Note: Descriptions are shown in the official language in which they were submitted.
WO 93/04581 PCT/US92/07709
21 187 9 4
1
SYNERGISTIC INTERACTION OF HERBICIDAL ARYLOXYPROPIONIC
ACID DER7CVATIVES AND CYCLOHEXANEDIONES
Background of the Invention
The p~rotect_ion of crops from weeds and other vegeta-
tion which inhibit crop growth is a constantly recurring
problem in agriculture. To help combat this problem, re-
searchers in th.e field of synthetic chemistry have produced an
extensive variety of chemicals and chemical formulations
effective in th.e coni:rol of such unwanted growth. Chemical
herbicides of many types have been disclosed in the literature
and a large number are in commer~;ial use.
In some cares, active herbicides have been shown to
be more effective in combination than when applied individu-
ally. The result is often termed "synergism", since the
combination demonstrates a potency or activity level exceeding
that which it should be expected to have, based on a knowledge
of the individual potencies of the components. The present
invention residles in the discovery that certain aryloxypro-
pionic acid derivatives and certain cyclohexanediones, already
known individually for their herbicidal potency, display a
synergistic effect wizen applied in combination.
Prior Art
The t:wo classes of compounds forming the combination
which is the subject of the present invention are independently
known in the art for their effects on plant growth. Herbicidal
aryloxypropionic acid derivatives are disclosed in U.S.
Patents Nos. 4,267,3:36, 4,317,913 and 4,414,391; British
tzcv. wv:~;r.~ ~mc~w m we- ~-~:.~ : m:~_>_~ : n:~~.~ ~m i m- T.~.;3 r~;j
_:3;3~.n.~~s.--,:" :~
- 21 18 7 9 4 _rR-8659
Patents Noa. 1,595,121 and 2,00Z,368. Also, seo tna
9th ed. , i~ditad by C. R. tiorthing and R. J. Fiance, pp.
400, 401 arid 463.
D~rivati,vea of cyclohexanediones era disclosed as
herbicides in U.S. Patent 3,950,420, EPA BC3C1, EP-8-85529.
The effects of mixtures of one cyclohexandione~ ssthoxydim, and one
atyloxy prcpionit acid darivat:ve, ~iuazifop, oa annual grass weeds have
beer, desczibed by Harker et e1, in Weed Technology, volume 5, 191 issue 2.
DESCHIF'1'ION OF THE INV=VTTON
It has noW been discovered that synergism in the
' control of undesirable vegetation i~ exhibited by compositions
comprising:
(a) An aryloxypzopionic acid derivative of the
f orntu la
CF3 d ~ O- H-CGORl
~J
3
in which
X is hydrogen or halogen;
R1 is hyclrcgen, Cl-C6 alkyl, C1-C6 alkoxyaikyl; and
(b~ a cyc~ohaxanediona derivative of the
formula
0
HORZ
R3
(R)n
in which
SU~T~TUTE SHEET
_ z _
WO 93/04581 ~ ~ ~~ ~ ~ ~~ DCT/US92/07709
3
R is independently hydrogen; halogen; vitro; cyano;
C1-C6 alkyl; C1-C:6 alkyl substituted with a substituent
selected from the: group consisting of halogen, vitro, hydroxy,
C1-C6 alkoxy and C1-C6 alkylthio; C2-C6 alkenyl; C2-C6 alkynyl;
hydroxy; C1-C6 al.koxy; C1-C6 alkoxy substituted with a sub-
stituent selected fram :halogen and C1-C6 alkoxy; C2-C6 alkenyl-
