FR2569530A1 - FUNGICIDE COMPOSITION BASED ON TRIS ETHYL PHOSPHONATE ALUMINUM - Google Patents

Abstract

IT CONTAINS PHOSETHYL-AL AS AN ACTIVE SUBSTANCE AND AS A LOW ACID ZINC SALT STABILIZER. AQUEOUS SOLUTION FOR INJECTION INTO THE TRUNKS OF TREE CROPS.

Description

The subject of the present invention is new fungicidal compositions with

  phosphorous acid ester base and a method for combating

  fungal diseases of plants using these compositions.

  French Patent 2,254,276 describes compositions for combating fungal diseases of plants containing as active ingredient at least one salt of an alkylphosphorous acid. These compositions are effective against many phytophagous fungi such as Phycomycetes including Plasmopara viticola and various Phytophthora. In practice, it is aluminum ethyl phosphite or aluminum tris 4thyl phosphonate or Phosethyl-Al which is used commercially in the form of a wettable powder in foliar spray treatment. If this presentation is fully effective under these conditions, especially for the protection of the vine, its effectiveness is longer to manifest itself when applied curatively on attacked tropical cultures, often strongly, by Phytophthora type fungi, such as Phytophthora cinnamomi, responsible for rotting rot. avocado or citrus fruits. Indeed, the amounts absorbed by foliage poorly absorbing are relatively low, insufficient when treating previously infected trees. This requires more applications making the treatment prohibitive, in any case slow or insufficient because of the severity of the attack of fungi. It has now been found that these diseases can be effectively combated by application, in particular by injection into the tree trunks of a stabilized aqueous solution of phosethyl-Al. But this poses a problem insofar as this active substance gives rise in the middle; aqueous, hydrolysis decreasing substantially and gradually its concentration making it impossible to obtain stable concentrated aqueous compositions

in time.

  The invention therefore relates to a method of stabilizing aqueous solutions of phos4thyl A1 characterized in that is added to the aqueous solution phos4thyl A1 containing, as stabilizer, a water-soluble salt of zinc and weak acid. The invention also relates to aqueous solutions of phosethyl A1 stabilized by this process. As weak acid is meant a mineral acid or, preferably, an organic acid, for example an aliphatic acid of less than 1 to 4 carbon atoms, such as acetic, propionic or butyric acid, or else lactic acid, citric acid or an amino acid such as 'acid

ethylene diamine tetracetic.

  The amount of stabilizer depends on the nature of the stabilizer and the concentration of phosthyl Al in the aqueous composition. Indeed, if the stabilizer is either too small or too large amount, the solution is not clear which means that the stabilization of the active ingredient is insufficient with consequent corresponding limitation of efficiency. Surprisingly, it has further been found that the most appropriate amount is not that corresponding to the stoichiometry of phosethyl A1. In general, amounts between 30 and 80% of the stochiometry are suitable. For example, in the case of zinc acetate about half of the stoichiometry gives a clear, stable solution while

  the double dose gives rise to a precipitate.

  The aqueous composition according to the invention may also contain other water-soluble adjuvants such as surfactants, although this is not necessary for injectable solutions. It can also co-manage certain micronutrients that are favorable to tree growth or the fight against deficiencies, in appropriate quantities. Phosphethyl-Al is present in the compositions according to the invention at a concentration generally of between 1 and 120 g / l and preferably between 10 and 110 g / l. This solution can be applied by any appropriate treatment such as foliar spraying, root soaking. Excellent results have been obtained by injection into the trunk of diseased trees such as avocados, but the process is applicable to other trees such as citrus or hveva or cocoa. Treatment is done by first practicing

  holes distributed in the trunk of the tree.

  In a second step, a suitable amount of the aqueous solution used of Phos4thyl-Al, which may vary from 0.1 to 5 g / m 2, is injected into the holes by any suitable device, with or without pressurization.

of soil covered by foliage-

  The absorption of the liquid is slow, the liquid being maintained under pressure in the injection apparatus. When the injection is complete, it may be desirable to seal the hole or holes with a non-aggressive material against plant tissue, such as a wax that may contain adjuvants such as disinfectants to reduce the risk of introduction of secondary diseases. The number of treatments is very limited, especially in relation to the number of interventions required with foliar spraying. For example, in the first year, on a well-managed tree, an effective curative treatment is obtained with two injections, the following years, a treatment once a year sufficient to maintain the healthy or healing tree. The effectiveness of the treatment is remarkable, seriously damaged trees can be cured in 2 years, which is surprising, when we know that other systemic fungicides normally active on these fungi are ineffective injection under the same conditions. The following examples illustrate the preparation of a composition according to the invention and its application by

  injection into the trunks of diseased trees.

  The following three weight compositions are prepared by successive dissolution in water of phosphosyl-Al and the case of zinc acetate: Invention Control 1 2 Phosphethyl-Al 98% Technical ...... 102 .. 102 .. 102 Acetate of zinc dihydrate .......... -... 47 ... 70 Water ... qsp .. 1 liter ............ 948 ... 916 .. 893 The amounts of acotate added correspond respectively to half of the stoichiometric amount for composition 1 and to three quarters of this amount.

  stoichiometric for the composition 2.

  The three solutions are subjected to a stability test for 1 month at 50 ° C., at the end of which the relative degradation of the phosethyl-Al and the appearance of the solution are evaluated. The results are listed in the following table: Evaluation Criteria | I Invention I after 1 month at 50 C I I 1 2 relative degradation I Phosethyl-Al I 100% I 13% 16% I Appearance of the solution I I (initially clear) I precipitate I limpid ladle |

_.......-

  This table clearly shows that after 1 month

at 50 C:

  in the reference solution, phosethyl-Al is completely degraded and the solution precipitates. This solution is therefore neither stable nor clear; in solutions 1 and 2 according to the invention, the degradation of phosethyl-Al is acceptable; moreover, while solution 2 gives rise to a slight ladle, solution 1 is clear. So only the

  solution 1 is fully satisfactory.

  1) Fungicidal composition based on an alkylphosphorous acid salt, characterized in that it consists of an aqueous phosethyl-Al solution, containing as stabilizing agent a water-soluble salt of zinc and weak acid. 2) Composition according to claim 1 characterized in that

  that the stabilizer is zinc acetate.

  3) Composition according to one of claims 1 and 2,

  characterized in that the stabilizer is present in an amount of between 30 and 80% of the stoichiometry of the

phos4thyl A1.

  4) Composition according to one of claims 1 to 3,

  characterized in that it contains from 1 to 120 g / l of phosethyl-Al. ) Process for obtaining stable aqueous solutions

  Phosthyl Al containing agent according to one of claims 1

  at 4 characterized in that one adds to these solutions a salt

  water-soluble zinc of weak acid.

  6) A method of protecting shrubby cultures against fungal diseases characterized by injecting into

  their trunk, a composition according to one of the claims

1 to 4.