AU701410B2 - The use of needle-free pressure-actuated injection devices for the administration of active substances to plants - Google Patents

Abstract

Needleless pneumatically actuated injection apparatus can be used to inject active substances into plants.

Description

the bore aperture in the trunk) on the one hand, and this injection method is time-consuming and requires heavy application technological expenditure on the other hand.

A useful alternative is the high-pressure injector developed in the USA in the seventies. An example relating to this injection device is the patent US 4 011 685. The main advantage of this device is the minimized risk of liquid leakage obtained by installing a pumping device and a so-called self-closing needle. When this injection device is used, lignin fibers of the tissue cells near the needle rapidly contract because of the high pressure used (up to 350 bar).- and therefore the previously formed cavity is sealed up, preventing possible emergence of active substance; This injection: system is...

suitable for repeated application to inject liquids of various viscosities. However, the disadvantage lies in the fact that an accommodation space must generally be pre-drilled into the plant trunk when this system is used. Moreover, it is possible that the sealing degree of the opening depends on the lignification extent of the cell walls and therefore on the kind of plant concerned. This means that an injection by means of this device finally involves a potential risk of liquid leakage.

U.S.-patent 4 078 087 discloses an injection system as another injection technique. Here the main concern is that the plant trunk is uniformly supplied with the injection medium. In this case it is decisive that the liquid is not injected into one single cannula but into a delivery system. The delivery system, into which the injection medium is forced under pressure out of a container, consists of a coupling, a varying number of so-called 'T'-connectors which are inserted into pre-drilled openings in the trunk, and a closing valve. The 'T'-connectors which represent flow switches wherein part of the liquid is injected into the trunk and the remaining portion is passed on ensure that the conductive system of the plant is evenly supplied with active substance fluid on all sides.

Like in the injection devices described in the present document so far, this system also involves the problem of undesired emergence of injected medium.

The injection system described in U.S.-patent 3 576 276 is mentioned as another injection system known from the art. The injection device described therein uses the well-proven operating principle of a subcutaneous syringe. The new thing is the use of an application aid in the form of a pipe inserted into the tree trunk at the desired depth prior to injection. This additional feed pipe, in which the injection needle is located during application, permits refilling of the needle with the medium to be injected prior to applying the injection cylinder with the displacement piston. This modification of the usual sequence of working steps during application is used to inject the liquid in a fast and effective manner, caused by freedom from air bubbles.

However, the disadvantage of this process lies in the relatively heavy investment in time and work caused by using the additional application aid.

Among the other injection processes described in the art, that disclosed in CA-PS 1 089 645 is to be mentioned, this operates by using an injection device. The subject matter of this invention is a pressure-injector for use in plants, particularly developed for con- Strolling mycetogenic vascular diseases elm death) in trees.

This device has primarily been developed to permit injections without active substance losses. The minimization of liquid leakage required for this purpose is obtained by using a feed pipe (feed needle) whose surface is serrated or toothed. This uneven surface structure forms a close contact to the adjacent plant tissue; for this reason the medium already injected cannot flow back, or it flows back to a minor degree.

Finally, the injection device described in U.S. 4 164 093 is a mini pressure-injector for the use in small-diameter plant sprouts, for example in seedlings, tree branches, or young plants. The device comprises a syringe (according to the construction of a commercial subcutaneous syringe with single-use needle) and a commonly used multipurpose gardening tongs, the syringe being rigidly fastened at the stationary jaw. The free adjustability of the jaw width permits the mini-injector to be positioned at optional sites at the shoot axis and ensures flexible handling of the total device in dependence on the kind of plant used.

None of the injection devices known from the art for the use in plants succeeded in solving the problem of leakage of the injected medium in a perfect and satisfactory way. Moreover, most of the above-mentioned injection systems require a relatively heavy investment with respect to equipment and time. In addition, these devices are only suitable for injecting liquid media.

Since none of the publications mentioned so far, gives an indication as to using injection devices in plants which are not lignified, one may assume that they are not suitable for such an application.

It is the object of the present invention to provide an injection method with which both solid and liquid media are injected, in the last-mentioned case avoiding the disadvantage of leakage, and which can be used both in woody plants and in plants having unlignified shoot axes.

Most surprisingly, it has been found that the use of injection devices without needles and actuated by pressure according to the characterizing features of the main claim 1 and subclaim 2 fully meets this requirement.

The present invention will be described in greater detail in the following description.

Pressure-actuated injection devices without a needle have been known in human and veterinary medicine for some time. For several years now, they have been used for diagnostic and therapeutic purposes where painless injection or puncture is required. They are commercially available under various names (for example, the vaccination syringe manufactured in the former Soviet Union "Bienchen", "Jet" developed in the USA, and the Hungarian vaccination device "Viper") and are described at great length in several patent documents and published patent applications DE 34 67 301, EP 0 119 286, US 4 966 581, DE 31 15 373). Up to the present, they have not been used in plants.

Most surprisingly, it has been found that needle-free injection devices having the basic or general construction as described in the above patent documents are excellently suitable for injecting various substances into plants.

The injection devices of the mentioned kind are devices wherein the medium to be injected leaves the jet chamber of the device through a nozzle under such an energy that an injection without needle is possible. On the object (plant organ) to be injected the generated short pressure burst forms the injection opening with desired depth required for the injection medium. The injection depth can be varied by the angle and the distance of the device to the object to be injected: for example, the closer the nozzle to the object surface, the deeper the injection cone.

