Novel process and compositions for delivery of foliar herbicides

Background of the Invention

Weeds cost farmers billions of dollars annually in crop losses and in the expense of keeping the weeds under control. Much of the cost of intertillage of row crops, maintenance of fallow, seedbed preparation, and seed cleaning is chargeable to weed control. Another expensive item is suppression of weeds along highways and railroad right-of-ways, and in irrigation ditches, navigation channels, yards, parks, grounds, and home gardens. Ragweed pollen is the source of annual periodic distress to several million hayfever sufferers. Poison ivy, poison oak, poison sumac, nettles, thistles, sandburs, and puncturevine also bring pain to millions. Weeds also serve as hosts for other crop diseases as well as for insect pests.

The losses caused by weeds in agricultural production environments include decrease in crop yield, reduced crop quality, increased irrigation costs, increased harvesting costs, decreased land value, injury to livestock, and crop damage from insects and diseases harbored by the weeds.

Chemical herbicides have provided an effective method of weed control in the past. However, the public has become concerned about the amount of chemicals applied to the food that they consume, to the land on which they live, and to the ground water which they use. Stringent restrictions on the use and development of new herbicides and the elimination of some effective herbicides from the market place have limited economical and effective means for controlling costly weed problems.

There is a great need for novel methods of controlling weeds which reduce the amount of chemical herbicide needed to achieve control. One important area of research aimed at reducing the need for chemical herbicides has been the search for biological herbicides. Unfortunately, the highly empirical nature of this research and the many obstacles which must be overcome in order to identify and produce a useful bioherbicide have limited the commercial impact of this form of control.

Yeast extracts are well known and are used for a variety of purposes. Yeast extracts can be used as a source of proteins and nutrients in growth media and in food substances for laboratory insects. Its use in combination with other ingredients, as a component of non-toxic dispersing agents, has also been described (JP 2048502). No ability to enhance herbicidal activity has been attributed to yeast extracts in the past.

Brief Summary

The subject invention concerns the unexpected discovery that a mixture of a yeast extract and a chemical herbicide produces an enhanced herbicidal effect against weeds. This effect significantly enhances the value of the chemical herbicide by reducing the amount of chemical herbicide needed.

Specifically, a combination of at least one yeast extract and at least one chemical herbicide results in an enhanced effect as measured by the control of target plants. This enhanced effect is most advantageous when a sub-lethal concentration of a chemical herbicide is used.

Detailed Description

The subject invention concerns compositions and methods for the control of weeds through the simultaneous or sequential application of a yeast extract with a chemical herbicide. The chemical herbicide may be applied at a sub-lethal rate and the enzyme produces no useful control effect when applied alone.

For purposes of this application, a "weed" is any plant that is objectionable or interferes with the activities or welfare of man. A "herbicide" (or chemical herbicide) is a chemical used to control, suppress, or kill plants, or to severely interrupt their normal growth processes. Herbicide Handbook of the Weed Society of America, Fifth Edition (1983), xxi-xxiv. As used herein, the term "bioherbicide" means a biological organism used to control, suppress, or kill plants, or to severely interrupt their normal growth processes.

The invention can be used to control weeds in an agricultural setting and can also be used for nonagricultural applications. For example, the invention can be used for the control of weeds in turf and as a contact herbicide for the management of roadside vegetation.

The yeast extracts which can be used according to the subject invention are commercially available from a variety of sources, or can be prepared by standard methodologies which are well known to those skilled in this art. Commercially available yeast extracts which can be used according to the subject invention are readily available and sold, for example, under the tradenames BACTO YEAST EXTRACT (Difco Co., Detroit, MI) and AMBEREX 1003 (Universal Foods Corp., Milwaukee, WI) Alternatively, similar yeast extracts having proteins, peptides, amino acids, minerals and/or nutrients can be prepared using standard extraction procedures.

A variety of different chemical herbicides can be used alone or in combination according to the subject invention. The specific herbicides which should be used for a given application can be readily ascertained by a person skilled in the art. Following is a list of herbicides which may be used according to the subject invention.

CHEMICAL HERBICIDE FAMILIES AND EXAMPLES

HERBICIDE

EXAMPLE

1.

Phenoxy acids (acids, esters, salts)

2,4-D, MCPA, Dichlorprop

2.

