Molluscicides

Abstract: The use as a molluscicide of a chelate of iron (III) with a ligand of formula II II: [R³NO.N=O]⁻ in which formulae: R³ represents: C₁-C₆ alkyl, provided that when the alkyl group contains more than four carbon atoms the group is a branched chain alkyl group.

Description: This invention relates to molluscicides and in particular to slug and snail poisons. Chemical Abstracts, vol. 101, No. 19 November 5, 1984, p233 ref No. 165584k, an abstract of JP-A-59 122405 (Moon Star Chemical Corp.) describes the use of compositions containing metal salts, to control gastropods. Chemical Abstracts, vol. 105, No. 5 August 4, 1986 p228 ref No. 37193c, an abstract of Ann Rech. Vet. 1986, 17(1), 21-8 discloses the molluscicidal effect of iron and cuprous compounds. It has now been found that certain iron chelates are effective molluscicides. Accordingly the present invention comprises the use as a molluscicide of a chelate of iron (III) with a ligand of formula II in which formula: R³ represents: C₁-C₆ alkyl, provided that when the alkyl group contains more than four carbon atoms the group is a branched chain alkyl group. In general, chelates comprising three bidentate ligands, which may be identical or different, though which usually are identical, are preferred and especially those which lose one ligand molecule or ion to form a bis cation. The ligands of formulae II are readily derived respectively from compounds of formula IIA: R³NOH.N=O, by loss of a proton. It is preferred that R³ contains no more than four carbon atoms, R³ is preferably methyl, ethyl or n -propyl and the chelate is preferably a trischelate of Fe III comprising identical ligands. The following compounds of formula IIA are of particular interest: IIA: CH₃NOH.N=O CH₃CH₂NOH.N=O CH₃CH₂CH₂NOH.N=O (CH₃)₂CHNOH.N=O CH₃(CH₂)₂CH₂NOH.N=O CH₃CH₂CH(CH₃)NOH.N=O (CH₃)₂CHCH₂NOH.N=O The ligands and chelates hereinbefore described may be synthesised by modification of well established routes. Synthesis of complexes comprising the ligand II may be accomplished through the following route:- Mg + R³X → R³MgX In the foregoing formulae X represents halogen e.g. bromine or iodine. The present chelates of the present invention may be utilised by formulation in mollusc baits. Accordingly the present invention further includes within its scope a poison bait for molluscs comprising a molluscicidal chelate as hereinbefore described and a carrier therefor. The poison bait may comprise, in addition to one or more of the present molluscicidal chelates, other components, for example other molluscicides. Such components may confer additional advantages on the poison bait by, for example, synergising with the present chelates. The present invention yet further includes with its scope a method of killing a mollusc in which the mollusc or an environment inhabited by the mollusc is treated with a molluscicidal chelate as hereinbefore described. The present chelates are of particular interest for the control of slugs because the poisons at present used, such as metaldehyde and methiocarb suffer from a disadvantage in that a proportion of the slugs in a treated population, though at first immobilised eventually recover. Environmental pollution as a result of using the chelates is, furthermore, negligible. The present chelates also offer the advantage that they do not significantly affect ground beetles such as Carabidae beetles, which are attacked by other molluscicides e.g. methiocarb. Suitable baits usually comprise a mollusc food such as a cereal e.g. wheatmeal, comminuted cuttle fish, starch or gelatin, which may also serve as a carrier. A mollusc phagostimulant such as a sugar e.g. sucrose, or molasses is usually included. Non nutrient carriers of interest include non nutrient polymeric materials, pumice, carbon and materials useful as carriers for insecticides. The bait usually comprises a binder, which is suitably waterproof, such as paraffin wax or casein and may advantageously comprise a bird repellent, for example a blue colourant. In order to inhibit deterioration of the bait a fungistat may be included. Typically the bait contains at least 3% by weight and no more than 16% by weight of molluscicide. The preferred concentration in the bait is generally 10-13% by weight. The treatment of both terrestrial and aquatic molluscs in accordance with the present invention is envisaged, the species Deroceras reticulatum , Arion hortensis , Milax budapestensis , Cepaea hortensis , Helix aspersa and Achatina spp being of particular interest as targets. The invention is illustrated by the following Examples: Examples 1-8 Bioassay Method Test compounds were incorporated into a standard wheat-flour-based edible carrier containing 10% paraffin wax binder and 2.5% sucrose phagostimulant, in increasing concentrations 0, 1, 4, 7, 10, 13 and 16% a.i. Groups of ten field-collected D. reticulatum in the weight range 400-600 mg were confined with 0.5 g DM test bait at each concentration for a period of 4 days under a regime of 12 h dark @ 5°C and 12 light @ 15°C. Weight of bait eaten and number of slugs killed were recorded. The results are shown in Table I. Where six groups of ten slugs are offered bait containing 1,4,7,10,13 or 16% a.i., the results have been reduced to two values, (i), the total amount of a.i. ingested (mg) which gives an indication of the palatability of the compound, and (ii), the total number of slugs killed (x/60) which, with (i), gives an indication of its relative toxicity with metaldehyde and methiocarb under field conditions (grass/clover).

