GB2087723A - Improvements in pesticidal compositions - Google Patents

Abstract

A weather- and mould-resistant alternative to conventional cereal-based molluscicide compositions comprises an effective proportion of at least one molluscicide distributed substantially homogeneously therein and at least 50% by weight of a clay carrier.

Description

SPECIFICATIONS Improvements in pesticidal compositions This invention concerns improvements in pestici dal compositions and more particularly relates to improved molluscicidal compositions.

Molluscs such as slugs and snails, for example, the terrestrial slug Agriolimax reticulatus, are a serious pest of crops and other cultivated plants. It has long been the practice to destroy such pests with poisoned baits based, predominantly, on materials of vegetable origin such as cereals. For convenience the composition is generally converted into pellets, tablets or granules which are scattered on the ground in the vicinity of plants which are vulnerable to attack from snails or slugs. Such pellets have typically contained 80-95% by weight of organic material of vegetable origin. Although mineral carriers have been used to a limited extent, it has not previously been thought practicable to provide effective bait compositions based largely on a mineral carrier.

Pellets based on vegetable material suffer from several disadvantages. First, they can be attractive to domestic animals, pets and birds which can suffer ill effects from the molluscicide. Secondly, they can be subject to fungal attack, particularly under damp conditions. Thirdly, they tend to disintegrate quickly on exposure to rain or heavy dew and thus become less effective.

We have now found that surprisingly effective clay-based molluscicidal compositions can be made containing a greatly reduced amount of vegetable or other food material, or even none at all.

In one aspect our invention provides a molluscicidal composition comprising an effective proportion of at least one molluscicide distributed substantially homogeneously therein and at least 50% by weight of a clay carrier. Preferably the composition comprises at least 60%, and more preferably at least 65% by weight of said clay, which advantageously is china clay. Effective granules can even be made containing at least 80% by weight of clay.

It is very desirable to convert the composition into pellets, tablets, granules or the like physical form, for ease of distribution.

The composition preferably comprises sufficient of an alkali to serve as a binderforthe clay carrier.

The alkali is preferably calcium hydroxide or calcium oxide. These materials are not only cheap and acceptable to molluscs but resist leaching by water and confer considerable water resistance on the composition. They also reduce volatilisation of volatile components such as metaldehyde. Less preferably magnesium hydroxide, magnesium oxide or aluminum hydroxide can be used. Alkali metal hydroxides, although having binding properties for the clay, are less advantageous because oftheir high water-solubility.

The alkali may be present in the composition in a proportion of e.g. 0.5 to 10% by weight, more preferably 2 to 5% by weight.

Other binders can be used, such as sodium silicate or suitable cellulose derivatives.

Although the compositions can be made without any vegetable or other food material, it is preferable to incorporate these in an amount e.g. up to 30% by weight. This component should include at least one material having attractant properties for the mollusc pest, such as bran or malt. A proportion of cereal such as wheatmeal may also be included. This has the additional advantage of serving to bind the com position more firmly.

Any molluscicide effective against the target pest can be used. Often preferance will be given to metal dehyde, which is highly effective and has some attractant properties. A suitable concentration will generally be in the range 1-10%, preferably 2-8% by weight. Another effective molluscicide is methiocarb, which has the advantage of repelling birds. This may be used at similar concentrations to metaldehyde. Copper-based molluscicides, e.g.

copper sulphate; niclosamide; pentachlorophenol; bis (tributyltin) oxide; paris green; 1,3 - di (methoxycarbonyl) prop - 1 - en - 2 - yl dimethyl phosphate; aminocarb and trifenmorph can also be used.

The composition may contain activators to increase the effectiveness of the molluscicdeide.

One class of activators is those enzymes or other proteins which can stimulate pinocytosis in epithelial cells of the digestive tract of the mollusc. A test for pinocytosis is described by W. Strauss in J.

Biophysic and Biochem. Cytol. 5, No. 2,193 (1959), and this test may be used to identify enzymes and other proteins suitable for use as activators. Such materials include ribonuclease, blood albumin, bovine serum albumin, horseradish peroxidase, egg albumen and enzyme waste. Egg albumen is the most preferred since it has valuable binding properties. The enzyme or other protein may e.g. comprise from 0.5 to 10%, preferably from 2 to 6% by weight of the composition.