oxy; C2-C6 alkynyloxy; C2-C6 alkanoyloxy; (C1-C6 alkoxy)-
carbonyl; C1-C6 alkylthio; C1-C6 alkylsulfinyl; C1-C6 alkyl-
sulfonyl; sulfamoyl; N-C(1-C6 alkyl)sulfamoyl; N,N-di(C1-C6
alkyl)sulfamoyl; benzyloxy, substituted benzyloxy wherein the
benzene ring is substituted with from one to three substi-
tuents selected iErom the group consisting of halogen, vitro,
C1-C alkyl, C1-~~6 alkoxy and C1-C6 haloalkyl; the group
NR9Rg0 wherein R~~ and R.10 are independently selected from the
group consisting of hydrogen, C1-C6 alkyl, C2-C6 alkanoyl,
benzoyl and benzyl; the groups formyl and C2-C6 alkanoxyl and
the oxime, imine and Schiff base derivatives thereof; and at
least one of X is not selected from the group consisting of
halogen, C1-C6 alkyl and C1-C6 alkoxy;
R2 is C1-C~ alkyl, C2-C6 alkenyl, C2-C6 haloalkenyl,
C2-C6 alkynyl, C2-C6 haloalkynyl, a substituted C1-C6 alkyl,
substituted with halogen, C1-C6 alkoxy, C1-C6 alkylthio,
phenyl, substituted phenyl wherein the phenyl is substituted
with halogen, vitro, cyano, C1-C6 alkyl, C1-C6 haloalkyl,
C1-C6 alkoxy and C1-C6 alkylthio;
R3 is hydrogen, C1-C6 alkyl, C1-C6 fluoroalkyl,
C2-C6 alkenyl, C2-C6 alkynyl and phenyl;
R4 is hydrogen or the keto tautomer; C1-C6 alkyl;
C2-C6 alkenyl; C2-C6 alkynyl; substituted C1-C6 alkyl wherein
the alkyl group is substituted with C1-C6 alkoxy, C1-C6
alkylthio, C1-C6 alkoxycarbonyl, phenyl, and substituted
phenyl wherein the benzene ring is substituted with 1 to 3
substituents selected from the group consisting of halogen,
vitro, cyano, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkoxy, and
C1-C6 alkylthio; C1-C6(alkyl) sulfonyl; benzene sulfonyl;
substituted benzene su:Lfonyl wherein the benzene ring is
substituted with. 1 to :3 substituents selected from the group
consisting of halogen, vitro, cyano, C1-C6 alkyl, C1-C6
I - 1 J 'c3.1 l:)-1--~tii,
RC? . Wi\ : E:Y~. ''i1 ',CHE:'~,_ (l 1~ _'. .._... . . ',. : .~~; ~'3'.l ~: ~~
:-'- . ~ ;:;.~.~ ~l ti 1 l '- ' ~ '
21 18 ~ 9 4 PR~8559
haloalkyl, cz-C6 a:Lxoxy and ci-C8 alkylthio; an aayl group and
an inorganic or or~~anic cation; and
n is an :lntsger chosen from ~ tc 5.
- The term:: "alkyl", ~~alkoxy", ~~al.kenyl", "alkylthio~',
and the like era u~ced herein to embrace both 6traiQht-chain
and branched-chain radicals.
Examples of aryloxygropionic acid deriYativas useful
in the present invention arc:
(D) -butyl, 2-[4-,;5-trifluoromethyl-Z-pyridyloxl~) -
phenoxy3-propionate:, (fluazitop-butyl);
' (f3uazffc~Py;
(R)-2-(4-~(5-trifluoromathyi-Z-pyridyloxy)pbenoxy]
propionic acid, (fluazifop-P and fiua~ifop-P-butyl);
(RS)-2-[4-~3-chioro-5-trifluoromethyZ-~-pyridyloxy)
phonoxy~propionie acid, (haloxyfop);
haloxyfop-etotyl; haloxytop-methyl.
Thess and other aryioxypropionic acid derivatives
within the aavps of the irvantion can be prepared by the
procedures dnscribs~d in L?.S. Patants Nos. 4,257,336, x,317,913,
4,414,391; ~P1~ Z37S5; and British Patents Non. 1,599,iZ1 and
2,G02,36g.
