FR2825895A1 - Method for eliminating aquatic plants comprises inhibiting photosynthesis by spreading opaque sheet over them which is held down by longitudinal, weighted strips and e.g. pegs at its edges - Google Patents

Abstract

The method for eliminating aquatic plants comprises inhibiting photosynthesis by spreading an opaque sheet (1) over them. This is held down by longitudinal, weighted strips (4) and e.g. pegs (6, 6') at its edges and tensioned by guy ropes (3) attached to bars (2) at each end.

Description

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 The present invention relates to a method of eradicating "in situ" aquatic plants rooted in open water or dry based on the blocking of photosynthesis by the use of shade cloths fixed on the meadows or tufts of said aquatic plants rooted.

 The purpose of this process is to provide a new solution to the arsenal of methods of treatment and control of aquatic plants in marine and lake sites.

The observation: The raising of vases is a widespread phenomenon in bays, estuaries and bodies of water.

This enhancement is accompanied by the colonization of rooted aquatic plants which bring a certain number of nuisances, both by the acceleration of sedimentary deposits which favor the reclamation of large areas, and by their impact on the general hydraulics of the sites involved in these processes. .

In the European marine aquatic domain, Spartine and rush are the two species mainly involved in the reclamation process and which pose environmental problems.

 Spartine is the first level indicator of marine mudflats which announces the forthcoming reclamation of the site, and whose presence, in the form of meadows, accelerates sedimentation and prepares the establishment of rushes and salt marshes.

 The Spartine, which is present on all the European Atlantic coast is called "Green Peril" in the bay of Mont Saint Michel, as its development is both rapid and detrimental to the environment.

It is found in the Arcachon basin where its eradication is becoming a priority in maintaining hydrology.

With regard to immersed rooted aquatic plants, the treatment techniques are confronted with strict rules for the protection of natural sites which no longer allow the application of traditional products or processes.

So there is still room for more and more natural techniques.

References :
To control the development of these rooted aquatic plants, phyto-sanitary products such as herbicides are used, or the aerial part of the plant is hacked, or the pH of the sediments in which the roots of the said plants are found is changed.

Herbicides: * In herbicides absorbed by the leaf. we can distinguish: 1 / Contact herbicides whose action is local such as calcium cyanamide, copper sulphate, sodium arsenite, sodium chlorate.

21 Systemic herbicides whose action is teletoxic, such as synthetic phytohormones, MCPA, 2, 4-D, 2, 4, 5-T, Dipyriliums, Paraquat and Diquat, Dalapon, Dichlone, Amitrol and f Amitrol-T, Fluridone, NH4 Thiocyanate, Isopropylamine salts of Glyphosate ... these substances are absorbed by the leaves and transported to the growth centers, causing

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des perturbations dans la crois-sance capables de faire périr les plantes qui y sont sensibles.

disturbances in growth capable of destroying sensitive plants.

* In the herbicides absorbed by the roots, we can note: Monuron, Amitrol, Amitroi-T, Simazine, TCA, Dalapon, Sodium Chlorate, Chlorthiamide.

All these products are spread or sprayed on plants in open water or dry, repeatedly.

Their use is often contraindicated in sensitive environments. Cutting: Cutting only controls the development of the aerial part of the plant, which immediately grows back.

Chemical treatment by changing the pH of sediments: This technique consists in injecting and mixing chemicals in the sediments, acid products to eradicate basophylous plants, basic products to eradicate acidodophylic plants.

This method is protected by French patent 96 02918 requesting the use of agricultural-type equipment (Rotavator) to carry out a homogeneous mixture of chemicals. As the use of chemicals is increasingly avoided, it was therefore interesting to develop new techniques for the eradication of aquatic plants adapted to each site and to each level of environmental sensitivity.

Burning: It is a method used in viticulture to avoid using weed killers.

It is a method of depletion of the plant that must be repeated 5 to 6 times.

Its application in an aquatic environment, on the foreshore at low tide is long, costly and has not brought significant results.

Solution presented: The process of eradicating aquatic plants "in situ" which is the subject of this patent is based on the physical action of a shade cloth on the development of the plant, in particular by prohibiting photosynthesis then causing accelerated rotting of stems and roots.

The shade cloths are positioned on the plants for durations of two to six weeks either from the spring vegetation, or during the summer period during the development of the aerial vegetative organs.

The treatment can be renewed if necessary.

The shading method is widely used in terrestrial agriculture to avoid the germination of herbs around the plans of certain vegetable crops, its use as an eradication process for adult or developing plants in the marine environment is innovative.

In the aquatic environment, this process requires many important adaptations, in particular with regard to ballasting the canvas, its anchoring, the management of trapped gases ...

The shade fabric can be of various shape to cover either large areas, in this case rectangular shade fabrics will be used to allow easier installation, 3 meters by 100 meters to give a non-limiting standard dimension and fabrics more limited in size and

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 variable shape generally circular or square to cover smaller areas like tufts.

 The fabrics can be made of woven or solid materials with shading coefficients of 70 to 100%.

 Lower coefficients can be used depending in particular on the plants to be eradicated and the length of stay on the site.

 The choice of the use of braided materials allowing water and gases to pass can be motivated to avoid too strong an impact on the fauna.

 The material used must preferably be rot-proof and protected from ultraviolet rays in order to increase the lifespan of the fabrics.

 The main problem with the use of shade cloths in an aquatic environment is to tackle and fix it to the ground so that currents or the wind at low tide do not tear them away.

To this end, several systems will be used, systems primarily suited to the installation of the shade cloth in open water or dry.

With regard to the installation of the shade cloth in open water, a canvas of rectangular shape (1) which will be able to be unrolled or unfolded will preferably be chosen but not limited to.