To take advantage of the binding properties of albumen, rather more is preferably used, e.g. from 4 to 8% by weight.

Another class of activators is surfactants, many of which increase the uptake of molluscicide by the molluscs. These activators are effective in a proportion below 1%, e.g. 0.1 to 0.4% by weight. Suitable surface active agents include non-ionic agents, such as condensation products of polyalkylene oxide and alkylphenols and fatty acid esters of polyoxyalkylenes, e.g. octylphenoxypolyoxyethanol; cationic agents such as quaternary ammonium salts, e.g.

cetyltrimethylammonium chloride or cetylpyridinium chloride; and anionic agents such as sodium salts of secondary long chain alkyl sulphates e.g. sodium lauryl sulphate, salts of alkyl aryl sulphates, sodium deoxycholate, sodium taurocholate and sodium tauroglycocholate. A particularly suitable surfactant is polyoxyethylene sorbitan monooleate. Surfactant activators in the proportions recommended do not adversely affect the weathering properties of the composition to any significant extent.

It may be desirable to incorporate some other minor additives in the compositions. A denaturant may be added to repel birds and mammals, for example, benzyl diethyl (2,6 - xylylcarbamoylmethyl) ammonium benzoate (available under the Trade Mark Bitrex1. The latter material may be employed at a concentration of e.g. 0.0001% to 0.01%. Another effective denaturant is that available from Lautier Aromatiques Limited, London, under the Trade Mark Alamask. The latter material, believed to be based on unsaturated ketones, can be incorporated at e.g.

0.1-4% by weight. Compositions containing vegetable or otherfood materials can be protected from fungal attack by the addition of a fungicide or biocide.

In making a composition according to the invention, it is merely necessary to mix the various components together with a liquid carrier, in practice generally water, and convert the plastic mass into the desired physical form by extrusion, tabletting, pelletting or like treatment. After drying off any excess liquid, the granules may be screened to remove oversized and undersized particles.

The compositions according to the invention show a considerable economic saving compared to conventional food-based molluscicidal compositions.

Moreover in pellet form they can be made to possess an outstanding resistance to water. They are thus able to survive wet weather conditions, at least for a time, and remain effective to kill the molluscs favoured by such conditions. Conventional compositions would have to be reapplied in order to maintain effective control.

The compositions according to the invention are also relatively unattractive to wild life and domestic animals or pets. These species do not favour eating a material based largely on clay. The clay carrier material is of course free from any tendency to spoilage.

Contrary to expectations, molluscs readily take such compositions - in fact we have found that the compositions of this invention are often comparable in effectiveness to the best cereal-based compositions.

The following Examples are given for illustration only. Parts are by weight.

Example 1 China clay 68.7 parts Wheatmeal 20.0 parts Bran 5.0 parts Metaldehyde 3.3 parts Calcium hydroxide 3.0 parts Water 24.0 parts The components, with the exception of the water, were mixed together. The water was then sprayed onto the mixture whilst continuing to mix. The mixture was put through a pelleting machine and then dried to a moisture content of about 10% and sieved to remove dust.

These pellets were compared for molluscicidal efficiency with cereal-based pellets (sold by Murphy Chemical Limited under the trademark "Slugit"). The cereal-based pellets are among the most effective available.

The mean kills of slugs overtwo weeks were as follows: Pellet of this Example 92 Slugitpellet 84 Example 2 The formulation is as Example 1 but with the inclusion of 0.0008 part or 0.0016 part Bitrex.

The pellets containing 0.0016 part (i.e. 16 ppm) Bit rex were included in the same trial as the pellets of Example 1. The pellets killed 95 slugs in 2 weeks, thus proving more effective than the Slugit pellets.

Example 3 The formulation is as Example 1 but with the inclusion of 1.0 part Alamask VPA.

The pellets were included in the same trial as the pellets of Example 1. The pellets killed 95 slugs in 2 weeks, during which time the cereal-based Slugit pellets killed 84 slugs.

Example 4 China clay 90 parts Metaldehyde 6 parts Calcium hydroxide 4 parts Water 35 parts The mixture was pelletted as in Example 1.

