GB1581277A - Pesticidal compositions - Google Patents

Description

(54) PESTICIDAL COMPOSITIONS (71) We, ICI AUSTRALIA LIMITED of 1 Nicholson Street, Melbourne, Victoria, Australia, a Company organized and existing under the laws of the State of Victoria, Australia, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to pesticidal compositions and their use in animal husbandry.

More particularly the invention relates to tickicidal compositions comprising at least one organo phosphorus compound and at least one pyrethroid.

It is known that there are certain cyclopropane carboxylic acids and esters which are useful as active ingredients in insecticidal compositions and particularly useful insecticidal compounds are the (+) cis and trans isomers of 3-phenoxybenzyl 2,2dimethyl-3-(2,2-dichlorovinyl)cyclopropane carboxylate which may be represented by the formula

These compounds are often referred to as permethrins. They are also referred to by an identification system comprising the letters NRDC and a number. Thus for example the (i) cis, trans isomer mixture of 3-phenoxybenzyl 2,2-dimethyl-3-(2,2-dichlorovinyl) cyclopropane carboxylate is often referred to as NRDC 143, whilst the corresponding (+) trans isomer mixture is often referred to as NRDC 146. Hereinafter in this specification these compounds may be referred to by their chemical name, by their common name or by the NRDC identification system referred to above.

In Australia, as well as in other countries, a problem of considerable economic importance is the control of ticks which infest cattle. In the past "susceptible" or " non-resistant " strains of ticks have been controlled by means of sprays or dips using as active ingredients certain chemicals such as carbamates, chlorinated hydrocarbons or organophosphates. However more recently it has been found that certain strains of cattle ticks have emerged and are now wide spread in Australia and elsewhere and are spreading further and which are not affected by certain of the broad spectrum tickicides normally used for this purpose. These strains are known as resistant strains of cattle ticks and represent a most serious problem to the Australian cattle industry.

A typical " susceptible " strain is the "Yeerongpilly" strain which is widely dis tributed and is controlled readily with commercial tickicides such as l-naphthyl N methylcarbamate, dichlorodiphenyltrichloroethane (DDT) or a wide range of organo phosphorus tickicides including compositions containing as an active ingredient chemi cals commonly named bromophos-ethyl, chioropyrifos, coumaphos, dioxathion, ethion or pirimiphos-ethyl. It is used by all authorities in Australia as the "susceptible" reference standard against which the degree of resistant strains is measured.

A typical resistant strain is the "Biarra" strain also known as the "Esk" or "Anderson" strain, and it has become increasingly resistant to organophosphorus tickicides with the passage of time since it was isolated in the Esk district of Queensland, Australia in 1966. Other strains of cattle tick which are resistant to organophosphorus tickicides include the so called "Mount Alford" strain and the "Mackay" strain. Certain strains of cattle tick may become resistant to treatment with tickicides after prolonged treatment therewith. For example whilst DDT was effecive as a tickicide when it was first used for the purpose, there are now strains of tick which are immune to treatment with DDT at concentrations which are economic. It is highly desirable that new tickicides be developed so that the cattle tick has little or no resistance to the tickicides when it is first used. Such tickicides should be effective in controlling and killing cattle ticks of both the " susceptible " strains and the strains which are resistant to tickicides already in use. Unless a tickicide is active against both the " resistant " and "susceptible" strains, the long range effect of treatment in a given treatment area is not to control cattle ticks, but merely to increase the population of the "resistant" strain in relation to that of the " sucepible" strain.

It has been suggested in Australia by the Commonwealth Scientific and Industrial Research Organization that NRDC 143 was capable of killing cattle tick, but such a capability has never been reduced to commercial practice since it was found that the cost of killing infestations of cattle tick was so high as to make the process uneconomic especially in instances where the cattle tick was of a "resistant" strain.

We have now found that the admixture of certain organophosphorus compounds with 3 -phenoxybenzyl 2,2-dimethyl-3 - (2,2-dichiorovinyl) cyclopropane carboxylate provides compositions which are more effective than would be expected from the combined additive tickicidal efficacy of the components.

