetration of pesticide actives into plant tissue. BREAK-THRU® OE 446 is a polyether polysiloxane.

Transport Ultra (RTM) comprises a blend of non-ionic surfactants, ammoniated ions, water conditioning agents and an antifoam agent.

Aduro (RTM) comprises a monocarbamide dihydrogen sulphate and alkylamine ethoxylates. In some preferred embodiments, at least one adjuvant is selected from a silicone, a siloxane, an alkylamine ethoxylate or a carbamide. Said adjuvants are particularly useful at enhancing the effect of the pyrocarbonate, or otherwise increasing or speeding up the take-up of the pyrocarbonate by plants (particularly vascular plants and mosses) and algae. In some embodiments, the adjuvant may comprise: a non-ionic surfactant; and/or antifoam; and/or ammonium ions; and/or water-conditioning agent; and/or polyether-polymethylsiloxan-copolymer; and/or polyether polysiloxane; and/or polyglycerol fatty esters and polyglycols; and/or polyglycerol esters and fatty acid esters; and/or non-ionic trisiloxane.

In preferred embodiments the composition comprises at least one surfactant, which may be a non-ionic surfactant. In some embodiments the composition comprises at least one silicone or siloxane, which silicone or siloxane may act as a surfactant and/or an anti-foam agent and/or a wetting agent. In some embodiments the pyrocarbonate comprises dimethyl dicarbonate or diethyldicarbonate and the adjuvant comprises a silicone or siloxane.

In some embodiments, the pyrocarbonate may be dimethyl dicarbonate and the adjuvant may be Transport Ultra. The invention also provides a composition consisting of dimethyl dicarbonate and Transport Ultra.

Transport Ultra is advantageous because inter alia it aids absorption by increasing permeability of the plant cuticle and/or cell membranes and it increases the proportion of DMDC in its undissociated, membrane-permeable form by decreasing the pH of the composition to about pH 2.6.

In some embodiments the adjuvant is not an alkylphenyl polyethyl glycol, a halogenoformic acid ester, or a combination thereof. Thus in some embodiments there is provided a composition comprising a pyrocarbonate and a herbicidal adjuvant, said pyrocarbonate having the general formula R1-0-CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group, and wherein the adjuvant is not an alkylphenyl polyethyl glycol, a halogenoformic acid ester, or a combination thereof.

In some embodiments, the ratio of the concentration of pyrocarbonate to the concentration of adjuvant or total amount of adjuvants in the composition is in the range 50: 1 to 1: 1, in the composition, such as between 20: 1 and 1: 1, between 10: 1 and 1: 1 or between 5: 1 and 1: 1, for example.

In some embodiments, the pyrocarbonate is present in a carrier or diluent (such as water or an aqueous carrier) in a concentration of at least 0.1% v/v, at least 0.15% v/v, at least 0.2% v/v or at least 0.25% v/v and may be present at between 0.25% v/v and 50% v/v. In such embodiments, the herbicidal adjuvant may be present in a concentration of at least 0.01% v/v, at least 0.02% v/v or at least 0.05% v/v, and may be present in a concentration of between 0.01 % v/v and 10% v/v. In some embodiments, the pyrocarbonate is present in a concentration of between 0.1% v/v and 50% v/v, such as between 0.25% v/v and 5% v/v, and the herbicidal adjuvant is present in a concentration of between 0.01% v/v and 10% v/v, such as between 0.05% v/v and 2.5% v/v.

In preferred embodiments, the composition comprises an aqueous solution of between 0.1% v/v and 5% v/v pyrocarbonate and between 0.05% v/v and 5% v/v adjuvant or total concentration of adjuvants.

Whilst aqueous compositions have been described hereinabove, it is to be noted that the pyrocarbonate may be present in a composition comprising a non-aqueous solvent (which may be mixed with water). Such non-aqueous solvents may include alcohols such as isopropanol, for example. In other embodiments, the compositions may comprise a hydrophobic carrier, such as a wax, oil or fat.

It is to be understood that, in use, any aqueous composition may be prepared immediately before application to the desired plants, algae or oomycetes, such as within 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, or 180 minutes before application.