Preferred cyclohaxanedionas included in the present
invention are those in which tra phenyl grosp is substituted
with methyl groups and include:
5-(3-acet~tl-2,x,6-trimsthylphanyl)-Z- ~1-l,ethoxy-
imino) -propyl ~ -3-hydroxycyclohox-~-en-1-; -and_
Z-(l-(ethc5xyimino)propyl7-.3-hydroxy-5-(2,4,6-tri-
mathyl-3-butyryiphenyl)cyelohex-2-enons.
SUBSTITUTE SHEET
- 4 -
FtCV.~U\:~:F'~ ~Il\CIIE:', UI '.' ~3-J:3 : l-3 '?:3 : l:3~k~~1 4f3111'?- +4;~
ti;-3 '_:.;:3;3~14E::>:N .;
__ __ __ ._.. . .. ~ .~.. _.. . , ~_~.._ .,.
21 18794
~t-sass
Th3l, most preferred substituents are on the 2- and
6-position of the phsny,l rinr~ and are preferably !selected from
halogen, methyl r;~nd msthoxy.
These i~nd other cyclorexanedianes along with their
tautomeric forms within the scope of the present invention,
can be prepared x~y the procedures described in V.S. Patent
3,9SO,4Z0, E8-7~-0080301 and EP-B-OOS5SZ9.
Ths terms "synergism" and "synergistic" are used
hrrein to convey the result observed Whon a combin8tion of
herbicides d~amonstrates a potoncy in excoss of that which the
combination would ba ~xpected to produce on the basis of Thai
potencies of each herbicide applied individually.
The term "herbicide" is used herein to denote a
compound which controls or aodifias the gro~rth of plants. The
term "herbicidall;y effective amount" is used to indicate the
quantity of such ,n compound or combination of such compounds
which is capable .of pxoducing a controlling or modifying
affect. Controlling or modifying effects include all devia-
tions frog natural development, for example: kill, rstar-
dat=on, Isaf burn, d~rarfing and the like. Tho term "plant"
refers to all physical parts o! a plant, including leads,
seedlings, saplings, roots, tubers, stems, stalks, foliage and
fruits.-- '
In the compositions of this invention, the aryloxy~
propionic acid derivactive:cyclohexansdione Weight ratio at
Which the herbicidal response is synergistic, lies within the
rahgs of 1:5 to about 30: 1, preferably about 1:5 to about .1~:1
and moat preferably about 1:2 to about='8-:~:- - -
Applicat:fon rates will depend upon the particular
compounds chosen t:or use, the particular plant sp~toies and
degree of control desired. In general, th~ compositions of
the invention are moat efficiently employed at a rats of o.ooi
- 5
~~~TpT1 m.,.~_~
WO 93/04581 '~ ~ ~ PCT/US92/07709
6
' to 50 pounds per acre (0.001 to 56 kilograms per hectare),
preferably 0.001 to 25 pounds per acre (0.001 to 28 kilograms
per hectare).
The following examples provide further illustrations
demonstrating the synergistic herbicidal response of the
present compositions.
Example I
This example demonstrates the synergistic response
of butyl (R)-2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy]
propionic acid (fluazifop-P-butyl) and 2-[1-(ethoxyimino)-
propyl]-5-(2,4,6-trimethyl-3-butyryl phenyl)-1,3-cyclohexane-
dione in combined postemergence application to the plants
giant foxtail and shattercane.
Plastic pots were filled with 2 parts sandy loam and
1 part peat moss mixed together containing the commercial
fungicide cis-N[(trichloromethyl)thio]-4-cyclohexene-1,2-
dicarboximide (Captan~) and 17-17-17 fertilizer (percentages
of N-P205-K20 on a weight basis). Each pot was seeded to a
single plant species. The plant species included giant
foxtail (Setaria faberi) and shattercane (_Sorcrhum vulaare).
The pots were placed in a greenhouse for approximately two
weeks where they were watered regularly. The greenhouse
temperature was approximately 85° F. day and 80° F. night.
