GB2098869A - Molluscicidal compositions - Google Patents

Abstract

The effect of molluscicide in molluscicidal pellets for use against terrestrial molluscs is improved by incorporating a surface active agent in the pellets. The pellets retain adequate weather resistance. The surface active agent is preferably non-ionic or anionic and combinations of non-ionic agents of low water solubility and high water solubility can be used. The proportion of surface active agent is preferably 0.1 to 0.7% by weight.

Description

SPECIFICATION Molluscicidal compositions This invention relates to improved molluscicidal compositions.

Various terrestrial molluscs are pests in agriculture. In particular, the terrestrial slug A.

reticulatus may cause serious damage to crops in horticulture and other forms of agriculture, and much effort has been directed to combating this pest. It has been found that certain chemicals, for example metaldehyde, methiocarb and copper compounds, are poisonous to terrestrial slugs, and molluscicidal compositions containing such compounds in admixture with a carrier or bait are used in large quantities. There is, however, a need for more effective molluscicidal compositions.

It has been proposed, when using diphenyl methylamine derivatives as a molluscicide, to formulate a wettable powder comprising the molluscicide and a dispersing agent, or a dispersing agent and a wetting agent, such a wettable powder to be used against aquatic molluscs by dispersing it in their aqueous habitat.

It has also been proposed to formulate a metaldehyde-containing molluscicide composition for dispersion and suspension in water, a wetting agent being added to the composition for this purpose.

It has also been proposed to make tablets containing a high proportion of a water-soluble organic tin compound as molluscicide and a small proportion of a surface active agent, the tablets to be introduced into water to keep it free of snails.

Molluscicide compositions for combating terrestrial molluscs are most conveniently used in pellet form, the constituents of such pellets being in addition to the molluscicide, an attractant such as a farinaceous base, e.g. bran, flour or wheatfeed, oil-cakes or cryptogamia and optionally additives such as anti-mould agents and binders e.g. gelatine or clay.

Molluscicides which may be used include methaldehydem copper salts, 4(methylthio) -3, 5xylyl methylcarbamate, 1 N methylcarbamate, S2-cyanoethyl-N-[(methylcarbamoyl)oxy] thioacetimidate and nicotinanilide. Suitable copper molluscicides are inorganic copper salts, for example copper sulphate and organic salts, for example copper dimethyl dithiocarbamate. The proportion of molluscicide depends on the particular compound used and may range up to about 6% by weight of the composition.

It is important to keep the proportion of molluscicide as low as possible, not only because of the cost of the material but because its presence in the composition may cause the mollusc to consume less of the composition with the consequence that a higher proportion of molluscicide in the composition may not necessarily result in a higher intake of molluscicide.

An important requirement in pelleted (by which term we also mean granular) molluscicide compositions for terrestrial molluscs is that they should be as weather resistant as possible, e.g..

that they should not be reduced to a disperse state or dissolve when wetted by rain.

We have now found that the effectiveness of pelleted compositions is markedly improved by incorporation therein of a surface active agent. Surprisingly, such pelleted compositions are more effective in killing terrestrial slugs whilst still retaining adequate weather resistance.

Whilst we do not wish to be bound by this theory we believe that the surface active agent in some way promotes the absorption by the mollusc of the molluscicide it has taken in. In any event, the improvement in effectiveness of the molluscicide resulting from the presence of the surface active agent makes it possible to reduce what was considered to be the optimum proportion of mulluscicide in the composition, thereby not only making a saving in the cost of the molluscicide used but also reducing any inhibiting effect the presence of the molluscicide may have on up-take by the mollusc of the composition. It is possible to reduce the proportion of molluscicide by, in some cases, nearly 50% and yet maintain a satisfactory rate of "kill" of molluscs.Metaldehyde is such a case, the commonly used proportion of about 4% being reducible to from 2-23%.

A paper by S A Visser published in Bulletin of the World Health Organisation 1965, 32, 713-719, describes tests of over 100 commercially produced surface-active agents against a bilharziasis vector snail. Some of these agents were found to have molluscicidal properties but this invention is based not on possible molluscicidal activity of surface active agents but on their unexpected property of making conventional molluscicides more effective. In fact, as described later, tests carried out using pelleted compositions containing surface active agents, but no conventional molluscicidle, indicated no significant molluscicidal activity of surface active agent alone.

The proportion of surface active agent to be used in the molluscicide composition of this invention will depend on the nature of the agent used. Relevant factors again are (a) cost of the agent and (b) any repellent effect it may have on molluscs.

With regard to the latter, it is noteworthy that in the paper by Visser it is reported that snails frequently tried to escape from his aqueous solutions containing surface active agent in the low proportion of 0.1 to 1000 ppm. We also have found that, when tested alone in solution in water, many surface active agents repel molluscs at proportions in some cases as low as 0.1% by weight. However, when such surface active agents are incorporated in molluscicide compositions of this invention they may be used in higher proportions without adversely affecting the attractiveness of the composition, and, particularly in combination with attractants such as a farinaceous base, may be incorporated in proportions as high as 1% by weight.The upper limit will depend to some extent on the nature of the attractants used in the composition, but the proportion above which any particular surface active agent begins to have an adverse affect by rendering any particular formulation repellent can readily be determined simply by exposing pellets to molluscs.

