GB2088212A

GB2088212A - Pest control

Info

Publication number: GB2088212A
Application number: GB8134831A
Authority: GB
Original assignee: Wellcome Foundation Ltd
Current assignee: Wellcome Foundation Ltd
Priority date: 1980-11-21
Filing date: 1981-11-19
Publication date: 1982-06-09
Also published as: GB2150026B; GB2150025A; GB2150026A; FR2494561B1; ZA818079B; GB8332684D0; IE812719L; GB2150025B; GB2088212B; ZA833066B; GB8332685D0; FR2494561A1; NZ199009A; IE52108B1

Abstract

Sheep ectoparasites including lice, keds, flies, mites and ticks are controlled by the localised application to the skin or fleece of the sheep of a pyrethroid. The treatment is effective even on long-woolled Merino sheep.

Description

SPECIFICATION Pest Control The present invention relates to a method of controlling sheep ectoparasites including keds, lice, flies, mites and ticks. The invention has special application to the cntrol of the sheep-biting louse (Damalinia ovis) and keds (Melophagus ovinus) particularly on merino sheep.

Traditionally, sheep have been treated for the control of ectoparasites by dipping or spraying the whole external surface of the sheep. However, this is an inconvenient and time-consuming operation.

Attempts have been made to treat infested sheep, particularly lice-infested sheep, with a large variety of known insecticides by various more conventional routes, including pour-on treatments, subcutaneous injection, and by oral dosage. Hitherto, none of the treatments had any significant effect on the control of the lice populations. In particular, merino sheep which have very dense wool have not responded to such treatments.

The present invention is based on the unexpected discovery that localised applications of pyrethroids are surprisingly effective in controlling and eradicating lice, keds, blow flies and other ectoparasites. It is particularly surprising that such localised application is effective even on long-wooled merino sheep.

Thus, the present invention provides a method of controlling sheep ectoparasites which comprises the application onto a localised region of the skin or fleece of a sheep of a pyrethroid of the formula.

wherein M is

and wherein X, toX4 are independently selected from halo, C1-C4 alkyl, halogen-substituted C1-C4 alkyl, and halogen-substituted phenyl; X5 is-H or halo; R1 is -H or cyano; and R2 is halogen-substituted phenyl.

By "localised application" is meant that the pyrethroid is only applied to a minor portion of the skin or fleece of the sheep, generally as a line or spot on the sheep's back. It has been surprisingly discovered that, notwithstanding the presence of a sometimes dense coating of wool, the pyrethroid appears to act over the entire surface of the sheep. It is believed as a hypothesis that the pyrethroid is transmitted over the surface of the sheep by diffusion through the wool grease.

The pyrethroid is generally applied as a liquid formulation, a paste or as a solid powder.

Surprisingly, it has been found that it is not necessary that the pyrethroid be dissolved to be effective.

The localised application is preferably carried out as a pour-on treatment by pouring a liquid formulation comprising the pyrethroid along the back of the sheep (i.e. a so-called "backline" application). Surprisingly, it is not necessary to totally immerse the sheep in the formulation so that the treatment of large numbers of sheep is facilitated.

Alternatively, the application may be carried out by means of a localised spray or aerosol, usually along the sheep's back as it passes through a sheep race. The aerosol might comprise the pyrethroid dissolved in a liquid carbon dioxide propellant Without wishing to be limited by any theoretical mode of action, it is believed that the pyrethroid acts superficially and is not dermally and systemically absorbed. it is therefore surprising that protection over the entire sheep is attainable from a localised application.

The pyrethroid is preferably selected from the group of light stable pyrethroids. Deltamethrin (also known as decamethrin is preferred and is a solid under normal conditions. Suitable pyrethroids are disclosed in Tables I to Ill.

TABLE I

No. X1 X2 X3 X4 X5 Rl trivial name 1 CI Cl - - H H permethrin 2 CH3 CH3 - - H H phenothrin 3 3 Br Br - - H CN deltamethrin 4 CI CI - - H CN cypermethrin 5 CI CF3 - - H CN cyhalothrin 6 Cl (I - F F CN flumethrin 7 7 CI Ol - - F CN cyfluthrin 8 CH3 CH3 - - H CN oyphenothrin TABLE II

No.X1 X2 X3 X4 Xs R, trivial name 9 Br Br Br Br H CN tralomethrin 10 Cl Cl Br Br H CN tralocythrin TABLE III

No. RI X1 R1 trivial name 11 o- Cl H CN fenvalerate It is a particular advantage of the present method that only small volumes of pyrethroid or pyrethroid-containing formula need to be applied. Depending on the size of the sheep, the volume applied will generally lie in the range 2 to 1 5 ml per sheep. For convenience, the pyrethroid will generally be applied in a liquid formulation.

