GB2407248A - Slug and snail repellent barrier - Google Patents

Abstract

The barrier comprises a structure, pattern or array of two dissimilar metal elements 2,3 joined at at least one point 4 so that in use a slug or snail which attempts to cross the barrier will come into contact with both elements causing a current to flow across its body. The elements may be arranged on adhesive tape or in the form of a physical barrier where one of the elements may form the body of the barrier. The elements may also be shielded.

Description

Patent specification

Slug and Snail Repellent Barrier Author: Simon Joseph Scott 267 High Kingadown, Bristol BS2 8DF This invention relates to a passive slug and snail barrier.

Slugs and snails can cause serious damage to plants. Present methods to prevent them gaining access to plants include the use of poisonous chemicals, salt, roughened surfaces, electrical wires and copper strips. Impending legislation will ban the use of many poisonous chemicals which are detrimental to the health of wildlife and pets. Salt is prone to weather erosion, can increase soil salinity and must be renewed periodically. Roughened surfaces are not totally effective and can be difficult to implement. Electrical wire barriers rely on current sources such as batteries which must be renewed periodically or transformed down mains supplies which are expensive and complicated to implement. Finally, copper strips, which are stated to work by creating an unpleasant, repellent electrolytic reaction with the mucous underside of the slug or snail, are generally 5-lOcm wide.

Consequently the strips are somewhat unwieldy and require a considerable effort to fit. Furthermore, if eaten the slugs or snails may transfer toxic copper compounds to wildlife.

An object of this invention is to provide a slug and snail repellent barrier which is easy to implement, non-toxic and maintenance free.

Accordingly this invention provides a slug and snail barrier, comprising a structure, pattern or array on which are presented two, separated dissimilar metals joined at at least one point. A snail or slug which wishes to cross the barrier must at some point bridge a gap between the two dissimilar metals. The structure, pattern or array of dissimilar metals forms a passive electrical circuit that is activated when the moist body surface of the slug or snail bridges and makes contact with the two dissimilar metals. The moist body surface contains electrically conductive ions and those lengths of the dissimilar metals that lie in contact with the slug or snail form the electrodes of an electrical cell. This cell is short circuited as a consequence of the two metals being already joined at a point or points outside the region in contact with the slug or snail. An electrical potential is formed across that part of the body surface of the slug or snail that lies between the dissimilar metals. Thus a current flows through the body surface and around the short circuited loop(s). The slug or snail experiences an unpleasant sensation and retreats. When the slug or snail has broken contact with one of the metals the electrical cell is effectively dismantled and the current stops. The slug or snail is thus repelled from crossing the barrier.

The barrier works in a non-toxic and passive manner. No external current source is required. Thus the disadvantages of the other types of barrier are avoided.

It will be appreciated that there are many possible implementations of this invention.

For instance, it is possible for all the metal components to be made of the same metal with one then coated in a different metal so that two dissimilar metals are presented externally. Furthermore, the metal components could be made of the same metal and each could be then coated in a different metal to each other and to the underlying metal, thus presenting dissimilar metal surfaces.

The metals could for instance be elements such as aluminium, zinc, iron, copper, silver or gold or alloys of these and of other metals.

Some of these metals will weather and develop layers of oxide or hydroxide, the overall efficacy of the barrier should be unaffected as these layers can also function as electrodes.

Descriptions of several implementations of the concept will now be presented.

Preferably the barrier is made of thin layers of the dissimilar metals which are affixed on a backing of insulating tape which itself has an adhesive backing. The dissimilar metals are present as two parallel strips running the length of the tape, with a gap between them less than the expected width of a slug or snail. The dissimilar metal layers would preferably have a thickness between 10pm to lOOpm, a width between 2mm to 20mm and have a separation between 2mm to 15mm. It will be appreciated that these dimensions are not to be considered exclusive and that other thicknesses, widths and separations could be used without prejudice to this specification. The strips are electrically connected at regular intervals. A preferable interval for the regular electrical connections is 10cm. This interval can however be varied. The tape may then be cut to length and affixed to a tree trunk, fence, pot or other physical barrier with the dissimilar metals facing outwards. There must be at least one link between the dissimilar metals on each length of tape used. The tape could be held in place on the physical barrier by the adhesive backing or by any other means.

An alternative embodiment is for two wires of dissimilar metals to be held in the correct juxtaposition to each other by an intervening structure. This can be insulating or conducting. The wires are electrically connected periodically. The wire pair may then be cut to length and affixed to a tree trunk, fence, pot or other physical barrier.

The wire thicknesses could preferably be between 0.5mm and 2mm although it will be appreciated that other thicknesses could be used.

The wire separation should be less than the expected width of a slug or snail and preferably between 2mm and 15mm.

An alternative embodiment is for a fence or structure to be made of one metal and for the second dissimilar metal to be mounted less than the expected width of a slug or snail away. This would be preferably between 2mm and 1 5mm away from the surface. The second dissimilar metal could be in the form of a wire (preferably between 0.5mm and 2mm diameter although it will be appreciated that other thicknesses could be used) or of a continuous strip (preferably between 0. 5mm and 2mm thick and between 2mm to 15mm wide although it will be appreciated that other dimensions could be used).

A modification of this form is for the fence or structure to be made of one of the dissimilar metals and for the second dissimilar metal to be present on an insulating strip which is affixed to the frame or structure. The distance between the edge of the second dissimilar metal and the frame or structure should less than the expected width of a slug or snail and preferably between 2mm and 1 5mm.