The algae referred to above may be freshwater algae (such as Ettlia carotinosa) or marine algae (such as Porphyridium purpureum). The invention also provides a kit comprising a composition according to the invention. For example the kit may comprise: (1) a composition according to the invention which comprises less than 10% (v/v) water, or less than: 9% (v/v), 8% (v/v), 7% (v/v), 6% (v/v), 5% (v/v), 4% (v/v), 3% (v/v), 2% (v/v), 1% (v/v) or 0.5% (v/v) water or an anhydrous (e.g. dry) composition according to the invention; and (2) a solvent or carrier (such as water) for addition to the composition immediately prior to use. The solvent in such a kit may comprise an adjuvant as defined above. Anhydrous compositions are preferred because pyrocarbonates such as DMDC may rapidly hydrolyse upon contact with water. A kit may also include instructions.

The kit may further comprise a composition delivery device, such as a spray container. The spray container may comprise a spray bottle, a spray tank or the like, and may be of any suitable volume, such as up to 100 ml, 250 ml, 500 ml, 1 litre, 2 litres, 5 litres, or 10 litres for a spray bottle, or up to 20 litres, 50 litres, 100 litres, 200 litres, 250 litres or 500 litres for a spray tank, for example.

The composition may be contained in a spray container, which may be a spray bottle, a spray canister or a spray tank, for example. Thus, the invention also provides a spray container comprising a composition of the second aspect of the invention. The composition in the spray container may be a liquid composition (e.g. a composition of the invention dissolved in a solvent), ready for spraying, or a solid composition (such as a powder or granules) which may be dissolved in a suitable solvent prior to use.

According to a third aspect of the invention, there is provided use of a pyrocarbonate-containing composition of the second aspect of the invention as a herbicide, oomyceticide and/or algaecide. The pyrocarbonate may be a pyrocarbonate having the general formula R1-0-CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group. The pyrocarbonate may be a pyrocarbonate as described for the first aspect of the invention, especially dimethyl dicarbonate or diethyl dicarbonate.

According to a fourth aspect of the invention, there is provided a method of killing, inhibiting the growth of, or inhibiting the reproduction of plants, algae, and/or oomycetes and/or inhibiting photo synthetic electron transport in plants and/or algae, said method comprising applying a pyrocarbonate to said plants, algae and/or oomycetes. The pyrocarbonate may be a pyrocarbonate having the general formula Rl- 0-CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group. The pyrocarbonate may be a pyrocarbonate as described for the first aspect of the invention, especially dimethyldicarbonate or diethyldicarbonate. The plants, algae and/or oomycetes may be present in a treatment area and the method may comprise applying the pyrocarbonate to the plants, algae and/or oomycetes within the treatment area. The pyrocarbonate may be present in a composition of the second aspect of the invention. The pyrocarbonate may be sprayed onto the plants, algae and/or oomycetes.

According to a fifth aspect of the invention, there is provided a method of killing, inhibiting the growth of, or inhibiting the reproduction of plants, algae and/or oomycetes and/or inhibiting photo synthetic electron transport in plants and/or algae in a treatment area comprising applying a pyrocarbonate-containing composition of the second aspect of the invention to said treatment area.

Brief Description of the Figures

Figure 1. Line graphs showing the relative photosynthetic electron transport rate (ETR) in moss at increasing photo flux densities, 3 hours (Fig. 1A) and 24 hours (Fig. IB) after treatment with various concentrations of DMDC (0 ppm, 250 ppm, 500 ppm, 1000 ppm or 2000 ppm).

Figure 2. Line graphs showing the relative photosynthetic electron transport rate at increasing photo flux densities in moss, 4 hours (Fig. 2A) or 24 hours (Fig. 2B) after treatment with 2000 ppm DMDC in the presence and in the absence of Transport Ultra.

Figure 3. Photographs of moss fragments 24 hours after treatment with deionized water plus Transport Ultra (Fig 3A), DMDC plus deionized water (Fig 3B), and DMDC plus Transport Ultra (Fig 3C).