Depending on the efficacy of the particular pyrethroid employed, the formulation generally contains from 0.1 to 500, preferably 1 to 250 mg/ml of the pyrethroid. Moreover, the pyrehroid is preferably applied to the sheep in an application of from 1 to 500, preferably 1.5 to 250 mg/kg body weight.

The formulation may be applied to full-woolled or sheared sheep. However, higher doses are required for full-woolled sheep.

The pyrethroid is preferably applied in the form of a pour-on formulation. The formulation may comprise one or more organic solvents, such as xylene, toluene, cyclohexanone, and a glycol.

One preferred solvent system comprises 30-70 wt % xylene, 20-40 wt % cyclohexanone and 5-25 wt % vegetable oil.

Suitable glycols include ethylene glycol and propylene glycol, polyethylene glycols and polypropylene glycols, ethylene glycol-propylene glycol copolymers, and alkyl ethers and alkyl ether esters of the general formula:

where R' = C1 alkyl or hydrogen, R2 = C1-C5 alkyl, hydrogen or -CO-R3, R3 = C1-C12 alkyl, and n =1-40.

Diethylene glycol mono-n-butyl ether has been found to be particularly useful. It has been found to have minimal adverse effect on the skin in terms of a mild epidermal shedding seen with other solvents in some sheep.

Alternatively, the formulation may be an aqueous formulation containing the pyrethroid in the form of a suspension or emulsion and comprising suitable surfactants to stabilise the suspension or emulsion, and prevent undue run-off from the back of the sheep. Thus, it has been surprisingly found that the pyrethroid is effective even when in the undissolved state.

Paraffin oils, vegetable oils, e.g. corn oil, peanut oil, castor oil, olive oil, can be added as viscosity modifiers and co-solvents.

Alkylamides and esters of fatty acids are useful formulation adjuncts e.g. n-butyl oleate, N,Ndimethyl oleamide and isopropyl myristate (IPM).

It has been found that the inclusion of an antioxidant such as 2,6-ditert-butyl-4-cresol (BHT) or 2tert-butyl-4-methoxyphenol (BHA) has a useful stabilising effect on the active ingredients in formulations based on glycols, glycol ethers, glycol ether esters and cyclohexanone.

The present invention will now be illustrated with reference to comparative tests showing the lack of activity of a large number of conventional insecticides, and with reference to specific examples illustrating the present invention.

(I) Comparative tests The effectiveness of a number of known insecticides in controlling sheep lice using pour-on formulations was assessed. A summary of the active agents and dose rates is given in Table 1.

TABLE 1 Pour-on Chemical (mg/kg) chlorfenvinphos 100 maldison 250 carbaryl 100 dimethoate 100 dioxathion 100 ethion 100 fenitrothion 100 trichlorphon 100 famphur 50, 100 ronnel 100 crotoxyphos 100 bendiocarb 100 bromophos ethyl 100 dichlofenthion 100 crufomate 100 naled 100 All the pour-on treatments were formulated in a solvent system containing xylene, cyclohexanone and corn oil.

A total of 1 8 groups of lice-infested merino sheep divided into control (1) and treatment groups (17) were selected and treated according to Table 1.

No pour-on treatment had any significant effect on existing lice burdens.

(II) Treatment according to the present invention A variety of pyrethroids were evaluated in the control of lice and keds on merino sheep, when applied by a liquid pour-on formulation.

Test 1 (xylene-cyclohexanone-corn oil solvent) Forty-eight merino sheep, half carrying full-wool and half carrying one month's wool, with significant louse infestations, were ailocated equally into four groups of six animals.

Treatments, with formulations comprising a xylene (55 wt %), cyclohexanone (30 wt %), corn oil (15 wt %) solvent system were made as follows: Group 1 deltamethrin 10 mg/kg 10 mg/ml formulation Group 2 deltamethrin 50 mg/kg 50 mg/ml formulation Group 3 permethrin 100 mg/kg 100 mg/miformulation Group 4 permethrin 250 mg/kg 250 mo/ml formulation.

On full-woolled sheep, partings were made along the backline to place the formulation at skin level. After treatment the various groups, each with three full-woolled and three short-woolled sheep, were held in separate pens, remote from each other.