 This fabric will be provided at each of its ends with rigid axes (2) (metal bar or any other heavy material) which will be fixed before an anchoring and tensioning system (3). type 1 cable 1 anchor or cable 1 anchor plug (the anchor plug can be simple or fitted with worm element).

 These rigid axex (2) can themselves be fixed by anchor plugs (6).

 Furthermore, the canvas may be provided on its edges or along its surface with ballast lines 4) if possible flexible but not exclusively, such as leaded braids as well as eyelets (5) into which we can directly introduce anchor plugs (6) or elastic braids which themselves will be stretched and fixed by anchor plugs.

 This fixing work in open water will be carried out by intervention of a diver.

 The installation itself can be done by diver or from a boat.

 In the case of installation by boat, the roll of shade cloth is unwound, positioned and pressed on the bottom by means of a cylindrical bar or a weighted roller (18) articulated by arms (19) to the boat (20).

 To facilitate the maintenance of the shape of the canvas during installation, then once installed, flexible stiffening rods or rods (8), semi-rigid or rigid will be positioned in the transverse direction, the ends of these rods being housed in fixing pockets (9) and held on the canvas by loops made of sewn strips (10).

 The transverse stiffening rods (8) can also be housed in a sheath produced by a sewn band or a fold produced with the shade cloth (11).

 The unclosed end of this sheath being provided with a closure system (12) which may consist of a strip called "Velcro" (13) fixed on the open end of the sheath, and another strip "Velcro "(14) positioned on a tongue or any other fastening system such as laces,

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 seams or end pockets.

The fixing being carried out by bringing the Velcro of the tongue into contact with that of the sheath.

To perfect the fixing to the ground in zones with strong turbulence, rigid bars (16) of a length greater than the width of the shade cloth and provided with holes (17) at their ends can be positioned transversely on the cloth and fixed to the ground by anchor plugs (6).

Regarding the establishment of the shade cloth at low tide, that is to say dry, it can be unrolled or unfolded manually or using mechanized means of agricultural type.

Subsequently, the same principles of anchoring and fixing the canvas are implemented.

The rigid end pins (2) can also be fixed by piles.

The use of an impermeable shade cloth in the intertidal zone implies the creation of gas exhaust holes (15), (Air, carbon dioxide, methane ...) in the shade cloth in order to avoid trapping gas under the canvas which could be detrimental to its retention on the bottom.

Figure 1 of Plate 1/2 represents one of the ends of a longitudinal shade cloth (1) with its anchoring system (3), the rigid end axis (2), the positioning of the leaded braids (4), the lateral fixing eyelets (5), the lateral anchoring plugs in position (6) and before keying (6 '), the elastic braid (7) and its anchoring plugs (6), a rod of lateral stiffening (8), the fixing pockets (9) of the rod (8), the loops (10) of rod fixing (8), the representation of a sheath (11) of rod fixing (8) with its closure system (12) shown in the open position with the Velcro fastening system, the two elements of which are glued or sewn in (13) on the sheath and in (14) on the tongue.

The gas discharge holes are shown in (15).

An additional rigid anchoring bar is shown in (16) with its fixing holes (17) and its fixing plug (6).

Figure 2 of plate 2/2 gives a representation of the installation of the shade cloth from a boat (20) with the cylindrical bar or the weighted roller (18) for positioning the net (1) at the bottom , the ballasted roller or the bar (18) being connected to the boat by two articulated arms (19).

l'ancre permettant le relevage ou la tension de la toile, ainsi qu'en coupe, l'axe rigide d'extrémité et la toile d'ombrage (1). Also shown in Figure 2 is the end anchor system (3) with a buoy (20) connected to

the anchor allowing the lifting or the tensioning of the fabric, as well as in section, the rigid end axis and the shade fabric (1).

The present process provides a new solution to the range of solutions for eradicating or controlling rooted aquatic plants.

It finds its application in the maintenance of bodies of water, seabed or freshwater increasingly colonized by aquatic species of external origin specially colonizing.

Claims (9)

Claims: 1) Method for eradicating rooted aquatic plants by blocking photosynthesis, characterized in that it consists in using shade cloth (s) (1) fixed on the surface of meadows or tufts of rooted aquatic plants.  2) Method according to claim 1 characterized in that the shade cloth (1) is ballasted on its edges and its internal surface by lead braids (4) or any other ballasting means.  3) Method according to claims 1 and 2 characterized in that the ends of the shade cloth are provided with rigid pins (2) connected to anchoring and tensioning means (3).  4) Method according to claims 1,2, 3 taken together characterized in that the shade cloths (1) are provided with gas exhaust holes (15).  5) A method of eradication according to claims 1,2, 3,4 taken together, characterized in that the shade cloth is provided with fixing means (6) such as anchor plugs positioned in eyelets (5) located at the edge of the fabric (1).  6) A method of eradication according to claims 1, 2, 3, 4 and 5 taken together, characterized in that an elastic braid (7) is threaded in the eyelets (5) located on each side of the fabric (1), elastic braid stretched towards the outside of the canvas and fixed by anchor plugs (6).  7) Method according to claims 1 to 6 characterized in that the shade cloth (1) is provided with transverse stiffening rods (8) housed in fastening means such as an assembly consisting of pockets (9) located on the edges of the fabric and loops (10), or sleeves (11) provided with closure systems (12).  8) Method according to claims 1 to 7 according to which the installation of the shade cloth (1) is carried out using a boat, characterized in that, during the pose, the shade cloth (1) is pressed to the ground by a weighted cylindrical bar or a weighted roller (19) articulated by arms (19) on the boat.  9) Method according to claims 1 to 8 taken together characterized in that additional fixed bars (16) are positioned on the canvas (1) and fixed by anchor plugs (6) plugged into holes (17) located at ends of bars.