Accordingly in one embodiment of our invention we provide a new composition of matter comprising as a pesticidally, preferably tickicidally, effective active ingredient a mixture comprising as a first component at least one isomer of 3-phenoxybenzyl 2,2-dimethyl-3-(2,2-dichlorovinyl) cydopropane carboxylate and as a second component at least one organo phosphorus compound; but excluding those compositions of matter wherein said second component is 0-(2 - diethylamino - 6 - methylpyrimidin - 4 - yl) 0,0 - dimethyl phosphorothioate or 0,0 - dimethyl 0 - (4 - nitro tolyl) phosphorothioate and said compositions of matter are characterised by being substantially free of organic solvent material as defined in UK patent specification Serial No. 1,462,319.

In another embodiment of our invention we provide a process for killing undesired Boophilus microplus (cattle tick) which process comprises treating media infested with Boophilus micro plus (cattle tick) with a tickicidally effective amount of a mixture comprising as a first component at least one isomer of 3 - phenoxybenzyl 2,2-dimethyl-3-(2,2-dichlorovinyl) cyclopropane carboxylate and as a second component at least one organo phosphorus compound.

The (+) trans isomer mixture of 3 - phenoxybenzyl 2,2 - dimethyl - 3 - (2,2 dichiorovinyl) cyclopropane carboxylate, often referred to as trans permethrin or NRDC 146, and the corresponding cis isomer, often referred to as bio permethrin, are useful as components of the active ingredient of our compositions. It is preferred that the compositions comprise a mixture of isomers and it is more preferred that the compositions comprise NRDC 143.

The nature of the organophosphorus compound may be varied widely. For example suitable organophosphorus compounds include aliphatic compounds, aromatic compounds or compounds comprising heterocyclic rings. Typical classes of organo phosphorus compounds suitable for use in the invention indude organophosphates (which may be represented by the chemical known by the common name of chlorofenvinphos); phosphorus bearing phenyl esters (bromophos-ethyl), which optionally may contain sulphur bearing substituents (fenthion); phosphorus bearing derivatives of thioethers (ethion); or phosphorylated heterocyclic ring compounds having at least one oxygen or nitrogen atom in the heterocyclic ring (coumaphos, diazinon). Particularly useful organophosphorus compounds include those wherein the phosphorus bearing radical is a phosphate, a phosphorothioate, a phosphorodithioate, or a di (phosphorodithioate). Examples of typical organophosphorus compounds suitable for use in the invention are set out below. In referring to these compounds they are described as set out in the well known and authorative dictionary of pesticides and chemical pollutants entitled "Nanogen Index", published by Nanogens International of Freedom, USA 1975 edition and having a Library of Congress Catalog Card Num ber 75-14751. For ease of description the compounds are also referred to by their common name, by a designation (indicated by an invented word in inverted commas) which is a registered trade mark in some countries and, in some instances, by an abbreviation used hereinafter in the examples which illustrate the invention.

A particularly preferred organophosphorus compound for use in the invention is 0,0 - diethyl 0 - (2 - diethylamino - 6 - methyl - pyrimidin - 4 - yl)phosphorothioate, and this may advantageously be combined with a (+) cis, trans isomer mixture of 3 - phenoxybenzyl 2,2 - dimethyl - 3(2,2 - dichlorovinyl) - cyclopropane carboxylate in a composition or process according to the invention.

Invented Chemical Name Common Name Word Abbreviation Mixed cis/trans isomers of 2-chloro-1-(2,4- chlorfenvinphos "Birlane" CHLOR dichlorophenyl)vinyl diethyl phosphate O-(4-bromo-2,5-dichlorophenyl) O,O-diethyl bromphos-ethyl "Nexagan" phosphorothioate O,O-diethyl O-3,5,6-trichloro-2-pyridyl- chloropyrifos "Dursban" phosphorothioate O,O-diethyl O-(3-chloro-4-methyl-7- coumaphos "Asuntol" ASUN coumarinyl) phosphorothioate O,O-diethyl O-(2-isopropyl-6-methyl-4- diazinon "Basudin" DIAZ pyrimidinyl) phosphorothioate O,O-dimethyl O-p-(dimethylsulphamoyl) famphur "Famophos" FAMP phenyl phosphorothioate O,O-dimethyl O-(3-methyl-4-methylthiophenyl) fenthion "Baycid" FEN phosphorothioate O,O-diethyl O-(2-diethylamino-6-methyl- pirimophos-ethyl "Primicid" pyrimidin-4-yl) phosphorothioate "Solgard" S-[(p-chlorophenylthio)-methyl] O,O- carbo- "Trithion" CARBO diethyl phosphorodithioate phenothion S,S'-p-dioxan-2,3-diyl O,O,O',O'- dioxathion "Delnav" tetraethylphosphorodithioate O,O-dimethyl phthalimido methyl phosmet "Prolate" PROL phosphorodithioate O,O,O'O'-tetraethyl-S,S'-methylene ethion "Nialate" di(phosphorodithioate) The ratio of the components of the pesticidally active material in our compositions may be varied to suit the conditions under which the composition is to be used and also to provide an economic, effective composition dependent on the cost of the components and the extent to which the composition exhibits synergism. By synergism we mean the cooperative action of two or more agents in a composition in such a way that the total effect is greater than the sum of the individual effects taken individually. Suitable compositions include those having a weight ratio of the first component to the second component in a range from 5:1 to 1:5. At the present time the cost of the permethrin type components is more than the cost of an equal weight of the organophosphorus component and thus from an economic aspect it is desirable that the organophosphorus component comprise at least half of the pesticidal mixture in the compositions of the invention. Preferably therefore in such compositions the weight ratio of the first component to the second component lies in a range from 1:1 to 1:5 and often in a range from 1:1 to 1:2.

