WO2013011299A1 - Insecticidal treatment - Google Patents

Abstract

A method of killing or controlling insect pests of the Cimicidae family such as Cimex leticularis (bed bugs)by applying an effective amount of cymene to the pest or to the habitat thereof.

Description

Insecticidal Treatment

The invention relates to methods of killing and controlling crawling pests, in particular those of the Cimicidae family such as Cimex leticularis (Bed bugs) as well as to compositions and components useful in these methods.

Background of the Invention

Pyrethrum is a highly effective pesticide which has been used for centuries against all manner of insect pests.

Pyrethrum is a natural plant oil that is present in the pyrethrum daisy, Chrysanthemum (Tanacetum) cinerariae

folium, a member of the chrysanthemum family. It is found mainly in tiny oil containing glands on the surface of the seed case in the tightly packed flower head and is the

plant's own pesticide that keeps insects away. Pyrethrum is made up of six complex chemical esters known as pyrethrins, which work in combination to repel and kill insects.

Pyrethrum is a unique pesticide in that, used correctly, it is safe for use near humans and warm blooded animals, and for example in kitchens and restaurants, food processing factories and other sensitive environments.

Many synthetic insecticides based to some extent upon the chemical structure of the pyrethrins that make up pyrethrum have been developed and these are known as pyrethroids.

Collectively these are sometimes known as pyrethrin

insecticides .

One of the most important problems associated with

pyrethrum, pyrethrins and the related pyrethroids is that resistance is already beginning to be found in many insect species in several parts of the world. Pyrethrin insecticide resistance, caused either by specific

detoxification enzymes or an altered target site mechanism (kdr-type mutations in the sodium channels) , has been reported in most continents. The problem is particularly acute in relation to certain crawling pests such as bed bugs and in particular Cimex leticularis . It has recently been reported (Bai et al . (2011) PLoS ONE 6(1) : el6336. doi : 10.1371/journal .pone .0016336) that there is a genetic element associated with the development of resistance in this particular species. However, as a result of this resistance to pyrethrins in particular, these blood-feeding insects are now a major pest threat in homes around the world including in the USA.

There is an urgent need for finding alternatives to the current insecticide treatments .

Cymene is hydrocarbon of the monoterpene type. It may be produced synthetically, and has the structure of formula

(I)

(I)

Paracymene or p-cymene is a naturally occurring isomer that forms a constituent of many plant essential oils. It has the formula (II)

:ιΐ⁾

Many plant essential oils including some that contain cymene have been used as pesticides in a variety of applications. However, in general, the identity of the specific active component or components of the oils has not been elucidated. Thus it is not clear that individual components of these oils could be used in isolation as pesticides since the effects observed could be attributable to multiple components of the oil working together.

Some limited use of cymene in the field of pesticides has been reported. However, none of these reports have led to the widespread use of cymene as a commercial insecticide.

In particular, cymene and in particular p-cymene has been reported previously as having activity against water-borne pests and in particular mosquito larvae (WO2006/064511 ) . However, the effects reported were not as good as those obtained with other monoterpene products and in particular thymol . Monoterpenes including p-cymene have been evaluated previously for use as fumigants for the treatment of coleoptera species (C. Regnault Roger et al . , (1995) J. Stored Prod. Res. Vol 31. 4 p 291-299) but p-cymene was again not the best compound tested and the use of such fumigants has not been taken forward. An attempt to enhance the fumigant activity against thrips species by adding carbon dioxide was reported in 2001 (Janmaat et al . , Pest Manag. Sci. (2001) 58: 167-173) but, again, no commercial products were developed as a result of this work .

More recently, combinations of cymene and pyrethrins or pyrethroids, as well as insect growth regulators have been found to be particularly useful insecticides

(WO2008/015413) .

Summary of the Invention

The applicants have found that cymene alone is particularly effective in killing and controlling certain species of crawling pest and specifically bedbugs, with rapid and effective "knock-down".

Thus the present invention provides a method of knocking down, killing or controlling insect pests of the Cimicidae family by applying an effective amount of cymene to the pest or to the habitat thereof. The cymene may be administered in combination with another pesticidal agent provided that this is not a pyrethrin insecticide or an insect growth regulator, or that the combination constitutes a plant extract such as a plant essential oil. In a particular embodiment however, the cymene is applied in the absence of any pyrethrin or pyrethroid insecticide or insect growth regulator, and preferably in the absence of any additional pesticidal agent. Cymene itself is a natural product, and so it is not expected to have an adverse effect on the environment. Compositions used in the invention therefore constitute a safe and "green" bio- insecticide product.

