IE54723B1 - Rodenticidal bait - Google Patents

Abstract

The invention relates to a rodenticidal block bait consisting essentially of brittle-hard polyvinyl acetate, or of a brittle-hard copolymer of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, and a foodstuff treated with a rodenticidal poison and dispersed in the polymer carrier. The polymer component (polyvinyl acetate or vinyl acetate copolymer) serves simultaneously as a taste-tempting, hardening and water-resistant constituent in the bait. The invention relates also to a process for producing this block bait from aqueous polymer- dispersions.

Description

The present invention relates to a rodenticidal hard bait, to processes for producing it, and to its use tor controlling rodents, particularly rets and mice.

The control of rats, mice and other harmful rodents is 5 a problem of primary importance, because these animals are carriers of serious infectious diseases, and they also constitute an enormous loss factor with regard to the role they play in the destruction and contamination of •foodstuffs. Within this genus of animals, the commensal rodents, especially the rats, assume a prominent position since they share with man the same environment and also his food resources. The brown rat or water-rat (Rattus norvegicus), the house rat (Rattus rattus), the house mouse (Mus musculus), the field mouse (Microtus arvalis) and the black water rat (Arvicola terrestris) belong to the most abundant group of rodents.

The rodents, living as tribe animals, have a high level of adaptability and a keen sense of smell. They are provided among themselves, in particular the rats, with a remarkable warning system. Any success in controlling rodents depends largely on the degree to which their characteristic habits and behaviour patterns are understood 4 Mice and rats cake up cheir food basically in a nonsystemacic manner and ac random: chey rarely keep co one single cype of food when a range of different foodstuffs is available. Alone chis aspect of cheir behaviour renders the combating'of chem difficult.

Poisoned bait is moreover immediately rejected by the rats when they have identified it as such on the basis of taste and comparability. Mass control of rodents hence inevitably results in difficulties when members of the same species connect the death of one of the animals among them with the bait being consumed and thus avoid it.

There have been no shortage or attempts to make bait palatable for rats by means of enticements and taste corrigents, and at the same time to ensure that the poison is not immediately absorbed in the upper gastro-intestinal tract of the rat, where the. poison commences to take effect during the actual intake of food, that is to say, prematurely. It is regularly observed in such cases that the affected rat straight away ceases to eat, and that consequently none of the animals belonging to the same tribe again touches the poisoned bait concerned or any other similar bait.

The subacute rodenticides, particularly the anticoagulants, at present form, by virtue of their delayed, but certain, action, the most important group of effective preparations. The success of the mass application thereof has however fallen short of expectations .

There still remains therefore the problem of how to obtain rodenticidal compositions specifically designed to take account of the behaviour of the rodent, in order to ensure greater success.

Whereas great attention has been paid to the problem of enticement and flavouring substances, the behaviour pattern specific to rodents has been studied to a far lesser degree with respect to practical application.

The gnawing urge of the rodent is a behaviour characteristic which in the fonaulation sf effective types of bait for rodents has been hitherto quite insufficiently taken into account.

The hard paraffin blocks (containing bait) commercially available have shown that they do not, from the point of view of taste and consistency, come up co expectations.

Solids with sliding layers (for example hard paraffin), semisolid material and also gel-like substances do not satisfy the material requirements for an effective bait.

It is the object of the present invention thsrefore to provide, as a rodenticidal preparation, a formed hard bait-block or granule whicn has a) a sufficient hardness, especially brittle hardness, and b) at the same time a pleasant taste (palatable), in consequence of which the rodents are induced to continue gnawing and consuming the bait.

It has been shown that this problem can be solved surprisingly quickly and simply by intimately mixing polyvinyl acetate on its own, or copolymers of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, in an aqueous dispersion, with the desired solid or pasty, edible component of the poison bait; and subsequently casting or shaping the resulting semiliquid mixture into fairly large granules, or preferably into blocks, 4 co 1000 g in weight, of the shape required, and finally drying the product obtained. In addition to containing the three essential components, namely: polymer, feed-constituent and poison, the hard bait according to ths 4 7 2 3 - 5 invention can contain in small amounts (up to about 10 % by weight) other additives adapted to suit the given practical requirements .

The hard bait or block bait which is thus produced using the process according to the invention described in the foregoing, by bonding with polyvinyl acetate or with a copolymer thereof as binder, and which has a weight of from 4 to 1000 g, preferably 10 to 100 g, has the following properties simultaneously existing and very desirable for practical application: 1) adequate brittle hardness, which is particularly suitable for gnawing and which is very much liked by wild rats end mice; 2) high level of palatableness, which is the cause, in particular in the case of wild rats, cf block bait of this type being clearly preferred to a .similar feed without an addition of polymer; 3) resistance to water, which can indeed result in a slow (maximum 20%) swelling of the block bait, but which does not impair its firmness, and does prevent it over a period of several weeks in position from disintegrating.

