DE2325686A1 - Herbicidal compsns - contg non persistent cpds - Google Patents

Abstract

Selective herbicidal agents for combatting unwanted plant growth in crop cultures contain cpds. of formula (I): (where R is halogen, alkyl and/or alkoxy and n is 0-5). (I) can be tolerated by crop plants (esp. potatoes) over a wide range of concns. while displaying an optimal spectrum of activity against undesired mono- and dicotyledonous plant species. Residual action is sufficient, but persistence is not so great as to endanger later crops.

Description

Selective Herbicidal Agents The invention relates to the use of N-methyl-N'-phenylureas as active ingredients for selective herbicidal agents for combating unwanted vegetation in crops, in particular Potato crops.

It is known that phenylurea has the general formula where n = 0 to 5, Y z. B. can represent lower alkyl radicals, halogen atoms and / or other substituents and R can be a lower alkyl radical, R 'can be hydrogen or a lower alkyl radical, can be used for weed killing (e.g. DBP No. 935165).

The active ingredients fenuron, Monuron and Diuron as total herbicides or components of total herbicide combinations Use in practice.

In the professional world, these dialkylphenyl ureas are considered physiological not selective.

It is also known from the literature that monoalkyl-plienylureas have lower herbicidal potencies than the corresponding dialkylphenyl ureas. The former are not used in practice for these reasons. Exceptions form a few complicated monoalkyl-phenyl-ureas (e.g.

Siduron, Buron), dealing exclusively with specialized areas, such as combat of weeds in lawns and weed control in onion crops. The selective effect of such compounds is shown in the cases mentioned on the Butoxy substituents in the phenyl nucleus or on the relatively large methylcyclohexyl radical returned.

To control weeds in potatoes are off the range of the known urea herbicides only a few N-methoxy-N-methyl-N'-phenyl ureas (e.g. Bo Metobromuron) applied in practice.

As this urea and other complicated urea compounds mentioned above require a high synthesis effort and therefore the economy of potato cultivation heavily load, the purpose of the invention is to provide a simpler and thus to find more economical means of weed control in the manufacture and use.

The object of the present invention is to provide urea derivatives to find those of crops, especially of the potatoes in a possible way large concentration range can be tolerated, compared to an optimal spectrum of activity have undesirable monocotyledonous and dicotyledonous plant species and those mentioned above meet economic requirements.

It has been found that N-methyl-N'-phenyl ureas of the general formula I, in which R is halogen, in particular chlorine or bromine, alkoxy and / or alkyl and n can assume the values from 0 to 5, are suitable as active ingredients for selective herbicidal agents for controlling undesired vegetation in crops, especially in potato crops.

The agents according to the invention can be absorbed both by the roots and by the leaves and can therefore be used before and after the emergence of the weeds. In potato crops show the agents according to the invention a surprisingly high tolerance to crop plants, depending on the type of soil at application rates of up to a maximum of 4 kg of active substance / ha is to be addressed as physiological tolerance.

In concentration ranges of 1 to 3 kg of active substance / ha are in Depending on the type of soil, optimal control success against all important ones to achieve monocotyledon and dicotyledon weed species, z. B. Stellaria media, Senecio vulgaris, Thlaspi arvense, Agrostemma githago, Lamium purpureum, Chenopodium album, Polygonum lapathifolium, Anthemis arvensis, Spergula arvensis, Galium aparine, Apera spica-venti, Poa annua, Setaria viridis, Bromus secallnus and Echinocloa crusgalli.

The means are sufficient for the desired weed killing Residual effect on, but show over don for the fight necessary Period of time only low persistence so that z. B. the reproduction of grain and Rapeseed on the treated potato fields is possible without risk. This result was based on the state of the art and the prevailing opinion of the professional world not foreseen.

