EP0228464A4

EP0228464A4 - Plant microbiocidal compound and method.

Info

Publication number: EP0228464A4
Application number: EP19860904660
Authority: EP
Inventors: Shirley Ann Schafer
Original assignee: AGRI-SHIELD Inc; AGRI SHIELD Inc
Current assignee: AGRI-SHIELD Inc; AGRI SHIELD Inc
Priority date: 1985-07-09
Filing date: 1986-07-09
Publication date: 1989-07-26
Also published as: EP0228464A1; FI870978A; WO1987000006A1; PT82952B; ES2000656A6; OA08497A; FI870978A0; PT82952A; DK92487A; BR8606761A; DK92487D0; HUT42293A; GR861797B

Abstract

A microbiocidal method and organo-silicon compound for plants. The microbiocidal organo-silicon compound can be mixed with water and applied to a plant to kill or inhibit a wide variety of micro-organisms. The plant microbiocidal compound and method is highly effective in controlling a wide variety of pathogenic micro-organisms including the citrus canker bacterium Xanthomonas campestris and ice nucleation bacteria such as Pseudomonas syringae and Erwinia herbicola. In addition, the plant microbiocidal compound is also effective against fungi such as peanut leaf spot fungus (Cercospora arachidicola).

Description

"PLANT MICROBIOCIDAL COMPOUND AND METHOD"

Cross-reference to Related Applications

This application is a continuation-in-part of U.S. Application Serial No. 753,251.

Technical Field

The present invention relates to a microbiocidal method and compound for plants and more particularly a microbiocidal method and compound for protecting plants from infection by micro-organisms and for protecting plants from freezing due to the presence of ice nucleation- active bacteria.

Background of the Invention

Microbiocidal compounds of various chemical compositions have been used on plants to inhibit or kill microorganisms that have a detrimental effect on the plant These microorganisms include bacteria, yeasts and fungi. However, conventional microbiocides have several drawbacks. Conventional microbiocides must be applied to the plant at frequent intervals because the compound is washed off the plant. This multiple application requirement is expensive because relatively large amounts of the compound must be used during the life of the plant. In addition, the labor required to apply the antimicrobial compounds is expensive.

The application of large quantities of a biologically active antimicrobial compound also creates an environmental hazard. Many of the conventional antimicrobial compounds are not quickly degraded and will remain in the environment for relatively long periods of time. These biologically active compounds can cause severe damage as the concentration of the compound increases due to multiple applications to plants.

Microbiocides that are used to treat fruits, vegetables and grains can be introduced into the food chain where they are eventually consumed by humans. As the concentration of these microbiocidal compounds increases in the food chain, the detrimental effect on humans and animals is increased.

The antimicrobial compounds currently available are often genus specific. A different chemical compound may be required to treat each genus of microorganism found on a plant. Each multiply-infected plant must

' therefore receive a series of treatments to effectively protect from or eliminate all of the harmful microorganisms.

Some microorganisms, such as those recently imported from foreign countries, are resistant to conventional antimicrobial compounds. The citrus canker bacterium, Xanthomonas campestris pv citri, is an example of a

» bacterium which does not respond to conventional microbiocidal treatment and has been responsible for the destruction of a large percentage of Florida's citrus crop.

Specific microorganisms, such as ice nucleation-active bacteria, have been postulated to be responsible for frost injury to plants. In the early spring, a short rapid decrease in temperature can destroy the newly developing buds or flowers when the sap within the plants freezes and ruptures cell walls. Normally, due to tl high concentration of nutrients, sugars and proteins in the sap and protoplasm in the plant's cells, the freezing point of the aqueous solution is lowered to less the -10°C. However, when ice nucleation-active bacteria such as Pseudomonas syringae are present, the bacteria provide nuclei for the formation of ice crystals which grow and spread rapidly throughout the cells of the plant, causing severe frost damage at temperatures as warm as - 2°C. (See Gross, et al., Distribution, Population Dynamics, and Characteristics of Ice Nucleation- Active Bacteria in Deciduous Fruit Tree

Orchards," Applied and Environmental Microbiology, vol. 46, pp. 1370-1379 (1983).