At the end of this period, the foliage on the
emerged plants was sprayed with herbicidal emulsions formed by
diluting emulsiffable concentrates of test compounds with
adjuvants and water. The dilutions were made such that at a
total spray volume of 25 gallons per acre, the amount of each
test compound applied per pot corresponded to the desired
application rate in ounces per acre. In control pots, the
test compounds were applied individually at various applica-
tion rates, whereas in the test pots, emulsions contained both
compounds. Untreated pots were used as standards.
WO 93/04581 2 1 1 8 7 9 4 P~/US92/07709
7
Sixteen days after treatment, the control and test
pots were compared to the standards and rated visually in
terms of percent control ranging from 0% to 100%, with 0%
representing no injury to the plant species and 100% repre-
senting complete kill of all plants. All types of plant
injury were taken into consideration.
For the plant species, the results of these tests
are listed in Table I ~,n the columns headed by the symbol "O"
(indicating the "observed" results), each figure represent the
average of three replications of the same test. These results
are compared with the expected results, shown in the columns
headed by the symbol "l~~", derived from the control data using
Limpel's formula. (Limpel et al., 1962, "Weed Control by
Dimethylchlorote:rephthalate Alone and in Certain Combinations",
Proc. NEWCC., vcrl. 16, pp. 48-53):
1: = X + Y - XY
100
where X - observed percent injury when one of the
herbicides is used alone, and
Y - observed percent injury when the other
herbicide is used alone.
An asterisk (*) is used to indicate the tests where
the results show synergism, i.e., where the observed result
exceeds the expected result by at least 10 percent. It is
clear from the 'table that synergism was observed at many of
the application rates tested.
WO 93/04581 PCT/US92/07709
21 18794
FABLE I
host emergence Applicationl: Averacte of Three Replications
Application Rates 4 Control2 O~Observ ed E~Ex pected
lOz/A1 Giant Foxtail Shattercane
A B O E O E
Control Data
0.063 -- 0 0
0.125 -- 0 27
0.250 -- 0 82
0.500 -- 7 ' 92
1.000 -- 37 100
-- 0.016 0 0
-- 0.031 0 0
-- 0.063 0 0
-- 0.125 32 43
-- 0.250 100 100
-- -- 0 0
Test Data
0.063 0.016 0 0 0 0
0.063 0.031 0 0 3 0
0.063 0.063 10 0 23* 0
0.063 0.125 75* 32 90* 43
0.063 0.250 100 100 100 100
0.125 0.016 0 0 10 27
0.125 0.031 0 0 33 27
0.125 0.063 13* 0 60* 27
0.125 0.125 75* 32 95* 58
0.125 0.250 100 100 100 100
0.250 0.016 0 0 85 82
0.250 0.031 3 0 85 82
0.250 0.063 13* 0 98* 82
0.250 0.125 80* 32 98 90
0.250 0.250 100 100 100 100
RCV. V!>~\ : 1~:Y1 111. ',C:tiL_ _ U 1 __. .__. , '?'> _, ;~_ ;).') '. , [.f
_~~') . ~::i.E.l I t; l l 1_ +.~'-~ ti;i _':3~~~~:-1-fi~~ : it r.
21 187 9 4
TABLE I (continued)
Application Ratss ! Contr o12 O:Obs erved. E:Ex fle
(Oz~a1 Giant Foxtail
0.500 0.018 10 '7 92 92
0.500 0.03 13 7 98 92
0.500 0.063 78! 7 100 92
0:30- 0.125 80~ 37 100 100
0.800 0.250 100 100 100 100
1.00C x.016 43 .3? 100 100
1.000 0.031 68* 3? 100 100
1.000 0.063 93* 37 100 100
3.000 0.12b 98* 57 100 100
1.000 0.250 100 100 100 100
-------------------------_--~--iai~-~-.r---_---~--~------_-_---
1 - Treatmerta contained 1! Ar'ridtx (registered grade Mar:)
Z = 16 days after application
* = denotes synergistic effect shown
- Fluatifop-P-butyl; butyl (R)-2-t4-(5-trifluotomethyl-Z-
pyridyloxy)phsnoxy~propionic acid
H~= 2-[1-(ethoxyimino)-propyl~-5-(2,4,6-trimethyl-3-butyry:-
phenyl~-1,3-cyclohaxanadions
rxamnle II
In this example, the tallowing f oraulations ware
prepared from 2-[I-ethoxyimino)propyl~-3-hydroxy-5-(2,4,6-
trimothyl-3-butyrylphQ:~yl)'cyelohox-2-rnona (Herbicides A~ , and
the D isomer of butyl 2-C4-(5-trifluoromsthyl-Z-pyridyloxy)-
phe»oxyZ-propionate (Fisrbicida B) .
