WO2012104237A2

WO2012104237A2 - Herbicidal compositions

Info

Publication number: WO2012104237A2
Application number: PCT/EP2012/051410
Authority: WO
Inventors: Carl Andrew Formstone; Andrew James Pierce; Rupert Heinrich Sohm
Original assignee: Syngenta Limited; Syngenta Participations Ag
Priority date: 2011-02-01
Filing date: 2012-01-30
Publication date: 2012-08-09
Also published as: WO2012104237A3; GB201101743D0

Abstract

The present invention relates to aherbicidal composition comprising (i) an aluminium, copper and/or iron salt of an auxin herbicide, especially dicamba, and (ii) an ammonium containing water conditioner, especially one selected from the group consisting of ammonium sulphate (AMS), urea ammonium nitrate (UAN) and diammonium phosphate (DAP). The invention further provided a method of selectively controlling weeds at a locus comprising crop plants and weeds, wherein the crop plants comprisea auxin resistance gene,the method comprisingapplication to the locus of a weed controlling amount of a herbicidal composition comprising (i) an aluminium, copper and/or iron salt of an auxin herbicide, especially dicamba, and (ii) an ammonium containing water conditioner, especially one selected from the group consisting of ammonium sulphate (AMS), urea ammonium nitrate (UAN) and diammonium phosphate (DAP).

Description

HERBICIDAL COMPOSITIONS

The present invention relates to improved herbicidal compositions. It is known that the efficacy of certain herbicidal compounds, especially those which are weak acids (for example 2,4-D, dicamba and glyphosate), can be adversely affected by "hard water". More specifically certain salts, e.g. calcium, magnesium, sodium and potassium salts, often present in "hard water" supplies antagonise these weak acid herbicides. In the case of glyphosate, the antagonism is thought to be due to the formation of undesirable glyphosate salts e.g calcium / sodium salts during the application process which are poorly absorbed by plants. To ameliorate this problem, these weak acid herbicides are often applied in conjunction with a water conditioner. Thus, with regard to glyphosate for example, ammonium containing water conditioners such are ammonium sulphate are often added to herbicidal tank mix as it has been observed that, addition of such a water conditioner at the correct amount, reduces the antagonism. It is understood that the addition of the ammonium sulphate leads to the formation of the ammonium glyphosate salt, which is more readily taken up by plants.

Accordingly, the addition of ammonium containing water conditioners to spray tanks has become a widely adopted agricultural practice, especially in respect of weak acid herbicides and especially in "hard water" areas.

The present invention is based upon the finding that this practice does not appear to be compatible with regard to all weak acid herbicides. In particular we have found that the use of ammonium containing water conditioners in conjunction with weak acid auxin herbicides (e.g dicamba), or certain salts thereof, can lead to undesirable vapour movement of the auxin herbicide. Vapour movement of auxin herbicides, and the associated disadvantages is reported in the art (e.g Behren R, and Lueschen W.E (1979) Weed Science 27, No. 5, pp 486-493). However it appears that the problem is exacerbated when the auxin herbicide is applied in conjunction with an ammonium containing water conditioner.

As mentioned above, ammonium containing water conditioners are widely used in conjunction with glyphosate herbicides - and thus the present invention has particular utility in providing improved mixtures of glyphosate and auxin herbicides. The ability to use of such mixtures is likely to become increasingly important as crops engineered to be resistant to both auxin and glyphosate herbicides are introduced into the marketplace. The herbicidal compositions of the present invention thus improve the compatibility of auxin herbicides with ammonium containing water conditioners, which in turn improves compatibility with glyphosate herbicides.

Thus according to the present invention there is provided a herbicidal composition comprising:-

(i) an aluminium, copper and/or iron salt of an auxin herbicide and

(ϋ) an ammonium containing water conditioner.

In a preferred embodiment of the present invention the auxin herbicide is selected from the group consisting of 2,4-dichlorophenoxyacetic acid (2,4-D,), 4-(2,4- dichlorophenoxy)butanoic acid (2,4-DB), 4-chloro-2-methylphenoxy)acetic acid (MCPA) and dicamba, especially dicamba.