Our compositions may be in the form of concentrates which may be diluted appropriately to a desired concentration of active ingredient by means of pesticidally inert material. The inert material may be solid or liquid, and the latter, particularly aqueous liquid formulations, are preferred. Emulsifiable solutions or suspensions of the active material may be prepared by dissolving or suspending it in a solvent, or a mixture of solvents, which is non-toxic to the animals onto which the composition is to be applied, adding an emulsifier and/or wetting agent and, optionally, adding some water. A typical emulsifiable concentrate formulation of this type for use in our process could comprise 30% by weight of active ingredient, 45 C/c by weight of mineral oil, 10% by weight of a mixture of nonionic and anionic emulsifiers and 15% by weight of a substantially aromatic high boiling solvent.

Our compositions may also be dispersible powders wherein the active ingredient is mixed together with an inert solid carrier such as powdered chalk, talcs, clays, kieselguhr, bentonite and a dispersing agent. Suitable emulsifying and dispersing agents are known from the prior art; anionic, cationic and non-ionic agents may be used. A suitable non-ionic emulsifier is for example the condensation product of nonylphenol with ethylene oxide available commercially under the Registered Trade Mark "Lissapol" N; suitable dispersing agents are for example the disodium salt of dinaphthylmethane disulphonate, sodium lauryl sulphate and the condensation product of alkylphenol with ethylene oxide available commercially under the Registered Trade Mark "Lubrol" E. Our compositions may also be concentrated aqueous pastes or dusts.

Suitable dose rates of the active ingredient for the control of infestations of cattle tick on cattle are not narrowly critical and are dependent to some extent on the strain of tick being treated. Rates will also be related to the mode of application of the active ingredient, for example the rate will vary for each type of application such as dipping, spraying or dusting of the infested surface. As a general guide dips containing up to 1% w/w of active ingredient are satisfactory for most degrees of severity of infestation by "resistant" strains of tick and adequate ixiodic control may be effected in many instances where the concentration of active ingredient in a dip is in the range from 0.005% to 0.3% w/w.

Our processes produce high contact activity against various strains of Boolphilus micro plus (cattle tick) in the adult, larval and intermediate stages, and both "susceptible" and "resistant" strains may be controlled by its use. The simultaneous efficacy of the process against both " susceptible " and " resistant " strains of Boophilus micro plus is not only of considerable and increasing economic importance as discussed hereinbefore; it is remarkable and highly unexpected that a process using an active ingredient comprising individual components at concentrations at which each is at the most only marginally effective, should be capable of being highly effective when the components are used in combination. This unexpected property has the attendant advantage that strains of cattle tick which have developed or are developing a resistance to treatment by conventional tickicides may be treated the more easily and at lesser expense since the initial resistance to our compositions is negligible and will take time to develop.

Our invention is now illustrated by the following examples in which all parts and percentages are on a weight basis unless otherwise specified.

Examples 1 to 11 inclusive 31 and 32 are included for the purposes of comparison and do not lie within our invention.

Examples 1 to 4 inclusive.