Formulation (a): Herbicide (A), 125 g/1;
nonionic emulsifier (methyl capped derivat~.va of Renex 650),
20 g/1; Aerosol OT 100, 30 g/1; and Tar~sco 500/100 to 1 liter. -
Fcrmulatir~n (b): Herbicide (B), 1Z5 g/1;
phenyl s;~l:onate C7~L~c,*45 'g/1; Geopori SF_ 3sS. 45
9ynperionie*NPE 1800, 10 gjl and Solvaeso 100*~0 1.0 liter.
*!Regif9tered Trade Mark)
Field plots 2m x 2m s~rere seeded vrith oilseed rape
(~ ~g=etr~). and the plant spaeisi, perennial ryegrass
(Lolium baranna) and annual bluegrass (~o ).. At the
.. _ ~ -
SU~STIT!~'~~ SH~~T
PCT/US92/07709
WO 93/04581 ~ -
time of spraying, the oilseed rape was at the 2-true leaf
growth stage, the annual bluegrass was at the 3-leaf, 2-tiller
stage of growth, and the ryegrass was at the 2-leaf growth
stage. Formulations (a) and (b) above were each blended
separately with 0.1% by weight of Agral and the resulting
solutions were applied sequentially at various rates. Injury
ratings were taken by visual determination 87 days after
treatment. A scale of 0 to 10 is used where 10 is equivalent
to complete kill (or 100 percent control) and 0 indicates no
visual injury (or 0 percent control) as compared to untreated
control plants.
For the plant species, the results of these tests
are listed in Table II in the columns headed by the symbol "O"
(indicating the "observed" results). These results are
compared with the expected results, shown in the columns
headed by the symbol "E", as determined by the Colby formula.
The Colby formula is utilized to demonstrate the
presence or absence of synergism (Colby, R. S., "Calculating
Synergistic and Antagonistic Responses of Herbicide Combina-
tions", 1967 Weeds, vol. 15, pp. 20-22):
Expected effect - X + (100 - x)y
100
where X = observed effect of A and
Y = observed effect of B
The basis of demonstration by comparison with the
Colby formula is that Herbicide (A) tested alone will kill a
proportion of the target weeds and leave a proportion (a%) as
survivors. Similarly, Herbicide (B) tested alone will leave
(b%) as survivors. When combined, A + B will, however, if
synergy is absent, act independently on the target weed,
component A again leaving a% survivors, which survivors will
be controlled by component B, with an overall effect of
a x b
100
If, in practice, the percent control (degree of
kill) is greater than that predicted by the Colby formula,
WO 93/04581 PCT/US92/07709
21 18 7~ g 4 11 :
synergism is provided by the difference between the observed
and expected (C~ by determined) results. As can be seen from
Table II, synergism is widely evident.
FABLE II
2
gearee of Kill
1 O:Observed E:Ex pected
Rates
ti
li
on
ca
App
(a /hal Rvearass Bluegrass
A ~ p ,- E O E
g - 7 4 5 2
16
g 31 9 8 9 6
g 62.5 10 10 10 9
16 16 7 5 5 4
16 31 9 8 9 7
16 62.5 10 10 10 9
31 16 8 5 8 4
31 31. 10 8 10 7
31 6~:.5 10 10
62.5 6::.5 9 6 9 5
6 2 6:! . 5 10 8 10 8
.
