Method of protecting cultivations of agrarian interest from the action of nonselective herbicides

The present invention relates to a method of protecting cultivations of agrarian interest from the toxic: action of nonselective herbicides and, more particularly, said me- chod consists in utilizing, as antidotes, 2- or 4-thiazoli- line-carboxylic acids and derivatives thereof.

This invention relates furthermore to compositions con taining the abovesaid antidotes, to be employed in the pro tection of useful cultivations from the action of herbici- des.

The perbicides belonging to the class of chloroaceta nilides or of thiolcartamates are very useful compounds in the fight against the infesting plants of agrarian cultiva tions.

Many of these herbicides, however, exert their toxic aotion also towards certain useful cultivations such as, for example, maize and sorghum, and, by consequence, being not selective, they cannot be used for the weed-killing of such cultivations.

The availability of antidotes, i.e. of compounds which protect the useful cultivations from the action of the herbicides without contemporaneously reducing their herbicide action towards the infesting plants, permits to make use of these herbicides also for defending those useful cul tivations which otherwise would be damaged.

AMong the main herbicides which prove to be phyto- coxic for certain usefl cultivations there are those belonging to the class of the chloroacetanilides comprising, for example, N-methoxynethyl-2,6-diethyl-chloroacetanilide common name: Alachlro), N-butoxymethyl-2,6-diethyl-chloro acetanilide (common nane: butachlor), N-methoxyethyl-2-methyl-6-allyl-chloroacet anilide (reference item M 8669) and the cnes belonging to the class of the thiolcarbamates comprising, e.g., N,N-diisopropyl-S-(2,3-dichloroallyl)--thiolcarbamate (common name: Diallate); N,N-diisopropyl--S-(2,3,3-trichloroallyl)-thiolcarbamate (common name: Triallate); N,N-diethyl-S-(4-chlorobenzyl)-thiolcarbamate (common name: Benthiocarb); N,N-dipropyl-S-ethyl-thiolcarbamate (common name. Eptam).

Compounds belonging to different chemical classes are known, which are capable of protecting useful cultivations from the toxic action exerted by the herbicides. For example, dichloroacetamides useful as antidotes have been described in U.S. patent No. 4,021,224 (Stauffer) or in U.S. patent No. 4,228,101 (Montedison S.p.A.). 2-chloro--thiazoles disubstituted in positions 4,5, which are useful as antidotes in the defence of sorgnum cultivations have been described in Euro_lean patent application No. 27019 (Monsanto Co.).

We have now found that the toxic action of nonselective herbicides, belonging e.g. to the class of the chloroacetanilides and of the thiolcarbamates, towards useful cultivations can be sensibly reduced or eliminated, without decreasing, at the same time, the herbicide action towards infesting plants if use is made, as antidotes, of compounds of formula:

wherein: group COOR is in position 2 or 4 in the thiazolidine ring, R represents a hydrogen atom or an alkyl C₁-C₄; R¹ represents a hydrogen atom, an acetyl group optionally substi- tuved by 1 to 3 halogen atoms.

Thus, an object of the present invention consists in providing a method of reducing the damages towards useful cultivations caused by nonselective herbicides belonging, for example, to the class of the chloroacetanilides or of the thiolcarbamates, such method consisting in treating the seeds, the plants or the soil in which they grow with an effective amount of an antidote of formula I, either as such or in the form of a suitable composition.

Another object of the present invention are the compositions containing a compound of formula I as an active ingredient along with inert vehicles and optionally other additives, useful to treat the seeds of useful plants, the plants themselves or the soil in which they grow.

A further object of this invention are the seeds of use ful plants treated with an effective amount of a compound of formula I.

The compounds of formula I may also be in the form of salts, e.g. hydrochlorides, when in formula I R¹ = H.

For the uses according to this invention, the individual compounds of formula I, also in admixture with one another, and the corresponding salts are equally valid.

Some of the compounds of formula I are known, namely:

• - 2-thiazolidine-carboxylic acid and the lower alkyl esters thereof,
• - 4-thiazolidine-carboxylic acid and the lower alkyl esters thereof,
• - N-acethyl-2-aniazolicine-carboxylic acid,
• - the methyl ester of N-dichloroacetyl-4-thiazolidine--carboxylic acid,
• - N-acetyl-4-thiazolidine-carboxylic acid.

Some of these known compounds, such as the derivatives of 4-thiazolidine-carboxylic acid, are useful as bio- stamulants for agrarian uses. The others have been tested in the pharmaceutical field as hepatoprotectors or inter- nediates for antibiotics.

As far as we know, these compounds were never supposed to be associated with properties of antidotes for herbicides.

The new compounds of formula I are easily preparable by acylation of 2- or 4-thiazolidine-carboxylic acid or of the respective alkyl esters with the proper haloacetyl chlo ride, in an inert solvent and in the presence of a halogen- hydric acic-accepting base.

As an alternative; acylation can be accomplished by substituting the acyl halide by the corresponding anhydri de

The following compounds:

• - N-dichloroacetyl-2-thiazolidine-carboxylic acid

  [melting point = 196-140 °C; IR (cm^-1) : 1710 (ν COOH), 1660 (ν CO-N],

• - methyl ester of N-dichloroacetyl-2-thiazolidine-carbo xylic acid

  [melting point = 80-81 °C; IR (cm^-1) : 1740 (ν COOCH₃), 1670 (ν CO-N]

are new and represent, as such, a further object of this invention.

