WO2001076355A1

WO2001076355A1 - Injection treatment for control of plant diseases

Info

Publication number: WO2001076355A1
Application number: PCT/NZ2001/000058
Authority: WO
Inventors: Adrian Gale Spiers; Brian Gregory Ward
Original assignee: Horticulture and Food Research Institute of New Zealand Ltd; New Zealand Institute for Plant and Food Research Ltd
Current assignee: Horticulture and Food Research Institute of New Zealand Ltd; New Zealand Institute for Bioeconomy Science Ltd
Priority date: 2000-04-10
Filing date: 2001-04-10
Publication date: 2001-10-18
Anticipated expiration: 2002-10-10
Also published as: AU2001252792A1; NZ503884A

Abstract

A method of treatment for diseased plants, particularly trees or vines, against fungal attack of Chondostereum purpureum (silverleaf) and Eutypa lata (dead arm disease) in particular. The method of treatment comprises drilling a hole into the central region or heartwood of the stem, trunk, or branches of the tree or vine, and subsequently injecting an effective amount of a solution comprising low solubility acid or a salt thereof into said hole or holes to prevent, limit, control or cure an infection of the treated tree or vine without a phytotoxic reaction. The preferred form of low solubility acid is salicylic or its equivalent as salicylate.

Description

INJECTION TREATMENT FOR CONTROL OF PLANT DISEASES

FIELD OF INVENTION

The invention comprises a method for the treatment of infected trees and vines, in particular trees infected with the fungus Chondrostereum purp reum (synonym Stereum purp reum) or Eutypa lata.

BACKGROUND

Disease resulting from the infection of crop producing trees and vines with a pathogen results in yield losses, and severe infection can bring about the early death of the host plant. The plant disease silverleaf is caused by infection with the fungal phytopathogen Chondrostereum purpureum, which enters the plant via wounds or pruning cuts. The disease is manifested by the silvery or metallic appearance of the leaves. At first this may be on isolated branches, but progressively over the whole tree canopy. Control may be attempted by the burning of infected wood.

Eutypa dieback is a serious disease of grapevines throughout the world (Australasia, Europe, North & South America). The fungus Eutypa lata enters pruning wounds via wind/rain blown ascospores. Infection becomes established in xylem tissues where the fungus produces a toxin (Eutypine) which is translocated to growing tissues causing yellowing, stunting, shrivelling and eventually dieback, hence the term "dead arm disease". As expected, yield declines rapidly as severity of the disease increases.

Conventionally Chondrostereum purpureum or silverleaf is treated by the insertion into the diseased tree or vine of dowels inoculated with the fungus Trichoderma viride. Salicylic acid can be sprayed onto the foliage of the plant but only in very low concentration as a phytotoxic reaction results. Other control methods such as the selection of resistant varieties are also known. At present there is no control measure for treatment of vines infected with Eutypa lata other than cutting the vine back to healthy tissue and encouraging growth of a new shoot from soil level.

SUMMARY OF INVENTION

The present invention provides an improved or at least alternative method of treatment for diseased plants, against fungal attack of Chrondrostereum purpureum and Eutypa lata in particular.

In broad terms the invention provides a method of treatment of trees or vines comprising the steps:

(i) drilling a hole into the central region or heart wood of the stem, trunk, or branches of the tree or vine, and

(ii) injecting an effective amount of a solution comprising a low solubility acid or a salt thereof into said hole or holes to prevent, limit, control or cure an infection of the treated tree or vine without a phytotoxic reaction.

Low solubility as applied to an acid is defined herein as having a solubility in pure water of less than 5 g/L, most preferably 2.5 g/L.

In a preferred form the low solubility acid is salicylic acid or its equivalent as salicylate. Optionally the solution may also include one or more minerals or nutrients.

Preferably the tree or vine to be treated is infected or subject to infection with one or more xylem invading pathogens such as basidiomycete (e.g. Chondrostereum purpureum), ascomycete (e.g. Eutypa sp.) and oomycete (e.g. Phytophthora sp.) or is exhibiting signs of infection. More preferably the tree or vine to be treated is infected or subject to infection with the pathogen Chondrostereum purpureum or Eutypa lata. Most preferably the tree or vine has the plant disease silverleaf or dead arm disease.