Figure 4. A line graph showing the relative photosynthetic electron transport rate at increasing photo flux densities in a natural population of moss 24 hours, 48 hours and 1 week after exposure to lOOOppm DMDC + 0.5% (v/v) Transport Ultra in tap water.

Figure 5. A photograph of moss 4 days after treatment with 1000 ppm DMDC.

Figure 6. A line graph showing the relative photosynthetic electron transport rate (ETR) in moss at increasing photo flux densities, 24 hours after treatment with a composition comprising 1000 ppm DMDC and various adjuvants. Figure 7. Relative photo synthetic electron transport rate at increasing photo flux densities in Ettlia carotinosa 1 hour after exposure to various concentrations of DMDC.

Figure 8. Relative photo synthetic electron transport rate at increasing photo flux densities in Porphyridium purpureum 1 hour, 3 hours and 24 hours after exposure to 250 ppm DMDC.

Figure 9. A line graph showing the relative photo synthetic electron transport rate (ETR) in culinary basil leaves (Ocimum basilicum) at increasing photo flux densities, 24 hours after treatment with a composition comprising different concentrations (0.5% v/v, 1% v/v, 2% v/v and 4% v/v) of DMDC in de-ionised water. Figure 10. A line graph showing the relative photosynthetic electron transport rate (ETR) in culinary basil leaves (Ocimum basilicum) at increasing photo flux densities, 24 hours after treatment with a composition comprising different concentrations (0.25% v/v, 0.5% v/v, 1% v/v and 2% v/v) of DMDC and 0.1% BREAK- THRU® S 240 (a polyether trisiloxane spreading agent adjuvant that imparts super spreading and dramatically reduces surface tension) in de-ionised water.

Figure 11. A line graph showing the relative photosynthetic electron transport rate (ETR) in culinary basil leaves (Ocimum basilicum) at increasing photo flux densities, 24 hours after treatment with a composition comprising 1% v/v of DMDC and different herbicidal adjuvants (0.1% SP131, 0.1% S133, 0.1% S233, 0.5% LI700, 0.5% Transport Ultra, 0.2% Aduro, and 0.1 % S240, all v/v) in de-ionised water.

Detailed Description of the Invention

The invention provides in one aspect use of a pyrocarbonate or pyrocarbonate- containing composition as a herbicide, oomyceticide and/or an algaecide. This use may relate to one, two or three of the following uses: as a herbicide, as an oomyceticide and as an algaecide. For example, there is provided use of a pyrocarbonate or pyrocarbonate-containing composition as a herbicide or as an oomyceticide or as an algaecide. There is also provided use of a pyrocarbonate or pyrocarbonate-containing composition as a herbicide and as an algaecide and as an oomyceticide. There is also provided use of a pyrocarbonate or pyrocarbonate-containing composition as a herbicide and/or as an algaecide. The pyrocarbonate-containing composition may optionally comprise an adjuvant.

The invention provides in one aspect a method of killing plants, algae, and/or oomycetes in a treatment area and/or inhibiting photosynthetic electron transport in plants and/or algae in a treatment area, said method comprising applying a pyrocarbonate to said treatment area. There is provided a method of killing plants, algae, and/or oomycetes in a treatment area, said method comprising applying a pyrocarbonate to said treatment area. This method may comprise killing one, two or three of the following: plants, algae and oomycetes. For example, there is provided a method of killing moss and/or algae in a treatment area, said method comprising applying a pyrocarbonate to said treatment area. There is also provided a method of inhibiting photosynthetic electron transport in plants and/or algae in a treatment area, said method comprising applying a pyrocarbonate to said treatment area. The invention provides in one aspect a method of killing plants, algae and/or oomycetes and/or inhibiting photosynthetic electron transport in plants and/or algae in a treatment area comprising applying a pyrocarbonate-containing composition to said treatment area, wherein said pyrocarbonate-containing composition comprises an adjuvant. Thus, there is provided a method of killing plants and/or algae in a treatment area comprising applying a pyrocarbonate-containing composition to said treatment area, wherein said pyrocarbonate-containing composition comprises an adjuvant. There is also provided a method of inhibiting photosynthetic electron transport in plants and/or algae in a treatment area, said method comprising applying a pyrocarbonate - containing composition to said treatment area, wherein said pyrocarbonate-containing composition comprises an adjuvant.

