Patent Publication Number: US-RE28384-E

Title: Method of the control of weeds

Description:
United States Patent Re. 28,384 Reiasued Apr. 8, 1975 Matter enclosed in heavy brackets II appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.  
 ABSTRACT OF THE DISCLOSURE Methods of combating and controlling weeds using (2 nitro phenyl)-O-ethyl-N-isopropylphosphoro amido-thioate, or O (2 nitro phenyl)-O-ethyl-N-isopropyl-amido-thiono-phosphate, which is known, which pos sesses strong herbicidal properties, and which may be produced by conventional methods.  
  The present invention relates to and has for its objects the provision for particular new methods of combating and controlling weeds using 0 (2 nitro phenyl)- O ethyl N isopropyl-phosphoro-amido-thioate, or O- (2 nitro phenyl) O ethyl-N-isopropyl-amido-thionophosphate, which is known, which possesses valuable selective herbicidal properties especialy with respect to undesired weeds, active compositions in the form of mixtures of such compound with solid and liquid dispersible carrier vehicles, and methods for producing such compound, with other and further objects becoming apparent from a study of the within specification and accompanying examples.  
  It is already known that pentachloro-phenol (A), which may be designated PCP, and 2,4 dichloro phenyl 4&#39;- nitro-phenyl-ether (B), which may be designated NiP, as well as 2 chloro 4,6 bis-(ethylamine) 1,3,5 triazine (C), which may be designated CAT or Simazin, possess herbicidal properties.  
 It is furthermore known from British Pat. 659,682 that amido-thionophosphoric acid esters, generically, of the formula in which R is an alkyl or alkcnyl radical, R is an alkyl radical, R is an alkyl radical or a hydrogen atom, and one Y is a nitro radical and the other Y is a hydrogen atom or a nitro radical, possess insecticidal and fungicidal properties. In said British patent, it is indicated only that such compounds have insecticidal and acaricitlal activity as well as activity for the control of harmful fungi on plants, and that they can be used in the form of spray preparations. However, there is no actual test data showing their eflicacy, and no indication that such compounds might have herbicidal activity. Furthermore, no mention is made of the applicability of such compounds to soil or of any reason to expect them to have herbicidal activity.  
  On the other hand, US. Pat. 3,074,790 describes compounds, for example 0 (2,4 dichloro-phenyl) 0- methyl N isopropyl phosphoro-amido-thioate (D), which have herbicidal properties.  
  In accordance with applicants Japanese patent application No. 78,104/66, it has been found that a certain derivativc of this last-mentioned type of amido-thionophosphoric acid ester (which may be prepared in the same manner as the compound of the present invention) has especially excellent herbicidal activity, to wit, O-(2-nitrophenyl) 0 methyl N isopropyl-phosphoro-amidothioate of the formula:  
 t-CnnN (E) It has now been found, in accordance with the present invention, that O (2 nitro phenyl) 0 ethyl-N- isopropyl-phosphoro-amido-thioate, which is known, of the formula NO: Cut- K: l i&#39; 0- Q: isoxnlnxlt (1) alone or in admixture with a solid or liquid diluent or carrier. exhibits strong herbicidal, especially selective herbicidal. properties.  
  The compound of Formula I above may be produced by the process which comprises reacting O ethyl N- isopropyl amido thiono phosphoric acid ester halide of the formula iso-QdLNll (ii) in which Hal is a halogen atom such as chloro, bromo,  
 iodo or fluoro, especially chloro,  
 with 2-nitro-phenol, preferably in the presence of an acid binding agent, or with a salt of Z-nitro-phenol, correspondingly of the formula in which M is hydrogen, or a cation such as an ammonium or alkali metal cation, for example potassium, sodium, and the like.  
  Surprisingly, the particular compound of Formula I above according to the present invention shows both a higher and a more specific herbicidal effectiveness than the previously known compounds which are known to be usable for such purposes, such as compounds (A), (B) and (C) noted above. Such herbicidal effectiveness would not have been appreciated on the basis of the generic disclosure of related compounds for remote purposes in British Pat. 659,682. The instant compound is especially effective as a pre-emergence herbicide, and exhibits a remarkable effect in killing weeds, with only slight, if any, phytotoxic effect toward cultivated plants such as rice. The use of the instant compound in accordance with the method of the present invention therefore represents a valuable contribution to the art.  
 (III) The reaction course for producing the instant comround is illustrated by the following formula scheme:  
 n which Hail and M are the same as defined above.  
