CA1098331A - Method of protecting plants against damage by frost and composition for carrying out said method - Google Patents

Abstract

Case 5-10325/+
Canada Method of protecting plants against damage by frost and composition for carrying out said method Abstract of the Disclosure The present invention provides a method and composition of protecting plants, such as fruit, vegetables etc. against damage by frost. The method consists in treating the said plants, before outbreak of frost, with a composition containing as protecting ingredient a sufficient amount of a hydroxamic acid derivative of formula or

Description

1~?8331 The present invention provides a method of protecting plants, in particular plant cultures, such as fruit, vegetables, ornamentals including shrubs and trees, against damage by frost and a composition for carrying out this method.
The prevention of frost damage to crops of cultivated plants is an extremely important problem in agriculture and horticulture, For this reason numerous active substances and measures have been proposed in order to increase the freeze resistance, that is to say the resistance of cultivated and ornamental plants to the action of cold and frost and in this way to prevent frost damage. Besides the application of polymers, foams and mists, the application in question is often of substances which constitute protectives against the destruction of the plant cells by freezing caused by damage to the membranes. Frost damage is fr~quently attributable to irreversible structural changes in the cell membranes and con-sequently of associated proteins, that is to say for example to changes in the permeability which result in the collapse of vital cell functions, such as oxidative phosphorylation.
A large number of substances for protecting plant cells against destruction by freezing have been proposed, but -all of them are not entirely satisfactory, because their application is restricted only to specific plants or because they induce phytotoxic side-effects.

10~8331 It has also been proposed to use growth regulators which lower the metabolism of the plant and bring about a reduction of the vegetative growth and so maintain the plant in the dormant state, so that it becomes much less susceptible to frost.
Among the many frost protectives for plants, hydroxamic acids and the derivatives thereof have so far never been proposed.
According to the present invention there is provided a method of preventing frost damage on plants which comprises applying to the plants or to parts of the plants to be protected against frost damage, before the onset of winter or before a suspected occurrence of frost, an effective amount of a hydroxamic acid derivative of the formula Rl - CO - I - O - R3 (I) or of the "tautomeric" formula Rl - C = N - O - R3 (Ia) wherein Rl is a straight-chain or branched-chain Cl-C7 alkyl group, optionally substituted by chlorine, or a C3-C6 cycloalkyl group, R2 is hydrogen or a methyl group, R3 is hydrogen, a methyl group, an alkylcarbonyl group in which the straight-chain or branched-chain alkyl moiety has from 1 to 1] car-bon atoms, or is an equivalent of a metal selected from the group consisting of aIkali metals, alkaline earth metals, manganese, iron and copper, or is an amine or quaterna~rJ ammonio cation, and R4 is hydrogen, or a methyl or ethyl gro~p.

, . . - ~

lV9833~

The invention is particularly applicable to cultivated plants, such as fruit crops (citrus fruit, peaches, apples, etc), and also vegetables, and ornamentals including shrubs and trees.
The method of protecting plants against frost damage com-prises treating the p]ants or parts of plants to be protected, before the onset of winter or before a suspected occurrence of frost, with a composition which contains an effective concen-tration of a hydroxamic acid derivative of the formula I or Ia.
The active compounds of the formula I and Ia exert a substantial continuous protective action which, on application in the autumn, lasts intc the spring. The protective action occurs immediately, so that treatment on the day before an out-break of frost guarantees satisfactory protection against frost damage.
Preferably, those compounds of the formula I are used in which Rl represents an alkyl group of 3 to 7 carbon atoms, R2 and R4 represent hydrogen or methyl and R3 represents hydrogen or one of the cations referred to or a methyl or alkylcarbonyl group.
The majority of the active compounds of the formula I and Ia are known compounds and are described, for example, in Houben-Weyl, Vol. 8, pp. 684-692, Beilstein, Vol. 9, page 341 and in other literature sources. They are compounds which are stable and soluble in water and ordinary organic solvents.
A number of hydroxamic acid derivatives of the above mentioned type have already been proposed as herbicides and fungicides and as growth stimulators in ~eteri-nary med~cine (for 10~8331 example United States Patent specification 3,714,361). Some representatives of this active compound class can cause phyto-toxic side-effects. In this event it is expedient to optimize the ratio of frost-protective action to phytotoxic effect by additional measures (choice of dose etc.).
Some hydroxamic acid derivatives also exhibit plant growth-regulating properties, such as growth inhibition and the promotion of fruit and leaf abscission.
An alkyl group Rl can be straight-chain or branched-chain.
Active compounds which exemplify hydroxamic acid deriv-atives of the formula Rl - C0 - N - O - R3 (I) are listed in the following table:

Compound Rl R2 R3 in C

1 CH3(CH2)4- H H 63-65

2 cyclohexyl H H 130

3 tert.C4Hg H H 167-168

4 n C6H13 H H 67-69 CH3(CH2)4- H K amorphous 6 n-C3H7 H H 42 7 n-C4H9 H H
8 n-C7H15 H H 79 qr '~
~, 10~8331 Compound Rl R2 R3 m.p. in C
9 CH3(CH2)3 CH H H

tert.C4H9 H HN ( 2H4 )3 CH3\
11 j H-(CH2)3- H H

12 cyclopentyl H H
13 Cl-(CH2)5- H H
14 CH3(CH2)4- CH3 CH~
CH3(CH2)4- H HN~ (CH2)2H]3 16 CH3(CH2)4- H H ~(C2H5)3 17 tert.C4Hg H KG3 > 250 18 tert.C4Hg H -CO-CH3 114-116 19 5 11 3 3 b.p.ll 9 tert.C4H9 3 3 b-P-12 22 tert.CI~H9 H 1 Fe ~ 270 23 iso-C3H7 H H 116 24 tert.C4H9 H CH3 n2=1,4439 n-C4Hg H -COCH3 62-65 26 Cl-(CH2)3- CH3 CH3 b.p.l3 27 ~ H K 114-117 28 ~ H H 116 29 tert.C4Hg H -CO-tert.C4H9 147-148 CH3( 2)3 l H 1 Cu++ > 2000 ~Og8331 Compound Rl R2 R3 m.p. in C

33 ClCH2- H H 85-90 34 tert.C4Hg H C-CllH23(n) 36-38 n-C4Hg H H

37 iso-C4Hg H H 72-75 38 n-C4Hg-CH- H H

39 C2H5 \
CH- H H

Hydroxamic acid derivatives of the "tautomeric" formula R - C = N - O - R3 (Ia) Compound Rl 3 4 Physical Constants n-CsHll 3 3 b-p- 40=70 C
41 CH3 H C2H5 m.p. 25-26C

1~

- 10~8331 Suitable carriers and additives in the compositions of the present invention can be solid or liquid and correspond to the substances customarily used in the art of formulation, for example natural or regenerated mineral substances, solvents, dispersants, wetting agents, thickeners, binders or fertilisers.
For application, the compounds of the formula I can be formulated as follows:
Solid formulations: dusts,tracking agents, micro-granules .
Liquid formulations:
a) water-dispersible active substance concentrates: wettable powders, pastes, emulsions;
b) soluti~ns.
Solid formulations (dusts, tracking agents) are obtained by mixing the active substances with solid carriers. Suitable carriers are, for example: kaolin, talc, bolus, loess, chalk, limestone, ground limestone, attaclay, dolomite, diatomaceous earth, precipitated silica, alkaline earth silicates, sodium and potassium aluminium silicates (feldspar and mica), calcium and magnesium sulphates, magnesium oxide. ground synthetic materials, fertilisers, for e~ample am~onium s~lphate. ammonium phosphate, 2~moniu~
nitrate, urea, ground vegetable-products, such as corn meal, ' `~

10~8331 bark dust, sawdust, nutshell meal, cellulose powder residues of plant extractions, activated charcoal etc. These sub-stances can either be used singly or in admixture wlth one another . , .,, . . . ~, Polymer granules can also be prepared by impregnating a finished, porous polymer granulate (urea/formaldehyde, polyacrylonitrile, polyester and others~,which has a specific sur~ace area and a avourable predetermined sdsorption/desorption ratio, with the active substances, for example in the form of their solutions (in a low boiling solvent) and removing the solvent. Polymer granules of this kind in the form of microgranules having a bulk density of 300 g/litre to 600 g/litre can also be manufactured with the aid of atomisers. The dusting can be carried out from air-crat over extensive areas of cultures of useful plants.
It is also possible to obtain granules by compact-ing the carrier with the active substance and carriers and subsequently comminuting the product. - ~
To these mixtures can also be added additives which stabilize the active substa~ce and/or nonionics, anionics and cationics, which, for example, improve the adhesion of the active ingredients on plants or parts of plants (tacki~iers and agglutinants) and/or ensure a better wettability (wetting agents) an~ dispersibility (dispersing agents).
Examples of such substances are: olein/chal'~ mixture, F~ ~