The pyrocarbonate-containing composition may be a composition as defined above.

The composition and/or the pyrocarbonate described above may be a photosynthetic inhibitor. Thus, the invention provides a photosynthetic inhibitor comprising a pyrocarbonate and an adjuvant, and the pyrocarbonate may have the general formula R1-0-CO-0-CO-0-R2, wherein Rl and/or R2 is an alkyl group.

Particular non-limiting embodiments of the present invention will now be described with reference to the accompanying drawings. EXAMPLES

Example 1 - Effect of DMDC on moss

Method

Circular fragments of moss, each about 5-cm in diameter, were gathered from areas of dense growth at Stowfield Business Park and placed in petri dishes. Solutions containing deionized water, 0.5% (v/v) Transport Ultra adjuvant and dimethyl dicarbonate (DMDC) were mixed immediately before the experiments. The concentrations of DMDC in these solutions ranged from 0 ppm to 2000 ppm. The petri dishes were placed in an incubator maintained at 20^° C, containing fluorescent white tubes providing photon flux densities (PFD) of 35-55 μιηοΐ m^"2 s^"1. After incubation for 3 hours, moss segments were removed and chlorophyll fluorescence was measured using a Hansatech FMS 1 modulated chlorophyll fluorometer. These measurements were used to determine the relative photosynthetic electron transport rate (ETR), by multiplying 0PSR (ratio of Variable Fluorescence FV against Maximum Fluorescence FM in dark adapted photosynthetic tissue) by PFD.

Testing of DMDC in situ was carried out on moss growing at Stowfield Business Park. An area of established and dense moss growth was chosen for experiments (which took place during a dry sunny day in mid April). Moss was sprayed at 11.30 am with a solution made up of 1000 ppm DMDC, 0.5% (v/v) Transport Ultra and tap water, which was prepared immediately prior to the experiments. An area of 1/16^ώ m² was sprayed with the equivalent of 1 L per m², i.e. 63 mL, using a 0.5 L plastic plant sprayer. Small samples of moss were taken from the sprayed area and chlorophyll fluorescence was measured using a Hansatech FMS 1 modulated chlorophyll fluorometer over 2 weeks.

Results

The relative photosynthetic ETR at increasing PFDs (μιηοΐ m^"2 s^"1) in the moss was analysed, following exposure to different DMDC concentrations after 3 hours (Figure 1A) and 24 hours (Figure IB) exposure.

Within 3 hours, DMDC addition substantially suppresses photosynthesis at all concentrations, although this is less marked at 250 ppm. 24 hours' exposure increased suppression at all concentrations except at 0 ppm and 250 ppm, both of which show increased photosynthesis compared to t = 3h.

To determine if the Transport Ultra adjuvant was affecting the moss, a further experiment was carried out in which moss was exposed to DMDC with and without adjuvant addition. The relative photosynthetic ETR at increasing PFD (μιηοΐ m^"2 s^"1) in moss was measured after exposure to 2000 ppm DMDC, with and without addition of Transport Ultra.

Relative photosynthetic ETRs were measured 4 hours after exposure (Figure 2A) and 24 hours after exposure (Figure 2B). The data show that photosynthesis in moss is almost completely inhibited 4 hours after exposure to DMDC plus Transport Ultra. DMDC in water without Transport Ultra also had a strong inhibitory effect, but some chlorophyll fluorescence could still be measured. 24 hours after exposure this inhibition was sustained: all moss samples exposed to DMDC had turned completely brown, whereas moss exposed to water plus Transport Ultra remained green (see Figure 3). Figure 3 also shows healthy blades of grass among the dead moss, demonstrating that DMDC acts as a selective herbicide.

The relative photosynthetic ETR at increasing PFDs (μιηοΐ m^"2 s^"1) was analysed in a natural population of moss situated at Stowfield Business Park, following exposure to 1000 ppm DMDC + 0.5% (v/v) Transport Ultra in tap water, 24 hours, 48 hours and 1 week after treatment. The results show that within 24 hours, photosynthesis in moss was almost completely inhibited by DMDC. Within 48 hours little or no photosynthesis was occuring, and this inhibition was maintained 1 week after treatment (Figure 4). Within 4 days it was observed that the moss had turned brown and had begun to disintegrate inside the white square that had been sprayed with the 1000 ppm DMDC solution 4 days prior (Figure 5).

