Note: Descriptions are shown in the official language in which they were submitted.
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USES OF THAXTOMIN AND THAXTOMIN COMPOSITIONS AS HERBICIDES
FIELD OF THE INVENTION
This invention relates to compositions and methods for controlling the
germination and
growth of broadleaf, sedge and grass weeds using compounds comprising
thaxtomin, a cyclic
dipeptide produced by Streptomyces sp., as an active ingredient.
BACKGROUND OF THE INVENTION
Natural products are substances produced by microbes, plants, and other
organisms.
Microbial natural products offer an abundant source of chemical diversity, and
there is a long history
of utilizing natural products for pharmaceutical purposes. However, secondary
metabolites produced
by microbes can also be successfully used for weed and pest control in
agricultural applications.
Thaxtomins (4-nitroindo1-3-yl-containing 2,5-dioxopiperazines) are a family of
dipeptide
phytotoxins produced by plant-pathogenic Streptomyces sp. (S. scabies, S.
acidiscabies) that cause
scab diseases in potato (Solanum tuberosum) (King, Lawrence et al. 1992).
Toxin production occurs
in diseased tissue and can also be elicited in vitro in an optimal growth
medium containing oat bran
(Loria, Bukhalid et al. 1995; Beausejour, Goyer et al. 1999). King and her
coworkers (King,
Lawrence et al. 2001) demonstrated that all plant pathogenic species in the
Streptomyces family
produce one or more thaxtomins with herbicidal activity. Hiltunen et al.
(Hiltunen, Laakso et al.
2006) purified four thaxtomin analogs (thaxtomin A, thaxtomin A ortho isomer,
thaxtomin B and
thaxtomin D) from cultures of S. scabies and S. turbidiscabies and showed that
all four compounds
induced similar symptoms of reduced shoot and root growth, root swelling, (at
10-200 ppb) and
necrosis (at 200-1000 ppb) on micropropagated in vitro cultures of potato. In
addition, thaxtomins
applied in combinations, showed additive effects, but no synergism (Hiltunen,
Laakso et al. 2006).
According to Duke et al. (Duke, Baerson et al. 2003), both thaxtomin A (Figure
1) and thaxtomin D
have marked activity as pre and post emergent, non-systemic herbicides, and
concentrations of less
than 1 uM of thaxtomin A causes cell swelling, necrosis and growth inhibition
in mono and
dicotyledonous seedlings (Healy, Wach et al. 2000). Thaxtomin has been
evaluated as an herbicide
by Dow Agro Sciences, Inc., and while active, it lacked systemic action (King,
Lawrence et al.
2001). The presence of the nitro group in the indole ring required for an L,L-
configuration of the
diketopiperazine appears to be the minimal requirement for phytotoxicity. The
position of the nitro
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group in the indole ring is very site specific, and the phenyl portion of the
phenylalanine plays a
necessary role in structural requirements of phytotoxicity (King, Lawrence et
al. 1989; King,
Lawrence et al. 1992; King, Lawrence et al. 2003). The herbicidal mode of
action is based on
disruption of cell wall synthesis (Fry and Loria 2002), with inhibition of
cellulose biosynthesis being
the main target (King et al., 2001; Duval et al., 2005; Johnson et al. 2007).
Recently, Kang et al.
(Kang, Semones et al. 2008) have described the use of thaxtomin and thaxtomin
compositions as
algaecides to control algae in water environments.
SUMMARY OF THE INVENTION
The present invention discloses the use of thaxtomin as a pre or post-
emergence herbicide
against most common weeds in the cereal, pasture grass, Timothy grasses and
turf grass growth
systems. A "growth system" may be any ecosystem for growing cereal, pasture
grass, Timothy grass
and turf grass. For example, a "cereal growth system" may be a cereal growth
culture or may be a
field containing planted cereal crops or cereal seeds. Similarly, a "turf
grass growth system" may be
a turf grass growth culture or may be a field, lawn or golf course containing
planted turf grass or turf
grass seeds. It can serve as a safer alternative to synthetic herbicides now
on the market. A primary
object of the invention is to provide novel herbicidal compositions against
both broadleaf, sedge and
grassy weeds, which include but are not limited to Chenopodium album, Abutilon
theophrasti,
Helianthus annuus, Ambrosia artemesifolia, Amaranthus retroflexus, Convolvulus
arvensis, Brassica
kaber, Taraxacum officinale, Solanum nigrum, Malva neglect, Setaria lutescens,
Bromus tectorum,
Poa annua, Poa pratensis , Lolium perenne L. var. Pace, Festuca arundinaceae
Schreb. var. Aztec II,
Anthem II, LS1100, Echinochloa crus-galli, and particularly, Lambsquarter ¨
Chenopodium album,
Redroot Pigweed ¨ Amaranthus retroflexus, Wild Mustard ¨ Brassica kaber,
Dandelion ¨ Taraxacum
officinale, and Black Nightshade ¨ Solanum nigrum,that contains thaxtomin as
an active ingredient.