The pressure required for shooting out the medium to be injected can be generated in various manners depending on the construction of the injection device. To this end, gas issuing from a sparket bulb (DE 34 67 301) or a pressure pump (DE 31 15 373) can be used as pressure generating means.

The particular advantage of the present invention lies in the fact that the risk of an active substance loss caused by leakage is completely eliminated by using this type of cannula- and needlefree injectors. This particularly applies to injections into unlignified plants wherein the injection opening closes very fast because of the osmotic pressure of the neighboring cells.

The further advantages achieved by the present invention lie in the fact that the medium to be injected may be present in a flowable, semisolid, or solid form. With this type of jet-nozzle-injection it is possible to inject also highly viscous liquids into the objects by using an appropriately high pressure. The reason is that cannulae and needles are not used in this case. Thereby the problem of needle occlusion, by clogging, usually occurring in case of viscous media is excluded.

The needle-free injection process also offers the possibility of injecting media in crystalline form. In this case individual particles of the injection agent must have a sufficiently small (microfine) dimension. The preferred particle size is the range of 1 prm.

In this connection, the active substances may be present either alone or in admixture with one another. They may be dissolved or dispersed in the injection medium.

Active substances which can be administered to plants by means of injection devices without a needle primarily include systemically active plant protection agents (insecticides, acaricides, fungicides, bactericides), as well as plant restoratives and growth regulators.

Systemic insecticides include, for example, butocaroxim, dimethoate, fenoxycarb, methamyl, oxamyl, oxydemeton-methyl, pirimicarb, or propoxur.

Systemic acaricides include, for example, clofentizine, fenbutatin oxide, and hexythiazox.

Systemic fungicides include, for example, benomyl, bromuconazole, bitertanole, etaconazole, flusilazol, furalaxyl, fosetyl-AI, imazalil, metalaxyl, penconazole, propiconazole, thiabendazol, triadimefon, triadimenol, or triforine.

Flumequine, for example, is to be mentioned among the systemic bactericides.

Plant restoratives include, for example, plant extracts from nettle, tansy, horsetail, or herbaceous knotweed. These bioactive substances may develop a local or a systemic action in the plant, depending on the site of injection.

Systemic growth regulators include, for example, ethephon and 3indolylacetic acid (IAA).

In this connection, a preferred application of the needle-free injectors is the administration of growth-inhibiting substances which is an alternative to manual corrective and cutting measures in public gardens. During the last few years, injection systems have gained increasing importance in this field (in particular in the USA).

Further substances which can be processed by using injection devices without needles are wood preservatives and wood impregnation agents.

For centuries, lumber has been impregnated with oil and wax mixtures or other chemicals against xylophagous insects) or provided with film-forming covers as a protection against aging and weather factors.

However, these treatments have the disadvantage that they must be renewed from time to time.

The use of needle-free high-pressure injectors offers a favorable alternative to the conventional impregnation method.

-Owing to the fact that relatively high-viscous media can be injected by means of this device, it is also possible to inject polymer-containing liquids into a piece of wood to be treated by using said devices.

This is of particular importance since the injection medium may be ma formulation having a-controlled active.substance release.- Since it is possible with this type of active substance preparations to determine the release profile (duration and rate of release), the needle-free injection process offers the advantage of providing a longterm protection of the objects.

For that reason injection methods without a needle are preferably suitable in the treatment of wooden articles requiring a long-term and persistent protection,. e.g.-the wooden-elements of plant supports (corrective frames, posts) in professional horticulture.

-Another important advantage achieved by using needle-free injection devices is the saving in working time. These devices allow rapid working, they are-robust and relatively long-lived. Since they are sterilizable by autoclaving they can also be used in such active substance administrations where freedom of viruses or risk of viral infections is important, for example, in the cultivation of virus-free species or in meristem multiplication.

The present invention will be illustrated in greater detail by the following examples: Example 1 parts by weight of powdery polyacrylic acid (Carbopol ETD 2050) was dispersed in 97 parts by weight. of water. parts by weight of the active substance Al-fosetyl was added to the suspension thus produced. The added active substance was homogeneously distributed in the mass under constant stirring.

The active substance-containing aqueous acrylic acid dispersion having a relative viscosity of 0.86 Pa-s (at 25 0 C.according to /:Brookfield LVF/measuring body).was then filled into a pressure- ".-:actuated needle-free injection device (type Dermo-Jet) and injected -into plant tissue at the base of a one-year-old raspberry sprout (Rubus idaeus) at a pressure of 8.1 bar.

Example 2 0.9 g of salicylic acid (resistance inducer for plants) was dissolved in 500 ml of distd. water under heating to 300C. 100 ml of the solution thus obtained was filled into a pressure-actuated needlefree injection device (type Dermo-Jet) and injected into plant tissue at the shoot axis base of a tobacco plant (Nicotiana tabakum).

-M

1. The use of needle-free pressure-actuated injection devices of general construction, as known and used according to the prior art in human and veterinary medicine for diagnostic or therapeutic purposes, for injecting a formulation which is present in solid, semi-solid or liquid form for the controlled release of a medium belonging to the group of systemically active plant protection agents, plant restoratives, growth regulators, fertilizers, and preparations for wood treatment.

2. The use according to claim 1 for the injection of a medium in the form of pellets having a diameter of 0.1 to 5.0 preferably of 0.2 to 1.0 im.