In the pelleted compositions of this invention the proportion of surface active agent should be at least 0.05% by weight and may be as high as 1% by weight. A proportion in the range 0.1% to 0.7% is preferred and generally 0.1% to 0.4% by weight is a useful proportion which enhances the effectiveness of the molluscicide without rendering the composition unattractive to molluscs or unduly degrading the weatherability of the pellets of the composition.

Accordingly, the present invention provides an improved pelleted molluscicidal composition for use against terrestrial molluscs comprising an effective proportion of a molluscicide and a surface active agent.

The invention may be applied to improve the effectiveness of molluscicides when present in a normal proportion in the pelleted compositions. Typical normal proportions, particularly in the case of metaldehyde are from 3% to 6% by weight. Alternatively, the invention may be applied in pelleted compositions in which the proportion of molluscicide is lower than that normally used, but without significantly reducing the normal effectiveness of the pelleted composition.

Such lower proportions, particularly in the case of metaldehyde, are suitably from 1% to 2.5% by weight.

Suitable surface active agents include non-ionic, anionic and cationic agents and of these nonionic and anionic agents are preferred.

Suitable non-ionic agents include:polyoxyethylenated alkyl phenols or alkylphenol-oxylates such as those derived from p-nonylphenol, p-octylphenol, p-dodecylphenol and dinonylphenol.

polyoxyethylenated straight-chain alcohols or alcohol-ethoxylates such as those derived from coconut oil and tallow, or synthetic straight chain alcohols, polyoxyethylenated polyoxypropylene glycols, long chain carboxylic acid esters, such as esters of natural fatty acids with glycerol, propylene glycol, sorbitol, sorbitan, polyoxyethylenated sorbitol or sorbitan and polyoxyethylene glycol, and polyoxyethylenated fatty acids, alkanolamine condensates and alkanolamides such as those of diethanolamine or monoisopropanolamine with coconut fatty acids.

A particularly suitable surface active agent is polyoxyethylene sorbitan mono oleate since, rather than having a repellent effect, it appears to be a phagostimulant. Related compounds of polyoxyethylene sorbitol or sorbitan include esters of mixed fatty acids, mixed fatty and resin acids, lauric acid, stearic acid and palmitic acid, blends of such esters with polyoxyethylene amine or alkyl aryl sulphonate, and derivates of lanolin and of beeswax.

Suitable anionic surface active agents include alkyl aryl sulphonates, fatty alcohol sulphates, olefin sulphates and sulphonates, sulphated ethers, sulpho succinates, alkane sulphonates, phosphate esters, alkyl isothionites, sucrose esters and fluorosurfactants.

Particularly useful are sodium salts of secondary long chain alkyl sulphates, e.g. sodium lauryl sulphate, salts of alkylaryl sulphates, sodium deoxycholate, sodium taurocholate and sodium tauroglychocholate (TGC). Cationic surface active agents include quaternary ammonium salts, e.g. cetyltrimethylammonium chloride, cetylpyridinium chloride.

The surface active agent is conveniently incorporated in the pellets by addition in solution, or dispersed, in water added to the solid ingredients in making up the composition to be extruded and pelleted. The surface active agent may be soluble in the amounts used but if it is to be dispersed in the water it may be used in conjunction with a water-soluble surface active agent to assist in its dispersion.

The less water-soluble the surface active ages: is, the less susceptible it is to leaching from the pellet by rain or dew. When using non-ionic gents it is therefore advantageous to use those having hydrophile lipophile balance (HLB) of less than 7. Such agents may not be readily soluble in the water used in the formulation but they may be dispersed or emulsified therein by use of minor proportion of a water soluble surface active agent. Particularly useful agents for this purpose are non-ionic surface active agents having HLB of 10 or more. A suitable proportion is from 7.5 to 12.5% by weight of the total surface active agent used, say 10% by weight of the surface active agent of low HLB. For example, a polyoxyethylenated sorbitan ester may be used to assist dispersion of 9 Dorbitan """.:. of !os tnr ee!tlhi!ity.

The invention is illustrated by the folllz?cyinc7: Pellets were made to the formulations (%by wt):- A. Farinaceous base 90% (wheatfeed/bran) Metaldehyde 3.3% Binder and anti mould 6.7% B. Farinaceous base 91% Metaldehyde 2.1% T.G.C. 0.2% Binder and anti-mould 6.7% C. Farinaceous base 91% Metaldehyde 2.2% Binder and anti-mould 6.8% D. Farinaceous base 90.7% Metaldehyde 2.2% Sodium lauryl sulphate 0.4% Binder and anti-mould 6.7% E.Farinaceous base 91% Metaldehyde 2.1% Polyoxyethylene sorbitan mono oleate 0.2% Binder and anit-mould 6.7% Equal quantities of pellets A, B, C and D were placed out in uniform grassland. The number of dead slugs in an area of 0.1 square metre surrounding each mound of pellets was counted daily.

