R&D
Herbicidal composition and method
Publication number: WO 1997016975 A1
Application number: PCT/AU1995/000739
Publication date: May 15, 1997
Filing date: Nov 6, 1995
Priority date: May 11, 1994
Inventors: John Selga, Wayne Andrew Kiely
Original Assignee: Selga, Wayne Andrew Kiely
ABSTRACT
The present invention relates to a herbicidal composition having, as an active ingredient, a terpene compound, a terpene derivative, or an essential oil comprising a terpene compound or derivative. In particular, the herbicidal composition will comprise a pine oil, a citrus oil or a terpene compound or derivative derived from pine oil or citrus oil. In a further aspect, the invention provides a method for controlling unwanted plant growth, wherein a terpene compound or derivative, an essential oil comprising a terpene compound or derivative, or a herbicidal composition having, as an active ingredient, a terpene compound or derivative or an essential oil comprising a terpene compound or derivative is applied to the unwanted plant or plants.
DESCRIPTION
BACKGROUND TO THE INVENTION
The present invention relates to a herbicidal composition having, as an active ingredient, a terpene compound, a terpene derivative, or an essential oil comprising a terpene compound or derivative. In particular, the herbicidal composition will comprise a pine oil, dipentene, pinene, a pine alcohol or a terpene compound or derivative derived from pine oil. A citrus oil or a terpene compound derived from citrus oil, e.g. limonene ( l-methyl-4-( 1-methylethenyl)- cyclohexene) , may also be used.
Many herbicidal compositions presently on the market are highly toxic to humans and domestic animals. A herbicide having lower toxicity is desirable, particularly for use by the home gardener.
The active ingredient of the present herbicidal compositions has the advantage of being an environmentally friendly, natural product, which is unlikely to cause environmental pollution or create toxicity problems for humans or domestic animals .
SUMMARY OF THE INVENTION
The present invention provides a herbicidal composition, having as an active ingredient a terpene compound or derivative, which may be either naturally occurring or synthetic. (Natural pine oil, for example, is virtually unobtainable. )
Although the terpene compounds or derivatives are believed to be the active ingredients of the herbicidal compositions, the same herbicidal effect is found using “whole” essential oils, such as pine oils and citrus oils, comprising such terpene compounds or derivatives. The addition of other essential or natural oils can enhance the activity of the preparation.
In a further aspect, the invention provides a method for controlling unwanted plant growth, wherein a terpene compound or derivative, an essential oil comprising a terpene compound or derivative, or a herbicidal composition having, as an active ingredient, a terpene compound or derivative or an essential oil comprising a terpene compound or derivative is applied to the unwanted plant or plants.
DETAILED DESCRIPTION OF THE INVENTION
The active ingredient of the present herbicidal compositions is a naturally occurring or synthetic terpene (e.g. dipentene, limonene or pinene) or terpene derivative (e.g. terpineol or a pine alcohol), or an essential oil (e.g. a pine or citrus oil), in either pure or diluted form. Examples of suitable citrus oils are orange, lemon, grapefruit, mandarin, tangerine or tangelo oil, and in particular orange oil.
Although the preferred active ingredient is a pine oil or a terpene compound or derivative derived from pine oil, other essential oils, terpenes and terpene derivatives may also be effective, e.g. citrus oils, citrus oil derivatives, terpenes or terpene derivatives derived from citrus oils, tea tree oil (Oil of Melaleuca) and eucalyptus oil. The major terpene derivative present in pine oil is terpineol. As with pine oil, the major terpene derivatives present in tea tree oil and eucalyptus oil are alcohol compounds, being terpinen-4-ol and cineole (eucalyptol) respectively.
In particular, dipentene, which is a synthetic derivative of pine oil predominantly comprising d,1-limonene, has been found to be effective. In a preferred embodiment, the major active component of the herbicidal compositions is pine oil, a pine alcohol, pinene, dipentene or d-limonene. The last-mentioned compound is found in many essential oils and is the major active component of citrus oils .
1-Limonene has also been trialled, and appears to be as herbicidally-effective as d-limonene.
Tea tree and eucalyptus oils display very high herbicidal activity, but are currently high cost materials available in limited volumes. Therefore, until prices drop with increased world production, it is preferred that these oils be incorporated in the herbicidal compositions of the present invention as minor additives . Both tea tree oil and eucalyptus oil were found to enhance the herbicidal activity of an emulsion of pine oil when added at concentrations as low as 1.5% by volume. If appears that they have a synergistic effect when added to pine oil.