The applicants have found that the "knock-down" effect, where the insects rapidly cease movement, of cymene is

surprisingly good against these particular pests and as good if not better than pyrethrum. This was unexpected since it has previously been suggested (Table A of

WO2008/015413) that the cymene did not have a noticeable knock-down activity. Thus cymene provides a very useful control as well as kill reagent, since the insects can be rapidly halted to allow a lethal dose to be administered.

Preferably, the cymene is applied m the form of a composition as is conventional in the pesticide art. The composition suitably comprises synthetically prepared and therefore highly pure cymene .

Cymene used in the method or the composition may also be derived from a plant extract, such as an essential oil. Particularly, the extract is derived from plants comprising cymene, such as Thyme (Thymus vulgaris L; Thymus ssp) , Monarda punctata L.

Savory (e.g. Satareja hortensis) , Cumin (e.g. Cuminum cyminum) and Labiatae. A "plant extract" according to the invention is an extract from plant material. "Plant material" is defined as a plant or a part thereof (e.g. bark, wood, leaves, stems, inflorescence, roots, fruits, seeds or parts thereof) . The extract may be prepared from plant material by one or more of the following processes: pulverisation, decoction or other processes known in the art. A plant extract may directly constitute a highly purified substance derived from natural sources but will generally also contain other plant-derived substances. Thus, a cymene-containing plant extract may be derived from one or more plants but this will generally comprise further components in addition to cymene. However, a skilled person will appreciate that such an plant extract may be further purified to obtain highly purified substances and so cymene for use in the present invention may be obtained by such procedures .

For the avoidance of doubt, for use in the present invention, the cymene may not be in the form of a whole plant essential oil. In particular, the cymene component of any material used will be at least 50%, suitably at least 60%, for instance at least 70% or at least 80%, 90% or 95% cymene.

Suitably, in accordance with the invention, the cymene is a synthetic material or a purified extract or isolate from an essential oil. Thus the composition will suitably be free of at least some and preferably all of the other components of an essential oil which contains cymene.

In a preferred embodiment the pesticidal composition of the present invention comprises p-cymene.

In one embodiment, this compound is used against pests of the Cimicidae family, in particular those of the genus Cimex (bed bugs) and in particular Cimex leticularis (human bed bug) .

In a preferred embodiment the cymene is present in the

composition in an amount of from about 1% to 20%w/w, for instance from 1% to 15%w/w, in particular from 2% w/w to about 10% w/w. In a particular embodiment, the composition contains from about 2.5% w/w to about 5% w/w for example from about 3-5% w/w .

An effective amount of cymene needed to kill or control

Cimicidae pests is generally equivalent to approximately an aerosol spray of at least 1 and suitably from 2-20g total composition, delivering for instance from 0.01-1.0 for instance from 0.08-0.5g active. In order to kill or control pests of the Cimicidae family such as bed bugs, it is usual to apply pesticide to areas or items including beds, mattresses, mattress covers, bedsteads or bedframes . In certain cases, it may be necessary to treat the surrounding area including carpets and skirting boards, or even entire rooms. The bugs tend to live in cracks and crevices found for example around the joints in a bed frame or the seams in mattresses as well around the edges of a room and so particular attention is required to these areas. In such cases, the compositions may be applied in the form of a spray such as an aerosol spray or a dusting powder to the infected area.

Alternatively, items such as mattress covers may be subject to immersion treatments in solutions comprising pesticide.

In some instances, an infestation may be treated using fogging or fumigation techniques applicable to an entire room or building and its contents.

For use in the method of the invention, the cymene is suitably formulated so as to be applicable in any such manner.

A further aspect of the invention provides a pesticidal composition for use in the method described above, comprising cymene, suitably as the sole pesticidally active component .

Such compositions may be in solid or liquid form and wi generally comprise conventional carriers and additives

understood in the formulation art.

In particular the pesticidal compositions can be formulated or mixed with, if desired, conventional inert diluents or

extenders of the type usable in conventional pesticide formulations or compositions, e.g. conventional pesticide dispersible carrier vehicles such as gases, solutions,

emulsions, suspensions, emulsifiable concentrates, spray powders, RTU micro-emulsions, oil-in-water emulsions, pastes, soluble powders, dusting agents, granules, foams, pastes, tablets, aerosols, ready to use trigger sprays, natural and synthetic materials impregnated with active compounds,

microcapsules, coating compositions, and formulations used wi burning equipment, such as fumigating cartridges, fumigating cans and fumigating coils, as well as ULV cold mist and warm mist formulations.

The compositions may be in the form of solutions, emulsions, suspensions, powders, pastes, and granules which are either ready for use, or require simple dilution or solution to make them ready for use.