Pellets A B C D E Dead slugs 20 39 1 5 22 42 after seven days 22 31 19 25 35 There was no discernible difference in weathering properties between pellets A, B, C, D and E.

In a comparative test, pellets F containing the farinaceous base, binder and anti-mould and 1% of polyoxyethylene sorbitan mono oleate, but no metaldehyde, were fed to slugs over a period of seven days. Although all the pellets were consumed the slugs remained healthly.

Similar results were obtained when part of the wheatfeed was replaced by clay. The control pellet consisted of 69.8% clay 20% wheatmeal, 5% bran, 2.2% metaldehyde and 3% biostat, to which in the test pellets was added a small proportion of surface active agent as follows (all % by weight).

G - control nil surface active agent H - control + 0.2% T.G.C.

I - control + 0.2% sodium lauryl sulphate J - control + 0.4% sodium lauryl sulphate K - control + 0.4% isoctylphenoxypolyethoxyethanol Trials were carried out in covered glass trays to each of which slugs and one type of pellet were added. The number of slugs killed was recorded after eight days.

Pellet G H I J K % kill 27.9 34.9 39.1 30.4 39.1 Again, there was no discernible difference in weathering properties between pellets G, H, I, J and K.

In normal circumstances slugs are nocturnal feeders and remain under cover during the day.

The molluscicidal effect of metaldehyde is largely due to its paralysing effect on slugs which then find it difficult to return to cover during the day and as a consequence become dehydrated and die. The paralysing effect of metaldehyde and the advantage resulting from the present invention were determined as follows: Control pellets were made up to the formulation: plain flour 91.64, crushed bran 5.0%, pnitrophenol 0.06% metaldehyde 3.3% (all by weight).

Test pellets were made up to the formulation: crushed bran 5.0%, p-nitrophenol 0.06% metaldehyde 2.2% surface active agent (see below). plain flour balance.

Pellet Surface active agent HLB M 0.5% polyoxyethylene sorbitan mono oleate 15.0 N 0.45% sorbitan mono oleate 4.3 0.05% polyoxyethylene sorbitan mono oleate 1 5.0 0 0.23% sorbitan mono oleate 4.3 0.02% polyoxyethylene sorbitan mono oleate 15.0 P 0.5% polyoxyethylene sorbitol lanolin 14.0 Q 0.5% polyoxyethylene sorbitol beeswax 5.0 In the case of pellets N and 0 the polyoxyethylene sorbitan mono oleate was used to emulsify the sorbitan mono oleate in the water used to make the mixture to be extruded and broken up into pellets. In the case of pellet 0, the surface active agent, which is a solid, was continuously stirred with water until it was adequately dispersed, the water then being added to the mixture of other ingredients to make a composition which could be extruded.

Trials were carried out in glass trays to each of which slugs and one type of pellet L-Q were added. After 24 hours the trays were checked and the percentage of slugs (a) unaffected, (b) totally paralysed (immobile) and (c) partially paralysed (limited uncoordinated movement) were noted. The results were: Pellet %(a) %(b) %(c) L 33.4 33.3 33.3 M 20 50 30 N - 50 50 0 20 40 40 P 20 20 60 Q - 40 60 These results confirm that even with a lower proportion of molluscicide in the test pellet as compared with the control, the pellets of this invention are more effective in causing paralysis of slugs.

Claims (16)

1. A pelleted molluscicidal composition for use against terrestrial molluscs containing an effective proportion of molluscicide and a surface active agent.

2. A composition as claimed in Claim 1 containing from 0.05% to 1% by weight of surface active agent.

3. A composition as claimed in Claim 1 containing from 0.1% to 0.7% by weight of surface active agent.

4. A composition as claimed in Claim 1 containing from 0. 1% to 0.4% by weight of surface active agent.

5. A composition as claimed in Claim 1, 2, 3 or 4 containing metaldehyde as molluscicide.

6. A composition as claimed in Claim 5 containing from 1% to 2.5% by weight of metaldehyde.

7. A composition as claimed in any preceding claim in which the surface active agent is nonionic.

8. A composition as claimed in Claim 7, in which the agent comprises an ester of polyoxyethylene sorbitan with at least one fatty acid.

9. A composition as claimed in Claim 7 in which the agent comprises a derivative of polyoxyethylene sorbitol and beeswax or lanolin.

10. A composition as claimed in Claim 7 in which the agent comprises an ester of sorbitan and at least one fatty acid.

11. A composition as claimed in Claim 7 in which the agent is a polyoxyethylene ether.

12. A composition as claimed in Claim 7 or 10 in which the agent has an HLB value of less than 7.

1 3. A composition as claimed in any of Claims 7 to 11 in which the agent comprises 92.5 to 87.5% by weight of agent of HLB value less than 7 and from 7.5 to 12.5% by weight of agent of HLB value greater than 10.

14. A composition as claimed in any one of Claims 1 to 6 in which the surface active agent is an anionic agent.

1 5. A composition as claimed in Claim 14 in which the agent is a sodium salt of an alkyl or alkyl aryl sulphate.

16. A composition as claimed in Claim 14 in which the agent is sodium deoxycholate, sodium taurocholate or sodium tauroglycocholate.