  The starting materials which may be used for the proluction reaction are clearly characterized by Formulae .I and Ill above, and are well known or readily prepared.  
  Advantageously, the instant active compound exhibits strong herbicidal potency and can therefore be used as l germination inhibiting agent or weed-killer. By weeds in he sense used herein are meant all plants which grow in ilaces where they are not desired. Whether the active :ompound according to the present invention acts as a otal or selective herbicidal agent depends on the amount applied, as the artisan will appreciate.  
  The active compound according to the present invenion can be used for example in the case of the following alants: dicotyledons, such as mustard (Sinapsis), cress fLepidium), catch weed (Galium), common chickweed fStellaria), camomile (Matricaria), French weed (Galnsoga). goose-foot (Chenopodium), stinging nettle &#39;Urtica), groundsel (Senecio), wild amaranth (Amaran- .hus), common purslane (Portulaca), cotton (Gossypurn), beets (Beta), carrots (Daucus), beans (Phaseolus), aotatoes (Solarium), coffee (Coffea), cabbage (Brassica), ;pinach (Spinacia); radish (Raphanus), cucumber (Cu- :umis), tomato (Lycopersicum); monocotyledons, such is timothy (Phleum), meadowgrass (Poa), fescue (Fesuca), finer grass (Digitaria), goosegrass (Eleusine), green foxtail (Setaria), raygrass (Lolium), cheat fBromus), barnyard grass (Echinochloa) maize (Zea), ice (Oryza), oats (Avena), barley (Hordeum), Wheat fTriticum), millet (Panicum) and sugar cane (Sac- :harum) etc: and the like.  
  The instant compound is preferably used as a selective lerbicide and especially when applied to soil before germiiation, although such compound exhibits a particularly good selectivity when applied before and after emergence, :.g. in upland and paddy fields.  
  Significantly, the active compound of the present intention is distinguished by the fact that it has little or no ahytotoxicity to rice plants or other cultivated plants alhough it is markedly effective in small dosages as com- :ared with PCP and NIP, i.e. compounds (A) and (B) toted above, etc. which have hitherto been used widely as ierbicides in paddy fields. Furthermore, the same effect is with CAT or Sirnazin, i.e. compound (C), is generally ichievable using the instant active compound without any term to crops, e.g. when applied to soil before germinaion for controlling weeds in upland fields. Especially vhen applied to soil before germination, the instant comaound is far better than the already known herbicides in bat such instant compound shows a superior selective ierbicidal activity, depending on the amount applied, with ittle or no phytotoxicity to cultivated plants.  
  Surprisingly, the instant active compound is particuarly efi&#39;ective against weeds in paddy fields, weeds of the Sraminae family, broad-leaved weeds and perennial weeds. Moreover, such active compound shows selective ierbicidal activity, for example in exhibiting little or no phytotoxicity to rice, as aforesaid.  
  The active compound according to the present invention significantly also shows a secondary insecticidal and fungicidal activity, eg against insects and phytopathogenie fungi which infest plants.  
  The active compound according to the instant invention can be utilized, if desired, in the form of the usual formulations or compositions with conventional inert (i.e. plant compatible or herbicidally inert) pesticide diluents or extenders, i.e. diluents or extenders of the type usable in conventional pesticide formulations or compositions, e.g. conventional pesticide dispersible carrier vehicles, such as solutions, emulsions, suspensions, emulsifiable ooncentrates, spray powders, pastes, soluble powders, dusting agents, granules, etc. These are prepared in known manner, for instance by extending the active compound with conventional pesticide dispersible liquid diluent carriers and/or dispersible solid carriers optionally with the use of carrier vehicle assistants, e.g. conventional pesticide surface-active agents, including emulsifying agents and/or dispersing agents, whereby, for example, in the case where water is used as diluent, organic solvents may be added as auxiliary solvents. The following may be chiefly considered for use as conventional carrier vehicles for this purpose: inert dispersible liquid diluent carriers including inert organic solvents, such as aromatic hydrocarbons (e.g. benzene, toluene, xylene, etc.), halogenated, especially chlorinated, aromatic hydrocarbons (e.g. chloro-benzenes), parafiins (e.g. petroleum fractions), chlorinated aliphatic hydrocarbons (eg. methylene chloride, etc.), alcohols (e.g. methanol, ethanol, propanol, butanol, etc.), ethers, ether-alcohols (e.g. glycol monomethyl ether, etc.), amines (e.g. ethanol-amine, etc.), amides (e.g. dimethyl formamide, etc.), sulfoxides (e.g. dimethyl sulfoxide, etc.), ketones (e.g. acetone, etc.), and/or water; as well as inert dispersible finely divided solid carriers, such as ground natural minerals (e.g. kaolins, alumina, silica, chalk, i.e. calcium carbonate, talc, kieselguhr, montmorillonite, clay, etc.), and ground synthetic minerals (e.g. highly dispersed silicic acid, silicates, e.g. alkali silicates, etc.); whereas the following may be chiefly considered for use as conventional carrier vehicle assistants, e.g. surfaceactlve agents, for this purpose: emulsifying agents, such as non-ionic and/or anionic emulsifying agents (e.g. polyethylene oxide esters of fatty acids, polyethylene oxide ethers of fatty alcohols, alkyl sulfonates, aryl sulfonates, etc., and especially alkyl aryl-polyglycol ethers, magnesium stearate, sodium oleate, etc.); and/or dispersing agents, such as lignin, sulfite waste liquors, methyl cellulose, etc.  
