Weed control method

Abstract

The present invention relates to a method of controlling the growth of monocotyledonous weeds that are resistant to an ACCase-inhibiting herbicide other than a compound of Formula (I) at a locus, said method comprising applying to the locus a herbicide composition comprising a compound of Formula (I).

Description

[0001] WEED CONTROL METHOD

[0002] Herbicides which inhibit acetyl-CoA carboxylase (ACCase) were introduced in the mid- 1970s and are now widely used to control grass (monocotyledonous) weeds in many crops including, for example, small-grain cereal crops and rice as well as dicotyledonous crops, such as soybean. Given their convenience for managing grass weeds post-emergence, ACCase- inhibiting herbicides (ACCase herbicides - HRAC Group 1)) were quickly adopted as they provided a marked improvement over the then commonly used method of selective grass weed control. Over time, however, extensive and recurrent use of ACCase herbicides has selected for resistance in key grass weed species and resistance to ACCase herbicides is now documented in numerous grass weeds and is particularly problematic in Lolium, Alopecurus and Avena species.

[0003] Accordingly, there exists a need to provide further agricultural methods that can provide sufficient control of these problematic monocotyledonous weeds that are resistant to ACCase-inhibiting herbicides (ACCase-resistant weeds) that are currently available. Surprisingly, it has now been found that certain ACCase-inhibiting herbicides previously disclosed in WO2019 / 158666 provide exceptionally good control of such ACCase-resistant weeds. Thus, according to the present invention there is provided a method of controlling the growth of monocotyledonous weeds that are resistant to an ACCase-inhibiting herbicide other than a compound of Formula (I) at a locus, said method comprising applying to the locus a herbicide composition comprising a compound of Formula (I)

[0004] The compound of Formula (I) is known from WO2019 / 158666 and provides effective control of problematic weeds in crops, especially cereal crops. The compound of Formula (I) is also known as 3-Acetyl-9-[2,6-dimethyl-4-(1-propyn-1-yl)phenyl]-10-hydroxy-3- azaspiro[5.5]undec-9-en-8-one having CAS Number 2374705-11-8. The compound of Formula (I) can exist in an alternative form, depicted below as compound (la): also known as 3-Acetyl-9-[2,6-dimethyl-4-(1-propyn-1-yl)phenyl]-3-azaspiro[5.5]undecane- 8, 10-dione having the CAS Number 2374704-95-5. The present invention is based on the finding that the compound of Formula (I) (or (la)) is particularly effective in controlling monocotyledonous weeds that are resistant to an ACCase-inhibiting herbicide(s).

[0005] The term “locus” is simply taken to mean a location where the ACCase-resistant monocotyledonous weeds are present. Examples include gardens, pathways, railway tracks but more often the locus will be a crop cultivation area, for example a field. For the avoidance of doubt it should be understood that the locus can further comprise other weeds, including those susceptible to ACCase herbicides. Where the locus is a crop cultivation area the methods of the present invention have broad utility in the control monocotyledonous ACCase- resistant weeds in a wide variety of crop plants. For example, the herbicide composition can be applied pre-planting (before the crop is planted in the field) to control monocotyledonous ACCase-resistant weeds in a wide range of crops that are planted subsequently at the locus, including, for example, corn, cereal, cotton and soybean crops. It should be understood that the crop plant may optionally comprise a herbicide tolerance and / or insect tolerance and / or nematode tolerance trait. Furthermore, it should be appreciated that some monocotyledonous crop plants, e.g cereals, are inherently resistant to the compounds of Formula (I) and thus in this situation it is possible for the herbicide compositions to be applied whilst the crop plant is present at the locus. Such application may be made pre-emergence (where the crop has been planted at the locus but not yet emerged) or post-emergence (or “over-the-top” where the crop has emerged at the locus). It should be appreciated that a combination of pre-plant, pre- emergent and post-emergent applications are utilised, depending on the particular needs of the grower.

[0006] Thus, in a preferred embodiment of the present invention there is provided a method wherein the locus further comprises a cereal crop plant and wherein said method selectively controls the growth of the ACCase-resistant monocotyledonous weeds at the locus. Examples of such cereal crop plants include wheat, including spring and winter varieties thereof; and barley, including spring and winter varieties thereof, durum wheat, rye and triticale. Wheat is particularly preferred, and includes including herbicide resistant cereals, such as Clearfield™ Wheat. Several ACCase herbicides have now been commercialised to help growers tackle grass weeds and include, for example, cyclohexanediones (“Dims”) such as clethodim, cycloxydim, tepraloxydim; aryloxyphenoxy-propionates (“Fops”) such as clodinafop-propargyl, fenoxaprop-ethyl, haloxyfop-methyl, cyhalofop-butyl, fluazifop-P-butyl and quizalofop-ethyl; and “Dens” such as pinoxaden. ACCase-resistant weeds are characterised using suitable dose response comparisons. Such weeds can be divided into target- and non-target-based- mechanisms. Non-target-site-mechanisms (NTSR) are, for example, metabolism-based resistance mechanisms, which can be mediated, for example, via cytochrome p450 and / or glutathione-S-transferase metabolism. The methods of the present invention can be used to control monocotyledonous ACCase-resistant weeds which feature target-site and / or nontarget site resistance and have particular utility in controlling weeds that show resistance towards various FOP, DIM and DEN ACCase herbicides. NTSR ACCase-resistant weeds may also exhibit tolerance to other mode-of-action herbicides, for example acetolactate synthase (ALS)-inhibiting herbicides (HRAC Group 2).