One treatment for the reduction of ice nucleation-active bacteria is exposure to dense smoke aerosols. Because this smoke is usually produced from bonfires or smudge pots, the size and density of a field or orchard may — make it impossible for the smoke to reach all the bacteria-colonized plants.

Likewise, the danger of fire and intense heat may destroy the plants. Also, the fires must be constantly maintained and can be easily extinguished by snow or freezing rain.

Another treatment for the reduction of ice nucleation-active bacteria is to treat the plant with an aqueous solution of Cu₂(S0₄)₃. Although this treatment is effective in reducing the ice nucleation-active bacteria, the chemical is very water soluble and quickly washes off the plant to which it is applied. Thus, to be effective, the compound must be applied before each expected freeze. This is both labor intensive and is very expensive.

Consequently, there is an immediate and increasing need for new, safe and effective antimicrobial compounds for use on plants.

Summary of the Invention ^• The plant microbiocidal compound of the present invention is an organo-silicon quaternary amine. Organo-silicon quaternary amines have been used on many non-living surfaces and have been used in water to inhibit the growth of microorganisms. (See U.S. Pat. No. 3,730,701). However, it is believed that organo-silicon quaternary amines have heretofore never been

^•20 _usecι _on living matter due to the compound's relatively high toxicity.

It has been unexpectedly found, however, that these organo- silicon compounds can be safely applied to many classes of plants. The plant microbiocidal compounds of the present invention are effective in killing or inhibiting a wide spectrum of microorganisms. These compounds covalently

25 attach to the surface of a plant and therefore are not easily or quickly washed off. The plant microbiocidal compound of the present invention effectively protects a plant from infection by a wide variety of microorganisms with only two to three applications of the organo-silicon compound per year.

The plant microbiocidal compound of the present invention is

30 unexpectedly effective against the citrus canker bacterium Xanthomonas campestris. pv citri . The plant microbiocidal compounds of the present invention are applied to a plant in an aqueous mixture by any conventional means, such as by spraying. After the compound is applied to citrus trees, the trees are protected against infection by the X. campestris organism. Because 35 the plant microbiocidal compound of the present invention is covalently bound to the surface of the leaves, branches and other exposed parts of the a citrus tree, such as an orange tree, a single application of the compound will protect the entire orange tree.

The plant microbiocidal compound of the present invention is also effective against ice nucleation-active bacteria such as Pseudomonas syringae and Erwinia herbicola. Thus, by applying an organo-silicon quaternary amine to a plant, the ice nucleation-active bacteria are either killed or inhibited and the natural colligative properties of the nutrients dissolved in the plant sap and cell protoplasm will protect the plant from ice formation. The plant microbiocidal compound of the present invention is an organo-silicon quaternary amine having the following structure:

wherein:

Y is an anion selected from the group consisting of chlorine, bromine, fluorine and iodine; " is a methyl radical or an aliphatic hydrocarbon radical of from 11 to 22 carbon atoms;

R' is a divalent hydrocarbon radical of 1 to 10 carbon atoms;

R is a monovalent hydrocarbon radical of 1 to 6 carbon atoms or the CF₃CH₂CH₂ — radical; n is an integer from 0 to 2; and a is an integer from 1 to 2.

Thus, it is an object of the present invention to provide an improved microbiocidal compound for plants. Another object of the present invention is to provide a microbiocidal compound for plants which will remain on the plant for a long period of time after a single application.

Yet another object of the present invention is to provide a microbiocidal compound for plants which is effective against ice nucleation- active bacteria. Another object of the present invention is to provide a microbiocidal compound which is not harmful to plants.

Still another object of the present invention is to provide a microbiocidal compound for plants which is effective against Pseudomonas syringae.

Another another object of the present invention is to provide a microbiocidal compound that is effective in protecting seeds against micro¬ organisms.

Still another object of the present invention is to provide a microbiocidal compound for plants which is effective against Xanthomonas campestris.

These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiment and the appended claims.

