CA1059780A - Urea derivatives as selective herbicides in cereals - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to a process for protecting a cereal crop from weeds, wherein a selectively phytotoxic amount of a urea derivative of the formula

Description

5~7 ~

OOZo 30,703 USE OF UREA DERIVATIVES AS SELECTIVE HERBICIDES IN CEREALS
The present invention relates to the use of substituted aryl ureas as selective herbicides in cereals such as wheat, rye, oats and barley.
It is known (U~S. 23655,445) that various aryl urea derivatives are suitable as total herbicides, especially for destroying all grass and weeds which usually grow for ;nstance on railway tracks and in drainage ditchesJ where the aim is to achieve complete destruction of all plant growthO
Preferred derivatives are said to be aryl ureas substituted in the 3- or 4-position. The abovementioned patent specification also mentions 3-(3,5-dichloro-4-methoxyphenyl)-1,1-dimethylurea, but no specific areas of use are disclosed. From more recent publications (e.g. German Laid~Open Applications DOS 1,905,598 and 1,9189114 and German Published Application DAS 1,966,298) it is known that certain aryl urea derivatives are also suitable for use in cereal crops although they are stated to be total herbicides in earlier publications~ However, these aryl urea derivatives are only substituted in the 3- or 4-position. The impression has thus been created and all commercial urea herbicides confirm this - that the only aryl urea derivatives likely to be successful in cereals are those bearing one or at most two substituents in the 3- and 4-position on the aryl ring There thus existed a prejudice against using highly subst;tuted 7~

~s~
aryl urea derivati~es in this special field.
We have now surprisingly found a process ~or protecting a cereal crop from weeds, wherein a selectively phytotoxic amount of a urea derivative of the formula Rl_o ~ C0 N ~ 3 Cl wherein Rl denotes methyl or ethyl and R2 denotes methyl, methoxy or butynyl is applied to the crop area. "Cereal crops", in this context, are taken to be wheat, rye, barley and oats.
The compounds of the invention are particularly suitable for controlling broadleaved and grassy weeds of the Alopecurus spp., Apera spica venti, Avena fatua, Lamium spp., Matricaria spp., and Stellaria media species.
The chemically closest known urea derivative used as a selective cereal herbicide is l-(3-chloro-4-methoxyphenyl)-3,3-dimethylurea disclosed in Swiss 466,~43. Compared with this active ingredient, the compounds of the invention have better selectivity in cereals combined with a similar or superior action on grassy weeds.
The compounds of the invention are thus a valuable extension of the art.
The following compounds are examples of active ingredients according to the invention:
1-(3,5-dichloro-4-methoxy)-phenyl-3~methylurea . ~ .

-~L~5978~
O~Z~ 30~703 1-(3,5~dichloro-4-ethoxy)-phenyl-3 methylurea 1-(3J5-dichloro-4-methoxy) phenyl-3-methyl-30methoxyurea 1-(395-dichloro-4-methoxy)-phenyl-3,3-dimethylurea 1-(3,5-dichloro-4-ethoxy)-phenyl-393 dimethylurea 1-(3,5-dichloro-4-ethoxy)~phenyl-3-methyl~3-(2-butynyl)-ureaO
The active ingredients are obtained for instance by reaction of 3,5-dichloro-4-methoxyphenyl isocyanate or 3,5-dichloro-4-ethoxyphenyl isocyanate with methylamine, dimethyl~
amine or O,N-dimethylhydroxylamine in inert solvents.
The isocyanates used as starting materials are obtained by conventional methods by phosgenation of the art compound 3,5-dichloro-4-methoxyaniline (C. de Trat, HelvO chim Acta~
30, 232, 1947; F.B. Mallory and SOP~ Varinbi, J. Org. ChemO, 28, 1~56, 1963) or 3,5-dichloro-4-ethoxyaniline (GO Bargellini, Gazz. Chim. Ital., 59, ~6, 1929) The preparation o~ the compounds of the invention is illustrated below.
1~(3,5-dichloro-4-methoxy)-pheny`1-3 3-dimethylurea At 10 to 15C, a solution of 218 parts ~by weight) of 3,5-dichloro-4-methoxyphenyl isocyanate in 750 parts of dry benzene is dripped over a period of 1 hour into a solution o~
54 parts o~ dimethylamine in 750 parts of dry benzeneO The mixture is stirred for 30 minutes at room temperature and for 1 hour at 50C. The urea derivative is precipitated, cooled, suctîon filtered, washed with 100 parts of benzene and then with 100 parts of n-pentane, and driedO