[0007] Genetic studies have shown that resistance to ACCase herbicides can be conferred by target-site mutations within the ACCase, and the methods of the present invention are particularly suited to controlling monocotyledonous ACCase-resistant weeds featuring such target-site resistance. Target-site resistance is caused by single amino acid changes in the carboxyltransferase domain of the ACCase. Much of the early resistance work was conducted using Alopecurus myosuroides and thus the single amino acid changes, although typically conserved between species, are often characterised with regard to the plastidic Alopecurus ACCase sequence. The skilled person is aware of sequence alignment software that can be used to identify corresponding amino acids in other species.

[0008] Thus, seven different single point mutation sites have now been identified within ACCase that confer resistance: Ile1781 (11781); Typ1999 (W1999); Typ2027 (W2027); He2041 (12041); Asp2078 (D2078), Cys2088 (C2088) and Gly2096 (G2096). Furthermore, at least 14 allelic variants have thus been implicated in resistance, namely I1781 L / V / A / T; W1999C / L / S; W2027C; 12041 N / V; D2078G, C2088R and G2096A / S. It’s further understood that species can be homozygous or heterozygous for the resistance trait. It is anticipated that the compounds of Formula (I) will also be effective in controlling weeds comprising other target-site mutations within the ACCase. The skilled person will appreciate the level of resistance observed will depend on, amongst other things, the particular herbicide, recommended field rates, weed species, plant growth stages, specific amino acid changes and the number of gene copies and mutant ACCase alleles. According to the International Herbicide-Resistant Weed Database (www.weedscience.org), as of 2022 over 250 unique cases of ACCase resistant weeds have been reported, including over 50 unique cases of pinoxaden-resistant weeds. These include Alopecurus sp. (e.g Alopecurus myosuroides), Apera sp. (e.g Apera spica-venti), Avena sp. (e.g Avena fatua, Avena sterilis), Brachypodium sp. (e.g Brachypodium distachyon), Lolium sp. (e.g Lolium perenne, Lolium multiflorum, Lolium persicum and Lolium rigidum), Phalaris sp. (e.g Phalaris minor, Phalaris paradoxa), Poa sp. (e.g Poa annua), Polypogon sp. (e.g Polypogon fugax) and Setaria sp. (e.g Setaria viridis). Even more preferably the methods of the present invention are used to control ACCase resistant Alopecurus sp. (e.g Alopecurus myosuroides), Avena sp. (e.g Avena fatua, Avena sterilis) Lolium sp. (e.g Lolium perenne, Lolium multiflorum, Lolium persicum and Lolium rigidum), Phalaris sp. (e.g Phalaris minor, Phalaris paradoxa) or Setaria sp. (e.g Setaria viridis), especially in cereal crops. In many cereal growing regions ACCase herbicides are often used to control grass weeds. However, resistance to ACCase herbicides is now widely reported and is expected to grow further due to intensification and lack of alternative solutions. Methods of the present invention are particularly suited to controlling ACCase-resistant weeds, especially pinoxaden-resistant weeds, and especially those comprising a 11781 , W2027, D2078 and / or C2088 mutation(s). The ACCase-resistant weeds controlled by the methods of the present invention may also be resistant to non-ACCase herbicides, for example glyphosate and / or acetolactate synthase (ALS) inhibitors.

[0009] In the methods of the present invention, the compound of Formula(l) (or Formula la) may be applied to the locus a rate from 1 to 500 g / ai. The actual rate applied will depend on a number of considerations including, for example, the timing of application, the ACCase- resistant weed to be controlled and the growth stage etc. For pre-plant application the typical application rate could be from 25 to 500 g / ha, more preferably from 100 to 400g / ha; for a post- emergent application the typical application rate could be from 25 to 200 g / ha. Split applications to the locus of the compound of Formula (I) are envisaged, for example 200g / ha could be applied to the locus in any given growing season as a one-pass 200 g / ha application, or 2x100g / ha applications etc. It should be further understood that the herbicide compositions used in the methods of the present invention may further comprise one or more additional pesticides, for example herbicides, fungicides, insecticides and / or nematicides. In a preferred embodiment of the present invention, the herbicide composition further comprises one or more herbicides selected form the group consisting of pyroxsulam, mesosulfuron-methyl, and florasulam. The herbicide composition may also comprise an additional ACCase-inhibiting herbicides such as clodinafop (including clodinafop-propargyl), fenoxaprop (including fenoxaprop-P-ethyl) and / or pinoxaden. The composition may also comprise a safener, for example cloquintocet-mexyl or mefenpyr-diethyl. The composition may also contain adjuvants, such as Tris(2-ethylhexyl)phosphate (TEHP), methylated rape seed oil adjuvants such as Adigor®, ethoxylated sorbitan esters such as Tween®20 and Tween®80, fatty alcohol ethoxylates such as Emulsogen® MTP 090 (CAS 68002-96-0) and Marlox RT 64 (CAS68002- 96-0). Other tank mix adjuvants may also be employed, such as Assist and Ochima®.

