It is known to use certain cinnamates, such as ethyl cinnamat for controlling mite infestations. The compounds may be provided in a variety of formulations, for example, as an oil preparation, spray, aerosol or fumigant. However, whilst these compounds are relatively effective against certain types of mites, such as house dust mites, the compounds have a strong smell and are often difficult to handle. Moreover, some cinnamates have been found to be an irritant to the skin. Accordingly, the use of such compounds, particularly in domestic environments, is not ideal.

It is an object of the present invention to provide compositions for exterminating pests, in particular mites, that aim to overcome, or at least alleviate, the abovementioned drawbacks.

A further object of the present invention is to provide an improved method of exterminating pests, such as mites, that aims to overcome, or at least alleviate, the abovementioned drawbacks.

Accordingly, a first aspect of the present invention provides a composition for exterminating pests, the composition comprising one or a combination of aLkyl esters of a carboxylic acid of the general formula :- wherein either A, B, C and D are all hydrogen, or A and B together form a carbonyl group and C and D are both hydrogen ; and R is an alkyl group having between 1 and 10 carbon atoms.

A second aspect of the present invention provides a method for exterminating pests, the method comprising the steps of applying a composition containing one or a combination of alkyl esters of a carboxylic acid of the general formula :- wherein either A, B, C and D are all hydrogen, or A and B together form a carbonyl group and C and D are both hydrogen; and R is an alkyl group having between 1 and 10 carbon atoms, to an area infested with pests thereby exterminating the pests.

It is to be appreciated that the compounds may be applied to an area to prevent infestation with a pest as well as being applied to an area already infested with pests thereby controlling pest infestation.

A preferred composition according to the present invention has the formula :- Alternatively, the compound may have the following formula :- The compounds of the present invention are inactive and innocuous and therefore particularly suitable for use in domestic situations for exterminating pests. It is believed that the compounds become converted by metabolic reactions that occur within the pest into active cinnamat compounds. Such reactions involve the action of enzymes, such as reductases, on the compound followed by an acid or base dehydration that results in the production of the active cinnamat which causes death of the pest.

The compounds are particularly active against mites, such as house dust mites, mites that infest wood, paper and leather products and mites that infest plants and animals, such as the Varroa mite, sheep scab mite and various poultry mites. This is due to the mites possessing the necessary enzymes to convert the compounds into an active form. Not all organisms would have sufficiently available enzymes to metabolize the compound.

One or a combination of compounds according to the present invention may be included with a suitable carrier material for assisting in the application of the compounds to the pest. For example, the compounds may be incorporated into cleaning agents, such as fabric conditioners or polishes, or may be applied as a fumigant or aerosol.

The present invention will now be illustrated by reference to the following examples in which Example 1 investigates the toxicity of ethylbenzoylacetate on the Acarus siro mite and Example 2 compares the toxicity of ethylbenzoylacetate, ethylnitrocinnamate and ethylcinnamate to the Dermatophagoides pterorzyssinus mite and with reference to the accompanying drawings in which:- Figure 1 is a graph illustrating the Acarus siro mortality at various concentrations of ethylbenzoylacetate ; and Figure 2 is a graph of the toxicity of ethylcinnamate, chtylbenzoylacetate and ethylnitrocinnamate to the the pteronyssinus mite.

Example 1 Working concentrations of ethylbenzoylacetate were prepared by dilution with ethyl alcohol. The concentrations were chosen on the basis of an initial dose finding experiment. Triplicate filter papers (42.5mm diameter) were impregnated with 150 Ill of four concentrations and pure ethyl alcohol acted as a control. The filter papers were dried at room temperature for a six hour period.

The vulnerability of 4camus siro to ethylbenzoylacetate was. determined using 6- cell well plates. A separate filter paper was pressed into each well and cell plates were humidified for 18 hours at 20'C, 90% RH prior to addition of the mites. This helped to ensure mite viability throughout the test period. Acarus siro were added to cell plates, ten in each cell, and the chambers were sealed separately using parafilm. The mites were exposed for a 24 hour period at 20°C, 90% RH, after which mortality was recorded.