Another object is to provide a safe, non-toxic herbicidal composition that
does not harm cereal crops,
pasture grass, Timothy grass or turf grass and a method that will not harm the
environment.
The above and other objects are accomplished by the present invention which is
directed to
herbicidal compositions containing at least one herbicidal agent, e.g.,
thaxtomin with optionally
certain carriers to control the growth and germination of weeds in the cereal
growth system and/or
turf grass growth system and/or Timothy grass growth system and/or pasture
grass growth system.
In particular, the invention is further directed to an herbicidal composition
for use in modulating the
germination and growth of monocotyledonous and/or dicotyledenous and/or sedge
weeds in a cereal
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growth system. In a particular embodiment, the cereal growth system is a non-
rice cereal growth
system comprising at least one herbicide in which said herbicide is thaxtomin.
The compositions of
the present invention may further comprise a carrier and/or diluent. In a
particular embodiment, the
composition is an aqueous composition. In another particular embodiment, the
thaxtomin in the
composition is dissolved in a diluent comprising an organic solvent such as
ethanol, isopropanol, or
an aliphatic ketone such as acetone, methyl ethyl ketone, methyl isobutyl
ketone.
In a related aspect, the invention is directed to the use of at least one
herbicidal agent, e.g.,
thaxtomin, in formulation of an herbicide for modulating monocotyledonous
and/or dicotyledenous
and/or sedge weeds a cereal growth system, e.g., a non-rice cereal growth
system. Similarly, the
invention is directed to the use of at least one herbicidal agent in
formulation of an herbicide for
modulating monocotyledonous and/or dicotyledenous and/or sedge weeds in a turf
grass growth
system and/or Timothy grass growth system and/or pasture grass growth system,
wherein at least one
herbicidal agent is thaxtomin.
The compositions of the present invention may comprise in addition to
thaxtomin, at least
one or more herbicides. Thus the invention may comprise a thaxtomin and a
chemical herbicide
and/or bioherbicide. Compositions comprising thaxtomin and at least a second
herbicide may be used
in cereal growth systems (e.g., wheat, triticale, barley, oats, rye, corn,
sorghum, sugarcane, rice or
millet) and/or turf grass growth systems and/or Timothy grass growth systems
and/or pasture grass
growth systems.
Given that the invention is directed to the use of thaxtomin as a pre- or post-
emergence
herbicide, the invention is directed to a method for selectively modulating
germination and growth of
monocotyledonous, dicotyledonous and sedge weeds in a cereal crop growth
system. In a particular
embodiment, the cereal growth system is a non-rice cereal crop growth system
comprising applying
to said weeds or soil in said cereal crop growing system at least one
herbicidal agent, wherein said
herbicidal agent is thaxtomin, in an amount of effective to modulate
germination and growth of said
weeds but not modulate growth of cereal crop in said cereal crop growth
system. The cereal crop
may include but is not limited to corn, wheat, triticale, barley, rye, oats,
sorghum, sugarcane, and
millet. The invention is further directed to a method for modulating
germination and growth of
monocotyledonous, dicotyledonous and sedge weeds in a turf, pasture and/or
Timothy grass growth
system comprising applying to said weeds or soil in said turf grass growing
system at least one
herbicidal agent, wherein said herbicidal agent is thaxtomin, in an amount of
effective to modulate
growth of said weeds but not modulate germination and growth of turf grass in
said turf grass growth
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system, pasture grass in said pasture grass growth system and/or Timothy grass
in said Timothy grass
growth system. The turf grass may be selected from the group consisting of
Festuca sp., Poa sp.,
Bromus sp., Lolium sp., Agrostis sp., Zoysia sp., Cynodon sp.