  As will be appreciated by the artisan, the active compound aocording to the instant invention may be employed alone or in the form of mixtures with such solid and/or liquid dispersible carrier vehicles and/or with other known compatible active agents, especially plant protection agents, such as other herbicides, or fungicides, insecticides, acaricides, nematocides, bactericides, plant growth regulators, soil disinfectants, Spreaders, wetting agents, adhesive agents, etc. including phenoxy compounds, chlorophenol compounds, carbamates, diphenyl ethers, urea compounds, triazine compounds, and other known agricultural chemicals and/or fertilizers, etc., if desired, or in the form of particular dosage preparations for specific application made therefrom, such as solutions, emulsions, suspensions, powders, pastes, and granules which are thus ready for use. Mixed application, especially with phenoxy herbicides, for example esters of MCP, i.e. 2-methyl-4-chloro-phenoxy acetic acid, is effective and gives rise to synergistic effects.  
  As concerns commercially marketed preparations, these generally contemplate carrier composition mixtures in which the active compound is present in an amount sub stantially between about 0.1 and 95% by weight, and preferably US. and by weight, of the mixture, whereas carrier composition mixtures suitable for direct application or field application generally contemplate those in which the active compound is present in an amount substantially between about 0.005-%, preferably 0.008- 5%, by weight of the mixture. Thus, the present invention contemplates over-all compositions which comprise mixtures of a conventional dispersible carrier vehicle such as (1) a dispersible inert finely divided carrier solid, and/ or (2) a dispersible carrier liquid such as an inert organic solvent and/ or water preferably including a surface-active effective amount of a carrier vehicle assistant, e.g. a surface-active agent, such as an emulsifying agent and/or a dispersing agent, and an amount of the active compound which is effective for the purpose in question and which is generally between about ODDS-95%, and preferably 0.008-95 by weight of the mixture.  
  In particular, the amount of active compound applied per unit area varies according to the purpose intended, i.e. the effect desired, and the mode of application. In general, higher quantities of substantially between about 5-40 kg, especially 6-40 kg., of active compound per hectare are applied for total or non-selective herbicidal activity, whereas lower quantities of substantially between about 1.25-5 kg. of active compound per hectare are applied for selective herbicidal activity, although such active compound may be applied generally in amounts of 125-40 kg. per hectare, irrespective of the presence or absence of the carrier vehicle.  
  Essentially, the active compound usable according to the present invention, e.g. when used in paddy fields or upland fields, tends to show non-selective or total herbicidal action in concentration of more than 500 g. per 10 acres, e.g. 550-1000 or 600-1000 g./10 a., whereas such compound tends to show selective herbicidal action, especially for weeds as opposed to valuable cultivated crops, such as rice, in smaller appropriate concentration, e.g. 50-500 or 100-500 or 100-400 or 125-500 g./l0 a., i.e. irrespective of the presence or absence of the carrier vehicle. As the artisan will appreciate, the instant active compound can of course be used generally in overall amounts of from 5-1000 g./l0 a., if desired, irrespective of the presence or absence of the carrier vehicle.  