62.5 62.5 10 10 10 9
1 A 2-[1-(ethoxyimino)propyl]-3-hydroxy-5-(2,4,6-trimethyl-
=
3-butyrylphenyl)cyclohex-2-enone.
B = D isamer of butyl-2-[4-(5-trifluoromethyl-2-pyridyloxy)
phenoxy]p:ropionate
2 where
O
=
no
:injury
= complete kill
WO 93/04581 PCT/US92/07709
21 187 9 4 12
~,xamole III
This example demonstrates the synergistic response
of Herbicide (B) used in Example I and 5-(3-acetyl-2,4,6-
trimethylphenyl)-2-[1-(ethoxyimino)-propyl]-3-hydroxycyclohex-
2-en-1-one (Herbicide C).
The following formulations were prepared: Formula-
tion (b) included Herbicide (B), 125 g/1; emulsifier 50 g/1;
made up to 1.0 liter with Solvesso 100; and formulation (c)
included Herbicide (C), 125 g/1; non-ionic emulsifier, 110
g/1; anisole, 400 g/1 made up to 1.0 liter with Solvesso 150.
Pots in the greenhouse were seeded with large
crabgrass (Dicritaria sanctuinalis), barnyardgrass (Echinochloa
crusQalli), goosegrass (Eleusine indica), guineagrass (Panicum
maximum), and johnsongrass (Sorghum halepense).
At the time of spraying, each plant species had 4 -
leaves per plant. The above formulations were blended and
the final solution blended with 0.1% by weight of AGRAL 90 and
1.0% by weight of ACTIPON. The final solution was applied
through a greenhouse track sprayer at a volume of 200 liters
per hectare.
Nineteen days after treatment, the degree of injury
was rated visually in terms of percent control ranging from 0
to 100%, with 0% representing no control and 100% representing
complete kill of all plants in the pot. The degree of kill
was then assessed and compared with the expected kill as
determined by the Colby formula presented in Example II. It
is clear from Table III that synergism was observed at many of
the application rates tested.
WO 93/04581 PCT/US92/07709
21 13794 13
TABLE III
gostemeraence Application
Application % Control 2 O-Observed- E-Expected
Rates Crab- Goose- Guinea- Johnson-
_Lq,/ha1 ara~ss _ lMillet crass crass crass
C O E _ O ~ O ~ O E O E
1 7 0 32* 7 45* 5 55* 8 10 15
1 - - 52* 17 97 92 48* 24 63 59
1 52* 7 100* 75 95* 78 95* 79 100 97
5 2 50* 3 98* 47 93* 15 85* 57 85* 37
10 2 60* 8 35* 53 97 93 97* 65 100 70
20 2 92* 10 100* 66 98* 80 100* 90 100 98
1 B = Fluazifop-P-butyl; (D) butyl 2-[4(5-trifluoromethyl-2-
pyridylo:Ky)phenoxy]-propionate
C = 5-(3-acetyl-2,4,6-trimethylphenyl)-2-[1-ethoxyimino)-
2 propyl]-:3-hydroxycyclohex-2-en-1-one
- 19 days after treatment
* - Synergistic effect shown, the observed result exceeded
the expected result by at least l0 percent
The compositions of this invention are useful <_.~
herbicides demonstrating synergistic activity for the control
of undesirable vegetation. The compositions can be formulated
in the same manner in which herbicides are generally formu-
lated. The compounds may be applied either separately or
combined as part of a two-part herbicidal system.
The object of the formulation is to apply the
compositions to the locus where control is desired by a
convenient method. The "locus" is intended to include soil,
seeds, and seedllings, as well as established vegetation.
Formulations will generally contain several addi-
tives. Among these are some inert ingredients and diluent
carriers such as organic solvents, water, oil and water, water
in oil emulsions, carriers of dust and granules, and surface
active, wetting, dispersing, and emulsifying agents.
WO 93/04581
PCT/US92/07709
14
Fertilizers, such as ammonium nitrate, urea, potash
and superphosphates may also be added.