~0'18331 cellulose derivatives (methyl cellulose, carboxymethyl cellulose), hydroxyethyl glycol ethers of monoalkyl and-dialkyl phenols having 5 to 15 ethylene oxide radicals per molecule and 8 to 9 carbon atoms in the alkyl moiety, lignin-sulphonic acids, the alkali metal and alk~line earth me~al salts thereof, polyethylene glycol ethers (carbowaxes), fat~y alcohol polyethylene glycol e~hers llaving 5 to 20 ethylene oxide radicals per molecule and 8 to 18 carbon atoms in the fa~ty alcohol moiety, condensation products of urea and formaldehyde, and also latex products.
- Water-disper~ible concentrates, i.e. wettable powders, -pastes and emulsi~iable concentrates, are compositions which can be diluted ~ith water to the desired concentration.
They consist of active substance, carrier, optionally additives which stabilize the active su~stance, surface-active substances and anti-foam agents and, if appropriate, solvents.
Wettable powders and pastes are obtained by mixing and grinding the active substances with dispersing agents and pulverulent carriers in suitable devices until homo-ge~ is attained. Suitable carriers are, for example, those already mentioned for the solid formulations. In some c~ses it is advantageous to use mixtures of different carriers.
As dispersing agents there can be used, for example, conden-sation products of sulphonated naphthalene and sulphonated v;- /G
-- ~3~ --10~8331 naphthalene derivatives with ~ormaldehyde, condensation pro-ducts of naph~halene or naphthalene sulphonic acids with phenol and formaldenyde, as well as al~;ali metal. a~monium and alkaline earth metal salts of ligninsulphonic acid. in addition alkylarylsulphonates~ alkali me~al and alkaline earth metal salts of dibutylnaphthalene sulphonic acid, atty alcohol sulphates,such as salts of sulphated hexa decanols, heptadecanols, octadecanols, and salts of sulphated fatty alcohol glycol ethers, the sodiu~ salt of oleyl methyl tauride, ditertiary ace~alene glycols, dialkyldilauryl-ammonium chloride and fatty acid alkali metal and all~aline earth metal salts.
Suitable anti-foam agents are for example silicones, The active substance is so mixed, ground sieved and strained with the additives mentioned above that, in wettable powders. the solid particle size of 0.02 to 0.04 mm and in pastes, of 0.03 mm, is not exceeded. Emulsifiable concentrates and pastes are manufactured by using dispersing agents, s-~ch ~s those cited previously above, organic solvents, and water.
Examples of suitable solvents are alcohols, aromatic hydro-carbons with a low freezing point (below -20C), such as o-xylene, m-xylene, toluene, and mineral oil fractions which boil between 120 and 350C. The solvents must be practically odourless, not phytotoxic, and inert to the active substances.
Furthermore, the compositions according to the invention _, !~, can be applied in the form of solutions. For this purpose the _ ~__ ~0~8331 active subs~ance or several active substances of the general formula I are dissolved in suitable organic solvents, mixtures of solvents or ill water. Aliphatic and aromatic hydro-carbons, chlorinated derivatives thereof, alkylnaphthalenes and mineral oils, singly or in admixture, can be used as organic solvents.
The abo~e described compositions contain between 0.1 and 95%, preferably between 1 and 80%, of active compound.
Application formulations can be diluted to the desired con-centration.
The active substances of the formula I can be formulat-ed for example as follows:

Dusts -The following subs~ances are used to obtain a) a SZ and b) a ~% dust:
a) S parts of active substance, 9S parts of talc;
b) 2 parts o~ active substance, part of highly disperse si~ icic acid, ~ 7 parts o~ talc.

- The active substances are mixed with the carriers and ground.