The N-methyl-N'-phenyl ureas of the general formula I leave can be produced by known methods. For example, if necessary substituted aromatic amines (anilines) reacted with methyl isocyanate, or the appropriately substituted Arylisoa cyanate react with methylamine brought. According to these procedures, the following compounds of the invention, among others manufactured: N-methyl-N'-phenyl-urea F. 149-150 ° C N-methyl-N'-4-methylphenyl-urea M.p. 178-178.5 ° C N-Methyl-N'-2-chlorophenyl urea M. 152-154 ° C N-Methyl-N'-3-chlorophenyl urea M.p. 107.5-111.5 ° C N-methyl-N'-4-chlorophenyl urea m.p. 202-205 ° C N-methyl-N'-3,4-dichlorophenyl urea M.p. 156-158 ° C N-methyl-N'-4-bromophenyl urea m.p. 210-214 ° C N-methyl-N'-4-methoxyphenyl urea 164-165 ° C, N-Methyl-N'-4-methoxy-2,5-dichlorophenyl-urine-F. 212-216 ° C substance N-methyl-N'-3-nitrophenyl urea F. 154-158 ° C Depending on the intended application method, you can use suitable Carriers and / or diluents and surface-active substances for wettable powders, Granules, emulsifiable concentrates or formulated solutions be around at the breakout. the means an optimal distribution and effect to ensure active components.

The agents according to the invention can be used to broaden their spectrum of activity and to achieve synergistic and selective effects together with other suitable Herbicides are applied in combination.

The invention is illustrated below using a few examples will.

Example 1 Spectrum of activity and crop plant tolerance of N-methyl-N'-phenylurea compared to N.N-dimethyl-N'-phenyl urea depending on the concentration and the time of application In jar experiments were carried out using a floor of the type sL with a water capacity (US9 of 50% the spectrum of action and the Crop compatibility of N-methyl-N'-phenyl-urea and N.N-dimethyl-N'-phenyl-urea compared in the pre- and post-emergence method 0 The active ingredients were applied formulated as a 20% wettable powder (WP 20%), in 100 ml water / m2 using a Injection syringe For the assessment of herbicidal effectiveness and crop tolerance the following scale was also used.

Phytotoxicity number damage level 1 plants totally dead 2 3 4th 5 6th 8 traces of damage 1) 9 No damage Slight, intermittent partial chloroses

From Table 1 it can be seen that at application rates of> i kg of active substance (AS) / ha N-methyl-N-phenyl-urea and N.N-dimethyl-N'-phenyl-urea compared Weeds and ua grasses have the same herbicidal effect and also the same Spectrum of activity include.

The crop tolerance results shown in Table 2 Can be tested at application rates of 1 kg AS / ha in contrast to N.N-dimethyl-N'-phenyl urea the noticeably lower phytotoxic effect of N-methyl-N '- phenyl urea against most of the crops listed. This works particularly well from the results obtained on potatoes with pre-emergence treatment with N-methyl-N'-phenyl urea emerged. Even with high application rates of 5 kg AS / ha there is still tolerance.

Example 2 Herbicidal activity and phytotoxicity of N-methyl-N'-phenyl urea in comparison to metobromuron in potato crops The experiments were carried out under field conditions in the Fisher block with applied three repetitions The application the active ingredients formulated as WP 50% took place in 1000 liters of water per hectare by means of a Rüokenspritze GS 116) at an injection pressure of 4 kp / cm2 immediately after planting the potatoes. The results of the experiment on a medium floor (sL) can be found in Table 3. These results also show a high level of tolerance of N-methyl-N'-phenyl-urea versus potato in a very good herbicide Effects Example 3 Persistence of N-methyl-N'-phenyl urea in comparison to Metobromuron Since, in general, urea herbicides have a good residual effect and have high persistence, tests were carried out in vessels with the aim of the possibility of reproducing winter rape, father's barley and winter wheat after potatoes to consider.

This was done 4 months after application from all test elements of Example 2, the removal of a repeat sample from the top 5 cm of the crumb. the Earth was then poured into the vessels and then with winter rape and winter barley and winter ways ordered.

The results of the phytotoxicity ratings are from Table 4 to derive.

The results clearly show that when treating potato crops, even from early potato crops, even with high application rates of N-methyl-N'-phenylurea of 4.5 kg AS / ha is the cultivation of winter rape. Winter barley and winter wheat can be done without risk.

Claims (2)

Patent claims Selective herbicidal agents for controlling undesired vegetation in crops, characterized by a content of N-methyl-Nt-phenylureas of the general formula I, in which R denotes halogen, in particular chlorine or bromine, alkoxy and / or alkyl and n can assume the values 0 to 5. 2. Selective herbicidal agents for controlling undesired vegetation in potato crops according to claim 1, characterized by a content of N-methyl-N'-phenyl urea.