Molluscicidal particle, bait and method of controlling harmful molluscs

Abstract

A molluscicidal particle formed of a solid including at least one metallic compound, including at least one metal selected from the group formed by iron, copper, zinc and aluminum, the solid being suitable for use as an ingested poison for harmful molluscs. The solid includes metaldehyde in a proportion which can vary towards the interior of the solid.

Claims

1. A molluscicidal particle formed from a solid suitable for use as an ingested poison for harmful mollusks, said solid comprising metaldehyde and at least one metallic compound, the metallic compound comprising at least one metal selected from the group consisting of iron, copper, zinc and aluminum, wherein the solid comprises metaldehyde in a proportion that increases towards the interior of said metaldehyde containing solid, wherein the at least one metallic compound is present in the solid of the outer surface layer of the particle in a mass proportion greater than the mass proportion of metallic compound in the inner core, and wherein the distribution of metaldehyde in the solid of the particle being so chosen to yield an enhanced molluscicide efficiency against harmful mollusks consuming a molluscicide amount of said solid within a period of 3 days at the maximum following the onset of consumption of the solid by said harmful mollusks and affording a rapid protection of plants and crops against said harmful mollusks.

2. The molluscicidal particle according to claim 1 wherein, the solid comprises metaldehyde in a proportion that varies discontinuously towards the interior of said metaldehyde containing solid, the molluscicidal particle is formed from an outer surface layer and an inner core inscribed within the outer surface layer and enveloped thereby, said outer surface layer and said inner core being formed from two solids containing different proportions of metaldehyde, the proportion of metaldehyde in the outer surface layer is less than the proportion of metaldehyde in the inner core, and the at least one metallic compound is present in the solid of the outer surface layer of the particle in a mass proportion greater than the mass proportion of metallic compound in the inner core.

3. The particle according to claim 2, wherein the particle is of substantially spherical shape and said proportion of metaldehyde varies in any radial direction of the particle towards the interior of the solid.

4. The particle according to claim 2, wherein the at least one metallic compound is iron phosphate.

5. The particle according to claim 2, wherein the solid comprises at least one complexing agent selected from the group consisting of polyorganic acids, salts of polyorganic acids, esters of polyorganic acids and mixtures in all proportions of at least two thereof.

6. The particle according to claim 2, wherein: the outer surface layer comprises iron phosphate and ethylenediamine-N,N,N,N-tetraacetic acid (EDTA), said outer surface layer being free of metaldehyde; and the inner core comprises metaldehyde and is free of iron phosphate and of ethylenediamine-N,N,N,N-tetraacetic acid (EDTA).

7. The particle according to claim 6, wherein the iron phosphate is present in the outer surface layer in a mass proportion of about 6%, and the metaldehyde is present in the inner core in a mass proportion of about 1.5%.

8. A solid molluscicidal bait in divided form comprising at least one molluscicidal particle according to claim 2.

9. A process for controlling harmful mollusks, comprising providing an effective amount of the molluscidal bait according to claim 8 to harmful mollusks, said molluscicidal bait being in divided form comprising at least one molluscicidal particle formed from a solid suitable for use as an ingested poison for harmful mollusks, said solid comprising metaldehyde and at least one metallic compound, the metallic compound comprising at least one metal selected from the group consisting of iron, copper, zinc and aluminum, wherein the solid comprises metaldehyde in a proportion that increases towards the interior of said metaldehyde containing solid, and the distribution of metaldehyde in the solid of a particle being so chosen to yield an enhanced molluscicide efficiency against harmful mollusks consuming a molluscicide amount of said solid within a period of 3 days at the maximum following the onset of consumption of the solid by said harmful mollusks and affording a rapid protection of plants and crops against said harmful mollusks.

10. A molluscicidal particle formed from a solid suitable for use as an ingested poison for harmful mollusks, said solid comprising metaldehyde and at least one metallic compound, the metallic compound comprising at least one metal selected from the group consisting of iron, copper, zinc and aluminum, wherein the solid comprises metaldehyde in a proportion that increases towards the interior of said metaldehyde containing solid, wherein the at least one metallic compound is present in the solid of the outer surface layer of the particle in a mass proportion greater than the mass proportion of metallic compound in the inner core, and wherein the solid comprises metaldehyde in a proportion that varies continuously towards the interior of said solid.

