IL97676A - Plant fungicidal compositions comprising citric acid and metal ions and fungicidal methods making use of such compositions - Google Patents

Description

97676/2 nxom o'^ an ο>ηα:ί!? JH >-IOD >^oi Q>-I>¾)DD ni no2 ΓΙ ΠΓΙ^ ηΐΌ> :nn D>JI M ri>->o>_< nt?ND ¾nn>vy rnvny IWN Plant fungicidal compositions comprising citric acid and metal ions and fungicidal methods making use of such compositions Amrion ZUSMAN intnr )MOH Yoram ZIVION yi>2_< a*n > C:- 82562 - 1 - 97676/2 FIELD OF THE INVENTION The present invention provides a method and composition for combating plant fungus.

BACKGROUND OF THE INVENTION AND PRIOR ART Fungus is one of the main pests infesting plants and combating this pest is highly desirable. While many anti-fungal preparations for use in combating plant fungus are available, most, if not all, utilize various toxic substances as active agents and their use may thus have various hazardous and environmental consequences. Accordingly, in recent years many attempts have been made to develop environmentally safe pesticides. Additionally, most fungicidally active agents, e.g. various azoles, are synthetic compounds and their production is at times expensive.

Copper, manganese and zinc ions are known to be fungicidally active but their use as fungicides for plants has been very limited, particularly in view of the non-availability of appropriate chelating agents for these ions. The use of organic compounds as chelating agents was found - 2 - 97676/3 to reduce the fungicidal activity of copper ions (James G. Horsfall, 1956, Principles of Fungicidal Action, Chronica Botanica Company, Waltham, Mass., U.S.A., pp. 145-153) and to date no satisfactory organic chelates have been developed (see also George N. Agrios, 1970, Plant Pathology, Academic Press, New York, N.Y., U.S.A., pp. 192-193).

^ Japanese Patent Application Kokai 73/75,724 (abridged in CA^l 04871 c) discloses a composition comprising copper ions in the form of a salt of a carboxylic acid, wherein one of the preferred carboxylic acid is citric acid. However, in addition to citric acid and copper ions, the composition of this patent application comprises, as active compound, 1,2-bis(3-ethoxycarbonyl-2-thioureido)benzene. Furthermore, from the preparation procedure described there it followed that the carboxylic acid is likely washed away during the preparation procedure and the composition itself is basic.

It is the object of the invention to provide an improved method and composition for combating plant fungus utilizing copper, manganese and zinc ions as active agents.

GENERAL DESCRIPTION OF THE INVENTION In accordance with the present invention it was surprisingly found that contrary to prior art belief citric acid is a very useful chelating agent of metal ions in plant fungicidal compositions. Furthermore, it has been found that such a fungicidal composition has a systemic plant fungicidal effect when administered through the plants' roots.

Accordingly, the present invention provides a plant fungicidal composition consisting essentially of one or more metal ions selected from the group consisting of Mn+~, Cu+2 and Zn+2 and citric acid, the molar ratio of citric acid to said metal ions being about 0.5 to about 2.5.

Preferably, the molar ratio of citric acid to said metal ions is about 0.8 to 2.0, the ratio of about 1.0 to about 1.5 being particularly preferred. A composition comprising both Mn+2 and Cu+2 was found to be - 3 - 97676/3 particularly useful, the ratio of Mn+2 to Cu+2 in such a composition being, for example, about 1 :4 to 1 : 1.

The composition of the present invention may be provided as a dry particulate solid, e.g. in the form of powder or granulates, which may be administered to the soil as such or after its dissolution in water. Compositions in accordance with the present invention may also be provided in the form of an aqueous solution, either ready for administration or as a concentrate which is diluted prior to use.

The present invention also provides a method for combatting a plant fungus comprising administering to the plant a composition consisting essentially of one or more metal ions selected from the group consisting of Mn+2, Cu+2 and Zn+2 and citric acid, in a molar ratio of citric acid to metal ions of about 0.5 to 2.5, preferably about 0.8 to 2.0 and most preferably about 1.0 to 1.5.

It was surprisingly found in accordance with the invention that the composition is very effective in combatting foliar fungus when administered systemically, i.e. to plant roots.

Thus, in accordance with a preferred embodiment of the present invention, the composition is administered to plant roots for systemic effect against plant fungus, e.g. foliar fungus. The composition of the present invention may, however, also be administered topically, e.g. by spraying.

The present invention will now be illustrated with reference to the following non-limiting example.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows two examples of plants infected with a fungus, which were treated with a composition of the invention (two applications, with a two weeks' interval between them). In each plant some leaves (indicated by arrows) were covered during application of the composition: I -covered only during the first application; II -covered during both applications. - 4 - 97676/3 Example 1 : stock solutions a) Copper solution: the solution was prepared by dissolving 290 gr. of copper sulfate (CuSO4, technical) together with 223 gr. of anhydrous citric acid in water to a final volume of 1.4 liters. b) Manganese solution: 196 gr. of manganese sulfate (MnS04.lH2O) was dissolved together with 223 gr anhydrous citric acid in water to a final total volume of 700 ml.

The solutions were stored for at least two days before use until they became clear.