In these comparative examples a composition was prepared by the admixture of 25 parts of NRDC 143, 45 parts of mineral oil available commercially under the designation of "Shell" 21, 6 parts of a composition comprising a blend of anionic and non-nonic surfactants and available commercially under the designation " Atlox " 3404F, 3 parts of a non-ionic surfactant available commercially under the designation "Teric" 17A6 and 21 parts of an aromatic solvent available commercially under the designation "Aromasol" H. (" Shell ", "Atlox", "Teric" and "Aromasol" are registered trade marks). Portions of the composition so prepared were then diluted with water to provide dilute compositions containing various amounts of NRDC 143 as indicated in Table I. Twenty engorged adult female cattle ticks of a "resistant" strain of Boophilus micro plus as indicated in Table I were supported on a mesh carrier and immersed in a dilute composition briefly until they had reached drip point and were then removed from the composition. After 14 days the mortality count of the adult ticks was assessed by counting the eggs laid by them and calculating the percentage of those eggs which had hatched. In Table I the tabulated concentration of NRDC 143 is expressed in parts of NRDC 143 per million parts of dilute composition (ppm).

TABLE I

% Mortality rate of ticks of the strains designated below Concentration of "Biarra" "Mount Alford" "Mackay" "DDT resistant" NRDC 143 Example 1 Example 2 Example 3 Example 4 1000 ppm 100 - - 20 500 ppm 85 100 100 10 250 ppm 65 90 70 5 125 ppm 20 20 40 0 62 ppm 10 0 30 31 ppm 0 - - - means that no test was done at the appropriate concentration, Examples 5 to 8 inclusive.

In these comparative examples the general procedure of Example 1 was repeated except that the dilute compositions of Example 1 were replaced by compositions obtained by diluting commercially available organophosphorus compositions with water to provide dilute compositions as set out below in Table II which also shows the mortality rate of ticks.

TABLE II

Example Organophosphate Concentration Mdrtality rate No. type (ppm) 5 'Asuntol"* 10,000 0 6 "Dursban"* 1,000 0 7 "Solgard"* 1,000 5 8 "Solgard"* 500 0 * These names are registered trade-marks.

Examples 9 to 11 inclusive.

In these comparative examples the general procedure of Examples 2, 3 and 4 was repeated except that the dilute compositions of those examples were replaced by dilute compositions obtained by diluting commercially available compositions containing the organophosphate "Nexagan" (registered trade mark). The mortality rate of ticks treated with compositions of various concentrations is set out in Table III.

TABLE llI

% Mortality of ticks of the strains designated below Concentration of "Mount Alford" "Mackay "DDT resistant" "Nexagan" Example 9 Example 10 Example 11 1000 ppm .- 100 60 500 ppm 10 90 50 250 ppm 0 30 40 125 ppm ~ 10 20 62 ppm 0 Examples 12 to 16 inclusive.

These examples demonstrate tickicidal compositions having synergistic characteristics and comprising NRDC 143 and a range of organophosphorus compounds.

The general procedure of Example 1 was repeated except that the dilute compositions of that example were replaced by compositions containing a mixture of NRDC 143 and an organophosphorus compound. The amount of NRDC 143 in a composition ranged from 62 to 500 ppm and the amount of organophosphorus compound in a composition ranged from the same amount as the NRDC 143 to five times the amount of the NRDC 143 i.e. from a ratio of 1:1 to 1:5. The organophosphorus compounds were those used in comparative examples 5 to 8 and as demonstrated in those examples they have no activity as tickicides at concentrations of 500 ppm and less when applied individually to the resistant "Biarra" strain of Boophilus microplus cattle tick. The efficacy of NRDC 143 as a tickicide against the "Biara" strain of tick is set out in Table I. In the absence of tickicidal activity of the organo phosphorus compounds it would have been expected that they would merely act as an inert carrier when admixed with NRDC 143 and would not change the mortality rate obtained in Table I. The results obtained in the present examples and tabulated in Table IV show a remarkable and unexpected increase in the efficacy of the mixture in comparison with the sum of the individual effect of each of the components.

TABLE IV % Mortality rate of "Biarra" strain of ticks when treated with mixtures of NRDC 143 and the tabulated organophosphorus compounds in a weight ratio as set out below

Organophosphorus Expected mortality for all compound (O.P.) "Asuntol" "Dursban" "Solgard" tabulated mixtures Weight Ratio of NRDC 143 to O.P. 1:1 1:2 1:5 1:1 1:1 Example No. 12 13 14 15 16 Concentration of NRDC 143 500 ppm 100 100 100 100 100 85 250 ppm 100 100 100 100 100 65 125 ppm 70 90 100 70 80 20 62 ppm 60 40 60 50 40 10 Example 17.