  The active compound can also be used in accordance with the well-known ultra-low-volume process with good success, i.e. by applying such compound if normally a liquid, or by applying a liquid composition containing the same, via very effective atomizing equipment, in finely divided form, e.g. average particle diameter of from 50-100 microns, or even less, i.e. mist form, for example by airplane crop spraying techniques. Only up to at most about a few liters/ hectare are needed, and often amounts only up to about 1 quart/acre, preferably 2-16 fluid.  
 ounces/acre, are sufficient. In this process it is possible to use highly concentrated liquid compositions with said liquid carrier vehicles containing from about 20 to about 95% by weight of the active compound or even the 100% active substance alone, e.g. about 20-100% by weight of the active compound.  
  While the active compound can be used particularly effectively according to the pre-emergence method, it is also effective when used according to the post-emergence method.  
  Especially when application is carried out mainly beforefore the germination of cultivated plants, the general conditions of cultivation are not so important, but the quantity of active compound to be applied per unit area and the application method are important, as the artisan will appreciate.  
  Furthermore, the present invention contemplates methods of selectively killing, combatting or controlling undesired plants, e.g. weeds and the like, which comprise applying to at least one of (a) such weeds and (b) their habitat, i.e. the locus to be protected, a herbicidally effective or toxic amount of the particular compound of the invention alone or together with a carrier vehicle as noted above. The instant formulations or compositions are applied in the usual manner, for example by spraying, atomizing, scattering, dusting, watering, sprinkling, and the like, whether for pre-emergence application to the soil or post-emergence application to the weeds.  
  It will be realized, of course, that in connection with the pre-emergence use of the instant compound as well as the post-emergence use thereof, the concentration of such particular active compound utilized in admixture with the carrier vehicle will depend upon the intended application and may be varied within a fairly wide range depending upon the weather conditions, the conditions of cultivation, the soil, the purpose for which the active compound is used, e.g. for total or only selective herbicidal effect, and the plants which are to be controlled or protected. Therefore, in special cases, it is possible to go above or below the aforementioned concentration ranges and ranges of amounts per unit area.  
  The following illustrate, without limitation, examples of formulations which may be used in accordance with the present invention:  
 FORMULATION A 5% by weight of instant Compound I, and by weight of a mixture of talc and clay are formulated into a dust by mixing and crushing, and applied by dusting as such to weeds and/or their habitat.  
 FORMULATION B 20% by weight of instant Compound I, 75% by weight of a mixture of talc and clay (3:2), 3% by weight of sodium alkylbenzene sulfonate, and 2% by weight of sodium dinaphthylmethane disulfonate are formulated into a wettable powder by mixing and crushing, and applied diluted with water at the concentration of l to 500 by spraying to weeds and/ or their habitat.  
 FORMULATION C 20% by weight of instant Compound I, 75% by weight of xylol, and 5% by weight of the emulsifier Sorpol (trade name of the product of Toho Kagaku K.K., Japan: polyoxyethylenealkylether) are formulated into an emulsifiable concentrate by mixing and stirring, and applied diluted with water at the concentration of 1 to 1,000 by spraying to weeds and/or their habitat.  
 FORMULATION D Instant Compound I is dissolved in xylol with heating, and the solution is sprayed onto clay granules while rotating and mixing so that about 10% by weight of the active compound is contained thereon. The granular formulation is applied as such by scattering on the surface of soil.  
 FORMULATION E 3% by weight of instant Compound I, 1.5% by weight of the ethyl ester of MCP, i.e. 2-methyl-4-chlorophenoxy acetic acid, and 95.5 parts by weight of bentonite are mixed together. Such mixture containing 10% of water is granulated, and the granular formulation is applied by scattering on the soil surface of paddy fields.  
  The herbicidal effectiveness of the active compound according to the present invention is illustrated, without limitation, by the following examples:  
 EXAMPLE 1 Test against weeds of paddy fields Preparation of active compounds:  
 Carrier vehicle: 5 parts by weight of acetone or 5 parts by weight of talc Emulsifier: 1 part by weight of benzyloxypolyglycolether To produce a suitable preparation of the particular active compound, 1 part by weight of such active compound is thoroughly mixed with either one of the stated amounts of carrier vehicle and the stated amount of emulsifier. A resulted emulsifiable concentrate or a wcttable powder is then diluted with water to a desired final concentration.  