Description of the Preferred Embodiment

The plant microbiocidal compound of the present invention is an organo-silicon quaternary amine compound with the following structure:

wherein:

Y is an anion selected from the group consisting of chlorine, bromine, fluorine and iodine;

R" is a methyl radical or an aliphatic hydrocarbon radical of from 11 to 22 carbon atoms;

R is a divalent hydrocarbon radical of 1 to 10 carbon atoms;

R is a monovalent hydrocarbon radical of 1 to 6 carbon atoms or the CF₃CH₂CH₂ — radical; n is an integer from 0 to 2; and a is an. integer from 1 to 2.

A preferred embodiment of the plant microbiocidal compound of the present invention is an organo-silicon quaternary amine that has the following structure:

(CH₃0)₃-Si -(CH , 2)'_τ3-

wherein:

R₃ is an alkyl group having from 8 to 18 carbon atoms; and

X is an anion selected from the group consisting of chlorine, bromine, fluorine and iodine.

An especially preferred embodiment of the plant microbiocidal compound of the present invention is an organo-silicon quaternary amine having the following structure:

CH,

X i ^{3 +}

(CH₃0) -Si -(CH ₂)₃- N - C₁₈H₃_₇

CH.

The organo-silicon quaternary amine shown above is commercially available as Dow Coming 5772 Antimicrobial Agent (Dow Coming, Midland, MI).

The plant microbiocidal compound of the present invention is preferrably applied to plants as an aqueous solution. The concentration of the organo-silicon quaternary amine in an aqueous solution is between approximately 0.05% to 5.0% by weight with a preferable concentration of between approximately 0.1% and 2% by weight. The plant microbiocidal compound of the present invention can be applied to a plant by conventional techniques, such as by spraying or by fogging. The plant microbiocidal compound of the present invention can also be painted on a plant

A surfactant can be optionally added to an aqueous mixture of the plant microbiocidal compound of the present invention to improve the spreading of the plant microbiocidal compound over the surface of the plant. Addition of a surfactant causes the plant microbiocidal compound of the present invention to be uniformly distributed over the plant surface. One such surfactant which can be used with the plant microbiocidal compound of the present invention is a nonionic surfactant and wetting agent comprising alkyl aryl polyalkoxynate alcohol available as Amway All Purpose Spray Adjuvant ( Amway Corp., Ada, MI). Other surfactants that can be used with the plant microbiocidal compound of the present invention include, but are not limited to, polyoxyethylene ethers (Triton X-100, Sigma Chemical Co., St. Louis, MI), polyoxyethylenesorbitan monooleate (Tween-80, Sigma Chemical Co., St. Louis, MI). These surfactants are used in an aqueous solution of the plant microbiocidal compound of the present invention at a concentration of between approximately 0.01% and 0.075% by weight

The following examples will serve to further illustrate the present invention without, at the same time, however, constituting any limitation thereof.

Example I

The following organo-silicon quaternary amine compound was tested for phytotoxicity against Citrus mitis trees.

The aqueous solution was prepared by adding the appropriate amount of the stock solution of the organo-silicon plant microbiocidal compound of the present invention (Dow Chemical Company, Midland MI) to water and thoroughly mixing the compound until it was unifoπnly distributed throughout the aqueous solution.

Three citrus mitis trees were purchased from The Golden Stem Florist and Plants in Atlanta, GA. Each tree was trimmed and lightly sprayed with tap water to wash any substances from the leaves. The trees were allowed to air dry before application of the organo-silicon compound.

The trees were sprayed one time according to Table A: Table A

Number of fruit

Tree Amount Treatment Height Width Green Yello Applied (inches) (Inches) Fruit Fruit

1. 50 ml 5% 28 19 19 12

2. 75 ml 1% 27 19 6 11

3. no leaf 1% 24 20 3 9 treatment

^a 25 ml of the plant microbiocidal compound of the present invention is poured on the soil around the plant -

None of the trees had blossoms on the day of treatment The trees received 16 hours of artificial light per day.

There were no signs of phytotoxicity or yellowing leaves on any of the trees one week after application of the plant microbiocide of the present invention.