Further, the invention is directed to a method for modulating germination and
growth of
weeds selected from the group consisting of Chenopodium album, Abutilon
theophrasti, Helianthus
annuus, Ambrosia artemesifolia, Amaranthus retroflexus, Convolvulus arvensis,
Brassica kaber,
Taraxacum officinale, Solanum nigrum, Malva neglectõ Setaria lutescens, Bromus
tectorum, Poa
annua, Poa pratensis , Lolium perenne L. var. Pace, Festuca arundinaceae
Schreb. var. Aztec II,
Anthem II, LS1100, Echinochloa crus-galli, comprising applying to said weeds
or soil an amount of
thaxtomin or salt thereof effective to modulate said germination and growth of
said weeds.
The method of the present invention may also involve the use of at least a
second herbicidal
agent. The two herbicidal agents may be applied together in one formulation or
separately in two
formulations. Control of weeds can be achieved by using thaxtomin A in a tank
mix or rotation with
other herbicidally active compounds known to have good activity against grass
weeds but no or low
phytotoxicity against cereal crops and/or turf grass and/or, pasture grass
and/or Timothy grasses. In
particular, the invention relates to a method for modulating growth of
monocotyledonous,
dicotyledonous and sedge weeds comprising applying to said weeds an amount of
thaxtomin and
amount of at least a second herbicidal agent to modulate growth of said weeds.
The two herbicidal
agents may be applied together in one formulation or separately in two
formulations. The thaxtomin
and second herbicidal agent may be applied in a cereal growth system (e.g.,
wheat, triticale, barley,
oats, rye, corn, sorghum, sugarcane, rice or millet) and/or turf grass growth
system and/or pasture
grass growth system and/or Timothy grass growth sysem.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows the structure of Thaxtomin A.
DETAILED DESCRIPTION OF THE INVENTION
Where a range of values is provided, it is understood that each intervening
value, to the tenth
of the unit of the lower limit unless the context clearly dictates otherwise,
between the upper and
lower limit of that range and any other stated or intervening value in that
stated range is encompassed
within the invention. The upper and lower limits of these smaller ranges may
independently be
included in the smaller ranges is also encompassed within the invention,
subject to any specifically
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excluded limit in the stated range. Where the stated range includes one or
both of the limits, ranges
excluding either both of those included limits are also included in the
invention.
Unless defined otherwise, all technical and scientific terms used herein have
the same
meaning as commonly understood by one of ordinary skill in the art to which
this invention belongs.
Although any methods and materials similar or equivalent to those described
herein can also be used
in the practice or testing of the present invention, the preferred methods and
materials are now
described.
It must be noted that as used herein and in the appended claims, the singular
forms "a," "and"
and "the" include plural references unless the context clearly dictates
otherwise.
Thaxtomin utilized in this invention may be derived in fermentation of the
following
actinomycetes cultures: S. scabies ¨ ATCC 49173 , S. acidiscabies ¨ ATCC 49003
and
BL37-EQ-010 - or it can be purchased from commercial sources.
The thaxtomin utilized in the invention include but are not limited to agents
described as
cyclic dipeptides having the basic structure cyclo-(L-4-nitrotryptophyl-L-
phenylalany1). In
embodiments, suitable diketopiperazne moieties may be N-methylated, and
include congeners
carrying phenylalanyl alpha andring-carbon hydroxyl groups. The chemical in a
particular
embodiment comprises:
NO2 0
R3 R6
R(
N
R5
R2
O R4
wherein R1 is methyl or H, R2 is hydroxy or H, R3 is methyl or H, R4 is
hydroxy or H, R5 is
hydroxy or H, R6 is hydroxy or H, and combinations thereof.
Non limiting examples of suitable thaxtomin is for use in accordance with the
present
invention include but are not limited to thaxtomin A, thaxtomin A ortho
isomer, thaxtomin B,
thaxtomin C, hydroxythaxtomin C, thaxtomin A p-isomer, hydroxythaxtomin A and
des-N-methylthaxtomin C and derivatives of any of these (See Figure 1).
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The compositions of the present invention may be sprayed on the plant or
applied to soil.
Particular embodiments are described in the Examples, infra. These
compositions may be in the
form of dust, coarse dust, micro granules, granules, wettable powder,
emulsifiable concentrate, liquid
preparation, suspension concentrate, water degradable granules or oil
suspension.