Claims: The use as a molluscicide of a chelate of iron (III) with a ligand of formula II in which formula: R³ represents: C₁-C₆ alkyl , provided that when the alkyl group contains more than four carbon atoms the group is a branched chain alkyl group. A use according to Claim 1, in which the chelate comprises three identical bidentate ligands. A use according to Claim 2, in which R³ contains no more than four carbon atoms. A use according to Claim 3, in which R³ is methyl, ethyl, or n -propyl. A use according to Claim 3, in which the chelate comprises a ligand formed by loss of a proton from one of the following compounds: CH₃NOH.N=O CH₃CH₂NOH.N=O CH₃CH₂CH₂NOH.N=O (CH₃)₂CHNOH.N=O CH₃(CH₂)₂CH₂NOH.N=O CH₃CH₂CH(CH₃)NOH.N=O (CH₃)₂CHCH₂NOH.N=O A use according to Claim 3, in which the chelate is of formula: Fe III [CH₃NON=O]₃ or Fe III [CH₃CH₂NON=O]₃ or Fe III [CH₃CH₂CH₂NON=O]₃. A poison bait for molluscs which comprises a chelate molluscicide as defined in any one of Claims 1 to 6 and a carrier therefor. A poison bait according to Claim 7, which comprises a mollusc food. A poison bait according to Claim 8, in which the mollusc food is a cereal, comminuted cuttle fish, mollases or gelatin. A poison bait according to any of Claims 7 to 9 which comprises a mollusc phagostimulant. A poison bait according to Claim 10, in which the phagostimulant is a sugar or starch. A poison bait according to Claim 7 which comprises a non nutrient carrier. A poison bait according to Claim 12, in which the non nutrient carrier is an artificial polymer, pumice, carbon or a material useful as a carrier for an insecticide. A poison bait according to any of Claims 7 to 13, which comprises a binder. A poison bait according to Claim 14, in which the binder is paraffin wax or casein. A poison bait according to any of Claims 7 to 15, which comprises a bird repellent. A poison bait according to Claim 16, in which the bird repellent is a blue colourant. A poison bait according to any of Claims 7 to 17, which comprises a fungistat. A poison bait according to any of Claims 7 to 18, which comprises at least 3% by weight of a molluscicidal chelate as defined in any one of Claims 1 to 6. A poison bait according to any of Claims 7 to 19, which comprises no more than 16% by weight of a molluscicidal chelate as defined in any one of Claims 1 to 6. A poison bait according to any of Claims 7 to 20, which comprises 10 - 12% by weight of a molluscicidal chelate as defined in any one of Claims 1 to 6. A process for the production of a poison bait for molluscs in which a chelate molluscicide as defined in any one of Claims 1 to 6 is formulated with a carrier therefor. A method of killing a mollusc in which the mollusc or an environment inhabited by the mollusc is treated with a molluscicidal chelate as defined in any one of Claims 1 to 6. A method according to Claim 23, in which an environment inhabited by the mollusc is treated with a poison bait comprising a chelate as defined in any one of Claims 1 to 6.

Inventors: BRIGGS GEOFFREY GOWER, BULLOCK JOSEPH IAN, HENDERSON IAN FINDLAY, LARKWORTHY LESLIE FOOT, BRIGGS, GEOFFREY GOWER, BULLOCK, JOSEPH IAN, HENDERSON, IAN FINDLAY, LARKWORTHY, LESLIE FOOT
Applicants: BRITISH TECH GROUP, BRITISH TECHNOLOGY GROUP LIMITED
Application year: 1988
Main classification: A01N51
IPC codes: A01N51