Example H

1% and 5% solutions of the plant microbiocidal compound from Example 1 was sprayed on grapefruit seedlings with both juvenile and mature foliage. No phytotoxicity was observed on any of the plants. Coverage was spotty on the waxy citrus foliage and the material dried on the leaves leaving an obvious glossy residue, especially with the 5% solution of the organo-silicon compound from Example 1.

Example HI

This test showed eradication of the citris canker bacterium (Xanthomonas campestris pv. citri) from artificially inoculated test surfaces. The plant microbiocidal compound from Example I was applied to several surfaces. The surfaces used were kraft paper, which represents a porous inanimate surface, and unwashed Orlando tangelos to test sanitizing capability on a citrus fruit surface. Inoculum concentration was 10⁶ cells/ml in water, which is approximately the highest concentration of citrus canker organisms that can be expected to be found exuding from the natural lesions. The bacterial inoculum was not washed. The bacterial cells carry their natural extracellular polysaccharide layers. This extracellular polysaccharide may play a protective role against conventional microbiocidal agents. Since citrus canker bacteria are sensitive to drying, the inoculum was applied to the treated test surface and allowed to remain for 10 minutes while in a humid chamber.

After 10 minutes on paper or 2 minutes on fruit, the test surfaces were swabbed with sterile cotton swabs and streaked out on nutrient agar. Untreated controls were also tested. In each test, the test surface was replicated three times. The percent kill figures are the mean of the three replicate experiments. A sterile water rinse was applied to the¹ surface of the fruits and checked for surviving X. campestris cells by transferring a small amount on a sterile cotton swab to nutrient agar. The results of this test are shown in Table B.

Table B

Percent Xanthomonas caπwestris Killed

Support Trial 1% plant 5% plant microbiocide microbiocide

Kraft Paper 1 98.25% 100%

2 97.0% 100%

Fruit surface 1 99.89% 100% 2 99.17% 100%

Fruit rinse 1 100% 100% 2 100% 100% As shown in Table B, the 5% solution of the plant microbiocidal compound of the present invention is capable of killing all of the X. campestris both on the kraft paper and on the fruit

Example IV

The plant microbiocidal compound from Example 1 was tested against the early peanut leaf spot fungus. Formulations of the plant microbiocidal compound from Example I were applied to peanut plants grown in the greenhouse at the Coastal Plain Experimental Station, Tifton, GA. Three 0 peanut plants per group were sprayed one time according to the following schedule.

I. The plant microbiocidal compound from Example 1 and 0.025% Amway all purpose spray adjuvent diluted with water.

II. The plant microbiocidal compound from Example 1 ^ diluted with water.

Peanut plants were sprayed with the formulation specified and are then - covered with plastic bags for 36 hours. The plants were then uncovered and allowed to remain in the normal greenhouse environment for the remainder of the experiment. Three peanut plants per group were sprayed one 0 time with a formulation of the plant microbiocidal compound from Example 1, allowed to dry, and then infected with the fungus Cercospora arachidicola. The infected plants were then covered with a plastic bag for 36 hours, uncovered and allowed to remain under greenhouse conditions for the duration of the experiment The results of the test are shown in Table C. 5

0

5 Table C

Infected with Cercospora Formulation amcHMJ Q Per Cent Necrosis on leaf surface

Concentration of active ingredient: 2.0% 1.0 % 0.5 % 0.1 % 0.0%

I Yes 25.8 17.8 1.0 1.4 40.7

II. Yes 24.1 31.3 9.8 9.6 40.7

I. No ^• 4.4 4.8 1.0 0.3 —

II. No 8.3 3.8 0.2 0.0

^""

As shown in this experiment, the formulation was highly effective in controlling the C. arachidicola infection at concentrations between 0.1% and 0.5% when compared to the control (no treatment with plant microbiocidal compound). In addition, there was very little phytotoxicity at concentrations of 0.5% and 0.1%.

