GB2228868A

GB2228868A - Molluscicidal granular aluminium sulphate compositions

Info

Publication number: GB2228868A
Application number: GB9002323A
Authority: GB
Inventors: Stanley Edward John Mernagh; Alan Mcclymont
Original assignee: GROWING SUCCESS ORGANICS Ltd
Current assignee: GROWING SUCCESS ORGANICS Ltd
Priority date: 1989-02-03
Filing date: 1990-02-02
Publication date: 1990-09-12
Anticipated expiration: 2010-02-02
Also published as: GB8902394D0; NZ232344A; GB9002323D0; GB2228868B; AU5020790A; WO1990008471A1

Abstract

Horticultural and agricultural molluscicide compositions, for destroying slugs and snails, comprise granules of aluminium sulphate, particularly a prill made by granulating a hot aluminium sulphate melt. The molten salt is tumbled in a drum to form hard rounded granules which are evenly sized between 0.5 and 3 or 4 mm and resist dust formation. The granules, optionally dyed, can readily be applied at controlled rates as low as 2 to 3 gm/m<2> by means of a spinner.

Description

MOLLUSCICIDES This invention relates to horticultural and agricultural molluscicides.

Many commercially available products for destroying slugs and snails in horticulture or agriculture are also toxic to other forms of life. A number of commonly used compositions are based on metaldehyde, and are used as baits in the form of pellets to be eaten by the molluscs.

These products may typically contain metaldehyde in 3% concentrations for garden use, or in 6% concentrations for commercial use. Even at the lower concentration they have to be used with care, to limit the risks of poisoning other small animals, including pets and birds, and even livestock.

Metaldehyde is also volatiles and the pellets lose their effectiveness quite rapidly. A typical effective life may be only 14 days, and less in wet conditions.

Aluminium sulphate, and with other ingredients such as aluminium silicate, copper sulphate and sodium tetraborate, has also been used in horticultural or agricultural molluscicidal compositions. Aluminium sulphate is generally available as a white crystalline powder. The salt may be hydrated, and is soluble in water to yield an acidic solution.

Fine powder can thus be an irritant in moist conditions. However, its toxicity to animals and humans is generally low, unless large quantities are ingested.

In its effect on slugs and snails (gastropods, subclass pulmonata), however, aluminium sulphate is highly toxic. It does not need to be ingested, but is effective by contact, whether solid or in solution. Its principal action is believed to be to dehydrate through its effect on the slime-forming organs.

In order to use the above products most efficiently, they must be distributed evenly over the soil to be treated, at the correct application rates. However, in agricultural use, it is not at all easy to apply powder in the open air accurately and evenly over a field.

For use on a small scale, over perhaps 10 m2 by an amateur gardener for example, it is also difficult to ensure proper application.

A possible alternative to application as a powder might be to use crystalline product, such as could be made by crushing and screening larger pieces. However, no matter how precise the screening process, subsequent handling and shipping of the crystal chips would result in further break up of the sharp edged particles, broadening their size distribution and creating a substantial quantity of fines and dust. This necessarily results in product of inconsistent quality, and whenever packaged loosely the larger particles would tend to accumulate towards the top of the pack and the material become progressively more dusty towards the bottom of the pack. Controlling the application of such a product to an even rate would clearly be very difficult.

Apart from difficulties in evenly measuring out powders or crystals with a significant dust content, fine dust tends to drift in moving air and it is difficult to avoid direct contact of the dust with adjacent crops or animals, or with the person or persons applying the product.

In a broad aspect, the present invention is concerned with the use of aluminium sulphate in granular form as a horticultural or agricultural molluscicide. It has been found that in this form the aluminium sulphate provides a molluscicide that is highly effective, particularly convenient and economical to apply, and yet relatively safe and long lasting.

The invention also more particularly provides a horticultural or agricultural molluscicide composition comprising granules of aluminium sulphate. In a particular embodiment, the aluminium sulphate is a prill, being formed by granulation from the molten salt, as further described below.

The major part of the granular aluminium sulphate by weight preferably has a grain size of at least 2 mm, and suitably in the range 2 to 4 mm. In a particularly preferred product, substantially all the granules are retained on a 3 mm sieve, and less than 1% passes a 0.50 mm sieve.

In a further aspect, the invention provides a method of controlling mollusc infestation in horticulture or agriculture comprising applying to the horticultural or agricultural growing medium a molluscicidally effective amount of granular aluminium sulphate. Application is most simply performed by scattering the granules over the surface of the growing medium.

In a still further aspect, the invention provides a method of preparing a horticultural or agricultural molluscicidal composition comprising forming granules of aluminium sulphate and applying a colouring agent thereto.

The granules are preferably formed by granulating molten aluminium sulphate. This may be achieved by treating a hot melt of aluminium sulphate, as formed in its conventional manufacture, typically from sulphuric acid and bauxite, in a granulator drum, where the molten salt can be tumbled and sprayed with water until it has solidified.

Granules formed from such a melt are of the hydrated salt, with a similar analysis to crystalline aluminium sulphate. However they are hard and rounded, and consequently can be maintained in a given size distribution and are much less liable to dust formation. This gives great benefits in the practical use of the product.

The colouring agent may advantageously be non-toxic, and of a colour adapted to distinguish the granules from autochthonous particles.