The compositions of the invention do comprise a carrier and/or diluent. The
term, 'carrier' as
used herein means an inert, organic or inorganic material, with which the
active ingredient is mixed
or formulated to facilitate its application to plant or other object to be
treated, or its storage, transport
and/or handling. Examples of diluents or carriers for the pre- and post-
emergence herbicides include,
but are not limited to, water, milk, ethanol, mineral oil, glycerol.
The compositions of the present invention may comprise at least two herbicidal
agents. One
herbicidal agent is thaxtomin set forth above. It may be present in one
embodiment thaxtomin is
present in an amount ranging from about 0.01 to about 5.0 mg/mL. The other
herbicidal agent may
be a bioherbicide and/or a chemical herbicide. The bioherbicide may be
selected from the group
consisting of clove, cinnamon, lemongrass, citrus oils, orange peel oil,
tentoxin, cornexistin,
AAL-toxin, leptospermone, sarmentine, momilactone B, sorgoleone, ascaulatoxin
and ascaulatoxin
aglycone. In a particular embodiment, the composition may comprise thaxtomin,
lemongrass oil and
optionally a surfactant and/or vegetable oil. In another embodiment, the
composition may comprise
thaxtomin, sarmentine and optionally a nonionic surfactant and/or vegetable
oil. The bioherbicide
such as lemongrass oil or sarmentine may be present in an amount ranging from
about 0.1 mg/mL to
about 50 mg/mL and more preferably between about 0.5 mg/mL to about 10 mg/mL
The chemical
herbicide may be selected from the group consisting diflufenzopyr and salts
thereof, dicamba and
salts thereof, topramezone, tembotrione, S-metolachlor, atrazine, mesotrione,
primisulfuron-methyl,
2,4- dichlorophenoxyacetic acid, nicosulfuron, thifensulfuron-methyl, asulam,
metribuzin,
diclofop-methyl, fluazifop, fenoxaprop-p-ethyl, asulam, oxyfluorfen,
rimsulfuron, mecoprop, and
quinclorac, thiobencarb, clomazone, cyhalofop, propanil, bensulfuron-methyl,
penoxsulam, triclopyr,
imazethapyr, halosulfuron-methyl, pendimethalin, bispyribac-sodium,
carfentrazone ethyl, sodium
bentazon/sodium acifluorfen and orthosulfamuron.
The chemical herbicide such as pendimethalin or clomazone may be present in a
pre-emergent weed control application in an amount ranging from about 0.5
mg/mL to 15 mg/mL
and a chemical herbicide such as cyhalofop, S-metolachlor, bispyribac-sodium,
penoxsulam in a
post-emergent application from about 1 mg/mL to about 40 mg/mL and more
particularly between
about 15 mg/ml to about 35 mg/mL. The composition may further comprise an
adjuvant which may
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be vegetable oil comprising ethyl oleate, polyethylene dialkyl ester and
ethoxylated nonylphenol.
The composition may additionally comprise a surfactant to be used for the
purpose of emulsification,
dispersion, wetting, spreading, integration, disintegration control,
stabilization of active ingredients,
improvement of fluidity or rust inhibition. The choice of dispersing and
emulsifying agents, such as
non-ionic, anionic, amphoteric and cationic dispersing and emulsifying agents,
and the amount
employed is determined by the nature of the composition and the ability of the
agent to facilitate the
dispersion of the herbicidal compositions of the present invention.
For post-emergent formulations, the formulation components used may contain
smectite
clays, attapulgite clays and similar swelling clays, thickeners such as
xanthan gums, gum Arabic and
other polysaccharide thickeners as well as dispersion stabilizers such as
nonionic surfactants (for
example polyoxyethylene (20) monolaurate or polysorbate 60 POE (20) sorbitan
monostearate,
ethylene glycol monostearate). The concentration of the clays may vary between
about 0-2.5% w/w
of the total formulation, the polysaccharide thickeners may range between
about 0-0.5% w/w of the
total formulation and the surfactants may range from about 0-5% w/w of the
total formulation.
EXAMPLES
The composition and method of the present invention will be further
illustrated in the
following, non-limiting Examples. The examples are illustrative of various
embodiments only and do
not limit the claimed invention regarding the materials, conditions, weight
ratios, process parameters
and the like recited herein.