It has been furthermore obsenved that N-acetyl-2-thia zolidine-carboxylic acid and the esters thereof with alcohols C₁-C₄ possess, besides antidotic properties, also biostimulating properties.

The action of these compounds, when employed as biosti mulants, results in a more luxuriant aspect of the plants and in an increase in the harvest.

Thus, a further object of the present invention resides in the use of N-acetyl-2-thiazolidine-carboxylic acid and of its esters with alcohols C₁-C₄ as biostimulants for erltivations of agrarian interest.

As mentioned hereinbefore, the antidotesof formula I can be applicated to the useful cultivations according to various modalities.

For example, they can be utilized for a preventive treatment of seeds, so that the plants developing therefrom will be protected from the toxic action exerted by nerselective herbicides.

As an alternative, tie compounds of formula I are employable for treating the plant itself or the soil in which it grows. In this case, the antidotes can be distributed alone or in combination with the nonselective herbicides.

The different types of applications require different conditions which affect the practical aspects of the treatment, such as antidote amount, period of treatment and type of composition.

Other factors influencing the practical aspects of the treatment are the type of cultivation to be protected, the nonselective herbicide employed, the climatic and environmental conditions.

When the antidote is applicated in a preventive seed treatment, it is employable as such or, preferably, as a proper composition.

The compositions for the treatment of the seeds may be in the form of powders wettable powders or emulsifiable concentrates, and generally consist of the active compound in amounts ranging from 0.5 to 95% by weight and of the usual inert vehicle which, depending on the composition ty- pe may be solid, such as talc, silica, diatomite, bentonite, caicium carbonate and mixtures thereof, or liquid, such as water, alkyl-aromatic: hydrocarbons, acetone, cyclohexano ne and mixtures thereof.

The compositions may also contain suitable additives, such as surfactants, wetting agents, dispersants and mix- tunes thereof.

As previously cited, the antidote amount to be distri buted on the seeds varies as a function of various factors, however, it. is generally sufficient to use product amounts ranging from 0.1 to 100 g/Kg of seeds.

The treatments directly effected on the plant or in the medium where the plant grows require, of course, that the antidote be used in the form of a suitable composition according to the usual practice for this kind of application.

In the applications in which the antidote is distributed on the vegetation cr into the soil along with the nonselective herbicide ir a single formulation, the type of formulation and the content vary both as a function of the above-mentioned facters, and as a function of the herbicide utilized and of the characteristics thereof.

The antidote amount to be used ranges from 0.1 to 10 Kg/ha and the ratio between antidote and herbicide in the composition may range frcm 1:5 to 5:1.

The following examples are given to better illustrate the present invention.

Example 1

Antidotic activity in maize plants by preventive treatment of the seeds.

General modalities : 60 maize seeds were treated with 60 or 120 mg of the antidote to be tested, dissolved in 3 ml of an aqueous solution of dimethylsulphoxide (DMSO) at 3% by weight, or in 3 ml of water optionally containing a wetting agent at 0.1%.

On a basis of 60,000 seecs/ha, the dose employed was corresponding to 60 or to 120 g of antidote per hectare, or corresponding to 2.8 or 506g g of antidote per Kg cf seeds. The treatment was accomplished by mixing the seeds for 10 minutes in said solution and then by allowing them to dry during 24 hours, stirring them at intervals in the course of the first hours.

The treated seeds were then sowed into a ground previously treated with the herbicide being tested, at a predetermined dose. As a control, also maize seeds left in a water bath not containing any antidote, under the same conditions, were sowed.

Aft.er a 10-day growth under continuous light and at a temperature of 25 °C, the antidotic activity was evaluated by comparing the growth of the plants treated with the herbicide and with the herbicide plus the antidote, with the growth of the plants treat.ed neither with the herbicide nor with the antidote.

In the antidotic activity tests, the following compounds of formula I were tested:

• A = N-acetl-4-chiazolidine-carboxylic acid
• B = 4-thiazolidine-carboxylic acid
• C = 2-thiazolidine-carboxylic acid
• D = N-acetyl-2-whiazolidine-carboxylic acid
• E = methyl este- of N-dichloroacetyl-4-aniazolidine-crbo- xylic acid
• F = N-dicnloroacetyl-2-thiazolidine-carboxylic acid
• G = methyl ester of acid C
• H = methyl ester of acid F
• I = methyl ester of N-chloroacetyl-4-thiazolidine-carboxy lie acid. I

The herbicides employed were Alachlor (chloroacetanilide) and Eptam (thiolcarbamate).

The results recorded on following Tables 1 and 2 refer to the toxic action of the herbicide in the presence of the ant idote on the maize plants and are expressed according to a scale of values from 4 (complete stop of growth or death of the plant) to 0 (plant growth like that of plants not treated with herbicide and antidote).

As a sonsequence. an evaluation equal to that of the herbi cide alone is indicative of the absence of an antidotic ef fect, while lower values are indicative of an antidotic effect increasing towards the lower values.

Preliminary laboratory tests proved that the antidotes of formula 1 are not toxic for maize and that the herbicide activity of Alachlor and Eptam towards the common infesting plants of maize (Solanum nigrum, Amarntus spp., Echinochloa spp., Digitaria spp., Setaria spp., Sorghum halepense, Panichum dichctomiflorum, Cyperus rotundus, Cyperus esclulantus) is rot affected by the presence of the antidote in this kind of tests.