The composition of the invention is suitably in the form of a solution or concentrate suitable for spraying for example in an aerosol or for immersion treatments, as a solid powder for dusting or as a concentrate useful in a fogging procedure. In particular, the compositions comprise solutions of cymene in water or an organic solvent, such as Ci_₆alkanols , for instance methanol, ethanol or propanol including iso-propanol, natural hydrocarbons such as isoparaffins (isopar) or mixtures thereof.

In a preferred embodiment the pesticidal compositions are used as aerosol-based applications, including aerosolized foam applications. Pressurised cans are the typical vehicle for the formation of aerosols. An aerosol propellant that is compatible with the pesticide composition is used. Preferably, a

liquefied-gas type propellant is used. Suitable propellants include compressed air, carbon dioxide, butane and nitrogen as well as liquefied petroleum gas (LPG) . The concentration of the propellant in the pesticide composition is from about 5% to about 75% by weight of the pesticide composition, preferably from about 15% to about 50% by weight of the pesticide composition for instance about 40% by weight.

The pesticide formulation can also include one or more foaming agents. Foaming agents that can be used include sodium laureth sulphate, cocamide DEA, and cocamidopropyl betaine . Preferably, the sodium laureth sulphate, cocamide DEA and cocamidopropyl are used in combination. The

concentration of the foaming agent (s) in the pesticide composition is in the ratio of foaming agent: active

ingredient of from about 0.5:4 to about 2:1, and

preferably from about 0.75:1 to about 1.5:1.

When the pesticide formulation is used in an aerosol

application not containing foaming agent (s), the

composition of the present invention can be used without the need for mixing directly prior to use. However,

aerosol formulations containing the foaming agents do

require mixing (i.e. shaking) immediately prior to use. In addition, if the formulations containing foaming agents are used for an extended time, they may require additional mixing at periodic intervals during use.

An area may also be treated with the pesticidal composition by using a burning formulation, such as a candle, a smoke coil or a piece of incense containing the composition. For example, composition may be comprised in household products such as

"heated" air fresheners in which pesticidal compositions are released upon heating, for example, electrically, or by burning . The invention will now be described with respect to the following examples. The examples are not intended to be limiting of the scope of the present invention but read in conjunction with the detailed and general description above, provide further understanding of the present invention and an outline of a preferred process for preparing the compositions of the invention

Example 1

Activity of cymene against insects

All tests were performed using an aqueous 3.0 % aqueous dilution of p-cymene.

Fresh 3 % working dilutions were made for each experiment using deionised water. 0.5 ml samples were applied directly onto the free-flying / free-crawling insects using a "Potter Tower" in accordance with standard operating procedures. Batches of adults or large nymphs numbering between 5 - 20 individuals of a range of insects including Cimex leticularis (depending upon size) were held in clean, disposable plastic tubs with wide- mesh netting covers. Insects were exposed to direct aerosol exposure in the Potter tower for a period of 15 seconds (actual application time is around 3 - 5 seconds for 1 ml used) after which they were removed. Following exposure, insects were transferred to clean tubs and supplied with 10 % glucose and held overnight at optimal environmental conditions of 24 °C ± 2°C and 75 - 80 % RH. Mortality was recorded after 1 hour and 24 hours post exposure. A minimum of 6 replicates were conducted on each insect species. Control replicates using 3 % ethanol were used in each case to ensure negative control mortality was below 10 %.

Results

Species % mortality

1 hour post exposure 24 hours post exposure

Musca domestica 46 88

(House fly)

P ri.pla.neta Americana 28 76

(American cockroach) Results (continued)

Species % mortality

1 hour post exposure 24 hours post exposure Blatella germanlca 55 % 84 % (German cockroach)

Phlebotomus papatasi 88 % 100 %

(Sandfly)

Stomoxys calcltrans 60 % 91 %

(Stable fly)

Glosslna morsltans 51 % 82%

(Tsetse fly)

Cimex leticularis 68 % 100%

(Bed bug)

Dermatophagoides sp. 100 %* 100 % * (House dust mite)

Ctenocephalides fells 44 % 87%

(Cat flea)

Rhodnlus prollxus 39 % 70 %

(Redjuvid bug)

Trlatoma Infestans 40 % 66 %

(Cone nose bug)

Cullcoldes varllpennls 86 % 100

(Biting midge)

Ixodes ricinus 10 % 22 % (Deer tick)

Simuliura damnosum 78 % 100

(Black fly)

Vespula vulgaris 65 % 84 %

(Common wasp)

reneibrio molitor 29 % 60 %

(Mealworm beetle)

* Difficult to verify due to possible drowning effects.

Results indicate that although cymene has efficacy against a very wide range of medically important insect species, the efficacy against specifically Cimex leticularis was

particularly high.