,, 1~

10~833 Granules __ ~he following substances are used to produce S% granut es:
parts of active substance, 0.25 parts of epichlorohydrin, 0.25 parts of cetyl polyglycol ether, 3.50 parts of polyethylene glycol, - :
91 parts o~ kaolin (particle size 0.3 - 0.8 mm).

The active substance ~ mixed w~ epichlorohydrin and the mixt~re is ~issolYed in 6 parts of acetone. The polyethylene glycol and cetyl polyglycol ether are then added. The resul-tant solution is sprayed on kaolin, and the acetone is subsequcntl~ evaporated in vacuo.

I~ettable po7der:

e following constituents are used for the preparation of a) a 7~%, b) and c) a 25%, and d) a 10% wettable powder:
a) 70 parts of active substance, parts of sodiu~ ligninsulphonate, 1 part of sodium dibutylnaphthalenesulphonate.
24 parts of s;licic acid, J~

10~8331 .

b) 25 parts o~ active substance, 4.5 parts of calcium ligl~insulphonate, 1.4 parts of Champagne chal~_hydroxyethyl cellulose mixture (1:1), 1.5 parts of sodi~ dibutylnaphthalencsulphonate~
19.5 parts of silicic acid, 19.5 parts o Champagne chalk, 28.1 parts of kaolin.
c) 25 parts of active substance, 2.~ parts of isooctylphenoxy_polyoxyethyleneethanol, 1.~ parts of Cha~pagne chalk/hydroxyeth~l cellulose ~ixture (1~
~` 8.3 parts of sodium aluminium silicaté, 16.5 parts of kieselguhr, 46 parts of kaolin.
d) 10 parts o~ active substance, 3 parts o~ a mixture o~ the sodium salts of s~ra~d fatty alcohol sulph~tes, parts of naphthalenesulphonic acid/ormaldehyde condensate, 82 parts of kaolin.

The acti~e substances are intimately mixed in suitable mixers with the additives, and the mixture is then ground in appropriate mills and rollers to yield wettable powders w~ich can be diluted with ~ater to give suspensions o the .. /~

1~)98331 desired concentration. Such suspensions are very suitable for treating plants to influence growth and development.

Emulsifiable concentrate:
The following substances are used to produce a 25%
emulsifiable concentrate:
parts of active substance, 2.5 parts of epoxidised vegetable oil, parts of an alkylarylsulphonate/fatty alcohol polyglycol ether miture, parts of dimethyl formamide, 57.5 parts of xylene.
By diluting such a concentrate with water it is possib-le to manufacture emulsions of the desired concentration, which are suitable for application to plants for inhibiting growth.
The use of the active compounds in the form of dusts, tracking agents, wettable powders and emulsifiable concen-trates, as well as frost-resistant solutions and aerosols, is particularly preferred The compounds of the formula I which are absorbed by plants and not prematurely metabolised and effect a slight growth inhibition without being noticeably phytotox.ic, there-ore best fulfill the expectations which can be placed in frost protectives.
/~

10~833~

The protective action of the compositions of the invention against frost was determined and evaluated by means of the followings tests:

1) Frost-resistant test on beans Bean plants of the Felix variety were reared in a green-house in earthen-ware pots and sprayed with an aqeuous preparation of the active compounds listed hereinafter at the commencement of flowering. The concentration of active compound in the spray broth was 1000 ppm. Eighteen plants were sprayed per treatment. Untreated plants were used as controls. Seven days after the application the test plants were placed in a climatic chamber, the temperature was slowly lowered to -1 C, kept thereat for a brief time, and thereafter slowly raised again to room temperature. Evaluation was made 10 days after this cold treatment and each plant was inspected for frost damage using the following evaluation scale:
- z all plants withered (as control) (+) + = ) intermediate stages ~ = ) +++ = all plants without any trace of frost damage.

,~ _ 10"83;~

Results _ Compound Frost-protective action 1 (+) 4 +

18 +
21 +
24 (+) ++
26 (+) 27 +
28 ++
29 +
__.