Post-treatment lice examinations were made at 1, 3 and 7 weeks, to assess the effects of the various treatments on the louse populations At seven weeks, groups 1 and 2 were run with a mob of fifteen infestor sheep, carrying considerable lice infestations, to gauge the persistence of deltamethrin. Further examinations were made at 9 weeks but subsequent examinations were prevented by wet weather.

Results The results of the pre-treatment and post-treatment lice examinations are shown in Table 2 and are outlined below.

Infestations fell rapidly to extremely full low levels and persisted at these low GROUP 1 wool levels throughout the trial.

deltamethrin short One light infestation was eradicated (10 mg/kg) wool by Week 1. Moderate to heavy infestations were eradicated by Week 7.

At one week, two newly emerged lice were found in matted wool on one animal, only after an exhaustive search.

No lice were seen on the other two GROUP 2 full animals. At Week 3 an exhaustive wool search of each animal revealed one or deltamethrin two newly emerged lice. No lice were (50 mg/kg) found at Week 7 or at Week 9, after a fourteen-day challenge period.

short No lice were seen at any examination wool after treatment.

Infestations were markedly reduced but full were maintained at low levels throughout GROUP 3 wool the trial.

permethrin short Infestations were reduced to extremely (100 mg/kg) wool low levels but lice were still present at Week 7.

Infestations were greatly reduced on full two out of three sheep but persisted GROUP 4 wool at low levels until Week 7. Lice were eradicated on the third animal by Week 7.

permethrin (250 mg/kg) short Light infestations were drastically wool reduced at Week 1 and eradicated at Week 3.

In the following tables, the numbers represent the total number of lice detected in twenty partings of the wool of the sheep, and L = light infestation 0 = no lice present M = moderate infestation + = lice present.

H = high infestation TABLE 2 (First Three Sheep per Group Carrying Full-Wool, Second Three Carrying One Month's Wool) Sheep Pre- Week Week Week Week Group No. Treatment 1 3 7 9 Comments B 34 H 13/20 24/20 16/20 2/20 GROUP 1 B 882 H L-M L-M 2/20* 8/20* *One heavy deltamethrin O 800 L O O O O patch found (10 mg/kg) B 28 M-H 14/20 0 0 0 in neck fold Y 798 M-H 3/20 1/20 0 0 B 883 M-H 0 5/20 0 0 G 790 H 2/20** 1/20 0 0 GROUP 2 Y 840 M-H 0 2/20 0 0 **Found in deltamethrin B 44 M-H 0 0 0 0 matted wool (50 mg/kg) Y 830 L-M 0 0 0 0 Y 738 M 0 0 0 0 B 50 H L L L Y 835 H M M-H H-H GROUP 3 Y 833 H L L 19/20 permethrin B 27 M-H 20/20 9/20 24/20 (100 mg/kg) B 49 M 17/20 6/20 11/20 Y 744 L-M 7/20 3/20 4/20 B 887 H 12/20 7/20 3/20 B 38 L-M 7/20 0 0 GROUP 4 B 42 H L-M L-M L permethrin B 35 L 1/20 0 0 B 29 L 1/20 0 0 V 991 L 1/20 0 0 47 L-M M-H M L L 877 H H H H H 742 H H H M-H M-H CONTROLS 754 L L-M L-M L L-M 37 M M L L L-M 736 L-M M L-M died Test 2 The results of the evaluation of deltamethrin on recently sheared merino sheep using xylene and DGBE-based solvent systems are given in Tables 3 and 4. The results of the untreated control group are given in Table 5.

The xylene-based solvent system is the same as that given in Test 1.

The DGBE-based solvent system had a composition as follows: diethylene glycol mono-n-butyl ether (DGBE) 85 wt % isopropyl myristate (IPM) 15 wt% 2,6-ditert-butyl-4-cresol (BHT) 2.5 g/l.