_3~

~ O S~ 7 80 oOz, 30,703 There is obtained 260 parts of the desired compound;

mOp.o 194 - 196C~

The following compounds are obtained analogously:

NoO Formula m~pO in C
(recrystallized ~rom) ,, ~
: Cl 3 ~ NH-C0-NH-CH3 188-90 (ethanol/water) Cl Cl CH
3 C2H5- ~ NH-C0-N 3 205-208 Cl : Cl 4 C2H5 0 ~ NH-C0-NH-CH3 201 (ethanol~water) Cl Cl . 5 C2H5 0 ~ NH-C0-N 3 . 54-56 y ~ CH-C-CH
Cl CH3 1-~3?5-dichloro-4-methsx~)-phenyl-3-methy_-3-met~hoxyurea At 0VC~ a solution of 506 parts o~ sodium.hydroxide i.n 15 parts of water, and subsequently 100 parts Or methylene chloride are added to a solution of 11.7 parts o~ 0,N-dîmethyl-hydroxylamine chlorohydrate in 25 parts of water.
This well stirred suspension has dripped.into.ît at 0C
to +10C a solution of 21.8 parts of 3,5-dichloro-4-methoxy-: phenyl isocyanate in 50 parts of methylene chloride~ The mixture is stirred for 1 hour at room temperature and the organîc phase . -4-~L~5~78(~
O.Z~ 30~703 is then separated9 washed with water, drled (Na2S04) and con-centrated O
There is obtained 25 parts of the desired compound;
m~pO~ 78Co ~ Application may be effected ~or instance in the form of : directly sprayable solutions, powders, suspensions (inelud;ng high-percentage aqueous, oily or other suspensions), dispersions9 emulsions, oil dispersions, pastes9 dusts3 broadcasting agents, or granules by spraying, atomizing~ dusting, broadcasting or .10 watering~ The forms of application depend entirely on the purpose ~or which the agents are being used; in any case they should ensure a fine distribution of the active ingredientO
For the preparation of ~dutions 9 emulsions, pastes and oil dispersions to be sprayed direct, mineral oil fractions of medium to h;gh boiling point, such as kerosene or diesel oil, further coal-tar oils, etc and oils of vegetable or animal origin, aliphatic, cyclic and aromatic hydrocarbons such as benzene, toluene, xylene, paraff;n, tetrahydronaphthalene, .
alkylated naphthalenes and their derivatives such as methanol, ethanol, propanol, butanol, chloroform, carbon tetrachloride, cyclohexanol, cyclohexanone, chlorobenzene~ isophorone, etcO 9 and strongly polar solvents such as dimethylformamide, d;methyl sulfoxide, N-methylpyrrolidone, water9 etcO are su;tableO
Aqueous formulations may be prepared ~rom emulsion con-centrates, pastes, oil d;spersions or wettable powders by adding waterO To prepare emulsions 3 pastes and o;l dispersions the ingredients as such or dissolved in an oil or sol~ent may ~0597BQ oozo 30 9 703 be homogenized in water by means of wetting or dispersing agents, adherents or emulsifiersO Concentrates which are suitable for dilution with water may be prepared from active ingredient 5 wetting agent, adherent~ emulsifying or dispersing agent and possibly solvent or oilO
Examples of surfactants are~ alkali metal, alkaline earth metal and ammonium salts o~ ligninsulfonic acid, naphthalene sulfonic acids, phenolsulfonic acids, alkylaryl sulfonates, ; alkyl sulfates, and alkyl sul~onates, alkali metal and alkaline earth metal salts of dibutylnaphthalenesulfon;c acid, lauryl ether sulfate, fatty alcohol sul~ates,.alkali meta~ and alkaline earth metal salts of fatty acids, salts of sulfated hexadecanols, heptadecanols, and octadecanols, salts.of sul~at.ed fatty alcohol glycol ether, condensation products or sulfonated naphthalene and naphthalene derivatives with formaldehyde~.condensat;on products of naphthalene or naphthalenesulfonic acids.with phenol and formaldehyde, polyoxyethylene octylphenol ethers, ethoxylated isooctylphenol, ethoxylated.octylphenol..and ethoxyl~
ated nonylphenol, alkylphenol polyglycol ethers, tributylphenol polyglycol ether~, alkylaryl polyester alcohols, isotridecyl alcohols, fatty alcohol ethylene oxide condensates, ethoxylated castor oil, polyoxyethylene alkyl.ethers, ethoxylated.polyoxy-propylene, lauryl alcohol polyglycol ether acetal3 sorbîtol esters, lignin~ sulfite waste liquors and methyl celluloseO
Powders, dusts and broadcasting agents may be prepared by mixing or grinding the active ingredients with a.solid carrierO