Example 2 - Effect of DMDC and different adjuvants on moss Method

Using essentially the method described in Example 1, the effectiveness of lOOOppm DMDC in combination with various adjuvants was tested. The relative photosynthetic ETR at increasing PFDs in the moss was measured after 24 hours' (Figure 6) exposure. The following adjuvants were tested:

Name Manufacturer Description Concentration

Polyether-polymethylsiloxane

S240 Alzchem AG copolymer 0.10%

Mix of fatty acid esters in poly-

S 131 Evonik glycol 0.10%

S 133 Evonik Mix of fatty acid esters 0.10%

S233 Evonik Polyether-modified polysiloxane 0.10%

OE446 Evonik Polyether-modified polysiloxane 0.05%

Transport Ultra: blend of nonionic

surfactants, ammoniated ions, water

TU Precisions Labs conditioning agents and antifoam 0.50% Results

At both the 3-hour and 24-hour time points, relative photosynthetic ETR in the moss was suppressed to a signficant extent by all of the DMDC + adjuvant compositions. Example 3 - Effect of DMDC on algae

Method

The effect of DMDC on photosynthesis in algae was tested using both a freshwater strain, Ettlia carotinosa, and a marine strain, Porphyridium purpureum.

An initial dose response experiment was carried out using healthy cultures of E. carotinosa growing in 1 L bottles: 25 mL were added to 100 mL glass conical flasks, which were then placed in an incubator at 20° C in 24 h light, PFD 35-55 μιηοΐ m^"2 s^"1. DMDC concentrations of 2.5, 25 and 250 mg/L were added to separate conical flasks and chlorophyll fluorescence was measured after an hour.

Cultures of P. purpureum growing in 1 L bottles of artificial seawater medium were used in experiments. Following the findings of the E. carotinosa dose response, cells were exposed to 250 ppm DMDC. 25 mL were added to 100 mL glass conical flasks which were then placed in an incubator at 20° C in 24h light, PFD 35-55 μιηοΐ m^"2 s^"1. DMDC concentrations of 2.5, 25 and 250 mg/L were added to separate conical flasks and chlorophyll fluorescence was measured after an hour. Because inhibition of photosynthesis was slower in this species, fluorescence was also measured at 3 hours and 24 hours.

Results The relative photosynthetic ETR was analyzed at increasing PFD (μηιοΐ m^"2 s^{" l}) in Ettlia carotinosa 1-hour after exposure to various concentrations of DMDC. Addition of DMDC at 25 ppm and above was shown to inhibit photosynthesis in Ettlia carotinosa. Minor inhibition was apparent at 25 ppm, and almost complete inhibition occurred at 250ppm. This indicates that DMDC would be an effective and rapid algaecide (Figure 7).

The relative photosynthetic ETR was analyzed at increasing PFD (μιηοΐ m^"2 s^{" l}) in Porphyridium purpureum 1 hour, 3 hours and 24 hours after exposure to 250 ppm DMDC. Exposure of P. purpureum to 250 ppm DMDC was shown to effectively inhibit photosynthesis, although substantial inhibition was achieved at 3 hour rather than 1 hour as shown with E. carotinosa. After 3 hours' inhibition was almost complete, and within 24 hours, little fluorescence was evident. At this point the cells had become colourless and observation under a light microscope revealed that cells were severely degraded or destroyed. These data suggest that DMDC may be an effective algaecide in the marine environment (Figure 8).

Example 4 - effect of pyrocarbonates on photosynthetic ETR in vascular plants

Method

The effect of various concentrations of dimethyl dicarbonate (DMDC) on the relative photosynthetic electron transport rate (ETR) in culinary basil (Ocimum basilicum) plants was tested. DMDC (obtained from Merck & Co, Germany) was added to deionised water exactly 5 minutes before the plants were treated and shaken vigorously to dissolve it. The following four concentrations of DMDC were tested: 0.5% (v/v), 1% (v/v), 2% (v/v) and 4% (v/v). Pure deionised water (i.e. 0% (v/v) DMDC) was used as a negative control.