The herbicidal compositions of the present invention are non- selective, non-systemic herbicides, which are effective against almost any vegetation, and specifically against common crop and garden weeds, both annual and perennial . They are “knock-down” herbicides, which must be sprayed over a substantial portion of the above-ground part of the plant, in order to have effect. Conveniently, the herbicides are applied as a fine droplet spray. The non-systemic nature of the present herbicidal compositions is a considerable advantage to the home gardener, as spray drift is unlikely to cause problems. If a small amount of the herbicidal composition lands on a wanted plant, that plant is unlikely to be killed or badly damaged. A further consequence of the non-systemic nature of the herbicide is that the weed does not have to be in an active growth stage, in order for the herbicide to be effective. The herbicide will even work on dormant plants. Furthermore, the herbicidal effect is not dependent on weather conditions, or adversely affected by moisture. Rain or irrigation after application of the herbicidal composition to unwanted plant growth does not destroy the herbicidal effect.
Most terpene compounds, terpene derivatives and essential oils have the advantage of being considerably safer than common agricultural chemicals, such as conventional herbicides. Terpene compounds and derivatives have been widely used, for some years, in medicines, cosmetics and foodstuffs, and thus their safety has been established. Accordingly, the terpene compounds, terpene derivatives and essential oils will also be non-environmentally-polluting and non-toxic to domestic animals. In particular, the herbicides of the present invention are non-residual, when purified pine oil or citrus terpenes are used as the active ingredient.
In use, the terpene, terpene derivative or essential oil may be applied to unwanted plant growth either by itself, or in the form of a conventional herbicidal composition. For example, the active ingredient of the present invention may be mixed with a carrier or diluent to form an easily applied formulation, which may be diluted according to the particular application.
Examples of herbicidal formulations include sprays, liquids, wettable powders, oily solutions, emulsions, dusts, granules, fumigants etc. Application may be by spraying or by means of a “touch” applicator, using a wick assembly.
In particular, emulsions comprising water, an essential oil and a commercial food grade emulsifying agent have been trialled. Whilst the amount of active ingredient is lower in such systems, trials conducted with limonene suggest that volatility is lowered, thereby prolonging contact between the weed and the herbicide. This effect offsets the reduction in active ingredient content.
Alternatively, terpenes, terpene derivatives or essential oils may be blended with other, cheaper, and somewhat less volatile oils to form effective herbicides. For example, various natural oils (such as cottonseed oil, soybean oil, rapeseed oil, sunflower oil, safflower oil, olive oil, coconut oil, coconut milk, corn oil, grape seed oil and peanut oil) have been tested, and found to lack significant herbicidal activity. Nevertheless, they can be blended with the herbicidally-effective essential oils of the present invention to form effective herbicidal compositions.
Because of their environmentally friendly nature and low toxicity, the herbicidal compositions of the present invention will be of particular benefit to the home gardener. However, they may also be used in large-scale agriculture.
In a preferred embodiment, the active ingredient is d-limonene derived from a citrus oil, e.g. orange oil. The fraction comprising d-limonene is separated off by vacuum distillation, or any other conventional separation process. d-Limonene is volatile, and is separated off in the distillate. The distillate is a highly concentrated composition of the terpene compound, comprising about 95-96% by weight of d-limonene and about 4-5% by weight of other components . This distillate may be utilised directly as the herbicidal composition of the present invention.
It should be noted that, although d-limonene is believed to be the active ingredient of this herbicidal composition, other components present in the distillate may also have a herbicidal effect. Furthermore, it may be possible to use unrefined citrus oil, instead of the vacuum distillate. However, vacuum distillation (or other separation process, such as steam distillation (azeotroping), solvent extraction, supercritical extraction etc.) has the advantage of separating the herbicidally active ingredient from flavour components of the citrus oil. The flavour components then form a valuable by-product, which can be utilised in e.g. foodstuffs or pharmaceutical compositions.
The invention will now be further described with respect to the following Examples, which are illustrative but not restrictive of the present invention.
EXAMPLE 1
d-Limonene, which can occur at levels of up to 95% in citrus oils, was distilled from Australian orange oil by vacuum distillation.
The d-limonene used in this trial was approximately 96% pure but, as with all commercially prepared citrus terpenes, contained various other natural compounds distilled in the “cut”. The main ones were:
- Ethanol alpha-Pinene
- Sabinene
- Myrcene
- Octanal gamma-Terpinene
- Linalool
- Citronellal alpha-Terpinene
- Decanal
- Nerol
- Neral
- Geraniol
- Geranial
- Dodecanol
- Dodecanal.
The d-limonene fraction was applied to vegetation as a fine droplet spray. Knockdown trials were carried out on vegetation growing in heavier (more clay) soils and lighter (more sand) soils. No significant differences in timing or effect were noted.
Knockdown trials were also carried out during different seasons and at different growth stages of the vegetation. Again, no significant differences in timing or effect were noted.
The d-limonene fraction was found to be non-selective and effective against most common vegetation types, including annual and perennial weeds (see Table 1 below). Most vegetation showed visible signs of stress (e.g. wilting or browning) within 2 to 24 hours of application of the herbicide.
Further trials were carried out, as described in Examples 2 to 4 below. The results of these trials are shown in Table 1.