59 ~ ~
O~ZO 30,703 Granules, e.g~g coated, impregnated or homogeneous gra-nules 9 may be prepared by bonding the active ingredients to solid carriersO Examples Or solid carriers are mineral earths such as silicic acid, silica gels9 silicates3 talc, kaolin, Attaclay~ limestone~ lime, chalk, bole9 loess9 clay, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate~ magnesium oxide, ground plastics, fertilizers such as ammonium sul~ate~
ammonium phosphate, ammonium nitrate, and ureas, and vegetable products such as grain flours, bark meal, wood meal, and nutshell meal, cellulosic powders, etcO
The formulations contain from 0~1 to 95 9 and preferably 0.5 to 90, % by weight of active ingredientO
There may be added to the compositions or individual active ingredients (if desired, immediately before use (tank-mix)) oils of various types, wetting agents or adherents, herbicides, fungicides, nematocides, insecticides, bactericides3 trace elements, fertilizers, antifoams (eOg., silicones), growth regulators, antidotes and other herbicidally e~ective compounds such as substituted alkylsulfonylglycolic amides and imides substituted alkylaminosulfonylglycolic amides:and imides substi~uted acetanilidoalkyl sul~ites substituted anilines substituted azides substituted aryloxycarboxylic acids and aryloxythlocarboxylic acids and salts; esters and amides thereo~
substituted ethanols, ethenols 5~
OOZ~ 30,703 substituted ethers substituted arsonic acids and arsenic acids and salts, esters and amides thereof substituted benzene sulfonamides substituted benzimidazoles substituted benzisothiazoles : dihydrobenzofuranyl alkylamino sulfonates substituted benzothiadiazinone dioxides substituted benzoxazines substituted benzoxazinones substituted benzoxazoline thiones substituted benzothiadiazoles substituted benZothiaZQlinyl alkyl carboxylic acids and salts, esters and amides thereof substituted biurets substituted quinolines substituted carbamates ` substituted aliphatic or cycloaliphatic carboxylic acids and thiocarboxylic acids and their salts, esters and amides substituted aromatic carboxylic acids and thiocarbox~Jl:ic acids and their salts, esters and amides substituted carbamoylalkylthiol- or -dithiophosphates substituted quinazolines substituted cycloalkylamidocarbothiolic acids and their salts, esters and amides substituted cycloalkylcarbonamidothiazoles substituted dicarboxylic acids and their salts, esters.and am;des ~1~S978~1~
OOZo 30~703 substituted dihydrobenzofuranyl sulfonates substituted dihydropyrane diones substituted disulfides substituted dioxanes substituted dipyridylium salts substituted dithiocarbamates substituted dithiophosphoric acids and their salts, esters and amides substituted ~luorenecarboxylic acids and their salts, esters and amides substituted ureas substituted hexahydro-lH-carbothioates hexahydro-lH-carbothioates substituted hydantoins substituted hydrazides substituted h~drazonium s~lts substituted h~dro~uranones substituted isoxazole pyrimidones substituted imidazoles substituted imidazolidinedione carboxamides substituted isothiazole p~rimidones substituted ketones substituted naphtho~uinones substituted naphthalic anhydrides substituted aliphatic nitriles substituted aromatic nitriles substituted oxadiazoles ~59780 O~Z~ 30,703 substituted oxadiazinones substituted oxadiazolines substituted oxadiazolidine diones substituted oxazolidines substituted oxadiazine diones substituted oxazole pyrimidinones substituted phenols and their salts and esters substituted phosphonic acids.and their salts, esters and amides substituted phosphonium chlorides substituted phosphonalkyl glycines substituted phosphites substituted phosphoric acids and their salts, esters and.amides substituted piperidines substituted pyrazoles . substituted pyrazole alkylcarboxylic acids and their salts, esters and amides substituted pyrazolium salts substituted pyrazolium alkyl sul~`ates ~ substituted pyridazines : 20 substituted pyridazones substituted pyridine carboxylic ac.ids and their salts, esters and amides substituted pyridines substituted pyridine carboxylates substituted pyridinones ~ubstituted pyrimidines substituted pyrimidones 7 ~
O.Z. 30,703 substituted pyrrolidine carboxylic acid and its salts, esters and amides substituted pyrrolidines substituted pyrrolidones substituted arylsulfonic acids and their salts, esters and amides substituted sulfamates substituted styrenes substituted sulfonyl toluidides substituted tetrahydrooxadiazine diones substituted tetrahydroxadiazole.diones substituted tetrahydromethanoindenes substituted tetrahydroxadiazole thiones substituted tetrahydrothiadiazine thiones substituted tetrahyd~othiadiazole diones substituted aromatic thiocarbonylamides substituted thiobenzamides substituted thiocarboxylic acids and their saltæ, esters and amides substituted thiol carbamates substituted thioureas substituted thiophosphoric..ac.ids and their salts, esters and amides substituted triazines substituted triazinones substituted triazoles substituted uracils substituted uretidine diones ~59~80 0,Z. 30,703 chlorates, and substituted azetidine carbothioatesO
The last-mentioned herbicidal compounds may.also be.applied before or after the active ingredients or compositions thereof accordin~ to the inventionO
These agents may be added to the herbicides according to the invention in a ratio by weight of ~rom 1:10 to 10:1.
i The same applies to oils, wetting agents and adherents~ fungî-cides, nematocides, insecticides, bactericides, an~idotes and growth regulatorsO
The new compositions have a strong herbicîdal action and may therefore be used.as weedkillers..or for.controlling the growth of unwanted piantsO Whether the.new active ingredients are used as total or selective agents depends in essence on the amount of ingredient used per unit.area.
By weeds and unwanted plant growth are meant all mono-cotyledonous and dicotyledonous plants which.grow in loci where they are not desired.
The agents according to..the invention may thererore be used for controlling ~or instance Gramineae, such as Gynodon spp. . ......... Dactylis 5pp q : Digitaria spp~ . Avena spp.
Echinochloa spp~ Bromus Spp4 Setaria spp. Uniola spp.
Panicum sppO Poa spp~
Alopecurus sppO Leptochloa sppO