Example 5 The composition of Example 1 was supplemented with 0.2 part p-nitrophenol to serve as a fungistat.

The effectiveness of these pellets is evident from the following results: Slugs killed Pellets in first week in 2 weeks This Example 124 169 Slugit 97 160 Example 6 China clay 69.6 parts Wheatmeal 20.0 parts Bran 5.0 parts Metaldehyde 2.2 parts Calcium hydroxide 3.0 parts p-Nitrophenol 0.2 parts I Water 24 parts The components were formed into pellets by the method of Example 1.

Portions of these pellets were then sprayed with solutions of sodium tauroglycocholate (TGC) and sodium lauryl sulphate (LS). After drying, the con centrations of these surfactants in the pellets were 0.2% by weight.

The percent kill of slugs under standard laboratory conditions was as follows: Pellet, additive - % kill None 28 0.2% TGC 35 0.2% LS 39 Slugit (control) 28 Example 7 The pellets of Example 6 were tested under field conditions. Also included in the trial were pellets containing 8 parts by weight of albumen and corms- pondingly less (i.e 61.6) parts of china clay.

The results below are the totals from three field trials at three different locations. The number of slugs trapped were those found in the vicinity of the bait during the assessment; not all these slugs were dead, so these figures reflect the attractant proper ties of the bait as well as their toxicity to the mol luscs.

Pellet No. ofslugs trapped No additive 301 0.2% TGC 341 0.2% LS 315 8% albumen 369 The pellets containing alubmen were particularly resistant to weathering.

We are aware of a proposal (Japanese Kokai 79-32619) to treat heat-treated clay granules with a copper compound and further heat-treat the product, e.g. at 800-1 000 C. We make no claim herein to a molluscicidal composition comprising clay granules which have been treated with a copper compound and partially vitrified at an elevated temperature.

Claims (22)

1. A molluscicidal composition comprising an effective proportion of at least one molluscicide distributed substantially homogeneously therein and at least 50% by weight of a clay carrier.

2. A composition according to claim 1 comprising at least 60% by weight of said clay carrier.

3. A composition according to claim 2 comprising at least 80% by weight of said clay carrier.

4. A composition according to any of the preceding claims wherein said clay is china clay.

5. A composition according to any of the preceding claims including a binder for said clay carrier.

6. A composition according to claim 5 including sufficient of an alkali to serve as a binder for the clay carrion

7. A composition according to claim 6 including from 0.5 to 10% by weight of said alkali.

8. Acomposition according to claim 7 including from 2 to 5% by weight of said alkali.

9. A composition according to any of claims 6 to 8 wherein said alkali comprises calcium hydroxide or calcium oxide.

10. A composition according to any of the preceding claims including a vegetable or other food material having mollusc-attractant properties.

11. A composition according to claim 10 wherein said material comprises bran or malt.

12. A composition according to any of the preceding claims including from 2 to 8% by weight of metaldehyde as said molluscicide.

13. Acomposition according to any of the preceding claims including an effective amount of an activator for said molluscicide, said activator being an enzyme or other protein.

14. A composition according to claim 13 including from 4to 8% by weight of egg albumen as said activator.

15. A composition according to any of the preceding claims including an effective amount of surfactant activator for said molluscicide.

16. Acomposition according to claim 15 wherein said surfactant activator comprises from 0.1 to 0.4% by weight of polyoxyethylene sorbitan monoleate.

17. Acomposition according to any of the preceding claims including a denaturant in an amount effective to repel birds and mammals.

18. Acomposition according to any of the preceding claims in the form of pellets, tablets or granules.

19. A composition according to claim 1, substan tialiy as described herein.

20. A composition according to claim 1, substantially as described herein with reference to any of the Examples.

21. A method of making a composition according to any of the preceding claims which comprises admixing said molluscicide, clay carrier and option ally other components with a liquid carrier, converting the plastic mass into a desired physical form, drying off any excess liquid carrier, and screening the product to remove oversized and undersized particles.

22. A method of controlling molluscs which comprises baiting said molluscs with an effective amount of a composition according to any of claims 1 to 20.