An alternative embodiment is a mesh fence in which adjacent strands of wire are made from alternating dissimilar metals. The maximum gaps between the strands must be less than the width or thickness of a slug or snail. Preferably these gaps will be between 2mm to 15mm at their widest point.

Reference is now made to the drawings: FIGURE l(a) shows the most basic form of the slug and snail barrier, 1. Dissimilar metal elements 2 and 3 are electrically joined by an extension of 2, 4.

FIGURE l(b) shows 1 with a slug or snail, 5, bridging the gap between 2 and 3. The portion of 2 that lies underneath the slug or snail is labelled 2a, the portion of 3 that lies underneath the slug or snail is labelled 3a. 2a and 3a are the electrodes of an electrical cell which is illustrated schematically. The potential difference between 2a and 3a is dependent on the metals 2 and 3, and the electrolyte ions that are present in the moist body surface of the slug or snail. The electrical resistance of the circuit formed by the cell and the external loop is represented by 6.

FIGURE 2 shows a plan view of an implementation of the concept.

Multiples of the basic structure, 1, are laid down on an insulating backing, 7. Thin layers of the dissimilar metals are positioned as strips, 2 and 3, on the insulating substrate, 7, with a gap between them that must be less than the width of a snail or slug's body. The dissimilar metal strips, 2 and 3, are electrically joined by 4. 4 is repeated periodically along the length of the tape so that if a section is cut off there will be a further electrical connection between 2 and 3 available on the next section of tape to be used.

FIGURE 3 shows an arrangement of two dissimilar metal wires, 2 and 3, held apart by spacers, 8, placed at regular intervals. The spacers can be insulating or conducting. If insulating there must also be regular electrical connections between 2 and 3.

FIGURE 4 shows an alternative embodiment with a comb like structure of alternating dissimilar metals, 2 and 3, connected at the top of the structure. In this arrangement many basic structures, 1, lie in parallel on an insulating backing, 7. The gap between the dissimilar metals must be less than the width of the slug or snail to be repelled.

FIGURE 5(a) shows an insulating structure, 9, to which the dissimilar metal strips or wires are attached and which has a projecting element, 10, which protects them from direct rainfall and sunlight. The dissimilar metals could be present on the insulating tape of FIGURE 2 which is then affixed to 9. Several of the structures, 9, can be pushed into the ground by means of prongs, 11, to form a fence around an area to be protected.

Figure 5(b) shows a variant in which the structure 9 is made of one of the dissimilar metals, 2, and the other metal, 3, lies on an insulating base which is affixed as shown. The metals are joined at 4. The gap between the edge of the metallic strip, 3, and the metallic frame, 9, is less than the width of a slug or snail and preferably between 2mm and 15mm.

Figure 6 (a) and (b) show mesh fence barriers in which the wire strands are made from dissimilar metals 2 and 3. These are joined periodically as a consequence of the mesh structure. The maximum open dimension should be selected so as to ensure local slugs or snails will make contact with both dissimilar metals if they attempt to pass the barrier. The mesh can be of any regular shape.

A preferred embodiment of the invention will now be described with reference to FIGURE 2 in which: The dissimilar metals, 2 and 3, are made of brass and aluminium and are 12mm wide, and lOpm thick. The gap between the strips is 4mm.

There is a bridging element, 4, every lOOmm of length which is lmm wide. They are attached by a thin layer of adhesive to a strong insulating tape, 7. The tape is 38mm wide and has an adhesive layer on its reverse side that is exposed by peeling off a protective backing layer. It is important not to coat the metal surfaces with adhesive as this could insulate the slug or snail from the metals and reduce the efficacy of the barrier. The tape is stored in a roll and lengths may be cut off to fit for instance to conventional plant pots, tree trunks or small conventional barriers. Alternatively the tape can be affixed with fasteners or tied in place.

Claims (9)

1. Claims 1. A slug and snail barrier, comprising a structure, pattern or

   array on which are presented two, separated dissimilar metals joined at least one point, such that a slug or snail that contacts both the metals simultaneously forms an electrical cell on its moist body surface with the two dissimilar metals providing the electrodes and a potential difference is thereby set-up between these electrodes on the body surface of the slug or snail which drives a current through the body of the slug or snail and the external circuit formed by the structure, pattern or array of dissimilar metals, and consequently the slug or snail is repelled from the barrier.
2. 2. A slug and snail barrier as claimed in Claim 1 where the structure, pattern or array of dissimilar metals is present on an insulating backing tape with electrical bridges between the dissimilar metals at regular intervals.
3. 3. A slug and snail barrier as claimed in Claim 1 where the freestanding dissimilar metal elements are held apart by conducting bridges.
4. 4. A slug and snail barrier as claimed in Claim 1 where the freestanding dissimilar metal elements are held apart by insulating bridges with periodic electrical connections between the dissimilar metals.
5. 5. A slug and snail barrier as claimed in Claim 1 where the dissimilar metals are arranged in repeating pairs in a comb like structure.
6. 6. A slug and snail barrier as claimed in Claims 1 and 2 where the dissimilar metals are affixed to an insulating tape which is affixed to a barrier structure in which the dissimilar metals are shielded from direct rainfall and sunlight.
7. 7. A slug and snail barrier as claimed in Claim 1 where one of the dissimilar metals is in the form of a physical barrier and the other metal lies on the outer surface of an insulating backing which in turn lies on the surface of the first dissimilar metal.
8. 8. A slug and snail barrier as claimed in Claim 1 where the dissimilar metals are present in a mesh structure such that a slug or snail wishing to pass the barrier must at some point make contact with the two dissimilar metals simultaneously.
9. 9. Any slug and snail barrier substantially as herein described and illustrated in the accompanying drawings.