This was surprising since although one might expect activity to be higher against the smaller insects such as sandflies, mites, midges and blackfly, it is usual that pesticides are less active against those larger, more robust species such as the bugs. In this test, cymene, whilst generally following this pattern, showed unexpectedly high activity against the robust Cimex leticularis, with significant (68%) mortality after just one hour and consistently 100% mortality within 24 hours of exposure.

Example 2

Knockdown and Mortality of Bed Bugs exposed to Cymene Treatment

In a further experiment, five adult Cimex leticularis were placed in a wire gauze box with an inside diameter of 70mm, a height of 10mm and a mesh size of 1.5mm. The test containers were placed in a holder and placed in a fume hood in which the ventilation can be regulated so that the spray jet from a spray can/trigger is not affected.

At a distance of 60cm, measured from the centre of the wire gauze up to the test aerosol spraying head, a spray can/trigger is inserted into the apparatus so that the jest strikes the wire gauze vertically.

The following composition was used in the test: - 5.01 % P-Cymene

-27.56% Isoparaffin K,

-27.35 % Isopropanol

-40.08% Liquified petroleum gas (LPG)

The composition (2.5-2.7g) was then applied using the spray can to the gauze. A similar test was carried out using a

commercial 0.2% pyrethrum spray conventionally used to treat bed bugs .

A stop watch was pressed simultaneously with the spraying valve, and the stop watch was used to time the knock-down effect on the insects. The insects were then provided with moisture (swabs soaked in water) and maintained at 22°C at 6 relative humidity. After 24 hours, the mortality of the insects was assessed.

The test was repeated five times .

Results are shown in the following Table.

Untreated control 0% after 24 hours

0% after 48 hours

The results show that at conventional dosages, the p-cymene was as effective as pyrethrum in killing bed bugs and actually gave a more rapid knock-down effect. The effect was found to be dose dependent. Comparative Example 3

Knockdown and Mortality of Cockroaches exposed to Cymene

Treatment

The effect of cymene on other species of crawling insect, specifically cockroaches was also tested. The method of

Example 2 was tested but with five cockroachs (German Cockroach Blattella germanica, 5 nymph stage or American cockroach Periplaneta americana 5^th nymph stage) instead of the bedbugs in the gauze box.

The results are shown in the following tabl

Results against German Cockroach Blattella germanica, 5 nymph stage

+ based upon 8 replicates

Untreated control 0% after 24 hours

0% after 48 hours Results against American cockroach Periplaneta americana 5 nymph stage Product Mean of % knock down after % mortality content minutes Γ) and knock

in gram seconds Γ) down

( range ) Mean Range after 24h 48h

2

hours

0.4% 2.6 2 ' 14 " 2' 04"- 100 100 100

Pyrethrum (2.3- 2' 30"

2.7)

5% p- 2.7 Not achieved -not 12 8 12 cymene (2.6- 2.7)

Untreated control 0% after 24 hours

0% after 48 hours

In this case, the results using cymene poor and significantly worse than the results obtained with pyrethrum. These results show that bedbugs in particular as a species are particularly susceptible to treatment with cymene alone.

Claims

Claims

1. A method of knocking down and killing or controlling insect pests of the Cimicidae family by applying an effective amount of cymene to the pest or to the habitat thereof.

2. A method according to claim 1 wherein the pest is Cimex leticularis (human bed bug) .

3. A method according to any one of the preceding claims wherein the cymene is administered as the sole pesticidally active component.

4. A method according to any one of the preceding claims wherein the cymene is administered in the form of a liquid.

5. A method according to claim 4 wherein the liquid is solution of cymene in an organic solvent or water.

6. A method according to claim 5 wherein the liquid is applied as an aerosol spray.

7. A method according to claim 6 wherein the aerosol spray is applied for a period of at least 2 seconds to area to be treated.

8. A method according to any one of claims 1 to 4 wherein the cymene is applied as a fog.

9. A method according to claim 2 wherein the cymene is applied to a mattress, a mattress cover, a bedstead or bed frame .

10. A method according to any one of the preceding claims wherein the cymene is synthetic p-cymene.

11. A composition for use in a method according to any one of the preceding claims comprising cymene and a carrier acceptable for public health application.

12. A composition according to claim 11 wherein cymene is the sole pesticidally active component of the composition.

13. A composition according to claim 11 or claim 12 in the form of an aerosol .

14. A composition according to claim 12 or claim 13 comprising from about 1% w/w to about 20% w/w cymene.

15. A composition according to claim 14 comprising about 5% w/w cymene.

16. The composition according to any one of claims 12 to 15 wherein the composition comprises a synthetically prepared cymene .

17. The composition according to any one of claims 12 to 16 wherein the cymene is p-cymene.