Mulch/herbicide composition

Details Mulch/herbicide composition Mulch/herbicide composition

2001-12-20

2003-07-29

Clardy, S. Mark (Department: 1616)

Plant protecting and regulating compositions

Plant growth regulating compositions

Organic active compound containing

C047S009000

Reexamination Certificate

active

06599859

ABSTRACT:

The present invention relates to a composition comprising a mulch and an herbicide useful for weed control.
Mulch is a covering spread over the ground that conserves moisture in soil and suppresses the growth of weeds. Mulches provide many advantages to a grower. They help prevent soil erosion and runoff from heavy rain. Moisture in the soil is conserved because evaporation is reduced. In addition, mulches suppress weed growth by either choking the weeds out or by preventing their seeds from contacting the soil. A layer of mulch over soil also acts as an insulator by keeping the soil cool in the summer and helping to eliminate danger to plants from freeze-thaw cycles in the winter. While doing its task of keeping moisture in the soil and suppressing the growth of weeds, mulch also creates a rich unified background for plants, shrubs, and trees. When organic mulch decomposes it becomes a valuable addition to the soil structure.
Many different materials have been used as mulches including pine nuggets, pine needles, shredded hardwood bark, chipped hard wood, sawdust, ground rubber, and plastic mats. Mulches are commonly used in new and existing ornamental beds to protect and beautify both annual and perennial plantings. They are often used in recreational areas around swing sets and climbing bars. Mulch offers several advantages in these areas. It retains soil moisture, protects young plants, suppresses weeds, prevents mud and erosion, adds nutrients to the soil as it decomposes and may add color and texture to the garden. However, one of the biggest deficiencies of mulch is incomplete weed control. Weeds such as nutsedges and thistles can grow through even thick mulch. If the mulch is disturbed or not evenly applied, large numbers of weeds can grow through the mulch.
Because mulches do not entirely control weeds, additional weed control measures must normally be employed in order to ensure a weed-free area. The standard additional weed control measure is to apply one or more herbicides to the area. These applications may be made before, at the same time, or after the mulch itself is spread. Because an additional application is required, additional costs are encountered by the grower. Therefore, it would result in cost savings and increased efficiency if mulch and herbicide combinations could be used. Such combinations are known. Attempts to add herbicides to mulches, especially mulching films, are well known. Unfortunately, adding herbicides to wood mulches has been problematic due to the nature of both the herbicides and the mulch. Most pre-emergent herbicides come from a group of compounds called dinitroanilines. These compounds (including pendimethalin, Prodiamine and Oryzalin) are yellow in color and when added to the mulch give it an unacceptable yellow color. Furthermore, these materials have a strong affinity for organic mater. As a result, they may bind to the mulch and not release to control the weeds. However, we have discovered a mulch/herbicide combination that provides significantly better weed control than would be expected, based on the weed control obtained using the mulch and the herbicide separately.
U.S. Pat. No. 4,692,184 discloses a class pyridinedicarboxylic acid herbicides which are useful for weed control under a variety of conditions. They are particularly effective for pre-emergence or early post-emergence weed control. We have discovered that incorporating these herbicides into a mulch before spreading the mulch provides unexpectedly high herbicidal activity and is effective in controlling a variety of weeds at lower application rates than those expected from separate use of the mulch and the herbicide. This invention solves the problem of the herbicide binding to the mulch by first incorporating the herbicide onto a carrier and then blending the carrier into the mulch. The herbicides of this invention are a unique choice for this use because, unlike the dinitroanilines they are clear white compounds and do not cause staining. This leaves the mulch it's natural color. By incorporating the herbicide onto a clay carrier, and then blending into the mulch, the small clay particles are then free to filter to the ground where it can release the herbicide at the most effective site of action.
