Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method of treating
grape plants to prevent infection and Bunch Rot.
More specifically, the invention relates to a
composition and method for treating grape plants to prevent ~-~
infection by the fungal pathogens Powdery Nildew (Uncinula i-
necator) and Bunch Rot (~otrytis cinerea ) using jojoba wax
and a suitable surfactant.
Each year, fungal pathogens such as Powdery Mildew
and Bunch Rot infect and destroy a significant portion of ~;~
grape crops. Present control methods are expensive in terms
of cost of labour and control substances; they have a
relatively short period of efficacy, in that they are --~
removed from the plant by washing or evaporation a few days
after application; and they may have undesirable medical
lS effects on both laborers and consumers.
An object of the present is to avoid these
drawbacks by providing a composition for treating grapes for
the prevention of fungal infection which is environmentally
safe and edible, and which ha6 a relatively long period of
efficacy. j~
S According to the composition aspect, this
invention involves a formulation comprising an aqueous
solution of 0.01% to 2.0% by volume jojoba wax and from 0.1
to 1.0% compatible eurfactant. With respect to the method
aspect, this invention involves spraying the composition a
minimum of one time onto the aerial portions of grape plants
starting at capfall (anthesis) and continuing until the
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beginning of ripening (veraison) as necessary to cover new
growth.
Studies by the inventor in 1991 and 1992 have --
shown that jojoba wax can be used to control both Powdery
Mildew and Bunch Rot. Jojoba wax is obtained from pressing
the seed of the desert jojoba bush native to the American
southwest. The wax has unusual chemical characteristics in
that it contain6 no acylglycerides (between 16-18 carbons
long), instead consisting of 9S~ monounsaturated esters
having lengths of between 38 and 44 carbon atoms. Because
these esters are known to be resistant to biotic
degradation, it was deduced that an application of jojoba
wax on the aerial parts of grape plants should provide a
complete shield against fungal attack. In addition, jojoba
wax has a high boiling point (398 degrees CelsiuR), and -
should not easily evaporate from plant surfaces. Finally,
jojoba wax has long been approved by health authorities for
use in cosmetics and human health aids. Accordingly, ~-
workers and consumers should experience no detrimental
effects from the jojoba wax.
In order to determine the optimum concentration of
jojoba wax for application to grape plants that would not `~
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produce any significant damage, a greenhouse study was ``
carried out using 96 Auxerrois grape plants. Each of the
young plants received was thinned for the strongest shoot,
then placed 20 centimeters apart in a random configuration
so that environmental conditions were controlled. All
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plants received 200 ml of water each day, and 100 ml of 2%
20-20-20 fertilizer available under the trademark Liqui-
Life. All plants were maintained at a height of l.Om. With
respect to the experimental spray program, 16 plants were
sprayed for each concentration of jojoba wax (0.1%, 1.0%,
2.0~, 5.0%, 10.0%); the jojoba wax spray was emulsified by a
1.0% Triton X series surfactant (a trademark). The
remaining 16 plants were sprayed with 1.0% of the surfactant
alone, as a control. These sprays were applied when the
plant leaves were young and unexpanded, and then 23 days
later, when the leaves were mature and expanded.
In order to quantify any effects of these sprays,
leaf area measurements to measure the amount of dead tis6ue
on each leaf were done using a Licor 3000 (trademark) leaf
lS aerometer 5 days before the second treatment. In addition,
leaf stomatal resistance and photosynthesis measurements
were made 26 days after the second treatment using a Licor
6200 (trademark) photosynthesis meter. Both sets of
measurements were taken at the same location of all plants.
Data collected were analyzed using analysis of variance
(ANOVA), followed by Tukey tests if multiple compari?on
tests were required. Moreover, subjective observations were
made.
Although there were no differences in rates of
photosynthesis between the groups, leaf damage and stomatal
resistance measurements indicated that there was significant
damage to leaves sprayed with higher concentrations of
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jojoba wax. It was determined that,in leaf damage,
concentrations of jojoba wax of 0.1~ and 1.0~ had no more
damage than the control, but concentrations over 2.0~ had
significantly more leaf damage. With respect to stomatal
resistance, jojoba wax concentrations of 0.1%, 1.0~ and 2.0%
were not different from the control, but concentrations
above 5.0% resulted in a decrea6e of stomatal resistance.
Subjective observations of all plants showed that
all plants, including the controls sprayed with the
surfactant, became lighter in colour and developed
translucent spots in leaf depressions. At concentrations of
jojoba wax greater than 1.0~, the translucent spots became
necrotic. This information in combination with the above
physiological data led to the conclusion that jojoba wax is
best sprayed on grape plants at a concentration of 1.0% or
le6s. The field 6pray trial u6ed 1.0% since, if the fungi
were not prevented, higher concentrations of jojoba wax
would do more damage than good. Moreover, lower -
concentration of surfactant were used to reduce the
incidence of the translucent spot6 ob6erved.
