Treatment of Plants against Disease

FIELD OF THE INVENTION

This invention relates to the treatment of plants against fire blight.

BACKGROUND

Averting plant disease is important in the agricultural and horticultural industries for maintaining the health of crops and therefore their profitability. A particularly problematic disease is fire blight caused by the bacterium Erwina amylovora, which is difficult to control and is apt to thrive in warm, humid and rainy conditions. Fire blight is often signalled in plants by one or more cankers on tree bark, by weeping wounds, drooping shoots, dead leaves, flowers or fruit that has turned brown, or dead fruiting spurs.

Fire blight is of a particular economic concern with apple and pear plants in many parts of the world. Under optimal conditions, it has the potential to destroy an orchard, or a significant part of one, in a single growing season.

Other economically important agricultural and ornamental plants can also be affected by fire blight, including almond, apricot, cherry, cotoneaster, crabapple, flowering quince, hawthorn, loquat, medlar, mountain ash, plum, quince, raspberry, rose, serviceberry and spirea.

Partial control of fire blight may be achieved in plants by removing infected wood in late summer, fall, or winter, when the bacteria are not actively spreading. However the task can be time consuming and inconvenient.

Partial control of fire blight may be achieved by using agricultural sprays, for example copper blossom sprays which can be applied when plants first begin to flower. However, they are often of limited effectiveness and can be phytotoxic to fruit. Antibiotic sprays such as Streptomycin have also been used to prevent new infections.

Alternative remedies are desirable to replace the use of copper containing products and antibiotics, the over use of which may lead to fire blight acquiring resistance to treatment. Copper based treatments in particular can lead to undesirably high residues of copper in soils, which can be toxic to useful soil organisms.

Antibiotic use in food production is facing market resistant due to the perception that they may consequently have lower efficacy when needed to control diseases in humans.

OBJECT OF THE INVENTION

It is an object of the invention to go some way towards providing an alternative for averting or reducing fire blight in plants.

DEFINITIONS

The term “comprises” or “has”, or derivatives thereof, eg “comprising” or “having”, if and when used in this document in relation to a combination of features should not be seen as excluding the option of additional features or steps that have not been mentioned.

The term “approximately” if and when used in this specification in relation to an amount of a substance, includes the value indicated, and optionally also ± up to 10%, or preferably ± up to 5%, or more preferably ± up to 2%, of the value indicated.

SUMMARY OF THE INVENTION

In one aspect, the invention is a method of treating a plant against fire blight comprising applying to the plant:

• fatty acid in soap form; and

• silicate; wherein the fatty acid is in solution or in suspension in water.

Optionally the method comprises applying a combination composition comprising both the fatty acid and the silicate.

Optionally the fatty acid and silicate kill, inhibit, directly control or eliminate Erwinia amylovora bacteria.

Optionally the fatty acid is in the form of one or more of: sodium salt; and potassium salt. Optionally the fatty acid comprises fat of animal origin.

Optionally the fatty acid comprises oil of plant origin.

Optionally the fatty acid comprises fat and/or oil of plant or animal origin.

Optionally fatty acid comprises one or more of the following-

• Caproic Acid

• Caprylic Acid

• Capric Acid

• Lauric Acid

• Myristic Acid

• Palmitic Acid

• Palmitoleic Acid

• Stearic Acid

• Oleic Acid

• Linoleic Acid (eg Alphalinoleic Acid)

• Arachidic Acid

• Gadoleic Acid

Optionally fatty acid comprises one or more of the following*-

• C6:0 : Caproic Acid

• C8:0 : Caprylic Acid

• C10:0 : Capric Acid

• C12:0 : Lauric Acid

• C14:0 : Myristic Acid

• C16:0 : Palmitic Acid

• C16:1 : Palmitolic Acid

• C18:0 : Stearic Acid

• C18:1 : Oleic Acid

• C18:2 : Linoleic Acid

• C18:3 : Alpha Linoleic Acid

• C20:0 : Arachidic Acid

• C20:1 : Gadoleic Acid * The number immediately following the “C” term notes the number of carbon atoms in the molecule, and the number immediately after that designates the number of double bonds in the carbon chain. So, for example, “C6:0 Caproic acid” indicates that the molecule has ‘6’ carbon atoms and ‘0’ double bonds.