  Test method: Pots l/5,000 a. are charged with paddy field soil and then filled with water. Paddy rice seedlings 8 EXAMPLE 2 Test against weeds of upland fields Preparation of the active compounds:  
  Carrier vehicle: 5 arts b wei ht of acetone or 5 arts b (Kinmaze variety) of 3 to 4 leaves stage are transplanted Weight of talc p y g p y into the pots under irrigated conditions. After the seedlings E mulsifier: 1 art b wet ht of benz x 01 l colether have taken root, seeds of barnyard grass and broadleaved p y g y yp yg y weeds are sown and spikerush are planted in such pots To produce a suitable preparation of the particular acsimultaneously. 10 tive compound, 1 part by weight of such active compound The preparations of the given active compound are is throughly mixed with either one of the stated amounts sprayed at the rate of 500, 250 and 125 g. of active comof carrier vehicle and the stated amount of emulsifier. pound per 10 a. of pot soil. After 3 weeks, the herbicidal A resulted emulsifiable concentrate or a wettable powder effect against the barnyard grass, spikerush and bread is then diluted with water to a desired final concentration. leaved weeds and the phytotoxicity to the paddy rice are Test method: After filling up pots of 30 x 30 cm. with determined in accordance with the following scales: soil of diluvial volcanic ash, seeds of the below-mentioned weeds, upland rice (Hataminori variety) and vegetables are sown. After covering with soil, the preparations of a Herbicidal 6mm? Phywwmny particular active compound are sprayed on the surface of 5... Flange are completely dead or no gennl- 5... Plalnttslareicorlnthe soil at the rate of 400, 200 and 100 g. Of active com- IlB OIIOOOLUS. DGEY BE. 4-. Plants are partially destroyed or 20% or 4... Remarkable pound 10 9 SO11 After 3 waeks the less germinated. damage. effect against various kinds of weeds and the phytotoxicity g g gg gm&#39;ggf damaged 50% Mmked damage&#39; to upland rice and certain vegetables are determined in 2.. Pllants alrlenmagksdly damaged or 70% or 2-.. Small damage. accordance With the following scales:  
  853 e mi 8 1... Plants are slightly damaged or 90% or 1... Blight damage.  
  less germinated. 0.. No eflect. (1... No phytotoxicity.  
  The particular active compounds tested and the results obtained can be seen from the following Table 1.  
 TABLE L-HERBICIDAL EFFECT AGAINST WEEDS OF PADDY FIELDS AND PHYTOTOXICI&#39;IY T0 RICE Herbioidal efl&#39;ect Herbicidal eificacy Phytotoxicity Amount Phyto- 01 active Barn- Bi&#39;oedtoxi 0 5.-- Plants are completely dead or 5... Plants are completely dead compound yard Splkeleaved ity, no germination occurs. or no germination occurs. A i compound in E/ 10 81385 111 Weeds i 4.-- Plants are partially destroyed 4... Plants are remarkably damatter germination or 20% or aged after germination or Com 11nd of invention: less germinated. 50% or less germinated.  
 () 500 5 5 5 0 8.-- Plants are remarkably dam- 3... Plants are markedly dam- 250 5 5 5 0 aged after germination or aged after germination or 125 5 4-5 5 0 40 or less germinated. or less germinated. Known compounds- 2... Plants are markedly damaged 2... Plants are considerably dam- Com 11: after germination or 70% or aged alter germination or (A) Pentaohloro less germinated. 70% or more lgerminated.  
  phenol 500 5 3 5 0 1..- Plants are slightly damaged 1... Plants are sllg tly damaged 250 3 0 2 0 after germination or or after germination or 90% 125 1 0 0 0 less germinated. or more germinated. (B) 2,4-dichloro 45 0.-. No eflect. 0..- No phytotoxieity.  
 phenyHl-nitrophenyl ether 5m 5 5 250 5 5 5 1 125 3 2 (E) 0-(2-nltrophenyD-O- methyl-N- lsoprogyl- 5O phos oroami othioate...-. 500 5 4 4 o 250 4 a 3 0 125 2 1 2-1 0 Control. 0 0 0 0 Nora.-Broed-leaved weeds are Monochoria uaginulia, Rotate indies 55 Linda-mu pvridariu, Dopatrium jlmaeum, etc.  
  The particular active compounds tested and the results obtained can be seen from the following Table 2.  
