AU700670B1 - A method of controlling plant pathogens residing in the bark of plants and vines - Google Patents

Description

TITLE

A METHOD OF CONTROLLING PLANT PATHOGENS RESIDING IN THE BARK OF PLANTS AND VINES FIELD OF THE INVENTION This invention relates to a method of killing or controlling plant pathogens residing in the outer skin or bark of plants.

BACKGROUND OF THE INVENTION Many plant pathogens such as scale, mealybugs, ants, etc.

reside in the bark under the bark or the outer skin of vines and plants and io migrate to leaves and fruits at certain times of the season and cause damage.

Many pesticides have been developed to kill or control these pathogens, but ouooo these chemicals are not only dangerous but also have limitations in their ability to kill these insects that are hiding inside the crevice of bark as most of these pesticides work on contact. Further, there is always a concern about pesticide tolerance as overall usage of the pesticide increases.

~SUMMARY OF THE INVENTION It is an object of this invention to provide a method for killing and controlling pests residing in the outer skin or on the bark or under the bark of plants by applying a heated medium to the outer skin of bark for a predetermined period of time and insulating it, for instance with a polymer layer to form a barrier to new infections.

~In the novel method, a heat medium of oil or water based liquid or heated air is applied to the plants, vines or trees at a predetermined temperature and for a predetermined period of time. A heat transfer medium such as heated air, hot liquid or a hot foam can be used. A polymer, such as acrylate can be applied to the treated plants immediately after to form a barrier coat for preventing secondary invasion of pathogens.

DESCRIPTION OF THE PREFERRED EMBODIMENT Heat is applied from a mobile equipment in a variety of ways to the bark or outer skins of vines, branches, and stems of plants in sufficient amounts to kill pathogens, but not damage the plant. The heat may be applied as hot air or hot liquids or hot foam to deliver thermal input in sufficient amounts necessary to kill pathogens residing in the bark or outer coverings of vines or plants without harming the plant or buds. The temperature of the heated medium is in the range of 800C to 1000C in liquid and 800C to 2500C in heated air and must be applied for a predetermined time in order to effectively kill the pathogens. Equipment can be used to cover the plant and apply the heated medium. The time the bark or vine is exposed will depend on the volume of liquid and speed at which the equipment is moving. It has been found that the heating be maintained for a predetermined period of time preferably with the range of half a second to five seconds depending upon the particular medium being used and at what temperature the medium is impacting the vine or bark.

-If hot water or other heated liquids are applied to the plants, the equipment applying the hot water or other liquids is positioned in covering relation with respect to the plants so that the residence time for maintaining

S•

the heated liquids at a temperature of 800C to 100C be within the range of ~two seconds to ten seconds depending upon the kind of plant, climate conditions, etc. This same residence time of two seconds to ten seconds will also be sufficient if the heated medium is an oil, preferably soybean oil and mineral oil.

On the other hand, if hot foam is applied to the plants, the residence time will be shorter and will vary as the foam will stay on the plants and hold the heat. However, the foam may be allowed to remain on the plants up to one hour.

The present processes uses as a prophylactic barrier, a coating treatment to prevent secondary invasion of pathogens to the plants after heat treatment. In this regard, a suitable air permeable polymer will be applied to the treated areas and allowed to dry to form an air permeable coating. The polymer coating serves as a barrier to insects but to also allow air exchange to permit the plants to maintain a health metabolism. It has been found that methyl-ethyl acrylate serves as an excellent air permeable insect barrier, and other barriers are envisaged.

FIELD EXPERIMENTS EXAMPLE 1 Eight vines infected with mealy bug were selected and replicated four times in four treatments. They were made with hot foam four times replicated on eight vines at 80, 90 and 95 0 C. Controls were untreated.

The results shown in Table I show that hot foam at 95°C provided the optimum control on mealy bags.

;TABLE

I

Pretreatment One week One month At Harvest No. of live Post Treat Post Treat Post Treat S mealy bugs No. of live No. of live No. of live 1. 5 In 2 vines mealy bugs mealy bugs mealy bugs In next 2 vines in next 2 vines in next 2 vines

AVERAGE

FOAM at 80 degrees C. 18 0 8 14 FOAM at 90 degrees C. 20 0 4 8 FOAM at degrees C. 21 0 0 2 Untreated 22 35 40 EXAMPLE II Another series of experiments as structured in Example I were undertaken with the hot water but with a polymer coating of methyl-ethyl acrylate behind with hot water. The temperatures were all 95 0 C. Time of residence of hot water on the vine from impact was 0.5 seconds, 2 seconds, 4 seconds.

TABLE II Number of live mealy bugs found on the vines Pretreatment One week One month At Harvest Post Treat Post Treat Post Treat

AVERAGE

Hot Water degrees C.

sec. 28 0 2 4 Hot Water 95 degrees C.

1 sec. 30 0 0 6 Hot Water 95 degrees C.

2 sec. 24 0 0 0 25 Untreated 28 30 42 The polymer applied after the heat treatment did improve the efficacy of the kill.

From the foregoing description, it will be seen that I have 30 provided a novel process for treating plants with heated medium to kill or control plant pathogens and thereafter coating the plants, for instance, with an air permeable polymer to prevent secondary invasion by insects and other pests.

It should be appreciated that various other changes and modifications can be made to the embodiments described without departing from the spirit and scope of the invention.

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method for killing or controlling plant pathogens residing in the bark or outer skin of plants and vines comprising applying a heated medium selected from the group consisting of hot air or hot liquids or hot foam having a temperature within the range of 800C to 2500C to the bark or outer skin covering and substantially maintaining said temperature for a predetermined period of time within the range of 0.5 seconds to 10 seconds to thereby kill pathogens including scale, mealy bugs, ants and other pathogens infesting the bark or the outer skins of the plants or vines being treated, and treating these parts of the plant with a polymer barrier to prevent re-entry of these pathogens.

The method as defined in claim 1 wherein the heated medium comprises hot air at temperature of 800C to 2500 and impact time of this hot air to be between 0.5 seconds to 10 seconds.

15 3. The method as defined in claim 1 or claim 2 where the heated medium is a liquid at temperatures of 80"C to 1000C and impact time of the heated liquid to be from 0.5 seconds to 10 seconds.

4. The method as defined in any one of the preceding claims S° wherein said heated medium comprises a hot foam at 800C to 100C.

5. The method of any one of the preceding claims wherein the polymer barrier is an acrylate.

6. The method of any one of the preceding claims substantially as hereinbefore described.

DATED this 9 th day of November 1998 DEBRANA PTY. LTD.

010 835 140) By their Patent Attorneys CULLEN CO.