11. A process for controlling harmful mollusks, comprising providing an effective amount of a molluscidal bait to harmful mollusks, said molluscicidal bait being in divided form comprising at least one molluscicidal particle formed from a solid suitable for use as an ingested poison for harmful mollusks, said solid comprising metaldehyde and at least one metallic compound, the metallic compound comprising at least one metal selected from the group consisting of iron, copper, zinc and aluminum, wherein the solid comprises metaldehyde in a proportion that varies discontinuously towards the interior of said metaldehyde containing solid, the molluscicidal particle is formed from an outer surface layer and an inner core inscribed within the outer surface layer and enveloped thereby, said outer surface layer and said inner core being formed from two solids containing different proportions of metaldehyde, the proportion of metaldehyde in the outer surface layer is less than the proportion of metaldehyde in the inner core, and the at least one metallic compound is present in the solid of the outer surface layer of the particle in a mass proportion greater than the mass proportion of metallic compound in the inner core, the distribution of metaldehyde in the solid of a particle being so chosen to yield an enhanced molluscicide efficiency against harmful mollusks consuming a molluscicide amount of said solid within a period of 3 days at the maximum following the onset of consumption of the solid by said harmful mollusks and affording a rapid protection of plants and crops against said harmful mollusks.

Description

EXAMPLE 1COMPARATIVE TESTS OF THE TOXICITY OF THE BAITS ON GREY SLUGS (DEROCERAS RETICULATUM) UNDER CONTROLLED CONDITIONS

(1) Tests on grey slugs are performed with the following baits: bait free of active material (control), control baits comprising metaldehyde in a mass proportion of 4% (ME 4%) or of 2.5% (ME 2.5%). The ME 4% and ME 2.5% baits contain metaldehyde homogeneously distributed throughout the volume of the solid of the bait particles; control (FeP/EDTA) bait comprising iron phosphate in a mass proportion of 3% and EDTA (ethylenediamine-N,N,N,N-tetraacetic acid) in an equimolar proportion with the iron of the iron phosphate. The (FeP/EDTA) bait contains iron phosphate and EDTA distributed homogeneously throughout the volume of the solid of the bait particles; control FeP 1%/EDTA/ME 1% and FeP 2%/EDTA/ME 1% baits comprising iron phosphate in a mass proportion of 1% and 2%, respectively, EDTA (ethylenediamine-N,N,N,N-tetraacetic acid) in an equimolar proportion with the iron of the iron phosphate, and metaldehyde in a mass proportion of 1%. The FeP 1%/EDTA/ME 1% and FeP 2%/EDTA/ME 1% baits contain iron phosphate, EDTA and metaldehyde distributed homogeneously throughout the volume of the solid of the bait particles.

(2) The above tests are performed as comparative tests: a test performed with a two-layer bait (TL FeP 2%/EDTA/ME 1%) according to the invention comprising iron phosphate in a mass proportion of 2%, EDTA in an equimolar proportion with the iron of the iron phosphate, and metaldehyde in a mass proportion of 1%, and formed from an inner core comprising metaldehyde and from an outer surface layer comprising iron phosphate and EDTA, and a test performed with a two-layer bait (TL ME 1%/FeP 2%/EDTA) according to the invention comprising iron phosphate in a mass proportion of 2%, EDTA in an equimolar proportion with the iron of the iron phosphate, and metaldehyde in a mass proportion of 1%, said bait being formed from an inner core comprising iron phosphate and EDTA, and an outer surface layer comprising metaldehyde.

(3) The two-layer bait TL FeP 2%/EDTA/ME 1% according to the invention has an inner core forming about of the volume of the bait and comprising the metaldehyde of the bait, and an outer surface layer forming about of the volume of the bait and comprising the iron phosphate and the EDTA. The mass proportion of iron phosphate in the outer surface layer is then about 6%, the EDTA being present in the outer surface layer in equimolar proportion relative to the iron of the iron phosphate. The mass proportion of metaldehyde in the inner core is about 1.5%.

(4) The two-layer bait TL ME 1%/FeP 2%/EDTA has an inner core forming about of the volume of the bait and an outer surface layer forming about of the volume of the bait. The mass proportion of metaldehyde in the outer surface layer is then about 3%. The mass proportion of iron phosphate in the inner core is about 3%, the EDTA being present in the inner core in equimolar proportion relative to the iron of the iron phosphate. In the two-layer bait (TL ME 1%/FeP 2%/EDTA), the proportion of metaldehyde decreases towards the interior of the solid.

(5) The overall compositions of the baits described above are given in Table 1 below, in which the percentages are mass percentages relative to the total mass of the bait.