The general procedure of Example 2 was repeated except that dilute compositions of that example were replaced by compositions containing a mixture of NRDC 143 and "Nexagan". Table V sets out the concentration of these components in the composition, the percentage mortality found amongst the ticks after treatment, and the percentage mortality to be expected in view of the results obtained in comparative Examples 2 and 9.

TABLE V

Concentration Concentration % Mortality of NRDC 143 of "Nexagan" (ppm) (ppm) Found Expected 250 500 100 100 125 250 90 20 62 125 60 0 Example 18.

The general procedure of Example 3 was repeated except that the dilute compositions of that example were replaced by compositions containing a mixture of NRDC 143 and "Nexagan". Table VI sets out the concentration of these components in the composition, the percentage mortality found amongst the ticks after treatment, and the percentage mortality to be expected in view of the results obtained in comparative Examples 3 and 10.

TABLE VI

Concentration Concentration % Mortality of NRDC 143 of "Nexagan" (ppm) (ppm) Found Expected 250 500 100 100 125 250 100 70 62 125 100 40 Example 19.

The general procedure of Example 4 was repeated except that the dilute compositions of that example were replaced by compositions containing a mixture of NRDC 143 and "Nexagan". Table VII sets out the concentration of these components in the composition, the percentage mortality found amongst the ticks after treatment and the percentage mortality to be expected in view of the results obtained in comparative examples 4 and 11.

TABLE VII

Concentration Concentration % Mortality of NRDC 143 of "Nexagan" (ppm) (ppm) Found Expected 250 500 95 55 125 250 60 40 62 125 50 20 Example 20.

The general procedure of Example 17 was repeated except that the dilute compositions of that example were replaced by a composition containing 125 ppm of NRDC 143 and 250 ppm of ethion. A mortality rate of 100% was achieved against the Mount Alford strain of cattle tick which is considered to be highly resistant to compounds of the organophosphorus type.

Example 21.

The general procedure of Example 20 was repeated except that the ethion of that example was replaced by 250 ppm of dioxathion. A mortality rate of 100% was again achieved Example 22.

Approximately 100 larval ticks of the " Biarra " strain were immersed briefly in a composition used in Example 14 and containing 500 ppm of NRDC 143 and 2500 parts of "Asuntol". A mortality count on the larval ticks 48 hours after treatment showed that 100% kill had been achieved.

Example 23.

A dispersible powder was prepared by mixing 10 parts of NRDC 143, 30 parts of coumaphos, 50 parts of clay, 2 parts of a non-ionic surfactant available commercially under the designation of "Teric" GN8 and 8 parts of water. The resultant product was dispersed in water to give concentrations of the active ingredient of 0.05%, 0.2%, 0.5% and 1% w/v.

The products so obtained were used to spray calves, weighing approximately 150 kilograms, at the rate of 5 litres per calf. The calves were heavily infested with various stages of the susceptible "Yeerongpilly" strain of cattle tick. Examination of the calves after treatment showed that the treatment at each concentration was effective in killing cattle tick at all its stages of development.

Examples 24 to 31 inclusive.

Concentrated emulsifiable compositions were prepared by mixing 50 parts of a pesticidally active ingredient, 5 parts of "Teric" 200 and 5 parts of "Kemmat" SCl5B and adding to the mixture sufficient toluene to produce a composition of 100 parts by volume. ("Teric" 200 is a registered trade mark for a nonionic surfactant obtained by condensing nonylphenol with ethylene oxide and propylene oxide. " Kem- mat" SCl5B is a registered trade mark for an anionic surfactant comprising a 70% solution of calcium dodecylbenzene sulphonate in a non-aqueous solvent). Each composition was emulsified in water and to give various concentrations as tabulated below and the emulsion so obtained was sprayed on two year old calves weighing approximately 150 kilograms at the rate of 5 litres per calf. The calves were heavily infested with various stages of the resistant "Mt Alford" strain of cattle tick. The effect of the active ingredient on the ticks was assessed as follows: All adult female ticks which were fully engorged at the time of spraying were collected as they dropped off calves kept in isolation for 24 hours. They were then placed in a Petri dish in an incubator for an assessment of mortality based upon capacity to lay eggs, and if eggs were laid, the viability of the eggs as shown by hatching of viable larvae. This result is shown in Table VIII as" % mortality of engorged adults".