EXAMPLE 1
In a pot study test in greenhouse conditions, 6-inch corn plants (Zea mays
var. Sunglow) were
sprayed with increasing concentrations of thaxtomin A mixed in a carrier 4%
ethanol, 0.02 %
polysorbate 60 POE (20) sorbitan monostearate solution. The spraying solutions
contained 0.125,
0.25, 0.5 and 1.0 mg thaxtomin A/mL, and the plants are sprayed until total
coverage. Each treatment
was done in three replicates, and a control solution consists of water with 4%
ethanol and 0.02 %
polysorbate 60 POE (20) sorbitan monostearate as a surfactant. Prior to and
after treatments, plants
are grown in a greenhouse under artificial lights (12-h light/dark cycle) at
25 C.
Plants are evaluated in one-week intervals starting at 7 days after treatment.
The final
evaluation is done three weeks after treatment, at which time point, no
phytotoxicity is observed in
any of the test plants even at the highest thaxtomin A concentration.
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EXAMPLE 2
A pot study is conducted to test the phytotoxicity of thaxtomin A on corn (Zea
mays var.
Early Sunglow) and wheat (Triticum aestivum var. PR1404). To confirm the
activity on broadleaf
weeds, pigweed (Amaranthus sp.) is planted in the same pot with either three
corn or five wheat
seeds, and sprayed simultaneously with the cereal test plants. The less than 3-
inch tall plants grown
under growth lights (12-h light/12-h dark) at 28 C are sprayed with thaxtomin
A solutions derived
from a liquid culture of S. acidiscabies containing 0.5, and 1.0 mg thaxtomin
A per mL of solvent (4
% ethanol and 0.2% non-ionic surfactant). A solution of 4 % ethanol + 0.2% non-
ionic surfactant
without thaxtomin A is used as a control treatment. Each treatment is
conducted in three replicates.
Treated plants are kept at 28 C under growth lights and observed at three time
points ¨ 7, 14 and 21
days after treatment - for visual symptoms of phytotoxicity on corn and wheat
and % control of
pigweed.
At each time point, no symptoms of phytotoxicity are observed in the cereal
plants treated
with thaxtomin A. The highest concentration of thaxtomin A (1.0 mg/mL) results
in a complete
control of pigweed grown in the same pots with corn and wheat.
EXAMPLE 3
To test the phytotoxicity of thaxtomin A on sorghum plants, five seeds of
sorghum (Sorghum
bicolor) are planted in each 4"x 4" plastic pot filled with soil. Plants were
grown under optimal
conditions in a greenhouse before and after treatment with solutions
containing 0.5 and 1.0 mg
thaxtomin A /mL. At the time of the treatment, the plants are about 3 inches
tall. Each treatment is
applied in three replicates, and a control treatment included plants treated
with just the carrier (4%
Et0H, 0.02 % polysorbate 60 POE (20) sorbitan monostearate). Evaluations for
phytotoxicity are
performed at 7-day intervals starting one week after treatment. The last
evaluation is performed three
weeks after the treatment at which point, no phytotoxicity is observed in the
treated plants in any
treatment concentration.
EXAMPLE 4
A strain of S. acidiscabies (ATCC-49003) is grown in oat bran broth for 5 days
(25 C,
200rpm). The whole cell broth with thaxtomin A is extracted using XAD resin.
The dried crude
extract was resuspended in 4% ethanol and 0.02 % non-ionic surfactant at a
concentration of 10
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mg/mL, and the solutions with two different concentrations of thaxtomin A (0.5
and 1.0 mg/mL) are
tested the following broadleaf weed species:
Lambsquarter ¨ Chenopodium album
Velvetleaf ¨ Abutilon theophrasti
Sunflower ¨ Helianthus annuus
Ragweed, Common ¨ Ambrosia artemesifolia
Pigweed , Redroot ¨ Amaranthus retroflexus
Bindweed, Common ¨ Convolvulus arvensis
Mustard, Wild ¨ Brassica kaber
Dandelion ¨ Taraxacum officinale
Nightshade, Black ¨ Solanum nigrum
Mallow, Common ¨ Malva neglecta
and on the following grass weed species:
Foxtail ¨ Setaria lutescens
Brome, Downy ¨ Bromus tectorum
Bluegrass, Annual ¨ Poa annua
Bluegrass, Kentucky ¨ Poa pratensis
Ryegrass, Perennial ¨ (Lolium perenne L. var. Pace)
Fescue, Tall ¨ (Festuca arundinaceae Schreb. var. Aztec II, Anthem II, LS1100)
Barnyard Grass - Echinochloa crus-galli
All plant species are tested in 4"x4" plastic pots in three replicates. The
untreated control
plants are sprayed with the carrier solution (4% Ethanol, 0.02% glycosperse)
and the positive control
plants with Roundup at a rate corresponding to 1 fl. oz/acre. Treated plants
are kept in a greenhouse
under 12h light/12h dark conditions. Data for broadleaf species from weekly
evaluations are
presented in Table 1.