One embodiment of this invention provides a composition comprising:
a) an herbicidally effective amount of a compound of the formula (I)
 wherein:
R is (C
1
-C
7
)alkyl, (C
2
-C
7
)alkenyl, (C
2
-C
7
)alkynyl, (C
3
-C
7
)cycloalkyl, haloalkyl, or (C
3
-C
6
)cycloalkanylalkyl;
R
1
and R
2
are independently (C
1
-C
3
)alkyl, fluorinated methyl, or chlorofluorinated methyl, provided that at least one of R
1
and R
2
is fluorinated methyl or chlorofluorinated methyl; and
R
3
and R
4
are independently (C
1
-C
3
)alkyl; and wherein the herbicide is incorporated onto a carrier; and
b) an organic or inorganic mulch.
In a second embodiment of this invention, there is provided a method for controlling weeds comprising applying a composition comprising:
a) an herbicidally effective amount of a compound having the formula (I)
 wherein:
R is (C
1
-C
7
)alkyl, (C
2
-C
7
)alkenyl, (C
2
-C
7
)alkynyl, (C
3
-C
7
)cycloalkyl, haloalkyl, or (C
3
-C
6
)cycloalkanylalkyl;
R
1
and R
2
are independently (C
1
-C
3
)alkyl, fluorinated methyl, or chlorofluorinated methyl, provided that at least one of R
1
and R
2
is fluorinated methyl or chlorofluorinated methyl; and
R
3
and R
4
are independently (C
1
-C
3
)alkyl; and wherein the herbicide is incorporated onto a carrier, and
b) an organic or inorganic mulch; to the locus of the weeds.
The term “alkyl” means a straight or branched alkyl group having one to seven carbon atoms per group such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl.
The term “alkenyl” means a straight or branched alkenyl group having two to seven carbon atoms per group such as, for example, ethenyl, 2-propenyl, 2-butenyl, 1-methylethenyl, 2-methyl-2-propenyl and the like.
The term “alkynyl” means a straight or branched alkynyl group having from two to six carbons per group such as, for example, ethynyl, 2-propynyl, 2-butynyl and the like.
The term “cycloalkanylalkyl” means an alkyl radical substituted with a (C
3
-C
6
)cycloalkyl radical.
The term “fluorinated methyl” means a methyl group wherein from one to three of the methyl group hydrogens is replaced by a fluorine. The term “chlorofluorinated methyl” means a methyl group wherein at least one hydrogen is replaced by a fluorine and at least one hydrogen is replaced by a chlorine.
“Halo” means chloro, fluoro, bromo and iodo.
The term “locus” means any area where weeds grow or are likely to grow and where the use of mulch is desired.
Preferably R is (C
1
-C
7
)alkyl. More preferably, R is 2-methylpropyl. Preferably, R
1
and R
2
are independently methyl, fluorinated methyl, or chlorofluorinated methyl. More preferably, R
1
and R
2
are independently fluorinated methyl or chlorofluorinated methyl. Most preferably, one of R
1
and R
2
is difluoromethyl and the other of R
1
and R
2
is trifluoromethyl Preferably, R
3
and R
4
are independently (C
1
-C
3
)alkyl. Most preferably, R
3
and R
4
are both methyl.
Most preferably, the herbicide is 2-difluoromethyl-4-(2-methylpropyl)-6-trifluoromethyl-3,5-pyridinedicarbothioic acid, S,S-dimethyl ester, a material commonly referred to as dithiopyr.
The term “mulch” in its broadest sense means any material spread over the ground that conserves moisture in soil and suppresses the growth of weeds. Mulches include organic materials such as, for example, pine straw, shredded pine, shredded hard wood, shredded licorice root, shredded wood waste, shredded cedar, cedar chips, pine bark, pine nuggets, pine needles, shredded wood and bark, chipped wood and bark, sawdust, ground rubber, grass clippings, leaves, straw, hay, compost, newspaper, ground plastic, plastic sheeting, and landscape fabric, as well as inorganic materials such as, for example, stones and marble chips, or combinations thereof.
As used herein,

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