In a series of control tests as set out above, and wherein the sole active ingredient was one of the organophosphates as set out in Table VIII, it was found that when the concentration of any of the organophosphates in the spray was 500 ppm or less than the " % mortality of engorged adults" was zero. In a similar series of control tests and wherein the sole active ingredient was NRDC 143 the " % mortality of engorged adults" is set out in Table VIII in the column headed " 143 ". The active ingredient of the composition according to the invention was, in each example, a mixture of NRDC 143 and the designated organophosphate in a weight ratio of 1:2. For convenience concentration of the NRDC 143 component of the spray is tabulated in Table VIII. The organophosphates which were used are set out in Table VIII and are designated using the abbreviations set out hereinbefore.

TABLE VIII

31 Example No. 24 25 26 27 28 29 30 comparative Organo- ASUN FEN DIAZ CHLOR FAMP PROL CARBO "143" phosphate Concentration of NRDC 143 ppm % Mortality of engorged adults 1000 - - - - - - - 100 500 - - - - - - - 90 250 100 100 100 100 100 100 100 70 125 100 100 100 100 50 90 100 30 62 80 70 60 90 40 50 80 20 31 30 20 | 50 50 10 | 10 20 5 Since none of the above organophosphates exhibited any activity against the Mount Alford strain of tick at concentrations of 500 ppm or less, it would have been expected that they would act only as an inert carrier when used as a component of a spray in admixture with NRDC 143 and that the expected % mortality of engorged adults would have been as tabulated in comparative example 31. However the results shown in Examples 24 to 30 inclusive show a remarkable and unexpected increase in the efficacy of each mixture in comparison with the sum of the individual effects of each of the components.

Example 32.

The general procedure of comparative Example 31 was repeated except that in the present comparative example the calves were infested with various stages of the "Biarra" strain of cattle tick. The % mortality of engorged adults is shown in Table IX.

TABLE IX

Concentration of NRDC 143 ppm % Mortality of engorged adults 250 100 125 60 62 50 Example 33.

The general procedure of Example 26 was repeated except that in the present example the calves were infested with various stages of the "Biarra" strain of cattle tick. The results obtained are shown in Table X.

TABLE X

Concentration of NRDC 143 ppm % Mortality of engorged adults 250 100 125 100 62 100 31 70 In a control test performed by the above procedure and wherein the spray contained 1000 ppm of diazinon and no NRDC 143 It was found that the % mortality of engorged adults was zero. These results show a remarkable and unexpected increase in the efficacy of the composition according to the invention in comparison with the sum of the individual effects of each of the components.

Example 34.

The general procedure of Example 26 was repeated except that in the present example the calves were infested with various stages of the susceptible "Yeerongpilly" cattle tick. It was found that the % mortality of engorged adults was 100% with each of the sprays.

Example 35.

The general procedure of Example 16 was repeated except that the weight ratio of NRDC 143 to "Solgard" was changed from 1:1 to 1:2. The mortality rate of the ticks was as tabulated below.

Concentration of Expected % Mortality NRDC 143 % Mortality of ticks of ticks 500 ppm 100 85 250 ppm 100 65 125 ppm 96 20 62 ppm 78 10 3lppm- 65 0

Claims (21)

WHAT WE CLAIM IS:

1. A composition of matter comprising as a tickicidally effective active ingredient a mixture comprising as a first component at least one isomer of 3 - phenoxybenzyl 2,2 - dimethyl - 3 - (2,2 - dichlorovinyl)cyclopropane carboxylate and as a second component at least one organophosphorus compound; but excluding those compositions of matter wherein said second component is O - (2 - diethylamino - 6 - methylpyrimidin - 4 - yl) 0,0 - dimethyl phosphorothioate or 0,0 - dimethyl 0 - (4 - nitrom - tolyl) phosphorothioate and said compositions of matter are characterised by being substantially free of organic solvent material as defined in UK patent specification Serial No. 1,462,319.

2. A composition according to Claim 1 wherein the said composition comprises a (I±) cis, trans isomer mixture of 3 - phenoxybenzyl 2,2 - dimethyl - 3 - (2,2 dichlorovinyl ) cyclopropane carboxylate.