[0010] Biological Examples

[0011] A study is conducted using individual populations of Lolium multiflorum, each homogenous population is characterised as containing one of the mutations known to be associated with resistance to ACCase herbicides (I1781 L, W2027C, D2078G, C2088R). A sensitive population was also included and was the population for which RFs were referenced to. Seeds of each population were sown in standard soil in pots. For each treatment, three replicate pots containing 20 plants per one-inch pot were sprayed at the 2-3 leaf stage. Pinoxaden and Compound (I) were each applied at 3.25, 7.5, 15, 30, 60, 120, 240 and 480 g ai / ha. The test plants were then grown in a glasshouse under controlled conditions in a glasshouse (at 24 / 16oC, day / night; 14 hours light; 65% humidity) and watered twice daily.

[0012] Plants were assessed for visual damage compared to the untreated control 21 days after application (0 = 0% damage; 100 = 100% damage). ED50 values (Estimated Dose to achieve 50% damage) were obtained from the straight line regression analysis of logit-transformed visual percent weed control against the logarithm of the rate applied. RFs were then generated from ratios of respective ED50s to the ED50 of the sensitive population.

[0013] Table 1 Resistance Factors (RFs) based on ED50 (LOLMU).

[0014] A similar study is conducted using individual populations of Alopecurus mysuroides, each homogenous population is characterised as containing one of the mutations known to be associated with resistance to ACCase herbicides (LL1781 , CC2027)). RFs were then generated from ratios of respective ED50s to the ED50 of the sensitive population as described previously.

[0015] Table 2 Resistance Factors (RFs) based on ED50 (ALOMY).

[0016] A further study is conducted using individual populations of Lolium multiflorum exhibiting non target site resistance (NTSR). Two independent populations were identified in the UK and sequenced to confirm that they contain no ACCase target site mutations and are characterised as non-target site resistance as demonstrated by high resistance to the ACCase-inhibiting herbicide clodinafop. The resistance factors for clodinafop could not be determined due to the very high levels of resistance, but are estimated to be >50. Table 3 Resistance Factors (RFs) based on ED50 (LOLMU - NTSR).

Claims

CLAIMS1 . A method of controlling the growth of monocotyledonous weeds that are resistant to an ACCase-inhibiting herbicide other than a compound of Formula (I) at a locus, said method comprising applying to the locus a herbicide composition comprising a compound of Formula (I)2. A method according to claim 1 , wherein the locus further comprises a monocotyledonous crop plant and wherein said method selectively controls the growth of the monocotyledonous weeds that are resistant to an ACCase-inhibiting herbicide other than a compound of Formula (I) at the locus.

3. A method according to claim 2, wherein the crop is a cereal crop.

4. A method according to claim 3, wherein the cereal crop is wheat or barley.

5. A method according to any one of the previous claims, wherein the monocotyledonous weeds are resistant to pinoxaden.

6. A method according to any one of the previous claims, wherein monocotyledonous weeds comprise one or more mutations in the ACCase at an amino acid position selected from the group consisting of 11781 , W1999, W2027, 12041 , D2078, C2088 and G2096.

7. A method according to claim 6, wherein the monocotyledonous weeds comprise one or more mutations in the ACCase at an amino acid position selected from the group consisting of 11781 , W2027, D2078 and C2088.

8. A method according to any one of the previous claims, wherein the monocotyledonous weeds are selected from the group consisting of Alopecurus sp., Avena sp., Lolium sp., Phalaris sp. and Setaria sp.

9. A method according to claim 8, wherein the monocotyledonous weeds are selected from the group consisting of Alopecurus myosuroides, Avena fatua, Avena sterilis, Lolium perenne, Lolium multiflorum, Lolium persicum, Phalaris minor, Phalaris paradoxa and Setaria viridis.

10. A method according to claim 9, wherein the monocotyledonous weeds include Lolium multiflorum.

11. A method according to any one of the previous claims, wherein the compound of Formula (I) is applied to the locus at a rate of from 1 to 500 g / ha.

12. A method according to any one of the previous claims, wherein the herbicide composition further comprises a herbicide safener.

13. A method according to any one of the previous claims wherein the herbicide composition comprises one or more additional herbicidal compounds.

14. A method according to claim 13, wherein the one or more additional herbicides is selected from the group consisting of pyroxsulam, mesosulfuron-methyl, and florasulam.

15. Use of a compound of Formula (I)to control monocotyledonous weeds are resistant to an ACCase-inhibiting herbicide other than a compound of Formula (I).

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