Preferably the tree or vine to be treated is a species of pip fruit or stone fruit, or is a grapevine.

Preferably the solution comprising salicylic acid, or its equivalent as salicylate in a buffered solution, is at a concentration in the range 0.5 to 5% (w/v), preferably 0.9 to 3.7 % (w/v), most preferably about 1.8 % (w/v).

Preferably the solution of salicylic acid has a pH less than 8, and most preferably less than about 7.

The solution comprising salicylic acid maybe prepared from a concentrate, which is provided with instructions for use in accordance with the method of invention. Preferably the concentrate is diluted with water prior to injection.

Injection is performed by delivery into a recently drilled hole of the solution comprising salicylic acid by such means of delivery as allows the delivery to be achieved under pressure. An example of an injection device that allows the delivery to be achieved under pressure is illustrated in figure 1 wherein a bottle (1) containing the solution comprising salicylic acid is fitted to the injection device comprising of a positive displacement pump (4). Preferably the design of the injection device incorporates an extra reservoir (3) as illustrated in figure 1 so that the user can pull knob (6) out to a required calibration line and hold until the reservoir is filled to the calibration line with the desired volume. The solution comprising salicylic acid is first bled through the injector by use of the handles (2) to pump said solution through the injection device. The tapered thread on the fitting (5) is then screwed into the pre-drilled hole in the tree or vine. Ensuring that the extra reservoir (3) remains filled to the calibration line, the solution comprising salicylic acid is pumped from the reservoir into the tree or vine being treated. If more than one volume from the extra reservoir is needed to treat the tree or vine the extra reservoir is refilled to the calibration line and the pumping procedure repeated. In one embodiment only a single hole drilled to a depth of 80-90% of the diameter of the trunk of the tree or vine is required and the volume of solution comprising salicylic acid at a given concentration to be injected may be ascertained by simple calculation. Preferably this calculation is performed by the use of a "guide belt" as herein described.

In another embodiment the "guide belt" comprises part of a kit for the treatment of trees or vines with a solution comprising salicylic acid in accordance with the method of the invention. Optionally this kit may also comprise said solution or concentrate from which said solution may be prepared. Alternatively or in addition said kit may comprise an injection device as herein described.

The treatment parameters of volume and concentration of salicylic acid solution are sufficient so as to prevent, limit, control or cure an infection of the treated tree or vine. Preferably the residues of salicylic acid detected are not substantially greater than the level at which salicylic acid occurs naturally in the crop. More preferably there is no relative increase in the levels of salicylic acid detected in the crop following treatment in accordance with the present invention.

DETAILED DESCRIPTION OF INVENTION

The phytopathogenic fungus Chondrostereum purpureum may infect trees and vines via wounds or pruning cuts. Symptoms of infection are a silvery or metallic appearance of the leaves, characteristics of the silver leaf disease. Activation of pathogenic protein accumulation by the plant may protect the plant from infection or restrict its progression.

Eutypa dieback is a serious disease of grapevines throughout the word (Australasia, Europe, b

North & South America). The fungus Eutypa lata enters pruning wounds via wind/rain blown ascospores. Infection becomes established in xylem tissues where the fungus produces a toxin (Eutypine) which is translocated to growing tissues causing yellowing, stunting, shrivelling and eventually dieback, hence the term "dead arm disease". As expected, yield declines rapidly as severity of the disease increases.

Salicylic acid occurs naturally in plants and has been detected in rice, barley, and soy bean, amongst others. Exogenously applied salicylic acid mimics certain aspects of pathogen infection, namely the ability of the plant to activate pathogenic related protein accumulation. This may protect the plant against infection.