In accordance with the invention, the aluminium sulphate composition is in granular form, and preferably is also substantially dust free. It has been found that this permits considerably sparser application rates than powders while retaining effectiveness. The application rate of the granules can be readily controlled, and the granules are visible after application, especially if they have been dyed, whereas the quantity or uniformity of a spray application cannot so readily be judged by eye. In outdoor conditions, sprays, powders and dust from crystal chips may also drift, and cannot be applied in the presence of livestock. Powders and dust may also drift on to foliage.

Effective application rates for aluminium sulphate in powder form are typically 15 to 20 g/m2, whereas rates for granules may be as low as 2 to 3 g/m2. In agricultural applications, these rates mean that effective treatment may be achieved using the granular compositions of the invention at application rates of only 25 kg/ha, and the composition may be broadcast by means of a spinner, such as a fertiliser spinner. Higher application rates may of course be used if preferred. Hand application for amateur use in the garden is also made easier.

It has been found that it is not necessary to closely cover the soil (or other growing medium) with the molluscicide for the granular compositions to be effective. The slugs and snails move about and will soon contact a granule. If conditions are wet, with much rain, the granules will dissolve and the aluminium sulphate will move into the soil surface where the is still effective. The compositions can retain their effectiveness for many months after application and destroy slugs and snails in both the adult and the egg stages.

The aluminium sulphate granules may be still be dissolved in water, for application as a solution, preferably as a spray. Suitable dilutions for spraying are 5 to 20 g/l, typically 15 g/l for application around established plants and shrubs and 7 g/l for application around seedlings. The coverage in each case is about one square metre, more generally 0.5 to 2 m2. The aluminium sulphate concentrations of these sprays are not substantially detrimental to foliage.

Light sprays may also be used to treat solid surfaces, such as glass in frames and greenhouses.

The following examples illustrate the invention.

Example 1 Liquid molten aluminium sulphate from the reactor vessel is introduced into a granulator drum where it is formed into a prill with rounded or somewhat cylindrical granules. The grain size is less than 3 mm, the major proportion by weight being greater than 2 mm grain size, and less than 1% passing a 0.50 mm sieve.

The aluminium sulphate granules contain 17.2% Al203 (according to DIN 19600), 0.5% free Al203, 0.007% Fe as Fe203, 43% H20 and 0.03 /O insolubles. They have a high bulk density of about 0.97 tonne/m3.

The prill is tumble mixed with the colouring agent Lissamine Green (E142, Acid Brilliant Green, Colour Index 44090) to coat the granules to a distinctive pale green colour.

Example 2 The prill from Example 1 is sprinkled around both edible and nonedible garden plants, in spring, at a rate of 2.5 g/m2, around the outside and inside perimeters of greenhouses and tunnel cloches, and behind garden walls and fences. Garden slugs and snails in the area are successfully killed, as are incoming slugs and snails for up to 6 months, and no breeding takes place for up to 8 months. A further application of the prill is made in autumn to ensure that all eggs in the soil are destroyed before the following spring.

The prill runs smoothly without clogging the applicator used. Storage in silos and storage spaces is reliable, the slightly hygroscopic product being unaffected by atmospheric and temperature variations under normal conditions. A minimum of dust is formed.

Claims

1. A horticultural or agricultural molluscicide composition comprising granules of aluminium sulphate.

2. A composition according to claim 1, wherein the aluminium sulphate is a prill formed by granulating molten aluminium sulphate.

3. A composition according to claim 1 or claim 2 wherein the major part of the granular aluminium sulphate by weight has a grain size of at least 2 mm.

4. A composition according to claim 3 wherein the major part of the granular aluminium sulphate by weight has a grain size in the range 2 to 4 mm.

5. A composition according to any one of the preceding claims wherein substantially all the granules are retained on a 3 mm sieve, and less than 1% passes a 0.50 mm sieve.

6. A composition according to any one of the preceding claims wherein the granules are coloured with a colouring agent applied thereto.

7. A composition according to claim 1 substantially as herein described and with particular reference to Example 1.

8. A method of preparing a horticultural or agricultural molluscicidal composition comprising forming granules of aluminium sulphate and applying a colouring agent thereto

9. A method according to claim 8, wherein the granules are formed by granulating molten aluminium sulphate.

10. A method according to claim 9, wherein the granules are formed from a conventionally manufactured hot melt of aluminium sulphate by tumbling the melt in a granulator drum.

11. A method according to claim 10, wherein the melt is sprayed with water in the granulator drum until it has solidified into granules.

12. A method according to claim 8, substantially as herein described and with particular reference to Example 1.

13. A horticultural or agricultural molluscicide composition prepared by a method as claimed in any one of claims 8 to 12.

14. A method of controlling mollusc infestation in horticulture or agriculture comprising applying to the horticultural or agricultural growing medium a molluscicidally effective amount of granular aluminium sulphate.

15. A method according to claim 14 wherein the granular aluminium sulphate comprises a composition according to any one of claims 1 to 7 or claim 13.

16. A method according to claim 14 wherein the granular aluminium sulphate comprises a composition according to claim 6 or claim 13 and the colouring agent is of a colour adapted to distinguish the granules from autochthonous particles.

17. A method according to any one of claims 14 to 16 wherein the granular aluminium sulphate is applied to the horticultural or agricultural growing medium at a rate of 2 to 3 g/m2.

18. A method according to any one of claims 14 to 17 wherein the granular aluminium sulphate is broadcast by means of a spinner.

19. The use of aluminium sulphate in granular form as a horticultural or agricultural molluscicide.

20. The use of aluminium sulphate in granular form as a horticultural or agricultural molluscicide substantially as herein described with particular reference to Example 2.