Optionally the silicate is water soluble (eg readily or naturally soluble in water at room temperature).

Optionally the silicate is in metallic salt form.

Optionally the silicate comprises one or more of:

• potassium silicate;

• sodium silicate; and

• lithium silicate;

Optionally the molar ratio of the silicate ranges from 2.0 to 3.3. By way of example, if the silicate is potassium silicate and the molar ratio is 2.0, this means it contains 2.0 mol of SiO ₂ for every 1 mol of K ₂ O. And if the silicate is potassium silicate at a molar ratio of 3.3, it contains 3.3 mol of SiO ₂ for every 1 mol of K ₂ O.

Optionally the plant is a member of the Rosaceae botanical family.

Optionally the plant comprises apple, pear, almond, apricot, cherry, cotoneaster, crab apple, quince, flowering quince, hawthorn, loquat, medlar, mountain ash, plum, raspberry, rose, serviceberry and spirea.

Optionally the silicate is applied as a watery spray in which: a) the silicate is at a concentration of 55-280, 55-210, 55-140, or approximately 63, grams per 100L of spray material; b) the silicate is at a concentration of approximately 63, 127, 190 or 254 grams per 100L of spray material; c) the silicate is at a concentration of 0.1 - 1 .1 mol per 100L of spray material; or d) the silicate is at a concentration of approximately 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or 1.1 mol to per 100L of spray material. Optionally the fatty acid in soap form is applied as a watery spray in which: a) the fatty acid in soap form is at a concentration of 20 -185, or 41 -152, grams per 100L of spray material; b) the fatty acid in soap form is at a concentration of approximately 23, 46, 69, 92, 115, 138, 161 or 184, grams per 100L of spray material; c) the fatty acid in soap form is at a concentration of approximately 0.1 -0.8 mol, or 0.2-0.6 mol, per 100L of spray material; or d) the fatty acid in soap form is at a concentration of approximately 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, mol per 100L of spray material.

Optionally the silicate is applied as a watery spray in which:

• the silicate is at a concentration of approximately 63g to approximately 254g per 100L of spray material, and the fatty acid in soap form is at a concentration of approximately 46 - 138g per 100L of spray material.

Optionally the silicate is applied as a watery spray in which:

• the silicate is at a concentration of approximately 0.4 - 1 .6 mol per 100L of spray material, and the fatty acid in soap form is at a concentration of approximately 0.2 - 0.6 mol per 100L of spray material.

According to a further aspect, the invention comprises the use of:

• fatty acid; and

• silicate; in the preparation of a composition for treating a plant against fire blight. Preferably the fatty acid and/or silicate and/or plant are as per any of the options set out above.

According to another aspect, the invention is a treatment for fire blight formed according to any of the above criteria and/or for any of the above purposes.

According to a further aspect, the invention is a spray formulation for treating a plant against fire blight, comprising:

• fatty acid in soap form; and

• silicate; wherein these components are in accordance with the statements in any of the preceding statements in this Summary of Invention section, for example in terms of the identity and/or amount(s) and/or use of the components.

IMAGES

In describing preferred embodiments of the invention reference will made to the accompanying images, of which:

Figure 1 is a log scale bar graph illustrating the efficacy of various treatments against Erwina amylovora as observed in laboratory tests; and

Figure 2 is a contour plot further illustrating the outcome for the laboratory tests.

DETAILED DESCRIPTION

The invention involves applying a fatty acid soap and a silicate to plants to at least assist in protecting or treating them from fire blight disease.