Example 2: test results The compositions were administered to plants infected with fungus either topically, by spraying a solution comprising 0.1-2% v/v of the stock solution in water (concentration of the two solutions combined) or systemically by administering a stock solution per se to the plant roots, or by administration through the irrigation system. a) Systemic administration (I) Rose (Rosa sp. ) were grown in a greenhouse under normal horticultural growth conditions. The plants were naturally infected by a fungus, the infection being evidenced by a large number of white spots on their leaves.

The infected plants were daily administered with compositions prepared from the stock solutions of Example 1, the amount of daily administration to the plants being as follows (moles per 1 ,000 m2).

Mn+2 -0.01 17; ΟΓ2 -0.0139 (the compositions contained also citric acid in the relative concentration as in the stock solution of Example 1). - 5 - 97676/3 The administration of the composition was via the irrigation system to the plant roots.

Within 2-3 days, the infection was greatly diminished, as was evident by a considerable decrease in the number of white spots on the plants' leaves.

It is important to note that the plant did not show any apparent sign of stress.

(II) A similar experiment was repeated with squash plants (C curbita pepo) growing in a field.

A 10,000 m2 field was divided into two plots of about equal sizes. One plot received a treatment of 2 liters of a mixture of equal volumes of the two stock solutions of Example 1 per 1,000 m2 of the stock solutions of Example 1 , the amount of administered solution divided equally over the three month growth season, in two week intervals. The other plot was not treated and served as control.

The white fungal infection which was clearly evident on the plants in the non-treated field, was almost completely diminished from the plants in the treated plot.

(III) Apple {Mains sp. ) and Plum ' {Primus sp. ) trees having large white fungal appendages at the bottom of their trunks were systemically administered with a composition of Example 1. The composition was administered to the trees through holes dug in the soil beneath the specific drippers feeding the specific trees. The administration consisted of 30-40 ml. of either a 1 : 1 mixture of the manganese and the copper solutions of Example 1 or 30-40 ml. of the copper solution alone.

The anti-fungal activity became apparent through withering of the large fungal appendages which occurred within three days after administration. - 6 - 97676/2 Plum trees which were treated early after renewal of growth in the spring season regained much of their vitality, whereas the state of control trees which had a similar initial degree of infection but which were not treated, showed a considerable decline.

While both treatments, namely with the mixture of the two solutions and with copper solution alone were effective in their anti-fungal activity, it appeared that the treatment with the mixture was more effective. c) Topical administration Squash {Cucurbita pepo) plants were grown in individual pots in a greenhouse and became naturally infected by a fungus, the infection being apparent by a large number of white dots on the plants' leaves. The plants were sprayed with a composition comprising a 0.1-2% of a 1:1 mixture of the two stock solutions of Example 1.

The treatment consisted of two applications with a two weeks' interval between them. As a control, part of the leaves were covered during spraying with an aluminum foil which was removed immediately thereafter. Some leaves were covered during both applications and part covered only during the first application of composition.

As can be seen in the drawing, the leaves which were covered during applications of the composition remained infected with the fungus (arrow) while all the other leaves were totally devoid of any signs of infection. Furthermore, the leaves which were covered during both applications of the composition, (indicated as "II"), were more strongly infected than the leaves covered only during the first application (indicated as "I").

The same experiment was also repeated with rose plants grown in a greenhouse and with squash plants grown in open fields and similar results were obtained. - 7 - 97676/2 While all doses of the composition were effective as fungicides, the affectivity generally increased with the concentration, peaking at a concentration of about 1% of the stock solutions (total of both stock solutions).

Claims (12)

- 8 - 97676/2 CLAIMS:

1. A plant fungicidal composition consisting essentially of one or more metal ions selected from the group consisting of Mn+2, Cu+2 and Zn+2 and citric acid, the molar ratio of citric acid to said metal ions being about 0.5 to about 2.5.

2. A composition according to Claim 1, wherein the molar ratio of citric acid to said metal ions is about 0.8 to 2.0.

3. A composition according to Claim 2, wherein the molar ratio of citric acid to said metal ions is about 1.0 to 1.5.

4. A composition according to any one of Claims 1 to 3 being a dry particulate solid.

5. A composition according to any one of Claims 1 to 3 in the form of an aqueous solution.

6. A composition according to any one of Claims 1 to 5, for the administration to plant roots for systemic effect.

7. A composition according to any one of Claims 1 to 5, for topical administration.

8. A method for combatting a plant fungus comprising administering to the plant a composition consisting essentially of one or more metal ions selected from the group consisting of Mn+2, Cu+2 and Zn+2 and citric acid, in a molar ratio of citric acid to metal ions of about 0.5 to 2.5.

9. A method according to Claim 8, wherein the molar ratio of citric acid to said metal ions is about 0.8 to 2.0.

10. A method according to Claim 9, wherein the molar ratio of citric acid to said metal ions is about 1.0 to 1.5.

11. A method according to any one of Claims 8 to 10, wherein the composition is administered to plant roots, for systemic effect. - 9 - 97676/2

12. A method according to any one of Claims 8 to 10, wherein the composition is administered topically onto the plants . For the Applicants, 82562SPC/IC/jg/be/18.4.1994