Uses of thaxtomin and thaxtomin compositions as herbicides

Abstract

Disclosed herein is a bacterial secondary metabolite, thaxtomin and another herbicide as an effective herbicide combination on broadleaved, sedge and grass weeds.

Claims

1. A synergistic herbicidal composition for controlling sprangletop weeds comprising 0.1 to 0.4 mg/ml thaxtomin A and about 0.97 to about 1.45 mg/ml cyhalofop, wherein the synergistic herbicidal composition has an increased herbicidal activity against sprangletop weeds.

2. The composition according to claim 1, wherein said composition further comprises an adjuvant, a non-ionic surfactant and/or an organic solvent.

3. The composition according to claim 1, wherein said composition further comprises a non-ionic surfactant and/or an aliphatic alcohol.

4. A method for modulating the emergence, growth or both emergence and growth of sprangletop weed comprising the steps of: applying the synergistic herbicidal composition of claim 1 to at least a portion of a plant, effective to modulate the emergence, growth or both emergence and growth of said weed.

5. The method according to claim 4, wherein the weed comprises Leptochloa uninervia.

6. The method according to claim 4, wherein said weeds are modulated in a cereal growth system.

7. The method according to claim 6, wherein the cereal growth system is a rice growth system.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the structure of Thaxtomin A.

DETAILED DESCRIPTION OF THE INVENTION

(2) Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention.

(3) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.

(4) It must be noted that as used herein and in the appended claims, the singular forms a, and and the include plural references unless the context clearly dictates otherwise.

(5) Thaxtomin utilized in this invention may be derived in fermentation of the following actinomycetes cultures: S. scabiesATCC 49173, S. acidiscabiesATCC 49003 and BL37-EQ-010or it can be purchased from commercial sources.

(6) The thaxtomin utilized in the invention include but are not limited to agents described as cyclic dipeptides having the basic structure cyclo-(L-4-nitrotryptophyl-L-phenylalanyl). In embodiments, suitable diketopiperazne moieties may be N-methylated, and include congeners carrying phenylalanyl alpha andring-carbon hydroxyl groups. The chemical in a particular embodiment comprises:

(7) ##STR00001##
wherein R.sub.1 is methyl or H, R.sub.2 is hydroxy or H, R.sub.3 is methyl or H, R.sub.4 is hydroxy or H, R.sub.5 is hydroxy or H, R.sub.6 is hydroxy or H, and combinations thereof.

(8) Non limiting examples of suitable thaxtomin is for use in accordance with the present invention include but are not limited to thaxtomin A, thaxtomin A ortho isomer, thaxtomin B, thaxtomin C, hydroxythaxtomin C, thaxtomin A p-isomer, hydroxythaxtomin A and des-N-methylthaxtomin C and derivatives of any of these (See FIG. 1).

(9) The compositions of the present invention may be sprayed on the plant or applied to soil. Particular embodiments are described in the Examples, infra. These compositions may be in the form of dust, coarse dust, micro granules, granules, wettable powder, emulsifiable concentrate, liquid preparation, suspension concentrate, water degradable granules or oil suspension.

(10) The compositions of the invention do comprise a carrier and/or diluent. The term, carrier as used herein means an inert, organic or inorganic material, with which the active ingredient is mixed or formulated to facilitate its application to plant or other object to be treated, or its storage, transport and/or handling. Examples of diluents or carriers for the pre- and post-emergence herbicides include, but are not limited to, water, milk, ethanol, mineral oil, glycerol.