The nature of field trial6 and the re6ults of such
trials will be described with reference to the accompanying
drawings, wherein:
Figure 1 i6 a graph of the number of powdery
mildew colonies counted per leaf sampled averaged over
treatments indicated for three sample6;
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Figure 2 is a graph of the number of Powdery ~-
Mildew or Bunch Rot infected clusters per grape plant in -~
indicated treatments at harvest;
Figure 3 is a graph of the yield of clusters of
harvested grapes in indicated treatments for a 1992 trial;
Figure 4 is a graph of percentage of Powdery
Mildew infections on leaves collected from indicated
treatments at various times;
Figure 5 is a graph of cluster weight for plants
treated at harvest; and
Figure 6 is a graph of infected yield for the same
plants.
The fir~t trial done to begin to ascertain whether
jojoba wax worked as protection against the fungi wa~ done
in 1991, using 162 Auxerrois plants at Torrs Vineyard,
Kelowna, B.C., with equivalent aspect and slope. All plants
were healthy, and had received the same standard of care by
the vineyard operator. The plants were separated into 6
treatments, sach treatment further separated into 6 blocks ~
assigned randomly throughout the vineyard to control the ~ -
environmental variation. All plants were watered, weeded,
and trained as required for plant health and grape
production. The six treatments were:
(1) a "zero" control, receiving no spray all season;
(2) a commercial control, Sulphur [Kumulus S - a trade -~
mark] biweekly from 10 to 15 cms new growth to 30
days prior to harvest, and Captan or Rovral
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(trademarks) (i) at bloom, (ii) at 80% capfall,
(iii) bunch closure, (iv) veraison and (v) 10 to
14 days later if needed.
(3) 1.0% jojoba wax + 0.2% Triton X100 surfactant at
the same frequency as the commercial applications i
until end of August;
(4) I.0% jojoba wax + 0.2~ Triton X100 surfactant for
3 sprays in June only; -
~5) 1.0% jojoba was + 0.2% Triton X100 surfactant for
3 sprays in July only;
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(6) 1.0~ jojoba wax + 0.2~ Triton X100 surfactant for
3 sprays in August only.
Sprays were applied using a tractor-mounted 220
liter sprayer with a rotary pump which both mixed the
components and generated the pressure for spraying. On ~ -
Augu6t 11, all plants were equally exposed to 200 G grape
clusters infected with Powdery Mildew. On September 28, all
grape clusters were equally 6prayed with a suspension of ;;~ ;
Bunch Rot 6pores.
Stomatal resistance and transpiration measurements
were taken in all plants the Saturday after each spray using
a Licor 1600 (trademark) porometer. In addition, leaves
were collected from 1.5m above the ground on September 7, 23
and October 11, and the chlorophyll was extracted from 2cm2
portions of the leaf using dimethylformamide. The amount of -'~
chlorophyll was determined spectrophotometrically. Grapes
were harvested between October 5 and 11; the number of grape
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berry clusters were determined, as well as berry cluster
weight, berry weight, sugar, pH, titratable acidity for all
treatments. With respect to the amount of Powdery Mildew
infection, this was assayed as the number of colonies per
leaf on September 1, 14 and 23, and as the number of
infected clusters at harvest. Bunch Rot infection was
assayed as the number of infected clusters at harvest. For
all measured quantities, data was analyzed using ANOVA, and
Duncan multiple comparison tests where required.
There was no significant difference between
treatments with respect to plant vigour, growth, stomatal
resistance or transpiration. However, the July treatment ~ ~
had slightly higher growth and vigour. Also there was no ~ ~-
significant difference between treatments in terms of berry
weight, sugar, pH, titratable acidity, and berry cluster
count and weight for the harvest. However, the July
treatment had slightly higher berry weight and sugar than
other treatments. Also, according to Fig. 1, for the period
starting 20 days after inoculation, all plants which were
fully or partially covered with jojoba wax (due to continued
growth beyond sprayed areas) were protected from Powdery
Mildew infection. Over the entire period, infection on the
plants increased in accordance with the length of time since
the last application of jojoba wax. In addition, in terms
of the amount of Powdery Mildew infection at harvest (Fig.
2), there is no significant difference between the all-
season August, and commercial treatments. With respect to
the amount of Bunch Rot, the all-season and August
treatments provided significantly more protection than the ;
commercial control.
Moreover, in order to confirm the greenhouse
conclusions that jojoba wax sprayed at concentrations of
1.0% with 0.2% Triton X surfactant causes no significant
damage to grape plants, this study demonstrated that jojoba ;~
wax sprayed in tnis formulation has no detrimental effect6
as compared to the commercial spray regimes with respect to
yield quantity or quality. Also, the slight (but not
significant) increase in yield and growth in the July
treatment may indicate the best time to spray jojoba wax on
the grape plant. Finally, it was also shown that, as long
as jojoba wax covers the aerial surface of the grape plant,
jojoba wax provides a protective barrier against Powdery
Mildew and Bunch Rot at least as proficiently as commercial
spray materials.