Unbuffered solutions of salicylic acid are of low pH and low concentration. They are believed to be ineffective or cause phytotoxic effects when applied directly to the foliage of plants, thus requiring careful control of application rates. In partial mitigation of this problem, solutions of salicylic acid are buffered to a pH that permits higher concentrations of salicylic acid, or its equivalent as salicylate, in solution when supplied exogenously.

In the method of the invention solutions comprising salicylic acid are directly injected into the central region or heart wood of trees or vines including into the pith/transition wood of pip fruit and stone fruit trees.

Improved activity is observed and phytotoxic reaction is reduced or minimised. While in the case of treatment of trees with silverleaf, the precise mode of action is not known, it is believed that the salicylic acid translocates readily within the plant and is more able to act as an elicitor, stimulating the plant's defence mechanisms.

Treatment by the method of injection also allows the application rate of the salicylic acid to be more readily controlled. Such control minimises wastage and allows treatment rates to be reliably optimised.

The depth of hole to be drilled and the volume of solution comprising salicylic acid to be injected may be readily calculated by use of a simple "guide belt." The right hand end of the guide belt is passed around the right hand side of the tree as it is faced. Making sure the belt is firmly against the trunk all the way around, the end is aligned with the top of the belt - the upper figure on the belt provides a measure of the tree diameter. Below this figure can be provided the required volume of solution comprising salicylic acid at a given concentration to be injected.

The invention will now be illustrated by reference to the following experimental section providing examples of the application of the invention. These examples will be understood to be non-limiting. Other applications of the method will be readily apparent to those skilled in the art.

EXPERIMENTAL - TREATMENT OF SILVERLEAF

Trees infected with silverleaf were rated using the Schreiner - van der Meiden rating system (Schreiner 1959, van der Meiden, 1961) originally devised for assessing poplars for Melampsora rust. This system provides an assessment based on the level of foliar silvering (light, medium, heavy, very heavy) and percentage of the foliage showing that degree of silvering. A linear scale was developed to permit statistical analysis of data [Table 1]. At the time of rating dots were painted on the trunks to indicate the severity of infection as follows:

• single dot = light infection - light silvering

•• two dots = medium infection - moderate silvering

••• three dots = heavy infection - extensive silvering

•••• four dots = very heavy infection - premature leaf fall

This system permits the rapid identification of treated trees and facilitates the assessment of recovery in subsequent years. Detailed plans of healthy and infected trees were kept.

¹ Spots painted on trunk when tree rated and treated.

² Light - slightly silvered leaves, Medium - moderately silvered leaves,

Heavy - strongly silvered leaves, Very heavy - leaves shrunken in size, distorted, premature leaf fall.

³ Percentage of foliage showing particular level of silvering

⁴ Field rating

⁵ Linear scale utilised for analysis of variance

Table 1. Rating scale for assessing Silverleaf infection.

Trees were stem injected using the tree injection system illustrated in Figure 1. In most instances a single hole was drilled in the trunk. Depending on the trunk diameter, between 20 and 200 mLs of product were injected.

A "guide belt" with markings can be employed to allow convenient and efficient calculation, on a tree by tree basis, of the required injection volume and number of injection holes required, in this case, for a solution containing 1.85 % (w/v) of salicylic acid. Typically an 8 mm diameter hole was drilled horizontally into the tree at a depth of 80 to 90% of the trunk diameter. Eg. for a tree diameter of 190 mm, a hole of 162 mm depth is drilled and a volume of 63 ml is injected. For a tree diameter of 95 mm, a hole of a depth of 81 mm is drilled and a volume of 79 ml injected. For a tree diameter of 275 mm, a hole of depth 220 mm is drilled, and a volume of 92 ml injected per hole.

A primary reservoir containing a solution of salicylic acid at 1.85% (w/v) was fitted to the injection device (Figure 1) and the solution bled through to the injection nozzle. The injection nozzle was firmly screwed into the hole to within one or two threads of the full length of the thread. For saplings with trunk diameters of 20 to 30 mm the injection nozzle was screwed in with three or four turns, just enough to seal the nozzle in the hole.