(11) The compositions of the present invention may comprise at least two herbicidal agents. One herbicidal agent is thaxtomin set forth above. It may be present in one embodiment thaxtomin is present in an amount ranging from about 0.01 to about 5.0 mg/mL. The other herbicidal agent may be a bioherbicide and/or a chemical herbicide. The bioherbicide may be selected from the group consisting of clove, cinnamon, lemongrass, citrus oils, orange peel oil, tentoxin, cornexistin, AAL-toxin, leptospermone, sarmentine, momilactone B, sorgoleone, ascaulatoxin and ascaulatoxin aglycone. In a particular embodiment, the composition may comprise thaxtomin, lemongrass oil and optionally a surfactant and/or vegetable oil. In another embodiment, the composition may comprise thaxtomin, sarmentine and optionally a nonionic surfactant and/or vegetable oil. The bioherbicide such as lemongrass oil or sarmentine may be present in an amount ranging from about 0.1 mg/mL to about 50 mg/mL and more preferably between about 0.5 mg/mL to about 10 mg/mL. The chemical herbicide may be selected from the group consisting diflufenzopyr and salts thereof, dicamba and salts thereof, topramezone, tembotrione, S-metolachlor, atrazine, mesotrione, primisulfuron-methyl, 2,4-dichlorophenoxyacetic acid, nicosulfuron, thifensulfuron-methyl, asulam, metribuzin, diclofop-methyl, fluazifop, fenoxaprop-p-ethyl, asulam, oxyfluorfen, rimsulfuron, mecoprop, and quinclorac, thiobencarb, clomazone, cyhalofop, propanil, bensulfuron-methyl, penoxsulam, triclopyr, imazethapyr, halosulfuron-methyl, pendimethalin, bispyribac-sodium, carfentrazone ethyl, sodium bentazon/sodium acifluorfen and orthosulfamuron.

(12) The chemical herbicide such as pendimethalin or clomazone may be present in a pre-emergent weed control application in an amount ranging from about 0.5 mg/mL to 15 mg/mL and a chemical herbicide such as cyhalofop, S-metolachlor, bispyribac-sodium, penoxsulam in a post-emergent application from about 1 mg/mL to about 40 mg/mL and more particularly between about 15 mg/ml to about 35 mg/mL. The composition may further comprise an adjuvant which may be vegetable oil comprising ethyl oleate, polyethylene dialkyl ester and ethoxylated nonylphenol. The composition may additionally comprise a surfactant to be used for the purpose of emulsification, dispersion, wetting, spreading, integration, disintegration control, stabilization of active ingredients, improvement of fluidity or rust inhibition. The choice of dispersing and emulsifying agents, such as non-ionic, anionic, amphoteric and cationic dispersing and emulsifying agents, and the amount employed is determined by the nature of the composition and the ability of the agent to facilitate the dispersion of the herbicidal compositions of the present invention.

(13) For post-emergent formulations, the formulation components used may contain smectite clays, attapulgite clays and similar swelling clays, thickeners such as xanthan gums, gum Arabic and other polysaccharide thickeners as well as dispersion stabilizers such as nonionic surfactants (for example polyoxyethylene (20) monolaurate or polysorbate 60 POE (20) sorbitan monostearate, ethylene glycol monostearate). The concentration of the clays may vary between about 0-2.5% w/w of the total formulation, the polysaccharide thickeners may range between about 0-0.5% w/w of the total formulation and the surfactants may range from about 0-5% w/w of the total formulation.

EXAMPLES

(14) The composition and method of the present invention will be further illustrated in the following, non-limiting Examples. The examples are illustrative of various embodiments only and do not limit the claimed invention regarding the materials, conditions, weight ratios, process parameters and the like recited herein.

Example 1

(15) In a pot study test in greenhouse conditions, 6-inch corn plants (Zea mays var. Sunglow) were sprayed with increasing concentrations of thaxtomin A mixed in a carrier 4% ethanol, 0.02% polysorbate 60 POE (20) sorbitan monostearate solution. The spraying solutions contained 0.125, 0.25, 0.5 and 1.0 mg thaxtomin A/mL, and the plants are sprayed until total coverage. Each treatment was done in three replicates, and a control solution consists of water with 4% ethanol and 0.02% polysorbate 60 POE (20) sorbitan monostearate as a surfactant. Prior to and after treatments, plants are grown in a greenhouse under artificial lights (12-h light/dark cycle) at 25 C.