:1~597~0 0,Z. 30~703 Lolium sppO Brachiaria sppO
Sorghum spp, Eleusine sppO
Agropyron spp. Cenchrus sppO
Phalaris sppO Eragrostis spp.
Apera sppO Phra~mitres communis etc.;
Cyperaceae, such as Carex 8ppo Eleocharis sppO
Cyperus spp~ Scirpus spp~
: 10 etc~;
dicotyledonous weeds, such as Malvaceae, eOg. 9 Abutilon theoprasti Hibiscus spp.
Sida 9pp. Malva spp.
etc.;
Compositae, such as Ambrosia sppO Centaurea spp~
Lactuca SPPD Tu~silago spp.
Senecio spp. Lapsana communis Sonchus spp. Tagetes sppO
Xanthium sppO Erigeron spp.
Iva spp. Anthemis spp.
Galinsoga sppO Matricaria spp.
Taraxacum spp. Artemisia sppO
Chrysanthemum spp. Bidens spp~
Cirsium spp. etc.;
Convolvulaceae, such as : -13-~S9~'80 O.Z. 30,703 Convolvulus sppO Cuscuta 5pp.
Ipomoea spp. Jaquemontia tamnifolia et c O , Cruciferae 9 such as Barbarea vulgaris Arabidopsis thaliana Brassica spp. Descurainia spp.
Capsella 5pp. Draba spp.
Sisymbrium spp. Coronopus didymus Thlaspi spp. Lepidium spp.
Sinapsis arvensis Raphanus spp.
etc.;
Geraniaceae, such as Erodium spp. Geranium spp.
etc.;
Portulacaceae, such as Portulaca spp. etc.;
Primulaceae, such as Anagallis arvensis Lysimachia spp.
etc.
Rubiaceae, such as Richardia spp. Diodia spp.
Galium spp. etc/;
Scrophulariaceae~ such as Linaria sppO Digitalis spp.
Veronica spp~ etc 7;
Solanaceae, such as Physalis spp. Nicandra spp.

1~35~780 OoZO 30,703 Solanum sppO Datura sppO
etc.;
; Urticaceae, such as Urtica spp.
Violaceae, such as Viola spp. etc.;
Zygophyllaceae, such as Tribulus terrestrls etc.;
Euphorbiaceae, such as Mercurialis annua Euphorbia spp.
Umbelliferae, such as Daucus carota Ammi majus Aethusa cynapium etc.;
Commelinaeae, such as Commelina spp. etc.;
Labiatae, such as Lamium sppO Galeopsis sppO
etc.;
LeguminosaeD ~uch as Medicago spp. Sesbania exaltata Trifolium spp. Cassia spp.
Vicia spp. I,athyruæ spp.
etc.;
Plantaginaceae, such as Plantago sppO etc.;
Polygonaceae, such as Polygonum sppO Fagopyrum spp.