Culinary basil plants were obtained from a local supermarket on the day of the experiments. Leaves were cut off the stems immediately before the experiments and placed in a petri dish (9 cm diameter) containing a circle of kitchen roll (approximately 9 cm diameter) dampened with 0.5mL deionised water. Each leaf was sprayed with the treatment solution whilst in the petri dish. Application of solutions was via a 50 mL plastic spray bottle. Each treatment comprised 5 sprays, which is equivalent to approximately 400 μΐ_^ of the solution. Immediately after spraying the leaves, the petri dish was covered with its lid and sealed at the edges with a strip of Parafilm to maintain a high humidity around the leaf and thus prevent desiccation. Petri dishes containing the treated leaves were incubated in a Sanyo environmental test chamber maintained at 20° C under constant light, at photon flux densities (PFDs) between 100 and 125 μιηοΐ m -2 s -1. Chlorophyll fluorescence was measured at various photon flux densities (PFD) in the cut leaves using a Hansatech FMS 1 modulated chlorophyll fluorometer, at PFDs from 0 to 1650 μιηοΐ m^"2 s^"1. These measurements were used to determine the relative photosynthetic electron transport rate (ETR), by multiplying 0PSR (ratio of Variable Fluorescence FV against Maximum Fluorescence FM in dark adapted photosynthetic tissue) by PFD. Three to five replicates were used for each treatment.

Results

Figure 9 is a dose response line graph showing the photosynthetic ETR at increasing photon flux densities (measured in μιηοΐ m^"2 s^"1), 24 hours after treatment with 0%, 0.5%, 1%, 2% and 4% (v/v) DMDC. The DMDC caused a concentration - dependent inhibition of photosynthetic ETR, which increased as the PFD increased. Thus, at 1650 μηιοΐ m^"2 s^"1, 0.5%, 1%, 2% and 4% (v/v) DMDC all produced a marked reduction in photosynthetic ETRs. The greatest inhibition of photosynthetic ETR was caused by 4% (v/v) DMDC, followed by 2% (v/v) DMDC, then 1% (v/v) DMDC and 0.5% (v/v) DMDC.

Example 5 - effect of a composition comprising DMDC and a spreading agent adjuvant on photosynthetic ETR in vascular plants

Method Using the method of Example 4, the effectiveness of compositions containing different concentrations of DMDC (0.25% v/v, 0.5% v/v, 1% v/v and 2% v/v DMDC) and 0.1% v/v spreading agent adjuvant BREAK- THRU® S 240 (a polyether trisiloxane spreading agent adjuvant that imparts super spreading and dramatically reduces surface tension, supplied by Alzchem AG) in de-ionised water, was tested on culinary basil (Ocimum basilicum).

A control in which no DMDC was present, solely 0.1% v/v S240, was also tested.

The relative photosynthetic ETR at increasing PFDs in the moss was measured after 24 hours. Results

Figure 10 is a dose response line graph showing the photosynthetic ETR at increasing photon flux densities (measured in μιηοΐ m^"2 s^"1), 24 hours after treatment with compositions containing different concentrations of DMDC, (0.25% v/v, 0.5% v/v, 1% v/v and 2% v/v DMDC) and 0.1% v/v spreading agent adjuvant BREAK- THRU® S 240.

The DMDC caused a concentration-dependent inhibition of photosynthetic ETR, which increased as the PFD increased. Thus, at 1650 μιηοΐ m^"2 s^"1, 0.25%, 0.5%, 1%, and 2% (v/v) DMDC with 0.1% v/v S240 all produced a marked reduction in photosynthetic ETRs. The greatest inhibition of photosynthetic ETR was caused by both 2% (v/v) DMDC and 1% (v/v) DMDC, which caused substantially complete cessation of ETR in the basil leaves, then 0.5% (v/v) DMDC and 0.25% (v/v) DMDC. The results also show that use of a spreading agent adjuvant (which reduces surface tension) in a composition comprising DMDC enhances the efficacy of the DMDC compared to compositions without the adjuvant. At 1650 μιηοΐ m^"2 s^"1, the 1% v/v DMDC solution in de-ionised water reduced ETR to around 550, as shown in Figure 10, whereas the same concentration of DMDC in a composition comprising 0.1% v/v S240 reduced the ETR to substantially zero, as shown in Figure 11.