Polymeric substances have already been used in practice as binders for active substances. Thus, the Japanese Published Specification No. 72/19 199 (Ikari Yakuhin AG) describes the kneading of norbormide [= 5-(a-hydroxy-a-2pyridylbenzyl)-7 - (β-2-pyridylbenzylidene) -ncrborn-5-ene2,3-dicarboximide], the ratio of about 2:1, with an aqueous polyvinylacetate emulsion, with subsequent fine grinding, filtering out and drying at 80'C. The poison powder thus produced is mixed in the ratio cf about 1:100 with cereal flour, and in this manner a bait for use in dust form is obtained. The problem to be solved in this case and the results obtained are completely different from those of the present invention. The palatableness which a largish polyvinyl acetate-(Co)polymer constituent induces has not been recognised in the solution suggested in the Japanese Publication any more than has the gc-asibiiity of producing, together with all auxiliaries, in a single operation, block bait which satisfies the gnawing urge of rats and mice. Furthermore, the said publication enables no conclusions to be drawn as to a resistance of whatever nature to water.

The present invention relates, in a narrower sense, to a process for producing a firm, gnawable, shaped rodenticidal hard bait, 4-1C00 g in weight, which process comprises mixing, for 1-60 minutes, 96-70 per cent by weight (relative to the finished bait) of a previously prepared feed component, which contains, in addition to the poison component of 0.001 - 1.0 per cent by weight, optionally up to 10% (of its weight) of mineral and vegetable fillers, taste corrigents, microbicides, germination inhibitors, dyes and/or other additives suitable with regard to application technique, with an aqueous dispersion of polyvinyl acetate, or of a copolymer of vinyl acetate with acrylic acid ester, methacrylic acid ester anc/'or acrylonitrile (which dispersion constituents, after drying, make up the weight portion of the other components of the mixture to 100%), water being if necessary added, to thus obtain a pourable mixture -, casting or otherwise forming this mixture, with drying, into blocks; and subsequently drying these at 10-60°C.

The air drying of the hardening mixture of tha hard bait is preferably carried out at room temperature.

For copolymerisation, suitable partners for vinyl acetate are essentially those monomers which produce hard 4 7 2 3 - 7 bonds and which with regard to taste are pleasant for rodents. Acrylic acid esters and methacrylic acid esters, the alcoholic components of which are derived from methanol, ethanol, butanol, hydroxyethanol or ethoxyethanol, are preferred. Also esters of higher alcohols, such as decyl alcohol and lauryl alcohol, can be used.

Commercial (poly)vinyl acetate dispersions frequently contain up to 57. of other unsaturated compounds, such as acrylic acid, crotonic acid, maleic acid or maleic anhydride, or higher homologues of polyvinyl acetate, such as polyvinyl propionate or polyvinyl butyrate. Such substances which favourably influence the hardening of the polymer for the purpose according to the invention count as copolymer constituents which are concomitantly embraced by the present invention.

Suitable mineral and vegetable additives or extenders are for example: kaolin, talcum, chalk, limestone, Attaclay, dolomite, diatomaceous earth, precipitated silicic acid, alkaline-earth silicates, sodium and potassium aluminium silicates (feldspars and mica), calcium and magnesium sulfates, magnesium oxide, ground plastics, ground vegetable products, such as bark flour, wood flour, nutshell flour or cellulose powder, each on its own or as mixtures with one another.

The feed portion of the bait can embrace all types of durable solid foodstuffs, preferably storable hard feed, particularly that based on cereals, such as bread and confectionary, flour, cereal grain and whole meal, and also appropriate mixtures thereof. Also suitable however are other types of feed of animal or vegetable origin, such as fish, meat or bone residues, cr grape-vine and maize residues, oil cake, dried fruit, fruit peel, and so forth.

Further subject matter of the present invention is a rodenticidal hard bait which weighs 4-1000 g, and which consists essentially of brittle-hard polyvinyl acetate, or of a brittle-hard copolymer of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, and also a foodstuff treated with a rodenticidal poison and dispersed in the polymer carrier.

In general, the polymer component constitutes 4-30 7. by weight of the hard bait, and the remainder, tr.at is, the feed component (including up to 10 7. by weight of possible additives), which makes the total portion up to 100« by weight, contains 0.001 - 1.0 % by weight, preferably 0.005 - 0.1 7L by weight, of poison component.

The polymer component in che hard bait amounts preferably to. 7-15 7. by weight, for example 10 % by weight, Vinyl acetate copolymers 2re preferred, and among these the vinyl acetate / acrylic acid-lower alkyl ester copolymers.