7 ~
O.Z. 30,703 Rumex sppO etc.;
Aizoaceae, such as Mollugo verticillata etc.;
Amaranthaceae, such as Amaranthus sppn etc.;
Boraginaceae, such as Amsinckia sppO Anchusa spp~
Myostis spp. Lithospermum spp.
etcO;
Caryophyllaceae, such as Stellaria spp. Silene spp.
Spergula spp. Cerastium spp.
Saponaria spp. Agrostemma githago Scleranthus annuus etc.;
Chenopodiaceae, such as Chenopodium Sppl Atriplex spp.
Kochia spp. Monolepsis nuttalliana Salsola Kali etc.;
Lythraceae, such as Cuphea spp. etc.;
- Oxalidaceae, such as Oxalis spp.
Ranunculaceae~ such as Ranunculus spp. Adonis spp, Delphinium spp. etc.;
Papaveraceae, such as Papaver spp. Fumaria of~icinalis 1~35~780 O.Z. 303703 etc.;
Onagraceae, such as Jussiaea spp. etc.;
Rosaceae, such as Alchemillia sppO Potentilla spp.
etc.;
Potamogetonaceae, such as Potamogeton spp. etc.;
Najadaceae, such as Najas spp. etcc;
Equisetaceae Equisetum spp. etct;
Marsileaceae, such as Marsilea quadrifolia e~c~;
Polypodiaceae, such as Pteridium quilinum Alismataceae, such as ; Alisma spp. Sagittaria sagittifolia etc.
The selective herbicidal action and the excellent compa-tibility o~ these active ingredients will be apparent ~rom the~ollowing examples. The good selectivity of these compounds is particularly clear ~rom the fact that the high applicat,ion rates used to destroy extremely resistant weeds cause no marked damage to cereal plants.

The plants wheat (Triticum,aestivum), barley (Hordeum vulgare), slender ~oxtail (Alopecurus myosuroides), wild oats ~ ~5~7~
O.Z. 30,703 (Avena fatua), henbit (Lamium amplexicaule), chamomile (Matricaria chamomilla)) wild mustard (Sinapsis arvensis) and chickweed (Stellaria media) were treated in the open at a growth height of from 3 to 20 cm with 1~5 kg/ha of each Or the following compounds, each being dispersed or emulsified in 500 liters of water per hectare:
1 1-(3,5-dichloro-4-methoxy)-phenyl-3,3-dimethylurea 1-(3,5-dichloro-4-methoxy) phenyl-3 methylurea 7 1 (3,5-dichloro-4-methoxy)-phenyl-3-methyl-3-methoxyurea 10 6 1-(3-chloro-4-methoxy)Dphenyl-3~3-dimethylurea (comparative agent) After 2 to 3 weeks it was ascertained that active.ingredients 1,2 and 7 had better crop plant compatibility than compound 6, combined with the same herbicidal action.
; The results are given below:
Active.in~redient _ _ 1 2 6 7 ~" _ Crop plants Hordeum vulgare 0 5 10 0 Triticum aestivum 0 0 20 0 Unwanted plants Avena fatua 95 90 95 95 Alopecurus myosuroides90 80 85 100 Lamium amplexicaule 100 100 85 100 Matricaria chamomilla100 95 100 100 Sinapis arvensis 100 100100 100 Stellaria media 100 100100 100 : 0 = no damage 100 - complete destruction ~5~7fl~
OOZ. 30,703 In the greenhouse, loamy sandy soil was filled into pots and sown with the seeds o~ wheat (Triticum aestivum) and Italian rye~rass (Lolium multi~lorum)~ The soil was then immediately treated with 2 kg~ha of each of active ingredients 296 and 7, each being dispersed in 500 liters of water per hectare. The soil was kept well watered during the experiment.
After 4 to 5 weeks it was ascertained that active ingredients

2 and 7 had better crop plant compatibility than compound 6, combined with the same herbicidal action~
The results are given below:
Active in~redient _ `2 6 -7 Crop plant;
Triticum aestivum 20 80 20 Unwanted plant:
Lolium multi~lorum 100 100 100 0 = no damage 100 = complete destruction An agricultural plot was sown with the seeds of rye (Secale cereale), barley (Hordeum vulgare)~ slender foxtail (Alopecurus myosuroides), common lambsquarters (Chemopodium album~, henbit (Lamium amplexicaule), chamomile (Matricaria chamomilla), wild mustard (Sinapis arvensis) and chic~weed (Stellaria media). The soil was then immediately treated with

3 kg/ha Or active ingredient 1 dispersed in 500 liters of water per hectare.