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Table 1. Weed control efficacy of a S. acidiscabies extract containing
thaxtomin A on
different weed species. Rating scale: 0 - no control, 1 - 10% control, 2 - 25%
control, 3 -
50% control, 4 - 75% control, 5 - 100 % control.
Weed UTC THAXTOMIN THAXTOMIN
species SOLUTION SOLUTION 1.0
mg/mL
0.5 mg/mL
7DAYS 14DAYS 21DAYS 7DAYS 14DAYS 21DAYS 7DAYS 14DAYS 21DAYS
Dandelion 0.0 1 0.0 1 0.0 1 2.0
2.3 1 4.0 2.0 1 2.0 1 3.7 1
Nightshade 0.0 0.0 0.0 2.7 2.2 2.3 2.7 2.0
2.3
Lambsquarter 0.0 0.0 0.0 2.0 2.0 2.0 2.0 2.0
2.0
Ragweed 0.0 0.0 0.0 1.0 0.5 0.0 1.0 0.5
0.0
Velvetleaf 0.0 0.0 0.0 1.7 1.0 1.0 2.0 1.0
0.3
Bindweed 0.0 0.0 0.0 1.0 1.0 0.0 1.2 1.0
0.0
Mustard 0.0 0.0 0.0 3.3 4.0 4.5 3.5 2.8
3.5
Sunflower 0.0 0.0 0.0 1.0 2.0 0.5 1.0 1.7
0.5
Mallow 0.0 0.0 0.0 1.0 1.0 1.0 1.2 1.0
1.0
Pigweed 0.0 0.0 0.0 3.5 4.0 4.0 4.2 3.0
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The extract from a bacterial culture of S. acidiscabies with a thaxtomin A
concentration
of 0.5 mg/mL or higher showed good efficacy (>50%) against at least three of
the most common
broadleaf weed species (dandelion, mustard and pigweed) in both cereal and
turf growing
systems. Control of some weeds such as Black nightshade and Common
lambsquarter was not
complete but thaxtomin A even at the lower concentration (0.5 mg/mL) results
in severe stunting
of these weeds. In this same study, no adverse effects are observed in grass
species treated with
either 0.5 or 1.0 mg/mL thaxtomin A. In all tested grass species, no
phytotoxic effects were
visible at even the higher thaxtomin A concentration.
EXAMPLE 5
The combined effect of thaxtomin A and two commercial herbicides (Bipyribac-
sodium
formulated as Regiment and Lemongrass oil formulated as GreenMatch EX) on
small-flower
umbrella sedge and watergrass is tested in a field study using small (1- sq
foot) plots. All single
product treatments and tank mix combinations were sprayed at 57 gal per acre.
Evaluation of %
control was done 14 days after treatment and the results are presented in
Table 2 below. Means in
each column marked with the same letter in Table 2 are not statistically
different from each other
at p<0.05
According to the results, lemongrass oil at 1.25% weight does not improve the
efficacy
of thaxtomin A (at 0.25 mg/mL) on sedge but it significantly increases the
efficacy on grass
weeds such as watergrass (field test) and sprangletop (greenhouse test).
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Table 2. Effect of thaxtomin A alone and in combination with bispyribac-sodium
and
lemongrass oil on two rice weeds, small-flower umbrella sedge and watergrass.