Suitable as active ingredients are essentially all known rodenticides, preferably those of tne anticoagulant class, such as 4-hydroxycoumarin derivatives, c£ which the following are preferred: 3-(3-biphenyl-4-yl-l,2,3,4-tetrahydro-1-naphthyl) -4hydroxycoumarin (Difenacoum), 3- [3-(41-bromobiphenyl-4-yl)-1,2,3,4-tetrahydro-l-r.aphthylJ4- hydroxycoumarin (Brodifacoum), 3-(4'-bromobiphenyl-4-yl-3-hydroxy-l-phenylprcpyI)-4hydroxycoumarin (Bromadiolone), 3-(o-acetonylbenzyl)-4-hydroxyeoumarin (Warfarin), 3-(u-acetonyl-4-chlorcbef-.Eyl)-^«hydroxyci?ur.arin (Cumaehler), 4-hydroxy-3-(1,2,3,4-tetrahydro-1-naphthyl) coumarin (Coumatetralyl), and 3-(2-acetonylfurfuryl)-4-hydroxycoumarin (Cumafuryl).

Further preferred active ingredients are the anti5 coagulants derived from 1,3-indandione, of which the following are preferred: 2-[2-(4-chlorophenyl)-2-phenylacetyl] -1,3-indandione (Chlorophacinon), 2-diphenylacetyl-l,3-indandione (Diphacinone) and 2-pivaloyl-l,3-indandione (Pindon).

A further rcdenticical active ingredienc which is preferred is 2,4,6-tribromo-N-methyl-2',41-dinitro-6'triflucrcmethyldiphenyIamine (Bromethalin).

The present invention relates also to the use of 15 a rodenticidal hard bait ae described in the foregoing for controlling rodents.

Further subject matter of the present invention is a process for controlling rodents, particularly rats and mice, by the administration and putting out of rodenticidal bait as described in the foregoing as gnawable hard bait.

The production of a particularly preferred preparation is described in the following.

Production Example (to produce 1 kg of dry bait) 900 g of wheat grains, treated withCumachlor(0.017.) and coloured with the food dye Patentblau V (0.05%) ICa salt of 2,4-disulfo-5-hydroxy-4’,4-bis(diethylamino)triphenylcarbinol anhydride, Colour Index 42051] are placed into a Kobarth mixer with a 3-litre agitator vessel.

While slow stirring is maintained, 179 g of an approx. 5c;c aqueous vinyl acetace/’acrylic acid butyl ester copolymer - 10 dispersion are added, and - depending on the viscosity of the dispersion - also 50-100 ml of water. There is formed, after 2-5 minutes' stirring, a viscous mixture, which is filled into prepared moulds in order to produce therefrom individual bait shapes each weighing 4-35 g and being in any desired form, for example as plates, cubes, truncated cones, rods, and so forth. Tha whitish, slightly frothy mixture is air-dried and, as a result of evaporation the water, the block bait according te the invention is 3.0 formed in the moulds, this block bait material being transparent and no longer water-soluble (but still swellable) .

Bromadiolon or Bromethalin can also be very advantageously used in place of Cuaachlor. And instead of patentblau, any other warning dye suitable for the purpose can be employed.

It is also possible to advantageously use, in place cf wheat grains, a coarse meal mixture consisting of: 26.66 % by weight of (oae) groats, 26.67 7. by weight of fodder rice, and 26.67 7. by weight of wheatmeal (shred), which, prepared in the same manner, is bonded with 20 % by weight of polyvinyl acetate, or with vinyl acetate/ acrylic acid ester copolymer or vinyl acetate/acrylonitrile copolymer.

Biological Example (feed-bait preference) Cn two groups of 24 laboratory rats and 24 wild mica, respectively, the inclination of the animals to show preference for the block bait according to the invention rather than for a similar feed bait without hard bonding with polyvinyl acetate (copolymer) was tested. a) 12 male and 12 female laboratory rats having bcc.y weights of between 174 and 261 g were kept in individual cates eash 4 7 2 3 with a wire-mesh bottom. There was situated under each cage a collecting tray with filter paper, in order co collect parts of feed and bait falling down from the cages and to make ic possible to carry out a re-weighing.

The animals had water available ad libitum from special drinking bottles. There was offered to the animals, beside the drinking bottles, the normal or standard feed, consisting of 1/3 (oat) groats, 1/3 fodder rice and 1/3 wheatmeal (shred), in a container.