(16) Plants are evaluated in one-week intervals starting at 7 days after treatment. The final evaluation is done three weeks after treatment, at which time point, no phytotoxicity is observed in any of the test plants even at the highest thaxtomin A concentration.

Example 2

(17) A pot study is conducted to test the phytotoxicity of thaxtomin A on corn (Zea mays var. Early Sunglow) and wheat (Triticum aestivum var. PR1404). To confirm the activity on broadleaf weeds, pigweed (Amaranthus sp.) is planted in the same pot with either three corn or five wheat seeds, and sprayed simultaneously with the cereal test plants. The less than 3-inch tall plants grown under growth lights (12-h light/12-h dark) at 28 C. are sprayed with thaxtomin A solutions derived from a liquid culture of S. acidiscabies containing 0.5, and 1.0 mg thaxtomin A per mL of solvent (4% ethanol and 0.2% non-ionic surfactant). A solution of 4% ethanol +0.2% non-ionic surfactant without thaxtomin A is used as a control treatment. Each treatment is conducted in three replicates. Treated plants are kept at 28 C. under growth lights and observed at three time points7, 14 and 21 days after treatmentfor visual symptoms of phytotoxicity on corn and wheat and % control of pigweed.

(18) At each time point, no symptoms of phytotoxicity are observed in the cereal plants treated with thaxtomin A. The highest concentration of thaxtomin A (1.0 mg/mL) results in a complete control of pigweed grown in the same pots with corn and wheat.

Example 3

(19) To test the phytotoxicity of thaxtomin A on sorghum plants, five seeds of sorghum (Sorghum Bicolor) are planted in each 44 plastic pot filled with soil. Plants were grown under optimal conditions in a greenhouse before and after treatment with solutions containing 0.5 and 1.0 mg thaxtomin A /mL. At the time of the treatment, the plants are about 3 inches tall. Each treatment is applied in three replicates, and a control treatment included plants treated with just the carrier (4% EtOH, 0.02% polysorbate 60 POE (20) sorbitan monostearate). Evaluations for phytotoxicity are performed at 7-day intervals starting one week after treatment. The last evaluation is performed three weeks after the treatment at which point, no phytotoxicity is observed in the treated plants in any treatment concentration.

Example 4

(20) A strain of S. acidiscabies (ATCC-49003) is grown in oat bran broth for 5 days (25 C., 200rpm). The whole cell broth with thaxtomin A is extracted using XAD resin. The dried crude extract was resuspended in 4% ethanol and 0.02% non-ionic surfactant at a concentration of 10 mg/mL, and the solutions with two different concentrations of thaxtomin A (0.5 and 1.0 mg/mL) are tested the following broadleaf weed species:

(21) LambsquarterChenopodium album

(22) VelvetleafAbutilon theophrasti

(23) SunflowerHelianthus annuus

(24) Ragweed, CommonAmbrosia artemesifolia

(25) Pigweed , RedrootAmaranthus retroflexus

(26) Bindweed, CommonConvolvulus arvensis

(27) Mustard, WildBrassica kaber

(28) DandelionTaraxacum officinale

(29) Nightshade, BlackSolanum nigrum

(30) Mallow, CommonMalva neglecta

(31) and on the following grass weed species:

(32) FoxtailSetaria lutescens

(33) Brome, DownyBromus tectorum

(34) Bluegrass, AnnualPoa annua

(35) Bluegrass, KentuckyPoa pratensis

(36) Rye grass, Perennial(Lolium perenne L. var. Pace)

(37) Fescue, Tall(Festuca arundinaceae Schreb. var. Aztec II, Anthem II, LS 1100)

(38) Barnyard GrassEchinochloa crus-galli

(39) All plant species are tested in 44 plastic pots in three replicates. The untreated control plants are sprayed with the carrier solution (4% Ethanol, 0.02% glycosperse) and the positive control plants with Roundup at a rate corresponding to 1 fl. oz/acre. Treated plants are kept in a greenhouse under 12 h light/12 h dark conditions. Data for broadleaf species from weekly evaluations are presented in Table 1.