Treatment Sedge control (%)
Watergrass control (%)
Thaxtomin 0.25 mg/mL 95a 5d
Thaxtomin 0.5 mg/mL 100a 5d
Bispyribac-sodium 87.5a
32.5a
(12 g/acre)
Bispyribac-sodium 1/2 (6g/acre) 47.5c
15c
Bispyribac-sodium 1/2 + 67.5b
25ab
Thaxtomin 0.5 mglmL
Bispyribac-sodium1/2 + 55bc
7.5c
Thaxtomin 0.25 mg/mL
Lemongrass oil 5 % 15d
10c
Lemongrass oil 2.5% 12.5d
10c
Lemongrass oil 1.25% 20d 5d
Lemongrass oil 1.25% + 100a
10c
Thax 0.25 mg/mL
Lemongrass oil 1.25% + 100a
20b
Thaxtomin 0.5 mg/mL
10
According to the results, lemongrass oil at 1.25% does not improve the
efficacy of
thaxtomin A (at 0.25 mg/mL) on sedge but it significantly increases the
efficacy on grass weeds
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such as watergrass (field test) and sprangletop. Thaxtomin A (at 0.5 mg/mL)
improves the
efficacy of an ALS inhibitor, bipyribac sodium; used at half label rate on
both sedge and grasses.
EXAMPLE 6
The efficacy of thaxtomin A derived from a liquid culture of S. acidiscabies
is tested in a
field study on rice using 4.9 sq-ft plots surrounded by a metal ring.
Treatments with either
thaxtomin A or thaxtomin A in combination with lemongrass oil (formulated as
GreenMatch EX)
or cyhalofop (formulated as Clincher CA) were done using a hand-held sprayer
with a water
volume corresponding to 57 gallons per acre. Rice (variety M209) was grown
until maturity and
harvested by hand for yield and weed count assessment. Results of yield
(kg/ha), and numbers of
redstem, small-flower umbrella sedge, and sprangletop in each plot are
presented in Table 3
below.
Table 3. Effect of thaxtomin A alone and in combination with lemongrass oil
and cyhalofop
on rice yield and weed control.
Treatment Yield (kg/ha) # of redstem # of sedge
# of sprangletop
1 7516b 10.3 0.8a 86.0a
2 7876b 0.5b 1.0a 76.0a
3 9054ab 0.3b 0.5a 69.3a
4 11296a 12.8a 0.5a 4.0b
1. UTC; 2. Thaxtomin A (180 g/acre); 3. Lemongrass oil 1.25% + thaxtomin A (90
g/acre);
4. Cyhalofop (half label rate; 52 g/acre) + thaxtomin A (90 g/acre) + veg oil
2.5 %
Means in each column marked with the same letter are not statistically
different from each other
at p<0.05.
Results indicate that thaxtomin at 180 g/acre significantly reduced the number
of sedges
but had no effect on sprangletop or yield. When used at half rate (thaxtomin A
90 g/acre), a
combination with lemongrass oil had better effect on sedges than a combination
with cyhalofop
(used at half label rate 52 g/acre). Good grass weed (sprangletop) control is
achieved when
thaxtomin (90 g/acre) is combined with cyhalofop at half the label rate ¨ this
combination also
improves the yield significantly.
EXAMPLE 7
Cyhalofop (244-(4-cyano-2-fluorophenoxy)phenoxylpropanoic acid, butyl ester)
is also
mixed together with adjuvant containing ethyl oleate, polyethylene dialky
ester and ethoxylated
nonylphenol (2.5 % v/v) and increasing concentrations of thaxtomin A (purified
from the ATCC
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strain 49003) at concentrations 0.1, 0.2 and 0.4 mg/ml. The concentrations of
the 244-(4-cyano-
-fluorophenoxy)phenoxylpropanoic acid, butyl ester before dilution are 29.6%
(2.38 lb/gal) and
21.7% (2 lb/gal), respectively. The effect of these mixtures on the growth of
common water
plantain, red stem, smallflower sedge and sprangletop is determined in the
greenhouse. Similarly,
rice plants of variety M104 are grown and tested for phytotoxic effects, and
all plants are
evaluated 7, 14, and 21 days after treatment. Results of from the study with
cyhalofop
formulated as Clincher CA at the 21-day evaluation point are presented in
Table 4 below.