The volume of solution to be delivered was calculated and drawn into the extra reservoir. The solution was then pumped from the extra reservoir into the tree. The pressure at which the solution was delivered into the tree was monitored. When the desired volume had been injected, the nozzle was unscrewed from the hole and a stopper inserted into the hole. The stopper serves to prevent the solution running out, and prevents insects from entering and colonising the wound.

Summary of treatments and results

Trial #1.

8 year old Golden Queen peach trees - well maintained Diameter trunk of trees: 100mm +/- 5mm Nolume of solution injected into trees: 0.6x (50mls) Rated and treated: Dec and Jan Assessed: Jan (following year)

See Linear scale, Table 1.

* Significant (P<=0.05)

NS Not Significant (P<=0.05)

% Reduction in level of foliar silvering

Trial #2.

8 year old Golden Queen peach trees - well maintained Diameter trunk of trees: 100mm +/- 5mm Nolume of solution injected into trees: 0.6x (50mls) Rated and treated: February Assessed: January

See Linear scale, Table 1.

* Significant (P< - 0.05)

NS Not Significant (P< - 0.05)

% Reduction in level of foliar silvering

Trial #3.

3- 4 year old Fiesta peach trees

Diameter trunk of trees: 60mm +/- 5mm

Nolume of solution injected into trees: 0.9x (45mls)

Rated and treated: March

Assessed: February

See Linear scale, Table 1.

* Significant (P< = 0.05)

NS Not Significant (P< = 0.05)

% Reduction in level of foliar silvering Trial #4.

4 year old Galaxy apple trees

Diameter trunk of trees: 40mm +/- 5mm

Nolume of solution injected into trees: lx (33mls)

Rated : 10 Apr Treated: 23 July

Assessed: 29 Feb

Trial #5. 4 year old Galaxy apple trees

Diameter trunk of trees: 60mm +/- 5mm

Nolume of solution injected into trees: lx (50mls)

Rated : 30 Apr Treated: 23 Jul

Assessed: 8 Dec

Trial #6.

3 year old Royal Gala apple trees Diameter trunk of trees: 60mm +/- 5mm Nolume of solution injected into trees: lx (50mls) Rated : 3 Apr, Treated: 23 July Assessed: 8 Dec

Trial #7.

8 - 10 year old Gala apple trees

Diameter trunk of trees: 150mm +/- 5mm

Nolume of solution injected into trees: lx (2 holes @ 50mls per hole) lx (2 holes @ lOOmls per hole, = 2x vol.)

Ν.B. Heavily silvered. Injected at 3 sites per tree, ca. 90-100 ml/tree.

Rated : 10 Apr Treated: 31 Jul, 6 Aug, 21 Aug

Assessed: 8 Dec

Trial #8.

5 year old Royal Gala grafted over Red Delicious apple trees

Diameter trunk of trees: 100mm +/- 5mm

Nolume of solution injected into trees: 0.6x (50mls)

Rated : 3 Apr Treated: 23 July

Assessed: 8 Dec

EXPERIMENTAL - TREATMENT OF DEAD ARM DISEASES

Trial 1

Twelve year old Cabernet Sauvignon vines were assessed for severity of E. lata by recording the extent of leaf yellowing and stem stunting on each vine. Nines were rated numerically 1- 4 based on the severity of these symptoms. For instance:

1. light infection, less than 25% of foliage showing yellowing and stunting,

2. moderate infection, up to 50% of foliage showing yellowing and stunting,

3. heavy infection, more than 50% of foliage showing yellowing and stunting,

4. very heavy, 100%) foliage showing extensive yellowing and stunting.

With experience infected vines were readily identified as being lightly, medium and heavily infected. Marked vines were injected with approximately 40 mis of fungicide (18.5 g/L salicylic acid) using high-pressure stem injection. Fungicide was injected into the stem of each vine at a point midway between the ground and the canopy. Because vines rated as 4 always died they were not included in injection trials.

1. Salicylic acid data

% Decline -27% -50% -50%

Notes

In these trials only vines with ratings 1-3 were recorded and treated. Nines rated 4 always died.