3. A composition according to Claim 1 or Claim 2 wherein the said organophos phonic compound is selected from the group consisting of organo phosphates, phos phorus bearing derivatives of thioethers, phosphorus bearing phenyl esters having sulphur containing substituents, phosphorus bearing phenyl esters having neither sulphur containing nor nitrogen containing substituents, and phosphorylated heterocyclic ring compounds having at least one oxygen or nitrogen atom in the heterocyclic ring.

4. A composition according to any one of Claims 1 to 3 inclusive wherein the said organophosphorus compound has a phosphorus bearing radical selected from the group consisting of phosphate, phosphorothioate, phosphorodithioate and di(phosphorodithioate).

5. A composition according to Claim 4 wherein the said phosphate bearing compound is a mixture of cis and trans isomers of 2 - chloro - 1 - (2,4 - dichlorophenyl)vinyl diethyl phosphate.

6. A composition according to Claim 4 wherein the said phosphorothioate bearing compound is. selected from the group consisting of O - (4 - bromo - 2,5 - dichlorophenyl) 0,0 - diethyl phosphorothioate, 0,0 - diethyl 0 - 3,5,6 - trichloro2 - pyridyl phosphorothioate, 0,0 - diethyl 0 - (3 - chloro - 4 - methyl - 7coumarinyl) phosphorothioate, 0,0 - diethyl 0 - (2 - isopropyl - 6 - methyl - 4pyrimidinyl)phosphorothioate, 0,0 - dimethyl O - p - (dimethylsulphamoyl)phenyl phosphorothioate, 0,0 - dimethyl 0 - (3 - methyl - 4 - methylthiophenyl)phosphorothioate and 0,0 - diethyl 0 - (2 - diethylamino - 6 - methylpyrimidin - 4 - yl) phos phorothioate.

7. A composition according to Claim 4 wherein the said phosphorodithioate bearing compound is selected from the group consisting of S - [(p - chlorophenylthio)methyl] 0,0 - diethyl phosphorodithioate and 0,0 - dimethyl phthalimido methyl phosphorodithioate.

8. A composition according to Claim 4 wherein the said di(phosphorodithioate) bearing compound is O,0,O',0' - tetraethyl - S,S' - methylene di(phosphorodithioate).

9. A composition according to any one of Claims 1 to 8 inclusive wherein the weight ratio of the said first component to the said second component is in a range from 5:1 to 1:5.

10. A composition according to Claim 9 wherein the said ratio is in a range from 1:1 to 1:5.

11. A composition according to Claim 9 wherein the said ratio is in a range from 1:1 to 1:2.

12. A composition according to any one of Claims 1 to 11 inclusive wherein the said mixture constitutes up to 1% w/w of said composition.

13. A composition according to any one of Claims 1 to 11 inclusive wherein said mixture constitutes from 0.005 to 0.3% w/w of said composition.

14. A process for killing undesired Boophilus micro plus (cattle tick) which process comprises treating media infested with Boophilus microplus with a tickicidally effective amount of a mixture comprising as a first component at least one isomer of 3 - phenoxybenzyl 2,2 - dimethyl - 3 - (2,2 - dichlorovinyl) cyclopropane carboxylate and as a second component at least one organo phosphorus compound.

15. A process according to Claim 14 wherein the said first component is a (+) cis, trans isomer mixture of 3-phenoxybenzyl, 2,2-dimethyl-3 (2,2-dichlorovinyl)cyclo- profane carboxylate.

16. A process according to Claim 14 or 15 wherein the said second component is 0,0 - diethyl 0 - (2 - diethylamino - 6 - methyl - pyrimidin - 4 - yl)phosphorothioate.

17. A process according to any one of Claims 14 to 16 wherein the said cattle tick is of a non-resistant strain.

18. A process according to any one of Claims 14 to 16 wherein the said cattle tick is of a resistant strain.

19. A composition according to Claim 1 or 2 wherein the said second component is 0,0 - diethyl 0 - (2 - diethylamino - 6 - methyl - pyrimidin - 4 - yl)phosphorothioate.

20. A composition according to Claim 1 substantially as described in any one of Examples 12 to 30 inclusive and 33 to 35 inclusive.

21. A process according to Claim -14 substantially as described in any one of Examples 12 to 30 inclusive and 33 to 35 inclusive.