Table 4. Effect of thaxtomin A alone and with cyhalofop on rice yield and weed
control
Clincher CA Redstem Waterplantain Sedge
Sprangletop
(6.5 oz/acre) + % control % control % control % control
Thaxtomin A
(mg/mL)
UTC 0 0 0 0
0 ¨ no thx A 75 8 0 90
0.1 100 85 87 100
0.2 97 87 88 100
0.4 100 85 100 100
As a conclusion, Clincher CA (29.6% cyhalofop by weight) applied at half label
rate (6.5 oz/acre)
has good efficacy against grass weeds ¨ not so good on broadleaves and poor on
sedges. A
combination of Clincher CA (cyhalofop) and thaxtomin A provides good control
of all rice weeds
tested in this study. Efficacy of thaxtomin A against grass weeds is
substantially improved if
combined with Clincher. Combination of thaxtomin A with Clincher CA did not
cause
phytotoxicity on rice at any tested concentration.
EXAMPLE 8
Penoxsulam(2-(2,2-difluoroethoxy)-N-(5,8-
dimethoxy111,2,41triazolo111,5clpyrimidin-2-y1
)-6-trifluoromethyl)benzenesulfonamide) is mixed together with adjuvant
containing ethyl oleate,
polyethylene dialky ester and ethoxylated nonylphenol (2.5 % v/v) and
increasing concentrations
of thaxtomin A (purified from the ATCC strain 49003) at concentrations 0.1,
0.2 and 0.4 mg/ml.
The concentrations of the 244-(4-cyano- -fluorophenoxy)phenoxylpropanoic acid,
butyl ester or
2-(2 ,2-difluoroethoxy)-N-(5 ,8-dimethoxy ll ,2 ,41triazolo111 ,5clpyrimidin-2-
y1)-6-trifluoromethyl)b
enzenesulfonamide before dilution are 29.6% (2.38 lb/gal) and 21.7% (2
lb/gal), respectively.
The effect of these mixtures on the growth of common water plantain, red stem,
smallflower
sedge and sprangletop is determined in the greenhouse. Similarly, rice plants
of variety M104 are
grown and tested for phytotoxic effects, and all plants are evaluated 7, 14,
and 21 days after
treatment.
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EXAMPLE 9
A strain of S. acidiscabies was grown in oat bran broth for 5 days (25 C, 200
rpm). The
whole cell broth was extracted using XAD resin, and the dried crude extract
was resuspended in
4% ethanol and 0.2 % non-ionic surfactant at a concentration of 10 mg/mL. The
diluted extracts
containing 0.2 and 0.4 mg thaxtomin A per mL were tested on three weed species
(redstem;
Ammania spp., smallflower umbrella sedge; Cyperus difformis and sprangletop:
Leptochloa
uninervia). Other treatments included sarmentine at 2.5 and 5.0 mg/mL, and a
combination
treatment containing 0.2 mg thaxtomin A and 2.5 mg sarmentine per mL. Each
treatment was
applied in three replicates. Treated plants were kept in a greenhouse under
12h light/12h dark
conditions. Results from an evaluation performed 25 days after treatment are
presented in Table
5.
Table 5. Efficacy of herbicidal treatments using thaxtomin A (0.2 and 0.4
mg/mL) or
sarmentine (2.5 or 5.0 mg/mL) alone or in combination (0.2 + 2.5 mg/mL) to
control
broadleaf, sedge and grass weeds in a greenhouse study.
treatment Control of redstem Control of sedge Control
of sprangletop
(%) (%) (%)
UTC Oa Oa
Oa
Thaxtomin A 0.2 mg/mL 5.0b 48.3b
8.3ab
Thaxtomin A 0.4 mg/mL 11.7c* 91.7d
10.0b
Thaxtomin 0.2 + 11.7c* 61.7c
73.3c
Sarmentine 2.5 mg/mL
Sarmentine 2.5 mg/mL Oa 8.3a
80.0c
Sarmentine 5.0 mg/mL 2.5ab 6.7a
92.3d
* stunted. In a column, Means followed by the same letter are not
statistically different from each
other at p< 0.05.
Thaxtomin A at the highest concentration of 0.4 mg/mL provides excellent
control of
sedge but poor control of the grass weed (sprangletop). When combined with
sarmentine, the
efficacy against grass weeds improves significantly. Also, efficacy against
sedge is improved
with the combination treatment compared with the single application of
thaxtomin A alone at the
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corresponding concentration. In this study, the control of the broadleaf weed
(redstem) is poor
with all treatments.
Although this invention has been described with reference to specific
embodiments, the
details thereof are not to be construed as limiting, as it is obvious that one
can use various
equivalents, changes and modifications and still be within the scope of the
present invention.
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