(6) TABLE-US-00001 TABLE 1 Bait composition Wheat Metal- Iron Fe/EDTA Bait flour dehyde phosphate (mol) Control 100% 0 0 0 ME 4% 96% 4% 0 0 ME 2.5% 97.5%.sup. 2.5%.sup. 0 0 FeP/EDTA 90.9%.sup. 0 3% 1 FeP 1%/EDTA/ME 1% 96% 1% 1% 1 FeP 2%/EDTA ME 1% 93% 1% 2% 1 TL FeP 2%/EDTA/ME 1% 96% 1% 1% 1 TL ME 1%/FeP 2%/EDTA 96% 1% 1% 1

(7) The results of the toxicity tests performed three times are given in Table 2 below in which CMMR, % represents the cumulative mean mortality rate of the grey slugs and BC represents the mean value of the mass (in milligrams) of bait consumed by each slug.

(8) TABLE-US-00002 TABLE 2 Test duration 3 days 8 days Active material CMMR, % CMMR, % BC, mg Control 0 3 18 ME 4% 10 81 6.72 ME 2.5% 6 72 7.57 FeP/EDTA 58 92 9.97 FeP 1%/EDTA/ME 1% 28 79 4.43 FeP 2%/EDTA/ME 1% 64 91 4.21 TL FeP 2%/EDTA/ME 1% 72 93 4.11 TL ME 1%/FeP 2%/EDTA 24 77 3.79 FeP = iron phosphate; ME = metaldehyde; EDTA = ethylenediamine-N,N,N,N-tetraacetic acid; the percentages are mass percentages.

(9) With the two-layer bait according to the invention, a CMMR, % value of 93% is observed at 3 days and at 8 days, which is higher than the CMMR, % value (92%) observed with the FeP/EDTA bait, but with an amount of bait according to the invention consumed by the slugs (4.11 mg) which is 2.4 times smaller than the amount (9.97 mg) of this control bait. A two-layer bait according to the invention has efficacy at 3 days and at 8 days that is improved for a reduced amount of bait consumed.

EXAMPLE 2TOXICITY ON BLACK SLUGS (ARION HORTENSIS) UNDER CONTROLLED CONDITIONS

(10) The results of toxicity tests performed three times under controlled conditions are given in Table 2 below, in which the CMMR, % represents the cumulative mean mortality rate of the black slugs and BC represents the mean value of the mass (in milligrams) of bait consumed by each black slug.

(11) TABLE-US-00003 TABLE 3 Test duration Active material 3 days 8 days in the bait CMMR, % CMMR, % BC, mg Control 0 1 18.18 ME 4% 12 78 9.16 ME 2.5% 10 68 10.50 FeP/EDTA 14 80 9.21 FeP 2%/EDTA/ME 1% 11 79 7.95 TL FeP 2%/EDTA/ME 1% 27 91 7.57

(12) By treating the slugs with the bait according to the invention (TL FeP 2%/EDTA/ME 1%), CMMR values at 3 days and at 8 days are obtained that are higher (27%, 91%) than the CMMR values at 3 days and at 8 days obtained with the FeP 2%/EDTA/ME 1% bait (11%, 79%), with the FeP/EDTA bait (14%, 80%) and with the ME 4% (12%, 78%) or ME 2.5% baits (10%, 68%). In addition, such an improved CMMR value is obtained with a mean amount (7.57 mg) of bait consumed (BC) by each slug that is smaller than the amount (7.95 mg) of FeP 2%/EDTA/ME 1% bait, than the amount (9.21 mg) of FeP/EDTA bait, than the amount (10.50 mg) of ME 2.5% bait and than the amount (9.16 mg) of ME 4% bait consumed by each slug.

(13) The two-layer bait according to the invention has efficacy at 3 days and at 8 days that is improved for a reduced amount of bait consumed.

EXAMPLE 3TOXICITY ON GREY SLUGS UNDER SEMI-CONTROLLED CONDITIONS

(14) The results of the tests repeated five times are given in Table 4 below in which CMMR, % represents the cumulative mean mortality rate and AM (in g/ha) represents the mass (in grams) of active material (iron phosphate or metaldehyde or iron phosphate and metaldehyde) applied per hectare of treated surface.