Benzoic acid

Dicamba

3.

Aryloxy phenoxypropionate (acids, esters, salts)

Fluazifop, Dichlofop

4.

Sulfonyl ureas (acids, esters)

Chlorimuron, Bensulfuron

5.

Imidazilinones

Imazethapyr

6.

Bipyridillium

Paraquat

7.

Diphenyl ether (acids, salts)

Acifluorfen, Fomesafen

8.

Cyclohexanedione

Sethdoxydim, Cycloxydim, Clethodim

9.

Methane arsonate

MSMA (Methylarsonic acid)

10.

Triazine

Atrazine, Cyanazine

11.

Aliphatic carboxylic acids

Dalapon

12.

Benzonitrile

Bromoxynil

13.

Carbamate

Barban

14.

Thiocarbamate

Benthiocarb, Triallate

OTHER CHEMICAL HERBICIDES

PYRAZON

GLYPHOSATE

PICHLORAM

METRIBUZIN

GLUFOSINATE

CLOPYRALID

BENTAZON

DESMEDIPHAM

QUINCLORAC

AMITROLE

PHENMEDIPHAM

TRICLOPYR

ETHIOZIN

Herbicides other than those which are specifically listed above may also be used according to the subject invention. In one preferred embodiment of this invention, a yeast extract is combined with one or more systemic foliar herbicides. Specifically, the compositions of the subject invention may advantageously comprise a herbicide from one of the following families: phenoxy acids, aryloxy phenoxypropionates, cyclohexanediones, sulfonyl ureas, and imidazilinones. Of these families, imidazilinones and sulfonyl ureas are particularly advantageous. A further preferred embodiment is the use of a yeast extract with glyphosate. This combination has shown substantial herbicidal activity as described in the example below.

Specific examples of the chemical herbicides which can be used together with the yeast extract in the composition of the subject invention include, but are not limited to, glyphosate (N-[phosphonomethyl]glycine, isopropylamine salt), imazapyr ([±],-2-[4,5-dihydro-4-methyl-4-[1-methyl ethyl]-5-oxo-1H-imidazol-2-yl]-3-pyridine carboxylic acid), sethoxydim (2-[1-[ethoxyimino]butyl]-5-[2-[ethyl-thio]propyl]-3-hydroxy-2-cyclohexen-1-one), acifluorfen (sodium 5-(2-chloro-4-(trifluoromethyl)-phenoxy)-2-nitrobenzoate), bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide) or paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride), used alone or optionally with agricultural adjuvants with which the herbicides are normally admixed. For other chemical herbicides that can be used to practice this invention, see Herbicide Handbook of the Weed Society of America, Fifth Ed. (1983) and H.J. Lorenzini and LS. Jeffrey, Weeds of the United States and Their Control, NY: Van Nostrand, 1987, Table 1.9.

It should be understood that in practicing this broad approach to weed control, each particular chemical agent and yeast extract at specific dosages may not necessarily be effective. This is consistent with the behavior of other broad range chemical herbicides, which are rarely, if ever, effective in controlling all types of weeds and are usually ineffective in controlling some weed species. Whether a particular combination of herbicide and yeast extract will be useful for a particular application, and the optimal conditions for the particular combination, can readily be determined by those skilled in the art without undue experimentation by simple testing in the greenhouse or the field. Certain principles may guide the selection of parameters. Where the herbicide at a particular dosage already produces a high degree of weed control, additional benefits from the addition of a yeast extract may not be as apparent. Enhanced control is most apparent when the weed shows partial response to the level of chemical herbicide employed. It will be apparent to those skilled in the art that while the rate of application of the chemical can advantageously be less than the usual field application rate, some level of the chemical will be too low to have a useful effect.

Certain weed species may not be controlled by a particular herbicide because the field application rate is too low. However, actions of the herbicide that are not otherwise manifested may be enhanced by combination with a yeast extract sufficient to result in herbicidal activity. Thus, combining a broad range chemical herbicide with a yeast extract may serve not only to control the same spectrum of weeds with a lower level of chemical herbicide, but may also permit the control of weed species that are not usually controlled by the chemical herbicide.