(40) TABLE-US-00001 TABLE 1 Weed control efficacy of a S. acidiscabies extract containing thaxtomin A on different weed species. Rating scale: 0 - no control, 1 - 10% control, 2 - 25% control, 3 - 50% control, 4 - 75% control, 5 - 100% control. THAXTOMIN SOLUTION THAXTOMIN Weed UTC 0.5 mg/mL SOLUTION 1.0 mg/mL species 7 DAYS 14 DAYS 21 DAYS 7 DAYS 14 DAYS 21 DAYS 7 DAYS 14 DAYS 21 DAYS Dandelion 0.0 0.0 0.0 2.0 2.3 4.0 2.0 2.0 3.7 Nightshade 0.0 0.0 0.0 2.7 2.2 2.3 2.7 2.0 2.3 Lambsquarter 0.0 0.0 0.0 2.0 2.0 2.0 2.0 2.0 2.0 Ragweed 0.0 0.0 0.0 1.0 0.5 0.0 1.0 0.5 0.0 Velvetleaf 0.0 0.0 0.0 1.7 1.0 1.0 2.0 1.0 0.3 Bindweed 0.0 0.0 0.0 1.0 1.0 0.0 1.2 1.0 0.0 Mustard 0.0 0.0 0.0 3.3 4.0 4.5 3.5 2.8 3.5 Sunflower 0.0 0.0 0.0 1.0 2.0 0.5 1.0 1.7 0.5 Mallow 0.0 0.0 0.0 1.0 1.0 1.0 1.2 1.0 1.0 Pigweed 0.0 0.0 0.0 3.5 4.0 4.0 4.2 3.0 3.7

(41) The extract from a bacterial culture of S. acidiscabies with a thaxtomin A concentration of 0.5 mg/mL or higher showed good efficacy (>50%) against at least three of the most common broadleaf weed species (dandelion, mustard and pigweed) in both cereal and turf growing systems. Control of some weeds such as Black nightshade and Common lambsquarter was not complete but thaxtomin A even at the lower concentration (0.5 mg/mL) results in severe stunting of these weeds. In this same study, no adverse effects are observed in grass species treated with either 0.5 or 1.0 mg/mL thaxtomin A. In all tested grass species, no phytotoxic effects were visible at even the higher thaxtomin A concentration.

Example 5

(42) The combined effect of thaxtomin A and two commercial herbicides (Bipyribac-sodium formulated as Regiment and Lemongrass oil formulated as GreenMatch EX) on small-flower umbrella sedge and watergrass is tested in a field study using small (1-sq foot) plots. All single product treatments and tank mix combinations were sprayed at 57 gal per acre. Evaluation of % control was done 14 days after treatment and the results are presented in Table 2 below. Means in each column marked with the same letter in Table 2 are not statistically different from each other at p<0.05

(43) According to the results, lemongrass oil at 1.25% weight does not improve the efficacy of thaxtomin A (at 0.25 mg/mL) on sedge but it significantly increases the efficacy on grass weeds such as watergrass (field test) and sprangletop (greenhouse test).

(44) TABLE-US-00002 TABLE 2 Effect of thaxtomin A alone and in combination with bispyribac-sodium and lemongrass oil on two rice weeds, small-flower umbrella sedge and watergrass. Sedge Watergrass Treatment control (%) control (%) Thaxtomin 0.25 mg/mL 95a 5d Thaxtomin 0.5 mg/mL 100a 5d Bispyribac-sodium 87.5a 32.5a (12 g/acre) Bispyribac-sodium (6 g/acre) 47.5c 15c Bispyribac-sodium + 67.5b 25ab Thaxtomin 0.5 mg/mL Bispyribac-sodium + 55bc 7.5c Thaxtomin 0.25 mg/mL Lemongrass oil 5% 15d 10c Lemongrass oil 2.5% 12.5d 10c Lemongrass oil 1.25% 20d 5d Lemongrass oil 1.25% + 100a 10c Thax 0.25 mg/mL Lemongrass oil 1.25% + 100a 20b Thaxtomin 0.5 mg/mL