Two field trials were done in 1992; a further,
confirmatory trial was done at Torrs Vineyard, to verify
1991 results and to see if less jojoba wax could provide the
same protection, and a trial was arranged at Agriculture
Canada Research Station at Summerland, B.C., to determine
the effects of jojoba wax on a second variety of grape
plants.
For the 1992 trial, 16 more plants were added to
the trial, making a total of 178 plants. These were
6eparated into 8 treatments, and 6 block6. The treatments
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were as follows, and included (except for the zero control)
0.2% Triton X-series surfactant:
Zero Control 0.2% Triton X all-season ~
1.0% jojoba all-season 0.2% jojoba all-season ~ ~4
1.0% jojoba in July only 0.2% jojoba in July only
1.0% jojoba in August only 0.2% jojoba in August only
All plants were cared for and treated in the same
manner as the trial in 1991. Also, while no stomatal
resistance, transpiration, of chlorophyll measurements were
taken, measurements to determine any differences in growth
throughout the season, vigour, and harvest cluster weights
were recorded. No infection of Bunch Rot occurred, but an
existing infection of Powdery Mildew provided data on how -
well jojoba wax worked.
There was no significant difference between -
treatments with respect to the amount of physical growth
throughout the season. However, the 1.0% July treatment had
a significantly higher vigour than all other treatments. ~ ; -
According to Fig. 3, the 0.2% all-season treatment yielded
better result6 than all other treatments, and the 1.0% all-
season and both July treatments had the second highest
yields. In addition, the Powdery Mildew showed least on
1.0% all-season jojoba treated plants (Fig. 4), and the 0.2%
all-season, both July treatments and the Triton control
provided the second highest protection. Jojoba wax again
provided the greatest fungal protection without great
decreases in yield, especially in terms of both all-season
treatments. However, mo~t significant in this information
is the 1.0% July treatment, which had the highest vigour,
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cost the least in terms of labour and spray component cost,
had one of the highest yields and the lowest Powdery Mildew
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previous to infections. In a vineyard where a pre-extant `~-
Powdery Mildew previous to jojoba wax application was not
allowed, the applications of jojoba wax starting at the
beginning of the July spray time period (anthesis) would
likely provide the greatest all-round benefit.
The Agriculture Canada Research Station trial
consisted of 39 Johannesburg Riesling grape plants separated
into 3 randomly-blocked treatments - 1.0% jojoba wax + 0.2~
Triton X100 surfactant, the commercial control (sulfur), ~nd
an unsprayed, zero control. The jojoba, commercial control,
and the zero control treatments were sprayed with the
commercial spray preparation until June 4; all treatments
began on June 16 (anthesis) and continued until August 18
(veraison), with 6 applications of the jojoba wax and
commercial spray6. All plants were cared for and treated in
the same manner as the plants in the ~orrs Vineyard plot,
except that Bunch Rot spores were applied equally to all the
clu~ters on Sep~ember 23. No Powdery Mildew infection could
be established at the Agriculture Canada vineyard.
While there was no significant difference in
growth between treatments throughout the season, there were
6ignificant differences between treatments in cluster weight
and the amount of Bunch Rot infection (Fig. 5). While there
is a small reduction in the weight of harvested clusters,
this was more than made up for by the decrease in Bunch Rot
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infection, as compared to both the commercial and zero ~ ~
controls. Hence, this trial, with jojoba spray between --
anthesis and veraison, confirms the conclusions made in -
Torrs Vineyard; that jojoba wax causes no significant
S decrease in growth, it causes little or no significant
decrease in yield, and it provides a significant increase in
the amount of protection afforded to sprayed plants versus
fungal pathogens as compared to present commercial
preparations.
In the 1991 study, it was shown that jojoba wax
could protect covered leaves of an uninfected plant for at
least 30 days after application to a plant that was free of
previous infection by fungal pathogens. It seems from the
1992 studies, that, on plants that are unaffected by fungal
pathogens, the spraying of 1.0~ (or slightly less) jojoba
wax starting the same time as the July spray (anthesis) and
continuing to the beginning of the August spray (veraison)
ehould result in protection of the plants during and
thereafter against Powdery Mildew and ~unch Rot, as well as
no or little decrease in yield, and an increase in vigour.
Previous to anthesis, commercial sprays could be used, to
control any fungal pathogen outbreaks.
In the foregong, and in the appended claim, the
expression "compatible surfactant" is intended to mean
surfactant such as Triton X207 or Triton X100 which is
completely miscible in water.
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