Aluminium, copper and/or iron salts of auxin herbicides are known in the art. For example aluminium dicamba is disclosed in US 3,923,849. Thus, in a preferred embodiment of the present invention the auxin herbicide is aluminium dicamba. In the context of the present invention it should be appreciated that the salt can exist in different forms depending on the valency of the metal cation. For example, with regard to Al-dicamba the salt may be, for example, provided as AlCCeltOCHaCfeCOi) (OH)₂ or AlCCeltOCHaCfeCOiMOH). The synthesis of the different salts is described in US 3,923,849.

Various ammonium containing water conditioners are known in the art, perhaps the best examples being ammonium sulphate (AMS), urea ammonium nitrate (UAN) and diammonium phosphate (DAP). Thus, in a preferred embodiment of the present invention the ammonium containing water conditioner is selected from the group consisting of ammonium sulphate (AMS), urea ammonium nitrate (UAN) and diammonium phosphate (DAP). In a particularly preferred embodiment the ammonium containing water conditioner is ammonium sulphate.

The skilled person will appreciate that the composition of the present invention can be provided in a variety of forms. Furthermore, the composition may take the form of a ready to use "tank mix" or a concentrated "pre-mix". The actual concentration of the auxin herbicide in the tank can vary - and will depend on the specific nature of the herbicide and the intended utility. Typically, the tank mix will contain from 0.05% to 1% of the auxin herbicide. Likewise the concentration of the ammonium containing water conditioner can vary, but will typically be from 0.1% to 5%. In the context of a concentrate "pre-mix" it is preferred that the composition is in the form of a solid wettable granule (WG) or an aqueous suspension concentrate (SC). Again, the concentration of the components can vary, however in a wettable granule the auxin herbicide will be present from 1% to 90% and the ammonium containing water conditioner from 10% to 90%. With regard to a suspension concentrate, the auxin herbicide will typically be present from 1% to 90% and the ammonium containing water conditioner from 10% to 90%. It should be appreciated that, in the context of an "aqueous" composition, it is possible for the salts comprised in the composition to dissociate depending, inter alia, on the solubility and concentration of the salts in the specific aqueous composition. Thus, for the avoidance of doubt, the composition of the present invention includes the situation wherein the auxin salt and/or ammonium containing water conditioner are in a dissociated state.

In another embodiment of the present invention, the herbicidal composition further comprises an additional pesticidal ingredient. The additional pesticidal ingredient may be present from 1% to 50%. Examples of additional pesticidal ingredients include herbicide(s), herbicide safener(s), fungicide(s) and insecticide(s). Particularly preferred additional pesticidal ingredients in the context of the composition of the present invention include alachlor, acetochlor, metolachlor, S-metolachlor, mesotrione, bicyclopyrone, tembotrione, tompramezone, glyphosate, glufosinate or, where appropriate, agriculturally acceptable salts of said herbicides. In a particularly preferred embodiment the additional pesticidal ingredient is glyphosate or an agriculturally acceptable salt thereof. Examples of agriculturally acceptable salts of glyphosate include potassium, isopropylamine, monoethanolamine, n- propylamine, methylamine, ethylamine, ammonium, diammonium, hexamethylenediamine, dimethylamine or trimethylsulfonium salts. Where the additional pesticidal ingredient is glyphosate, or an agriculturally acceptable salt thereof, it is preferred that this be present in the tank mix composition from 0.25% to 3% - and in a pre-mix composition from 10% to 40%). The glyphosate : auxin ratio in the composition will typically be from 1 : 1 to 10: 1.

The present invention further provides a method of preparing a tank-mix herbicidal composition, said method comprising admixing in a suitable container:-

(i) water in an amount suitable for application to the relevant locus; (ii) a herbicidally effective amount of a concentrate herbicidal composition comprising an aluminium, copper and/or iron salt of an auxin herbicide;

(iii) an ammonium containing water conditioner.

In another embodiment of the invention the method further comprises addition of a herbicidally effective amount of glyphosate or an agriculturally acceptable salt to the tank- mix herbicidal composition.