(45) According to the results, lemongrass oil at 1.25% does not improve the efficacy of thaxtomin A (at 0.25 mg/mL) on sedge but it significantly increases the efficacy on grass weeds such as watergrass (field test) and sprangletop. Thaxtomin A (at 0.5 mg/mL) improves the efficacy of an ALS inhibitor, bipyribac sodium; used at half label rate on both sedge and grasses.

Example 6

(46) The efficacy of thaxtomin A derived from a liquid culture of S. acidiscabies is tested in a field study on rice using 4.9 sq-ft plots surrounded by a metal ring. Treatments with either thaxtomin A or thaxtomin A in combination with lemongrass oil (formulated as GreenMatch EX) or cyhalofop (formulated as Clincher CA) were done using a hand-held sprayer with a water volume corresponding to 57 gallons per acre. Rice (variety M209) was grown until maturity and harvested by hand for yield and weed count assessment. Results of yield (kg/ha), and numbers of redstem, small-flower umbrella sedge, and sprangletop in each plot are presented in Table 3 below.

(47) TABLE-US-00003 TABLE 3 Effect of thaxtomin A alone and in combination with lemongrass oil and cyhalofop on rice yield and weed control. Yield # of Treatment (kg/ha) # of redstem # of sedge sprangletop 1 7516b 10.3 0.8a 86.0a 2 7876b 0.5b 1.0a 76.0a 3 9054ab 0.3b 0.5a 69.3a 4 11296a 12.8a 0.5a 4.0b
1. UTC; 2. Thaxtomin A (180 g/acre); 3. Lemongrass oil 1.25%+thaxtomin A (90 g/acre); 4. Cyhalofop (half label rate; 52 g/acre)+thaxtomin A (90 g/acre)+veg oil 2.5% Means in each column marked with the same letter are not statistically different from each other at p<0.05.

(48) Results indicate that thaxtomin at 180 g/acre significantly reduced the number of sedges but had no effect on sprangletop or yield. When used at half rate (thaxtomin A 90 g/acre), a combination with lemongrass oil had better effect on sedges than a combination with cyhalofop (used at half label rate 52 g/acre). Good grass weed (sprangletop) control is achieved when thaxtomin (90 g/acre) is combined with cyhalofop at half the label ratethis combination also improves the yield significantly.

Example 7

(49) Cyhalofop (2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid, butyl ester) is also mixed together with adjuvant containing ethyl oleate, polyethylene dialky ester and ethoxylated nonylphenol (2.5% v/v) and increasing concentrations of thaxtomin A (purified from the ATCC strain 49003) at concentrations 0.1, 0.2 and 0.4 mg/ml. The concentrations of the 2-[4-(4-cyano--fluorophenoxy)phenoxy]propanoic acid, butyl ester before dilution are 29.6% (2.38 lb/gal) and 21.7% (2 lb/gal), respectively. The effect of these mixtures on the growth of common water plantain, red stem, smallflower sedge and sprangletop is determined in the greenhouse. Similarly, rice plants of variety M104 are grown and tested for phytotoxic effects, and all plants are evaluated 7, 14, and 21 days after treatment. Results of from the study with cyhalofop formulated as Clincher CA at the 21-day evaluation point are presented in Table 4 below.

(50) TABLE-US-00004 TABLE 4 Effect of thaxtomin A alone and with cyhalofop on rice yield and weed control Clincher CA (6.5 oz/acre) + Redstem Water- Sedge Sprangle- Thaxtomin A % plantain % top % (mg/mL) control % control control control UTC 0 0 0 0 0 - no thx A 75 8 0 90 0.1 100 85 87 100 0.2 97 87 88 100 0.4 100 85 100 100
As a conclusion, Clincher CA (29.6% cyhalofop by weight) applied at half label rate (6.5 oz/acre) has good efficacy against grass weedsnot so good on broadleaves and poor on sedges. A combination of Clincher CA (cyhalofop) and thaxtomin A provides good control of all rice weeds tested in this study. Efficacy of thaxtomin A against grass weeds is substantially improved if combined with Clincher. Combination of thaxtomin A with Clincher CA did not cause phytotoxicity on rice at any tested concentration.