Trial 2

Fourteen year old Cabernet Sauvignon grapevines were assessed for severity of E. lata infection by recording the extent of leaf yellowing and shoot stunting of each vine. Nines were rated numerically 1 - 4 based on the severity of symptoms using the gradings described in Trial 1 above in this section.

Some vines were injected with 50 mis (where possible) of a salicylic acid solution using high-pressure stem injection, at a point midway between the ground and the canopy, while other vines were untreated as controls. The injected solution comprised salicylic acid, 18.5 g/L 2 hydroxy-benzoic acid as the potassium salt (salicylic acid) in the form of a soluble concentrate.

Nines were assessed for degrees of recovery approximately seven months later.

Results

The results are listed in Table 2. The percentage recovery or otherwise was calculated by comparing the sum of plant ratings at initial assessment with the sum following treatment, or not as with the controls.

Table 2 Percentage recovery/decline of Cabernet Sauvignon vines.

Untreated vines of Cabernet Sauvignon infected with E. lata progressively declined in health whereas those injected with salicylic acid exhibited on average a 75% reduction in foliar symptoms. Light and moderately infected vines generally exhibited complete recovery. In contrast with the previous trial where vines injected with salicylic acid exhibited 75% recovery 18 months following treatment, in the present study they showed 75% recovery six months following treatment.

REFERENCES

Malamy, J. and Klessig, D.F. Salicylic acid and plant disease resistance. Plant J. (1992) 2(5), 643-654.

Claims

1. A method of treatment of trees or vines comprising the steps:

(ii) injecting an effective amount of a solution comprising a low solubility acid or a salt thereof into said hole to prevent, limit, control or cure an infection of the treated tree or vine without a phytotoxic reaction.

2. A method according to claim 1 wherein the solution comprises a low concentration solution of salicylic acid or a salt thereof.

3. A method according to any of the preceding claims where the solution comprises salicylic acid, or its equivalent as salicylate in a buffered solution, at a concentration in the range 0.5 to 5% w/v.

4. A method according to claim 3 where the salicylic acid or its equivalent as salicylate is present at a concentration in the range 0.9 to 3.7% w/v.

5. A method according to claim 4 where the salicylic acid or its equivalent as salicylate is present at a concentration of about 1.8% w/v.

6. A method according to any of the preceding claims where the tree or vine is infected with one or more xylem invading pathogens and the method includes injecting an amount of said solution which is effective to reduce or eliminate said pathogens.

7. A method according to any of the preceding claims where the tree or vine is infected with one or more xylem invading Chondostereum purpureum, Eutypa sp or Phytophthora sp and the method includes injecting an amount of said solution which is effective to reduce or eliminate said Chondostereum purpureum, Eutypa sp or Phytophthora sp.

8. A method according to claim 6 wherein the xylem pathogen is Chondrostereum purpureum

9. A method according to claim 6 wherein the xylem pathogen is Eutypa lata.

10. A method according to claim 8 where the tree or vine has silverleaf.

11. A method according to claim 9 where the tree or vine has dead arm disease.

12. A method according to any one of the preceding claims where the solution of salicylic acid has a pH of less than about 8.

13. A method according to claim 12 where the pH of the solution of salicylic acid is less than about 7.

14. A method according to any one of the preceding claims wherein the hole is drilled to a depth of 80-90% of the diameter of the trunk of the tree or vine.

15. A method according to any of the preceding claims wherein the tree is a species of pip fruit or stone fruit.

16. A method according to any of the preceding claims wherein the vine is a grapevine.

17. A method according to any of the preceding claims where the solution of salicylic acid further comprises minerals or nutrients.

18. A kit for treating trees or vines infected with xylem invading pathogens comprising: i) a guide belt used for measuring the diameter of a tree or vine to be treated, ii) a solution of salicylic acid or a concentrate from which the solution may be prepared.

19. A kit according to claim 18 further comprising an injection device for injecting a solution of salicylic acid into the central region or heat wood of the stem, trunk, or branches of a tree or vine.