The employed block bait according to the present invention, consisting of: 26.66 7. by weight of (oat) groats, 26.67 7. by weight of fodder rice, 26.67 7. by weight of wheatmeal (shred), and 20.00 7. by weight of a vinyl acetate/ acrylic acid ester copolymer, had a mean weight of 35 g, and dimensions of 40 x 40 x 30 mm. The animals had the block bait offered to them in a container fixed to a side wall at right-angles to the drinking bottle. Normal feed and block bait were offered simultaneously during 4 days at 20 + 2°C with simulated light (light.phase: 13 hours, dark phase: 11 hours). The daily consumption was determined for each individual animal by re-weighing the offered feed. The average amount of feed consumed in 4 days was as follows: Species Average amount cf block bait normal feed male rats female rats 73.S + 10.3 g 69.0 + 10.1 g 52.4 + 9.1 g 21.4 + 6.6 g tctal average amount 71.4 + 10.2 g 36.9 + 7.9 g 4 72 - 12 The racs prefer the block-bait formulation co the normal feed by the ratio of 2:1. What is moreover striking is the clear 3:1 preference in the case of female rats. b) 24 mice of both sexes (Mus musculus dcmesticus), £rem the second generation of mice caught wild, hiving ucdy weights of between 18 and 32 g were subjected in their individual cages to the same test as described under a) . After a habituation phase of about cne and a half days, during which the animals disregarded the initially preferred soft feed more and more in favour of the block bait, the average feed intake per day was as follows. 3rd Day 4th Da? 4.0 : 1.1 g 4.0 : 0.7 g . block bait : soft feed 4 7 2 3

Claims (15)

1. CLAIMS:1. A rodenticidal hard bait which weighs 4-1000 g and which consists essentially of a carrier of brittle-hard polyvinyl acetate, or of a brittle-hard copolymer of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, and a foodstuff treated with a rodenticidal poison and dispersed in· the polymer carrier.

2. A bait according to Claim 1, wherein the polymer constituent amounts to 4-30 per cent by weight, and the poison component is present in an amount of 0.001 to 1.0 per cent by weight, relative to the foodstuff constituent.

3. A bait according to Claim 2, wherein the polymer constituent amounts to 7-15 per cent by weight.

4. A bait according to Claim 2, wherein the polymer constituent amounts to 10 per cent by weight.

5. A bait according to any one of Claims 1 to 4, wherein the polymer constituent is essentially a copolymer formed from vinyl acetate and acrylic acid ester.

6. A bait according to Claim 2, wherein the poison component is present in an amount of 0.005 - 0.1 per cent by weight, relative to the foodstuff constituent.

7. A bait according to Claim 2, wherein the foodstuff constituent contains up to 10 per cent by weight cf other additives selected from the group of mineral or vegetable fillers, taste corrigents, microbicides, germination inhibitors and dyes . - 14

8. A bait according to any preceding claim, wherein the foodstuff constituent consists of a hard feed based on cereals.

9. A bait according to any preceding claim, wherein the rodenticidal poison is selected from the anticoagulant class. 5 10. A bait according to Claim 9, wherein the anticoagulant is a 4-hydroxycoumarin derivative. 11. A bait according to Claim 10, which contains 3*(e= acetonyl-4-chlorobenzyl)-4-hydroxycoumarin («= Cumachlor). 12. A bait according to Claim 10, which contains

10. 3-[4' -bromobipheny 1-4-y 1-3-hydroxy-1-phenylpropy 1)-4hydroxycoumarin (» Bromadiolone).

11. 13 . A bait according to any one of claims 1 to 8 wherein the rodent iddal poison is 2,4,6-tribreffo-N-nethyl-2,4'-ciimtro-6'triflucromethyldiphenylamine (« Brometnaim).

12. 15 14. A bait according to Claim 1, which consists of 90 per cent by weight of prepared cereal grain containing 0.01 per cent by weight of Cumachlor or Bromadiolone and 0.05 per cent by weight of dye; and 10 per cent by weight of vinyl acetate/acrylic acid ester eopolymsr. 20 15. A bait according to Claim 1, which consists of 90 per cent by weight of prepares cereal grain containing 0.005 - 0.1 per cent by weight of Bromethalin; and 10 per cent by weight of a vinyl acetate/acrylic acid ester copolymer. 25

13. 16. A process for producing a brittle-hard rodenticidal bait weighing 4 to 1000 g, which process comprises mixing, for 1-60 minutes, the foodstuff constituent treated with ths rcasnticidal poison, which constituent is ultimately to constitute 56*70 east ty 5 4 7 2 3 - 15 weight of the finished dry bait, and which can contain, besides the poison component of 0.001 - 1.0 per cent by weight, up to 10 per cent by weight (of its own weight) of mineral and vegetable fillers, taste corrigents, 5 microbicides, germination inhibitors, dyes and/or other additives suitable with regard to application technique, with an aqueous dispersion of polyvinyl acetate, or of a copolymer of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, water being 10 if necessary added, to thus obtain a pourable mixture; then casting or otherwise forming this mixture into blocks or granules, and subsequently drying these at 10-60°C.

14. 17. A process for controlling rodents, particularly rats and mice, which process comprises the administration and putting out of a rodenticidal hard bait according to any one of Claims 1-15 inclusive.

15. 18. A method of controlling rodents, which method comprises the use of a rodenticidal hard bait according to any one of Claims 1-15 inclusive.