Example 8

(51) Penoxsulam(2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5c]pyrimidin-2-yl)-6-trifluoromethyl)benzenesulfonamide) is mixed together with adjuvant containing ethyl oleate, polyethylene dialky ester and ethoxylated nonylphenol (2.5% v/v) and increasing concentrations of thaxtomin A (purified from the ATCC strain 49003) at concentrations 0.1, 0.2 and 0.4 mg/ml. The concentrations of the 2-[4-(4-cyano- -fluorophenoxy)phenoxy]propanoic acid, butyl ester or 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5c]pyrimidin-2-yl)-6-trifluoromethyl)benz enesulfonamide before dilution are 29.6% (2.38 lb/gal) and 21.7% (2 lb/gal), respectively. The effect of these mixtures on the growth of common water plantain, red stem, smallflower sedge and sprangletop is determined in the greenhouse. Similarly, rice plants of variety M104 are grown and tested for phytotoxic effects, and all plants are evaluated 7, 14, and 21 days after treatment.

Example 9

(52) A strain of S. acidiscabies was grown in oat bran broth for 5 days (25 C., 200 rpm). The whole cell broth was extracted using XAD resin, and the dried crude extract was resuspended in 4% ethanol and 0.2% non-ionic surfactant at a concentration of 10 mg/mL. The diluted extracts containing 0.2 and 0.4 mg thaxtomin A per mL were tested on three weed species (redstem; Ammania spp., smallflower umbrella sedge; Cyperus difformis and sprangletop: Leptochloa uninervia). Other treatments included sarmentine at 2.5 and 5.0 mg/mL, and a combination treatment containing 0.2 mg thaxtomin A and 2.5 mg sarmentine per mL. Each treatment was applied in three replicates. Treated plants were kept in a greenhouse under 12h light/12h dark conditions. Results from an evaluation performed 25 days after treatment are presented in Table 5.

(53) TABLE-US-00005 TABLE 5 Efficacy of herbicidal treatments using thaxtomin A (0.2 and 0.4 mg/mL) or sarmentine (2.5 or 5.0 mg/mL) alone or in combination (0.2 + 2.5 mg/mL) to control broadleaf, sedge and grass weeds in a greenhouse study. Control Control Control of of of sprangle- redstem sedge top treatment (%) (%) (%) UTC 0a 0a 0a Thaxtomin A 0.2 mg/mL 5.0b 48.3b 8.3ab Thaxtomin A 0.4 mg/mL 11.7c* 91.7d 10.0b Thaxtomin 0.2 + 11.7c* 61.7c 73.3c Sarmentine 2.5 mg/mL Sarmentine 2.5 mg/mL 0a 8.3a 80.0c Sarmentine 5.0 mg/mL 2.5ab 6.7a 92.3d *stunted. In a column, Means followed by the same letter are not statistically different from each other at p < 0.05.

(54) Thaxtomin A at the highest concentration of 0.4 mg/mL provides excellent control of sedge but poor control of the grass weed (sprangletop). When combined with sarmentine, the efficacy against grass weeds improves significantly. Also, efficacy against sedge is improved with the combination treatment compared with the single application of thaxtomin A alone at the corresponding concentration. In this study, the control of the broadleaf weed (redstem) is poor with all treatments.

(55) Although this invention has been described with reference to specific embodiments, the details thereof are not to be construed as limiting, as it is obvious that one can use various equivalents, changes and modifications and still be within the scope of the present invention.

(56) Various references are cited throughout this specification, each of which is incorporated herein by reference in its entirety.

Cited references

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