Process for the control of weeds

Details Process for the control of weeds Process for the control of weeds

2001-02-26

2003-07-01

Clardy, S. Mark (Department: 1616)

Plant protecting and regulating compositions

Plant growth regulating compositions

Plural active ingredients

C504S128000

Reexamination Certificate

active

06586367

ABSTRACT:

The present invention relates to a new process for the control of weeds in useful plant cultivations, for example in the cultivation of maize, soya, cotton, rape, beet and sugar cane, which are resistant to phospho-herbicides.
The phospho-herbicides glufosinate and glyphosate are described for example in The Pesticide Manual, Tenth Edition, 1994, Crop Protection Publications, BCPC. In addition, the following herbicides are similarly known: prosulfuron, primisulfuron, dicamba, pyridate, dimethenamide, metolachlor, fluometuron, propaquizafop, atrazine, ametryn, terbutylazine, simazine, clodinafop, norflurazone, as well as prometryn. The S-enantiomer of metolachlor is known from U.S. Pat. No. 5,002,606; the S-enantiomer of dimethenamide from U.S. Pat. No. 5,457,985. The metabolite NOA-402989 is known from the Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz, Sonderheft X, 355-360 (1984) as 3-phenyl-4-hydroxy-6-chloropyridazine. The compound of formula
is described for example in U.S. Pat. Nos. 4,671,819; 5,183,492 discloses the compound of formula
and the compound of formula
is known from EP-A-496 701.
It has now surprisingly been found that a quantitatively variable combination of phospho-herbicides selected from the group comprising glufosinate and glyphosate with at least one of the above-listed other herbicides exhibits a synergistic effect which is capable of controlling the majority of weeds occurring preferably in useful plant cultivations that are resistant to glufosinate or glyphosate, both in pre-emergence and in post-emergence, without significantly damaging the useful plants.
Therefore, according to the present invention, a new process is proposed for the control of weeds in the cultivation of useful plants that are resistant to phopho-herbicides, the process being characterised in that a herbicidally effective amount of a composition containing, in addition to the usual inert formulation assistants, a phospho-herbicide selected from the group comprising glufosinate and glyphosate, a synergistic amount of at least one further herbicide selected from the group comprising prosulfuron, primisulfuron, dicamba, pyridate, dimethenamide and its S-enantiomer, metolachlor and its S-enantiomer, fluometuron, propaquizafop, atrazine, clodinafop, norflurazone, ametryn, terbutylazine, simazine, prometryn, NOA-402989, as well as the compounds of formulae
is allowed to take effect on the cultivated plant or its habitat, with the provision that compositions containing glufosinate and metolachlor, glufosinate and atrazine, glufosinate and metolachlor and atrazine, as well as glufosinate and atrazine and dicamba are not used in glufosinate-resistant maize, and further that compositions containing glyphosate and atrazine are not used in glyphosate-resistant maize, and compositions containing glyphosate and metalochlor or glyphosate and dimethenamide are not used in glyphosate-resistant soya.
It is highly surprising that the combination of a phospho-herbicide such as glufosinate or glyphosate with at least one of the above-mentioned further herbicides surpasses the additional effect to be expected in principle on the weeds to be controlled, and thus extends the limits of activity of both active ingredients in particular in two different respects.
On the one hand, the application amounts of the individual compounds applied are reduced, whilst maintaining a good level of activity. On the other hand, the composition used according to the invention still achieves a high rate of weed control where the individual substances have become no longer agronomically useful in small application amounts. The consequence of this is a considerable widening of the weed spectrum and an additional increase in selectivity for useful plant cultivations, which is necessary and desired in the case of an unintentional overdose of active ingredient. In addition, the composition according to the invention allows greater flexibility of subsequent cultivations whilst maintaining the outstanding control of weeds in useful plants.
The herbicide mixture used according to the invention may be used on glufosinate- or glyphosate-resistant useful plants, especially maize, cotton, rape, sugar beet, sugar cane and soya, against a large number of agronomically important weeds, such as Stelladia, Nasturtium, Agrostis, Digitaria, Avena, Setaria, Sinapis, Lolium, Solanum, Phaseolus, Echinochloa, Scirpus, Monochoria, Sagittaria, Bromus, Alopecurus,
Sorghum halepense
, Rottboellia, Cyperus, Abutilon, Sida, Xanthium, Amaranthus, Chenopodium, lpomoea, Chrysanthemum, Galium, Viola and Veronica. It may also be used for non-selective weed control and for all application methods that are usual in agriculture, e.g. pre-emergent application, post-emergent application and seed disinfecting.
Useful plant cultivations which are tolerant towards the herbicide glufosinate or glyphosate are preferably produced with the assistance of biotechnological methods. The assistance of biotechnological processes can be restricted to the usage of cell-biological selection processes, which are carried out in such cases preferably on cell or callus cultures that are capable of regeneration, so as to finally develop glufosinate- or glyphosate-tolerant plants. However, since precise knowledge is available about the mechanism of activity of these herbicides, gene technology may also be employed.
Resistance towards glufosinate may be essentially attained by two different experimental set-ups. On the one hand, the herbicide target which in the case of glufosinate is represented by the enzyme glutamine synthetase may be selected as the point of attack for the development of resistance. On the other hand, the herbicidally active substance itself may serve as the starting point for the development of resistance. For example, glufosinate tolerance may be effected through the transgenic expression of an enzyme which converts glufosinate into a physiologically inactive form.
The first set-up makes use of the knowledge of the site of action or the point of attack of glufosinate, namely the enzyme glutamine synthetase. The desired tolerance may thus be effected by over-expression of the enzyme in plants or preferably by transgenic expression of variants of the enzyme which are tolerant to the effect of glufosinate.
Glufosinate-tolerant plants are thus produced e.g. by amplifying the herbicide target in the plant. Such gene amplification is achieved for example by exposing plant cell cultures to selection pressure, and further cultivating the resistant variants or strains obtainable in this way and regenerating them into whole plants. The said resistant cell strains may also be fused with an appropriate receptor cell line in the manner of a protoplast fusion, and regenerated into whole plants. Alternatively, the desired gene amplification may also be attained with the assistance of genetic engineering, whereby the number of wild type genes in the plant genome of sensitive plants is increased by inserting further wild type gene replications. The source of wild type genes which encode the enzyme glutamine synthetase may be both procaryotes and especially eucaryotes. The eucaryotes are presented in particular by plant sources, e.g. various species of potato (
Solanum tuberosum
), tomato (
Lycopersicon esculentum
), pepper (
Capsicum annumm
), tobacco (
Nicotiana tabacum
), brassica, especially
Brassica napus,
various leguminosae e.g. alfalfa (
Medicago sativa
), clover (Trifolium sp.), soya (
Glycine max
), various species of bean (Phaseolus sp., Vici sp, Vigna sp.), peas (
Pisum sativum
), various root crops, e.g.
Beta vulgaris,
carrots (
Daucus carota
), sweet potatoes (
Ipomoea batatus
) as well as others, for example
Arabidopsis thaliana.
Glufosinate-tolerant plants may also be produced by inserting genes that encode a mutated glutamine synthetase enzyme which is resistant towards the inhibitory activity of glufosinate. As in the case of the above-mentioned wild type genes, these are cloned into expression cassettes developed especially for plants, and

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