~5978~) O.Z. 30,703 After 4 to 5 weeks it was ascertained that the active ingredient had almost completely destroyed all the unwanted plants, but the barley plants continued to grow undamagedO
The results are given below:
Active in redient g ~ .
Hordeum vulgare 0 Secale cereale 0 Unwanted plants:
10 Alopecurus myosuroides 90 Chenopodium album 100 Lamium amplexicaule 95 Matricaria chamomilla 100 Sinapis arvensis 100 Stellaria media 100 0 - no damage : 100 = complete destruction The following compounds have an analogous action:
1-(3,5-dichloro 4-ethoxy)-phenyl-3,3-dimethylurea 1-(3,5~dichloro-4-ethoxy) phenyl-3-methylurea 1-(3,5-dichloro-4-ethoxy)-phenyl-3-methyl-3-t2-butynyl) urea In the greenhouseS various plants were treated at a growth height of ~rom 6 to 15 cm with 2~0 kg~ha of each of the following active ingredients, each being dispersed or emulsified in 500 liters of water per hectareo 1 1-(3,5-dichloro-4-methoxy)-phenyl-3,3-dimethylurea 1~59780 O~Z0 30,703 6 N (3-chloro-4-methoxyphenyl)-N',N'-dimethylurea (comparative agent) The plants were kept well watered during the experimentO
After 4 to 5 weeks it was ascertained that active ingredient 1 had better crop plant compatibility than compound 6 9 combined with the same or superior herbicidal actionO
The results are given below:
Active ingredient 1 6 . k~/ha 2.0~0O _ - 10 Crop plantc Gossypium hirsutum 10 80 Unwanted plants:
Lolium multiforum 95 90 Echinochloa crus galli 100 100 Alopecurus myosuroides 95 95 Bromus tectorum 100 85 0 = no damage 100 = complete destruction In the greenhouse, loamy sandy soil was filled into pots and sown with various seeds. The soil was then immediately treated with lo 0 kg/ha of the compound of the formula Cl H3C0 ~ NH-G-N 3 ~I) ~ 0 CH3 dispersed in 750 liters of water per hectareO 80 to lOO mm of precipitate was added during the experimentO

~ 5~ ~ 8~ 0zO 30.703 After 4 to 5 weeks it was ascertained that the compoundhad a strong herbicidal action combined with good crop plant compatibilityO
The results are given below:
Active ingredient k~!ha _ 1,O
Crop plants:
Gossypium hirsutum 0 (5) Glycine max 6 (3) Unwanted plants .
Digitaria sanguinalis 100 (2) Echinochloa crus-galli 80 ~5) Panicum virgatum go (1) Cyperus difformis 100 (1) 0 = no damage 100 = complete destruction (the figures in brackets indicate the number of experiments;
in the case of more than one experiment, the score given is the average) An agrioultural plot was sown.with various see.ds. The soil was then immediately treated with 2.0 kg/ha of compound I dis-persed in 750 liters of water per hectareO 15 to 20 mm of precipitate fell during the experiment~
After 4 to 5 weeks it was ascertained that the compound had a good herbicidal action combined with favorable crop plant c.ompatibilityO

5~ 7 ~ ~
O,Z. 30,703 The results (preemergence action) are given below:
Active ingredient kg/ha_ 2.0 ; Crop plants:
Gossypium hirsutum 4 (11) Glycine max 10 (3) Unwanted plants:
Echinochloa crusogalli 88 (8) Amaranthus retro*lexus 77 (3) 10 Galium aparine 78 ~8) , . . . .
Polygonum persicaria 85 (8) O = no damage ~ 100 = complete destruction : (The figures in brackets indioate the number o~ experiments;
the score given is the average)

Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for protecting a cereal crop from weeds, wherein a selectively phytotoxic amount of a urea derivative of the formula where R1 denotes methyl or ethyl and R2 denotes methyl, methoxy or butynyl is applied to the crop area.

2. A process as claimed in claim 1, wherein the cereal crop is wheat, barley, oats or rye.