The present invention still further provides a method of selectively controlling weeds at a locus comprising crop plants and weeds, wherein the crop plants comprise a auxin resistance gene, the method comprising application to the locus of a weed controlling amount of a herbicidal composition comprising (i) an aluminium, copper and/or iron salt of an auxin herbicide and (ii) an ammonium containing water conditioner.

Several possible auxin resistance genes are known in the art. For example, US 7,022,896 teaches resistance genes which encode a dicamba-degrading oxygenase and which impart tolerance to dicamba. US 6,153,401 teaches a 2,4-D monooxygenase gene (tfdA) whilst WO05/107437 and WO07053482, for example, teach aryloxyalkanoate dioxygenase (AAD) genes which impart tolerance to herbicides such as 2,4-D.

Thus, in a preferred embodiment the auxin resistance gene is a dicamba-degrading oxygenase such as disclosed in US 7,022,896 and the auxin herbicide is dicamba. In an alternative embodiment the auxin resistance gene is an aryloxyalkanoate dioxygenase as taught in, for example, WO05/107437, WO07053482 and the auxin herbicide is 2,4-D.

The skilled person will appreciate that the term "weed controlling amount" will vary depending on the nature of the auxin herbicide and the weeds to be controlled. Typically, a "weed controlling amount" of an auxin herbicide applied to the locus will be from 100 to 2500 grams acid equivalent (gae)/ha. The ammonium containing water conditioner will typically be applied from 0.20 to lOkg/ha, more preferably from 0.25 to 5kg/ha.

In an especially preferred embodiment of the invention, the crop plants further comprise a glyphosate resistance gene and the herbicidal composition further comprises glyphosate of an agriculturally acceptable salt thereof. Again, numerous glyphosate resistance genes are known in the art, for example EPSP synthases such as those disclosed in US 5,804,425 and US 6,566,587 and glyphosate acetyl transferases, such as those disclosed in WO02/036782.

The glyphosate herbicide will typically be applied from 560 to 3360 gae/ha.

The crop plant may be selected from the group consisting of corn, soybean, wheat, barley, sugar beet, rice and sugar cane. In a particularly preferred embodiment the crop plants are soybean plants.

In the context of the method the locus can be any place that the crop plant and/or weeds may grow - typically a field. The composition may be applied to the locus as a pre- emergence application or as a post-emergence application. Where the composition further comprises glyphosate or an agriculturally acceptable salt therefore it is preferred that the composition be applied post-emergence.

EXAMPLE 1

Wind tunnel test.

A wind tunnel test was performed to assess the effect of co-application with AMS on the volatilisation of sodium and aluminum salts of dicamba. The following treatments are prepared.

• TREATMENT A Dicamba-Na

• TREATMENT B Dicamba-Na + 0.5% AMS

• TREATMENT C Dicamba-Al · TREATMENT D Dicamba-Al + 0.5% AMS

8 x 2μ1 (each 2μ1 sample containing 2.8 μg acid equivalent dicamba in water) droplets are applied using a micro-applicator to each glass microscope slide with three slides included per time point. Once the deposits have dried, they are distributed throughout the wind tunnel to compensate for differences in the set temperature (60°C) and wind speed at different levels. Three slides are removed for each treatment at a given sampling time. The residual material is removed from the slide with 50/50 MeCN/0.1% H₃P0₄ and analysed by LC. A plot of %T0 (slides not incubated) v. time allows T50 (time for loss of first 50% of dicamba) to be calculated. The results obtained are shown below.

The results obtained show that ammonium sulphate (AMS) increases the rate of volatilisation of sodium dicamba but not aluminium dicamba.

Example 2. Bioassay

The aim of this study was to investigate the vaporisation of sodium, aluminium and dimethylamine (DMA) dicamba in the presence/absence of ammonium sulphate (AMS).

A bioassay looking at the effect of vapour on tomato seedlings was used to record symptoms over a seven day period. Tomato seedlings (Ailsa craig) were grown on agar to 2/3 true leaf.

Samples are prepared then prepared as follows.