The control, with no DMDC (0% BVX) showed little to no reduction in ETR.

The results therefore show that S240 enhances the efficacy of DMDC in reducing ETR of basil leaves, and hence increases the efficacy of DMDC in killing or suppressing vascular plants. Example 6 - effect of compositions comprising DMDC and various adjuvants and adjuvant compositions on photosynthetic ETR in vascular plants

Using the method of Example 4, the effectiveness of compositions containing 1% v/v DMDC and various adjuvant compositions, in de-ionised water, was tested. The adjuvants and adjuvant mixtures used were 0.1 % v/v Break-Thru SP131 (RTM) (composed of polyglycerol fatty esters and polyglycols), 0.1% v/v Break-Thru S 133 (RTM) (a surfactant composition comprising polyglycerol esters and fatty acid esters), 0.1 % v/v Break- Thru S233 (RTM) (a non-ionic trisiloxane surfactant, which increases the deposition of agrichemical sprays and improves the penetration of pesticide actives into plant tissue), 0.5% v/v LI700 (soy-oil derived, non-ionic penetrating surfactant, supplied by Loveland Products, Inc.), 0.5% v/v Transport Ultra (RTM), 0.2% v/v Aduro (RTM) (a mixture of surfactants, acidifiers and pH buffering agents, supplied by WinField Solutions, LLC)) and 0.1% v/v Break-Thru S240 (RTM) (a polyether trisiloxane spreading agent adjuvant). All Break-Thru (RTM) products were obtained from Evonik Nutrition & Care GmbH, or Alzchem AG.

The relative photosynthetic ETR at increasing PFDs in the basil leaves was measured after 24 hours was tested.

Results Figure 11 is a dose response line graph showing the photosynthetic ETR at increasing photon flux densities (measured in μιηοΐ m^"2 s^"1), 24 hours after treatment with compositions containing different concentrations of 1% v/v DMDC and 0.1% v/v of Break-Thru SP131 (RTM), 0.1% v/v of Break-Thru S133 (RTM), 0.1% v/v of Break- Thru S233 (RTM), 0.5% v/v of LI700, 0.5% v/v Transport Ultra (RTM), 0.2% v/v Aduro (RTM) and 0.1% v/v Break-Thru S240 (RTM), in de-ionised water.

As can be seen from Figure 12, the DMDC caused a concentration-dependent inhibition of photosynthetic ETR, which increased as the PFD increased. The adjuvants and adjuvants mixures used increased the effficacy of the DMDC in all cases, compared to DMDC alone. Thus, at 1650 μηιοΐ m^"2 s^"1, each of the compositions containing 1% DMDC and an adjuvant or adjuvant mixture, reduced ETR compared to use of DMDC alone, as shown in the comparison of ETR for the relevant compositions at 1650 μιηοΐ m^"2 s^"1 in Figure 10 (DMDC alone) and Figure 12 (DMDC plus adjuvant or adjuvant mixture).

Particularly effective compositions were those in which the adjuvant/adjuvant mixture was Break-Thru S240 (RTM), Aduro (RTM) or Transport Ultra (RTM).

The above embodiment is/embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. Use of a pyrocarbonate as a herbicide, oomyceticide or algaecide.

2. The use according to claim 1, wherein the pyrocarbonate has the general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group.

3. The use according to claim 2, wherein Ri and R₂ are independently selected from methyl and ethyl.

4. The use according to any preceding claim, comprising use of the pyrocarbonate as a herbicide against vascular plants.

5. The use according to any one of claims 1 to 3, comprising use of the pyrocarbonate as a bryophyticide.

6. The use according to any preceding claim, wherein the pyrocarbonate is present in a composition comprising the pyrocarbonate and a carrier or diluent.