 TABLE 2.-HERBICIDAL EFFECT AGAINST WEEDS OF UPLAND FIELDS AND PHYTOTOXICITY TO VARIOUS CROPS Herbicide] eflect Phytotoxicity Amount of active Barnyard- Finger- Wild Common comgrass grass Dent timnranth purslane pound, tEchino- (Di ii&#39;oittall (Arnaran- (Portu- Upland Japan- Cucurn- Car- Active compound g./l0 a. chloa) tar a) (Betaria) thus) lace.) rice radish bar Tomato rot Compound of present invention (1)-. 400 5 5 5 5 5 0 0 1 0 0 200 o 5 5 5 5 0 0 0 0 0 5 4-5 4-5 5 5 0 0 0 0 0 Known compounds-Comparison:  
 (D) O-(Li-dlchiorophenyD-O- 400 5 5 5 1 2 0 0 1 0 0 methyl-NJsopropylphos- 200 4-5 4 4 0 0 0 0 1 0 0 phoro-amino-thioate 100 8 8 3 0 0 0 0 0 0 0 (C) 2ch1oro4.6-bis(ethyiamine)-1,B,5-triaaine-... 100 5 5 5 5 5 2 8 2 2 2 B 2 s-diehlero hen l4- iimbnsnn s im-1 400 5 s 5 s 5 a 1 s s a Control 0 0 0 0 0 0 O 0 0 The test results described in the above-mentioned Table 2 show that the particular active compound used according to the present invention has excellent selective herbicidal effect without causing any phytotoxicity to cultivated crops when used in a suitable quantity (e.g. 100-400 g. of active compound per 10 ares). Especially excellent herbicidal effect is shown against barnyardgrass (Echinochloa), wild amaranth (Amaranthus), common purslane (Portulaca), and the like.  
  The following example illustrates, without limitation the process for producing the particular compound usable according to the present invention.  
 EXAMPLE 3 ISO-CzHrNH (I) 14 g. (0.1 mol) of 2-nitro-phenol are dissolved in 100 ml. of aeetonitrile and 14 g. of anhydrous potassium carbonate are added to the resulting solution. 20.2 g. (0.1 mol) of O-ethyl N iso-propyl-amido-thionophosphoric acid ester chloride are added dropwise thereto at 50-60 C. with vigorous stirring. The mixture is further heated at 70 C. for 5 hours to complete the reaction. The inorganic salt produced is filtered oil? and the filtrate is distilled to remove the solvent. The residue is dissolved in 100 ml. of benzene and the benzene solution is washed with 1% aqueous solution of sodium carbonate, and then dried over anhydrous sodium sulfate. After distilling off of the benzene, 25.3 g. of O-(Z-nitro-phenyl)-O-ethyl-N- is?propyl-phosphoro-amido-thioate are obtained. (n 1. 322  
  It will be realized by the artisan that the foregoing compound contemplated by the present invention possesses the desired selective or total herbicidal properties, and especially the capability of selectively destroying weeds, as well as a comparatively low toxicity toward warm-blooded creatures and a concomitantly low phytotoxicity with respect to higher plants, depending upon the amount used, enabling such compound to be used with correspondingly favorable compatibility with respect to warm-blooded creatures and higher plants for more effective control and/or elimination of weeds by selective application of such compound to such weeds and/or their habitat. Nevetheless, the instant compound possesses total herbicidal action when used in large quantities although 10 selective herbicidial action is obtained when used in smaller quantities. As contemplated herein, the term weeds&#34; is meant to include not only weeds in the narrow sense, but also in the broad sense, whereby to cover all plants and vegetation considered undesirable for the particular purposes in question.  
  It will be appreciated that the instant specification and examples are set forth by way of illustration and not liimtation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention which is to be limited only by the scope of the appended claims.  
 What is claimed is:  
  1. Method of combating weeds in paddy field rice which comprises applying to at least one of (a) such weeds and (b) the rice field, a herbicidally etfective amount of 0-(Z-nitro-phenyl)-O-ethyl-N-isopropyl-phosphoro-amido-thioate of the formula 2. Method according to claim 1 wherein such compound is used in the form of a mixture with a dispersible carrier vehicle, said compound being present in a herbicidally effective amount and constituting substantially between about 0.00S-95% by weight of the mixture.  
  3. Method according to claim 1 wherein such compound is used in an amount of substantially between about -1000 grams per 10 ares.  
  4. Method according to claim 1 wherein such compound is used in an amount of substantially between about 550-1000 grams per 10 ares.  
  5. Method according to claim 1 wherein such compound is used in an amount of substantially between about 50-500 grams per 10 ares.  
  References Cited The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.  
 UNITED STATES PATENTS 3,472,920 10/ 1969 Schrader et al. 71-87 X LEWIS GO&#39;ITS, Primary Examiner C. L. MILLS, Assistant Examiner