Mites were recorded as dead if they show no movement in response to touch of a fine paintbrush.

The accompanying figure illustrates Acarus siro mortality at the various concentrations of ethylbenzoylacetate. Pure ethylbenzoylacetate was found to be lethal to the mite. In order to calculate EDso value more accurately, the value for pure ethylbenzoylacetate is not shown in the figure. The ED$o value was determined to be at approximately 0.0042 mg S ethylbenzoylacetate i. e. at 44 zg cm~2 filter.

Furthermore, the compound ethylbenzoylacetate has an oral mouse LDso of 6800mg/kg with no toxic effects. This is better than the prior art compound ethyl cinnamat because it does not cause sensitization of the skin. Additionally, the compound is not incompatible with polystyrene and other plastics materials which are often used in horticultural environments where pesticides may be employed.

An additional innocuous compound that have been found to be active against pests, such as mites, includes the following :- Again, it is believed that enzymes present in the organism convert the compound to an active cinnamat which then kills the organism.

Example The toxicity of ethylcinnamate, ethylbenzoylacetate and ethylnitrocinnamate to the Dermatophagoides pteronyssinus mite was investigated.

Duplicate filter papers (42.5mm diameter) were impregnated with 150 ul of the following: 1. Dichloromethane (100%) as a control 2. Ethylcinnamate in dichloromethane at 0. 001 mg µl-1 ; 0.01 mg µl-1 and O. 1mg µl-1 3. Ethylbenzoylacetate in dichloromethane at 0.001 mg µl-1 ; 0.01 mg µl-1 and 0.1 mg µl-1 4. Ethylnitrocinnamate in dichloromethane at 0. 001 mg µl-1; 0.01 mg µl-1 and 0.1 mg ul-l Filter papers were dried at room temperature for a six hour period. Vulnerability of Dermatophagoides pteronyssinus to the above was determined using well plates (6-cell).

A separate filter paper was pressed into each well and cell plates were humidified for 18 hours at 20°C, 90% RH prior to the addition of mites. This helped to ensure mite viability throughout the test period. Dermatophagoides pteronysyinss were added to cell plates, ten in each cell, and chambers were sealed separately using parafilm. Exposure took place for a 24 hour period at 20°C. 90% RH, after which mortality was recorded.

Mites were recorded as dead if they showed no movement in respone to the touch of a Sne paintbrush.

Figure 2 of the accompanying drawings illustrates the results of the investigation.

Ethylbenzoylacetate and ethylcinnamate displayed some toxicity to the Dennaíophagoides pteronyssinus mite. The EDso value for ethylbenzoylacetate was determined to be approximately 0.004 mg} ethylbenzoylacetate i. e. at 42 ug cm-2 filter. The ED50 value for ethyciiv2amate was found to be slightly lower at approximately 0.002 mg ethylcinnamate i. e. at 21 µg cm-2 filter. Ethylnitrocinnamate, by contrast, was not found to display significant toxicity to the Dermatophagoides pteronyssinus mite at the test concentrations. This clearly illustrates that not all inactive derivatives of ethylcinnamate are converted to the active ingredient by enzymes present in the pest to cause death thereof.

The compounds of the present invention may be used against a number of different pests, such as house dust mites and those that infest wood, paper and leather products. The compounds may also be used against mites that infest plants (agricultural and horticultural) and those that infest the living animals such as the Varroa mite, sheep scab mite and various poultry mites. Such organisms are readily treatable by the claimed compounds due to their innocuous nature. It is to be appreciated that the pests must have the necessary enzymes available to convert the compounds into an active form. The compounds are an improvement over the pesticides of the prior art in that they do not have a strong smell, are at least as potent as the earlier compounds and do not irritate the skin. Additionally, due to the required enzymes only being present in certain organisms, the compounds will only become active in particular organisms which should result in a reduction in toxicity in some environments.