Assessing the invention involved testing Potassium Silicate and NSA solutions for efficacy against fire blight in plants, caused by Erwina amylovora bacteria. The solutions were as follows -

The potassium silicate/water mixture above had a specific gravity of approximately 1 .44.

Therefore, each 1 L of the mixture had 440g potassium silicate.

A normal field dose of the potassium silicate/water mixture for good kill with application by spray, is 500 ml made up to 100L with further water, or in other words 220g potassium silicate made up to 100L with water.

A normal field dose of the NSA mixture for good kill with application by spray, is 500 ml made up to 100L with further water, or in other words 230g fatty acid made up to 100L with water.

Test Methodology

Test Samples were made up from the solutions as follows- o NSA

Samples at 0.2, 0.4, 0.6, 0.8 and 1 .0 L per 100L o Potassium Silicate

Samples at 100, 200, 300, 400 and 500 mL/100L o NSA + Potassium Silicate o Samples at 0.2 L/100L NSA with each of

100, 200, 300, 400 and 500 mL/100L Potassium Silicate o Samples at 0.4 L/100L NSA with each of

100, 200, 300, 400 and 500 mL/100L Potassium Silicate o Samples at 0.6 L/100L NSA with each of

100, 200, 300, 400 and 500 mL/100L Potassium Silicate o Samples at 0.8 L/100L NSA with each of

100, 200, 300, 400 and 500 mL/100L Potassium Silicate o Samples at 1.0 L/100L NSA with each of

100, 200, 300, 400 and 500 mL/100L Potassium Silicate

A 0.25 mL aliquot of each Sample was combined with a 0.25 mL aliquot of a bacterial suspension consisting of Erwinia amylovora in water. The combination was made up with water to a total volume of 1 mL.

Control Samples were also prepared for Erwinia amylovora in water and, also for the product KeyStrepto ¹ (a streptomycin bacteriacide with known efficacy against fire blight) in water (as 2.4, 12 and 60 g/100L).

The Test Samples and Control Samples were incubated for 1 hour at 20°C. Following this, the Samples were diluted with water in a ten-fold series down to 10 ⁷ and plated to Casitone-yeast extract agar (CYE agar) (Araujo et al. 2012) ² . They were then incubated at 20°C for 40-48 hours until individual bacterial colonies could be enumerated. The bacterial count data, being the number of colonies, was subjected to a generalized linear model with a Poisson distribution and a log link, with the selected dilution fitted as an offset.

More specifically, the above process assessed the number of colonies per 10 microlitre drop applied to ech plate (x 100) to give the number of colony forming units (CFU’s) per

¹ https://keyindustries.co. nz/View-A-Product/ID/89#ProductRange

² Araujo ER, et al, 2012,. Sensitivity of Xanthomonads causing tomato bacterial spot .... Journal of Plant Pathology 94: 71-78 mL. This was then multiplied by the dilution. For example, to calculate CFU’s per mL at a colony count of 10 colonies at a dilution of 1 x 10' ⁴ , 10 x c100 x 10 ⁴ =c1x10 ^-7 or 10000000 CFU’s per mL The results were reported as CFU per mL (not per 10 mL) which was the mean across 4 replicates.

Results

The test results are graphed in Figures 1 & 2 and also summarised in Table 1 below.

In Table 1 , the references to “NSA” and the numbers 0.2, 0.4, 0.6, 0.8 and 1 .0 are to the NSA Samples mentioned above, i.e. corresponding to the L/100L amounts noted.

Also in Table 1 , the references to “Silco” and the numbers 100, 200, 300, 400 and 500 are to the Potassium Silicate Samples mentioned above, i.e. corresponding to the mL/100L amounts noted above.

In the Table the references to “Bacteria” and KeyStrepto are to the Control Samples, also mentioned above.

The column titled “Mean” gives the average CFU/mL across four replicates. The mean values were calculated on a log 10 scale and back-transformed to a natural scale. For example, the mean on a logged scale of (100,10,1) = mean (log(100),log(10), log(1)) = mean (2,1 ,0) = 3/3 = 1. Therefore, the back-transformed mean will be 10 ¹ =10.