Foil squares were treated with droplets of Treatment A Dicamba-DMA (2 mg)

Treatment B Dicamba-DMA (2 mg) + 0.5% AMS

Treatment C Dicamba-Na (2 mg)

Treatment D Dicamba-Na (2 mg) + 0.5% AMS Treatment E Dicamba- Al (2 mg)

Treatment F Dicamba- Al (2 mg) + 0.5% AMS

Two dishes of seedlings were placed with a foil square in a humidity chamber and the chambers placed in a growth room (24°C day, 18°C night). Symptoms on the tomato seedlings are recorded after 7 days. The results obtained are shown in the table below.

The results show that sodium dicamba does not exhibit any vapour movement unless AMS was added. In this test dimethylamine dicamba showed some vapour movement in the absence of AMS, but the movement was increased significantly in the presence of AMS. There was no evidence of vapour movement with regard to aluminium dicamba in the presence or absence of AMS.

Example 3.

Bioassay An experiment is conducted to look at the effect of various ammonium containing water conditioners on sodium dicamba. The experimental conditions are as outlined in Example 2 above.

The foil squares were treated with droplets of

Treatment 3A Dicamba-Na (2 mg) + 0.5% ammonium sulphate Treatment 3B Dicamba-Na (2 mg) + 0.6% urea ammonium nitrate Treatment 3C Dicamba-Na (2 mg) + 0.5% diammonium phosphate

Treatment 3D Dicamba-Na (2 mg) + 0.5% potassium citrate

The results show that sodium dicamba exhibits vapour movement in the presence of various ammonium containing water conditioners. However, no vapour movement is observed in the presence of a non-ammonium containing water conditioner (potassium citrate).

Claims

What is claimed is:-

1. A herbicidal composition comprising (i) an aluminium, copper and/or iron salt of an auxin herbicide and (ii) an ammonium containing water conditioner.

2. A herbicidal composition according to claim 1, wherein (i) is an aluminium salt of an auxin herbicide.

3. A herbicidal composition according to any one of the previous claims, wherein the auxin herbicide is selected from the group consisting of 2,4-D, dicamba and MCPA.

4. A herbicidal composition according to any one of the previous claims, wherein the ammonium containing water conditioner is selected from the group consisting of ammonium sulphate (AMS), urea ammonium nitrate (UAN) and diammonium phosphate (DAP).

5. A herbicidal composition according to any one of the previous claims, wherein the herbicidal composition is an aqueous suspension concentrate or a solid wettable granule.

6. A herbicidal composition according to any one of the previous claims, wherein the herbicidal composition further comprises an additional pesticidal ingredient.

7. A herbicidal composition according to claim 6, wherein the additional pesticidal is glyphosate or an agriculturally acceptable salt thereof.

8. A herbicidal composition according to claim 7, wherein the glyphosate is a salt

selected from the group consisting of potassium, isopropylamine, monoethanolamine, n-propylamine, methylamine, ethylamine, ammonium, diammonium,

hexamethylenediamine, dimethylamine and trimethylsulfonium salt.

9. A method of preparing a tank-mix herbicidal composition, said method comprising admixing in a suitable container: - (i) water in an amount suitable for application to the relevant locus;

(ii) a herbicidally effective amount of a concentrate herbicidal composition comprising an aluminium, copper and/or iron salt of an auxin herbicide; (iii) an ammonium containing water conditioner.

10. A method according to claim 9, wherein a herbicidally effective amount of glyphosate or an agriculturally acceptable salt therefore is further added to the tank-mix composition.

11. A method of selectively controlling weeds at a locus comprising crop plants and

weeds, wherein the crop plants comprise an auxin resistance gene, the method comprising application to the locus of a weed controlling amount of a herbicidal composition comprising (i) an aluminium, copper and/or iron salt of an auxin herbicide and (ii) an ammonium containing water conditioner.

12. A method according to claim 11, wherein the crop plants further comprise a

glyphosate resistance gene and the herbicidal composition further comprises glyphosate of an agriculturally acceptable salt thereof.

13. A method accordingly to claim 12, wherein the crop plants are soybean plants.