(15) TABLE-US-00004 TABLE 4 Treatment duration AM, 4 days 8 days Active material g/ha CMMR, % Ratio CMMR, % Ratio Control 0 8.8 nd 18 nd ME 4% 200 61.6 0.308 73 0.365 ME 2.5% 125 58 0.464 70 0.56 FeP/EDTA 210 68.4 0.326 82 0.39 FeP 150 65 0.433 73 0.49 2%/EDTA/ME 1% TL FeP 150 73.4 0.489 82 0.547 2%/EDTA/ME 1% (nd: not defined)

(16) By treating the slugs with the bait according to the invention (TL FeP 2%/EDTA/ME 1%), a cumulative mean mortality rate (CMMR, %) after 4 days and 8 days of treatment is obtained which is greater than or equal to (73.5% and 82%, respectively) the CMMR observed with the FeP 2%/EDTA/ME 1% bait (65% and 73%, respectively) and the CMMR observed with the FeP/EDTA bait (68.4% and 82%, respectively), but with an amount (150 g/ha) of active material (AM) applied that is smaller than the amount (210 g/ha) of active material of the FeP/EDTA bait. The Ratio columns of Table 4 show the CMMR, % values relative to the amount of active material (AM) applied and reflecting the improved efficacy of the bait according to the invention. These results demonstrate the advantage in terms of efficacy afforded by the TL FeP 2%/EDTA/ME 1% bait according to the invention relative to a bait in which the active material(s) has (have) a homogeneous distribution.

EXAMPLE 4TOXICITY ON GREY SLUGS UNDER SEMI-CONTROLLED CONDITIONS

(17) The results of the toxicity tests on slugs under semi-controlled conditions repeated three times are given in Table 5 below in which CMMR, % represents the cumulative mean mortality rate and AM (in g/ha) represents the mass (in grams) of active material (iron phosphate or metaldehyde or iron phosphate and metaldehyde) applied per hectare of treated surface.

(18) TABLE-US-00005 TABLE 5 Treatment duration Active material AM, 4 days 8 days in the bait g/ha CMMR, % Ratio CMMR, % Ratio Control 0 2 nd 6 nd FeP/EDTA 210 57 0.271 82 0.39 FeP 150 69 0.46 82 0.55 2%/EDTA/ME 1% TL FeP 150 73 0.487 84 0.56 2%/EDTA/ME 1% (nd: not defined)

(19) By treating the slugs with the bait according to the invention TL FeP 2%/EDTA/ME 1%, CMMR values at 4 days and at 8 days are obtained that are higher (73% and 84%, respectively) than the CMMR values observed with the homogeneous FeP 2%/EDTA/ME 1% bait (69% and 82%, respectively) and than the CMMR values observed with the FeP/EDTA bait (57% and 82%, respectively). These improved CMMR values are also obtained with amounts of applied active material (150 g/ha) that are smaller than the amount of active material (210 g/ha) applied with the FeP/EDTA bait. The Ratio columns of Table 5 show the values of the ratio between the cumulative mean mortality rate (in %) and the amount of active material applied, reflecting the efficacy of the bait. These results demonstrate the advantage in terms of efficacy afforded for a two-layer bait according to the invention.

EXAMPLE 5TOXICITY ON BLACK SLUGS UNDER SEMI-CONTROLLED CONDITIONS

(20) The results of the toxicity tests repeated twice are given in Table 6 below in which CMMR, % represents the cumulative mean mortality rate and AM (in g/ha) represents the mass (in grams) of active material (iron phosphate or metaldehyde or iron phosphate and metaldehyde) applied per hectare of treated surface.

(21) TABLE-US-00006 TABLE 6 Treatment duration Active material AM, 4 days 8 days in the bait g/ha CMMR, % Ratio CMMR, % Ratio Control 0 2 nd 3 nd FeP/EDTA 210 24 0.11 61 0.29 FeP 150 53 0.35 72 0.48 2%/EDTA/ME 1% TL FeP 150 60 0.40 76 0.51 2%/EDTA/ME 1% (nd: not defined)

(22) On treating black slugs with the TL FeP 2%/EDTA/ME 1% bait according to the invention, CMMR values at 4 days and at 8 days are obtained that are higher (60% and 76%, respectively) than the CMMR values observed with the homogeneous FeP 2%/EDTA/ME 1% bait (53% and 72%, respectively) and with the FeP/EDTA bait (24% and 61%, respectively). Such an improvement in the molluscicidal efficacy is also obtained with an amount of applied bait according to the invention (150 g/ha) that is smaller than the amount (210 g/ha) of FeP/EDTA bait.

(23) The Ratio columns of Table 6 show the CMMR, % values relative to the mass of active material (AM) applied and reflecting the efficacy of the bait. These results demonstrate the advantage afforded by a two-layer bait according to the invention on the treatment of harmful molluscs.