Table 1

SUBSTITUTE SHEET (RULE 26)

Table Note: Analysis results of bacterial counts per mL, adjusted log 10 transformed means and standard error, back- transformed means and standard error. Treatments with the same letter in the far right-hand column may be seen as similar to one another in result (LSD, Fishers least significant difference test) at P<0.05).

To elaborate the test results, and by way of example -

Potassium Silicate 100 + NSA 0.2

Low dose Potassium Silicate (100 mL/100L) gave a bacterial count of 2.65 x 10 ⁸ , and low dose NSA (0.2 L/100L) had a bacterial count of 2.73 x 10 ⁸ . These counts were not, from a crop protection perspective, significantly better than the control Bacteria Sample (Erwinia amylovora alone) which had a bacterial count of 3.05 x 10 ⁸ .

However, the combination of low dose Potassium Silicate (100 mL/100L) with low dose NSA (0.2 L/100L) had a bacterial count of only 3.76 x 10 ⁴ . The improvement was many- fold synergistic, not additive.

Doubling the Potassium Silicate

Further, doubling the Potassium Silicate content (to 200 mL/100L) but keeping the NSA the same (0.2 L/100L) gave a bacterial count of 1.98 x 10 ³ , which is about a 19-fold improvement (not just a doubling) compared with the Potassium Silicate 100 + NSA 0.2 Sample.

SUBSTITUTE SHEET (RULE 26) Increasing the Potassium Silicate by 50%

Further, increasing the Potassium Silicate content by 50% (to 300 mL/100L) but keeping the NSA the same (0.2 L/100L) gave a bacterial count of 2.95 x 10 ² , which is about a 7- fold improvement (not just a 50% improvement) compared with the Potassium Silicate 200 + NSA 0.2 Sample.

By way of further example -

Doubling the NSA

Comparing the Potassium Silicate 100 + NSA 0.2 Sample with the Potassium Silicate 100 + NSA 0.4 Sample, the difference was a doubling in the NSA amount. Therefore, if additive, one would expect the bacterial count to be halved. However, the bacterial count went from 37,600 to 934, which is about a 40-fold improvement.

Increasing the NSA by 50%

Comparing the Potassium Silicate 100 + NSA 0.4 Sample with the Potassium Silicate 100 + NSA 0.6 Sample, the difference was a 50% increase in the NSA amount.

Therefore, if additive, one would expect the bacterial count to be halved. However, the bacterial count went from 934 to 125, which is about a 7-fold improvement.

Summary

The study shows a ‘many-fold’ synergistic improvement for combinations of Potassium Silicate and NSA at low and moderate doses. This is significant as it shows that the treatment of crops with only low or moderate doses of silicates when combined with low or moderate doses of fatty acids is effective. It avoids the need to subject crops to high doses of bactericides in order to protect them from Erwinia amylovora and in particular fire blight.

While not all fatty acids were trialled, it is considered that other fatty acids, including those that are commercially available, will work effectively, alone or in combinations, if substituted.

Similarly, while not all silicates were trialled, it is considered that at other silicates, including those that are commercially available, will work effectively, alone or in combinations.

SUBSTITUTE SHEET (RULE 26) Further, other fatty acids and silicates, may be used in a similar manner to that described above for protecting plants against ice nucleation induced frost damage caused by other bacteria.

It is considered to be within the normal capabilities of the person skilled in the art to test fatty acid and silicate combinations other than those specifically noted herein, and other bacterial pathogens, using a test technique as described in this document, to determine usefulness and the level of effectiveness.

While some forms of the invention have been described by way of example, it should be appreciated that modifications and improvements can be made without departing from the scope of the following claims.

In terms of disclosure, this document envisages and hereby posits any feature mentioned herein in combination with itself or any other feature or features mentioned herein, even if the combination is not claimed.

SUBSTITUTE SHEET (RULE 26)