Practice of this invention may make it possible to achieve further reductions in the amount of chemical herbicides employed by giving users the option to replace the traditional prophylactic preemergent herbicide application with more efficient postemergent application. A postemergent chemical herbicide used in conjunction with a yeast extract could be applied selectively only as required, providing an alternative to heavy preventative preemergent application of herbicides. This approach has not been generally feasible in the past due to the cost and limited spectrum of most postemergent herbicides.

Practice of this invention would have the additional advantage of reducing the costs associated with the disposal of chemical herbicide containers. This reduction would be accomplished by a reduction in the total amount of chemical herbicide used.

The chemical herbicide and yeast extract can be applied simultaneously. In other circumstances, it may be preferable to apply the yeast extract first, and to apply the chemical later. Alternatively, the chemical agent can be applied first followed by the yeast extract. Whether simultaneous or sequential application is optimal will depend on the particular combination of chemical agent and yeast extract selected. If the chemical herbicide and yeast extract are applied simultaneously, they can be mixed in the same formulation and sprayed on the weeds from the same tank. Compositions for practice of the invention can be formulated in numerous ways, including flowables, dry flowables, water dispersible granules or emulsified concentrates. The invention can also be practiced by applying a mixture of different chemical agents in conjunction with the yeast extract(s). The formulations of the invention may also contain adjuvants such as surfactants and suspension agents.

The advantageous combination of a chemical and yeast extract to achieve herbicidal activity can be used in conjunction with other herbicidal techniques. For example, the procedures of the subject invention may be used with non-traditional chemical herbicides including plant hormone mimics, plant growth regulators, and photosynthesis inhibitors. The methods of the subject invention can also be used in conjunction with biological herbicides, including phytopathic fungi and bacteria, as well as to enhance the effectiveness of fatty acid herbicides and their derivatives, and in conjunction with enzymes used to enhance the effectiveness of herbicides.

Following are examples which illustrate procedures, including the best mode, for practicing the invention. These examples should not be construed as limiting. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted.

Example 1:

A greenhouse trial using sicklepod was conducted to determine if yeast extracts would enhance the herbicidal activity of glyphosate. One plant was contained in each 2 x 2 inch pot, and the plants were grown to the 1 true leaf stage.

A 1.0% solution of Difco BACTO YEAST EXTRACT in water was prepared. Also, 700 µl of the commercial adjuvant DASH (BASF Corporation) was diluted into 29.3 ml water and was used as a positive chemical adjuvant control to illustrate a representative amount of herbicidal activity enhancement that is possible under the test conditions. The herbicide glyphosate was prepared by diluting the requisite amount of commercial RODEA 41 (Monsanto Corporation, St. Louis, MO) with sufficient water to provide spray mixes which, when applied at an application rate of 100 gpa by a track sprayer, would deliver to the plants the field equivalent of 0.25, 0.13, 0.06, and 0.03% a.i. w/v of the active isopropylamine salt of glyphosate in water.

Sicklepod was sprayed with water only (no adjuvant control), DASH (positive control), or the yeast extracts solution (test adjuvants) at a rate of 200 gallons per acre (gpa) using a handheld herbicide spray gun (Meterjet, Spraying Systems Company), then the plants were treated with the herbicide in a track sprayer as described above. Following these applications the plants were removed to the greenhouse and maintained under good growing conditions for the duration of the test period.

Herbicidal effects were assessed 14 days after treatment (DAT). The weed control ratings ascertained the extent of control, i.e., reduction in growth, obtained and scored on the basis of 0 to 100 where 100 represents complete killing of the plants and 0 represents no reduction in growth, as compared to the untreated check. Table 1 shows the effects of the yeast extracts on ultimate herbicidal effect.

Herbicide Rate (%)

Percent Control Sicklepod 14 DAT

Control^a

DASH^b

Yeast Extract

Yeast Extract Dialyzed^c

.25

80

85

98

95

.13

50

80

70

80

.06

20

60

65

50

.03

10

65

35

45

0

0

20

0

0

^aSprayed with 10mM sodium phosphate buffer, pH 7.

^bProduct of BASF Corp.

^cDialyzed against buffer in footnote α, above, in a Spectropore 3 (3500 molecular weight cutoff) dialysis membrane.

The results of this experiment clearly show the utility of the yeast extract in enhancing the herbicidal activity of a chemical herbicide.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.