Aids i~o rooting and growth, such as compost, manure,
humus, sand, etc. may likewise be added.
The formulations are commonly dusts, wettable
powders, granuleas, solutions or emulsifiable concentrates.
Dusts are free-flowing powder compositions contain-
ing the herbicidal compound impregnated on a particulate
carrier. The particle size of the carrier is usually in the
approximate range of 30 to 50 microns. Examples of suitable
carriers are ta7lc, bentonite, diatomaceous earth, and pyrophyl-
lite. Anticaking and antistatic agents can be added, if
desired. The composition generally contains up to 50% of
active ingredient. Dusts, like liquid compositions, can be
applied by spraying from boom sprayers, hand sprayers or
airplanes.
Wettable powders are finely divided compositions
comprising a particulate carrier impregnated with the herbi-
cidal compound wind additionally containing one or more surface
active agents. The surface active agent promotes rapid
dispersion of the powder in aqueous medium to form stable,
sprayable suspensions. A wide variety of surface active
agents can be u~;ed, fo:r example, long chain fatty alcohols;
salts of sulfoni.c acid; esters of long chain fatty acids; and
polyhydric alcohols, in which the alcohol groups are free,
omega-substituted polycethylene glycols of relatively long
chain length.
Granules comprise the herbicidal composition impreg-
nated on a particulate inert carrier having a particle size of
about 1 to 2 millimeters in diameter. The granules can be
made by spraying' a solution of the active ingredient in a
volatile solvent onto the granular carrier. Suitable carriers
in preparation of granules include clay, vermiculite, sawdust,
granular carbon, etc.
WO 93/04581 PCT/US92/07709
2~ 1 ~a~ ~ ~ _
Microcapsules and other slow release formulations
are advantageous as formulations to deliver and distribute the
active ingredients. Mic:rocapsules consist of fully enclosed
droplets or granules containing the active materials in which
the enclosing material is an inert porous membrane, arranged
to allow escape of the enclosed materials to the surrounding
medium at controlled rates over a specified period of time.
Encapsulated droplets are typically about 1 to 50 microns in
diameter. The enclosed liquid typically constitutes about 50
to 95% of the weight of the entire capsule, and may contain an
amount of salvent in addition to the active materials.
Encapsulated granules are characterized by porous membranes
sealing the openings of the granule carrier pores, trapping
the liquid containing the active components inside for con-
trolled release. A typical granule size ranges from 1 milli-
meter to 1 centimeter in diameter. In agricultural usage, the
granule size is generally about 1 to 2 millimeters in diameter.
Granules formed by extrusion, agglomeration or prilling are
useful in the present invention as well as materials in their
naturally occurring form. Examples of such carriers are
vermiculite, starch sintered clay granules, kaolin, attapul-
gite clay, sawdust and granular carbon. Useful encapsulating
materials include natural and synthetic rubbers, cellulosic
materials, styrene-butadiene copolymers, polyacrylonitriles,
polyacrylates, polyesters, polyamides, polyureas, polyurethanes
and starch xanth.ates.
The herbicidal compositions can also be applied to
the soil in the form of: a solution in a suitable solvent.
Solvents frequer.~tly used in herbicidal formulations include
kerosene, fuel oil, xylene, petroleum fractions with boiling
ranges above xyl.ene, and aromatic petroleum fractions rich in
methylated napht:halenes.
Emulsi.fiable concentrates consist of an oil solution
of the herbicidE: along with an emulsifying agent. Prior to
use, the concentrate is diluted with water to form a suspended
emulsion of oil droplets. The emulsifiers used are usually a
mixture of anionic and nonionic surfactants. Other additives
PCT/US92/07709
WO 93/04581
16
such as spreading agents and stickers can be included in the
emulsifiable concentrate.
It is not necessary that the compositions be admixed
with the soil particles. After application by the above-
discussed methods, they may be distributed below the soil
surface to a depth of at least one-half inch by conventional
means such as discing, dragging, or mixing.