7. The use according to claim 6, wherein the pyrocarbonate is present in an aqueous composition comprising between 0.1% and 10% v/v pyrocarbonate.

8. The use according to claim 7, wherein the pyrocarbonate is present at a concentration of between 0.25% and 5% v/v pyrocarbonate.

9. A herbicidal, oomyceticidal or algaecidal composition comprising a pyrocarbonate having the general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group and at least one herbicidal adjuvant, optionally selected from the list comprising a surfactant, a wetting agent, a spreading agent, or any combination thereof.

10. A herbicidal, oomyceticidal or algaecidal composition according to claim 9, comprising at least one herbicidal adjuvant, wherein the ratio of the concentration of pyrocarbonate to the concentration of adjuvant or total amount of adjuvants in the composition is in the range 250:1 to 1: 1.

11. A herbicidal, oomyceticidal or algaecidal composition according to claim 10, wherein the ratio of the concentration of pyrocarbonate to the concentration of adjuvant or total amount of adjuvants in the composition is in the range 50: 1 to 1: 1.

12. A herbicidal, oomyceticidal or algaecidal composition according to any one of claims 9 to 11, wherein at least one adjuvant is a silicone, a siloxane, an alkylamine ethoxylate or a carbamide.

13. A herbicidal, oomyceticidal or algaecidal composition according to claim 12, wherein at least one silicone, a siloxane, an alkylamine ethoxylate or carbamide acts as a surfactant or spreading agent, in use.

14. A herbicidal, oomyceticidal or algaecidal composition according to any one of claims 7 to 14, wherein the composition further comprises water, the pyrocarbonate is present in a concentration of between 0.1% v/v and 50% v/v, and the herbicidal adjuvant is present in a concentration of between 0.01% v/v and 10% v/v.

15. A herbicidal, oomyceticidal or algaecidal composition according to claim 14, wherein the pyrocarbonate is present in a concentration of between 0.25% v/v and 10% v/v, and the herbicidal adjuvant is present in a concentration of between 0.05% v/v and 2.5% v/v.

16. A herbicidal, oomyceticidal or algaecidal composition according to any one of claims 9 to 14, comprising an aqueous solution of between 0.1% v/v and 10% v/v pyrocarbonate and between 0.05% v/v and 10% v/v herbicidal adjuvant or total concentration of herbicidal adjuvants.

17. A herbicidal, oomyceticidal or algaecidal composition according to claim 16, comprising an aqueous solution of between 0.1% v/v and 5% v/v pyrocarbonate and between 0.05% v/v and 5% v/v adjuvant or total concentration of adjuvants.

18. A herbicidal, oomyceticidal or algaecidal composition according to any one of claims 9 to 17, wherein at least one herbicidal adjuvant enhances the herbicidal, algaecidal and/or oomyceticidal activity of the pyrocarbonate, for example by increasing the permeability of plant cuticles and/or cell membranes.

19. A method of controlling, supressing or killing a vascular or non-vascular plant, comprising applying to the leaves of the plant a pyrocarbonate in an amount sufficient to control, suppress or kill the vascular or non-vascular plant.

20. A method as claimed in claim 19, wherein the pyrocarbonate is a pyrocarbonate having the general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group.

21. A method of controlling, supressing or killing a vascular or non-vascular plant, comprising applying to the leaves of the plant a composition according to any one of claims 9 to 18.

22. A method of controlling, supressing or killing algae or oomycetes comprising applying to the algae or oomycetes a pyrocarbonate in an amount sufficient to control, suppress or kill the algae or oomycetes

23. A method as claimed in claim 22, wherein the pyrocarbonate is a pyrocarbonate having the general formula R1-O-CO-O-CO-O-R2, wherein Ri and/or R₂ is an alkyl group.

24. A method of controlling, supressing or killing algae or oomycetes, comprising applying to the algae or oomycetes a composition according to any one of claims 9 to 18.

25. A method according to any one of claims 19 to 24, wherein the method comprises applying dimethyl dicarbonate or diethyl dicarbonate, as a pyrocarbonate.

26. The use according to any one of claims 1 to 8 in which the pyrocarbonate is present in a composition according to any one of claims 9 to 18.