Example V The following organo-silicon quaternary amine compound (Dow Coming, Midland, MI) was tested for microbiocidal activity against Xanthomonas campestris pv. citri. '

CH. Cl

(CH₃0)₃-Si -(CH ₂)₃- N - C₁₄H 29

CH.

The plant microbiocidal compound was applied to several surfaces. The surfaces used were kraft paper, which represents a porous inanimate surface, and unwashed Orlando tangelos to test sanitizing capability on a citrus fruit surface. Inoculum concentration was 10⁶ cells/ml in water This is approximately the highest concentration of citrus canker organisms that can be expected'to be found exuding from the natural lesions. Bacterial inoculum was not washed. The bacterial cells carry their natural extracellular polysaccharide layers. This extracellular polysaccharide may play a protective role against conventional microbiocidal agents. Since citrus canker bacteria are sensitive to drying, the inoculum was applied to the treated test surface and allowed to remain for 10 minutes while in a humid chamber.

After 10 minutes on paper or 2 minutes on fruit, the test surfaces were swabbed with sterile cotton swabs and streaked out on nutrient agar. Untreated controls were also tested. In each test, the test surface was replicated three times. A sterile water rinse was applied to the surface of the fruits and checked for surviving X. campestris cells by transferring a small amount on a sterile cotton swab to nutrient agar.

A 1% aqueous solution of the plant microbiocdal compound of the present invention was found to kill greater than 99% of the X. campestris cells on both kraft paper and on the fruit surface..

Example VI

The phytotoxicity of the plant microbiocidal compound of the present invention was tested on several species of plants. The organo-silicon quaternary amine from Example I was applied at a concentration of 0.1 and

1% by weight in water to several different species of plants. The plants tested were as follows:

Poplar tree Rye grass turf Ivy (Hedera helix)

Alberta peach tree (Prunus persica) Tomato plants. No phytotoxicity was observed in any of the treated plants.

Example VH

Seeds of red winter wheat (Arrowhead Mills, Inc. Hereford Texas) were soaked in an aqueous solution of the plant microbiocidal compound of the present invention at concentrations of one and five percent for 15 minutes or thirty minutes. The seeds were then air dried, planted in peat pots and exposed to 16 hours of artificial light daily. Observations wre made each day to determine the percent of seeds that sprout, the average time to sprout, and the average growth rate. These data are presented in Table D.

Table D

Experiment Soaking Concentration Percent Average Growth ra

Number Time of Seeds Day to cm/day

Microbiocide Sprouting Sprout

15 min 1.0% 80 5 3.0 0 (control) 90 4 3.0

30 min 5.0% 60 4 4.0 1.0% 80 4 3.5 0 (control) 70 4 4.0

Phytotoxicity was not observed in any of these measurments. In addition, there was no abnormal leaf growth in any plants grown from either the control or treated seeds.

It should be understood, of course, that the foregoing relates only to a preferred embodiment of the present invention and that numerous modifications or alterations can be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

Claims

1. A microbiocidal composition for killing micro¬ organisms on plants comprising an aqueous mixture of a surfactant and an effective amount of organo-silicon quaternary amine with the following formula:

wherein:

R" is a methyl radical or an aliphatic hydrocarbon radical of from 11 to 22 carbon atoms; '

R' is a divalent hydrocarbon radical of 1 to 10 carbon atoms;

2. The microbiocidal composition of Claim 1 wherein said organo-silicon quaternary amine is present in said aqueous mixture at a concentration of between 0.05% and 5% by weight.

3. The microbiocidal composition of Claim 1 wherein said surfactant is selected from the group consisting of polyoxyethylene ether, polyoxyethylenesorbitan monooleate and alkyl aryl polyalkoxynate alcohol. 4/ A method of killing micro-organisms on plants comprising: applying an effective amount of an aqueous solution of organo-silicon quaternary amine to a plant, said organo-silicon quaternary amine having the following formula:

wherein:

R¹ is a divalent hydrocarbon radical of 1 to 10 carbon atoms;

5. The method of Claim 4 wherein said organo-silicon quaternary amine is present in said aqueous mixture at a concentration of between approximately 0.05% and 5% by weight.