In another test the bean plants were treated twice with a prep-aration of compound I, namely (a) twice at a concentration of 100 ppm and (b) twice at a concentration of 500 ppm. One week after the second treatment, the plants were exposed for 1 hour to a temperature of -4C and then restored to normal conditions.
The test was evaluated one week later. Whereas the damage to untreated bean plants was 100%, i.e. total, the frost ;''`

10~8331 damage to plants treated with active substance at a concen-tration of 100 ppm was 40% and only 15% to plants treated with active substance at a concentration of 500 ppm.

2) Frost-resistant test on citrus plants Citrus trees were treated with compound 1 in the ~oncentrations indicated below one day before a frost predict-ed in a weather forecast. In the following night the tempe-rature fell for 4 to 5 hours to -3C. Six days later the following results of the damage caused could be determined:

~reatment Hamlin oranges and Valencia with spray oranges broth /Oa~e dama~ to Compound 1 concentration old leaves new leaves blossoms in ppm untreated 0 90 90 3) Frost-resistant tests in fruit cultures a) For these tests, devices (cages) were used which make it possible to produce frost conditions on individual branches of a pear tree. Compound 1 was sprayed on blossom-bearing branches of pear trees at a time when the blossoms were just on the point of opening, viz. at the time of the r~ ,~

1~8331 greatest susceptibi~y to frost. Some days after this spray treatment, "cages" were placed over the treated and untreated branches of the same tree and then, at night, a frost with a minimum temperature of -3C was artificially produced in these cages. A few days later the frost damage to the blossoms was determined by microscopic examination and the following results were obtained:
treatment with 2000 ppm of compound 1 = 74% damage treatment with 4000 ppm of compound 1 = 26%~dama~e untreated branches = 97% damage b) Peach trees were sprayed in the autumn with a liquid preparation of compound 1 just as the leaves were beginning to turn in colour and wither. In January, branches were collected and subjected for 24 hours to a cold treatment in the course of which the temperature was lowered stepwise by 2C an hour to a minimum temperature of -21C and then raised again. The microscopic examination of many buds (embryos) was made two days later in order to ascertain how many had perished and how many had survived.

Result %a~e of survivin~ buds treatment with 1000 ppm 74%
treatment with 2000 ppm 83%
treatment with 8000 ppm 88%
untreated 63%

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preventing frost damage on plants which comprises applying to the plants or to parts of the plants to be protected against frost damage, before the onset of winter or before a suspected occurrence of frost, an effective amount of a hydroxamic acid derivative of the formula (I) or of the "tautomeric" formula (Ia) wherein R1 is a straight-chain or branched-chain C1-C7 alkyl group, optionally substituted by chlorine, or a C3-C6 cycloalkyl group, R2 is hydrogen or a methyl group, R3 is hydrogen, a methyl group, an alkylcarbonyl group in which the straight-chain or branched-chain alkyl moiety has from 1 to 11 carbon atoms, or is an equiva-lent of a metal selected from the group consisting of alkali metals, alkaline earth metals, manganese, iron and copper, or is an amine or quaternary ammonio cation, and R4 is hydrogen, or a methyl or ethyl group.

2. The method according to claim 1 for protecting cul-tures of fruit, vegetables or ornamentals.

3. The method according to claim 1 wherein, in the com-pound of formula I or Ia, R1 is a straight-chain or branched-chain C1-C4 alkyl group or a cyclopropyl group, each of R2 and R4 is hydrogen or methyl and R3 is hydrogen, an alkali metal cation or a lower alkylcarbonyl group.

4. The method according to claim 3 wherein the compound employed is n-pentanecarbohydroxamic acid of the formula CH3(CH2)4 - CO - NHOH

5. The method according to claim 3 wherein the compound employed is 2-methyl-propane-2-carbohydroxamic acid of the formula

6. The method according to claim 3 wherein the compound employed is the potassium salt of 2-methylpropane-2-carbohydrox-amic acid of the formula

7. The method according to claim 3 wherein the compound employed is methanecarbohydroxamic acid of the formula

8. The method according to claim 3 wherein the compound employed is 2-methylpropane-2-carbohydroxamic acetate of the formula

9. The method according to claim 3 wherein the compound employed is cyclopropane carbohydroxamic acid of the formula or its potassium salt.

10. The method according to claim 3 wherein the compound employed is n-butanecarbohydroxamic acetate of the formula CH3(CH2)3 - CO - NH - O - CO - CH3.