TABLE 3 Xylene-Based Solvent*

Post-Treatment Challenge Inspections Inspections (Group 1 and Group 2) Delta- Body methrin Sheep weight Dose week week week week week (g/l) Group No. (kg) (ml) 3 6 10 12 14 GROUP 1 (a) 51 50 6.3 0 0 0 0 1 8.0 1 mg/kg 90 46 5.8 0 0 0 0 2 1 ml/8 kg 106 44 5.5 0 0 0 0 0 GROUP 1(b) 52 44 11.0 0 0 0 lambed 4.0 1 mg/kg 55 48 12.0 0 0 0 0 1 ml/4 kg 139 43 10.8 0 0 0 0 GROUP 2 (a) 54 50 6.3 0 0 0 0 2 16.0 2 mg/kg 112 44 5.5 0 0 0 0 1 1 ml/8 kg 127 46 5.8 0 0 0 0 1 GROUP 2 (b) 53 44 11.0 0 0 slaughtered (injury) 8.0 2 mg/kg 88 48 12.0 0 0 0 1 3 1 ml/4 kg 146 43 10.8 0 0 0 0 2 GROUP 3(a) 76 50 6.3 0 0 20.0 2.5 mg/kg 126 44 5.5 0 0 1 ml/8 kg 134 46 5.8 0 0 GROUP 3 (b) 67 44 11.0 0 0 10.0 2.5 mg/kg 75 42 10.5 0 0 1 ml/4 kg 102 48 12.0 0 0 GROUP 4 (a) 113 50 6.3 0 0 24.0 3 mg/kg 131 44 5.5 0 0 1 ml/8 kg 137 48 5.8 0 0 GROUP 4 (b) 69 44 11.0 0 0 12.0 3 mg/kg 84 42 10.5 0 0 1 ml/4kg 143 48 12.0 0 0 GROUP 5 (a) 61 49 6.1 0 0 32.0 4mg/-g 141 44 5.5 0 0 1 ml/8 kg 147 46 5.8 0 0 GROUP 5(b) 71 44 11.0 0 0 16.0 4 mg/kg 110 42 10.5 0 0 1 ml/4 kg 118 47 11.8 0 0 GROUP 6 (a) 58 45 5.6 0 0 40.0 6 mg/kg 68 49 6.1 0 0 1 ml/8 kg 83 43 5.4 0 0 GROUP 6 (b) 80 44 11.0 0 0 20.0 5 mg/kg 124 47 11.8 0 0 1 ml/4kg 125 42 10.5 0 0 * Figures shown in "week" columns are the number of lice seen in twenty wool partings.

TABLE 4 DGBE-Based Solvent*

Post-Treatment Challenge Inspections Inspections (Group 1 and Group 2) Delta- Body methrin Sheep weight Dose week week week week week (g/l) Group No. (kg) (ml) 3 6 10 12 14 GROUP 1 (c) 60 45 5.6 0 0 0 1- 1 8.0 1 mg/kg 73 49 6.1 0 0 0 3 0 1 ml/8 kg 85 43 5.4 0 0 0 1 1 GROUP 1 (d) 78 41 10.3 < 1/20 0 0 4 1 4.0 1 mg/kg 81 44 11.0 0 0 1 0 1 1ml/4kg 129 47 11.8 0 0 0 0 0 GROUP 2 (c) 62 45 5.6 0 0 0 3 2 16.0 2 mg/kg 74 49 6.1 0 0 0 1 1 1 ml//8 kg 96 43 5.4 0 0 slaughtered (injury) GROUP 2 (d) 18 41 10.3 0 0 0 1 0 8.0 2 mg/kg 89 44 1.t.0 0 0 0 1 1 1 ml/4 kg 132 47 11.8 0 0 0 1 2 GROUP 3 (c) 86 49 6.1 < 1/20 0 20.0 2.5 mg/kg 107 45 5.6 0 0 1 ml/8 kg 114 43 5.4 0 0 GROUP 3 (d) 91 41 10.3 0 0 10.0 2.5 mg/kg 94 44 11.0 0 0 1 ml/4 kg 144 47 11.8 0 0 GROUP 4 (c) 108 45 5.6 0 0 24.0 3 mg/kg 117 43 5.4 0 0 1 ml/8 kg 120 49 6.1 0 0 GROUP 4 (d) 56 40 10.0 0 0 12.0 3 mg/kg 57 46 11.5 0 0 1 ml/4 kg 97 44 11.0 0 0 GROUP 5 (c) 119 43 5.4 0 0 32.0 4 mg/kg 128 49 6.1 0 0 1 ml/8 kg 135 45 5.6 0 0 GROUP 5 (d) 66 40 10.0 0 0 16.0 4 mg/kg 70 46 11.5 0 0 1ml/4kg 98 44 11.0 0 0 GROUP 6 (c) 133 43 5.4 - 0 0 40.0 5 mg/kg 136 49 6.1 0 0 1 ml/8 kg 145 45 5.6 0 0 GROUP 6 (d) 72 40 10.0 0 0 20.0 5 mg/kg 87 46 11.5 0 0 1 ml/4 kg 101 44 11.0 0 0 *Figures shown in "week" columns are the number of lice seen in twenty wool partings.

TABLE 5 Results of Examinations of Shorn Untreated Control Group* Untreated Controls Body Sheep weight Week Week No. (kg) 3 6 65 51 10 10 77 -56 9 8 79 52 17 15 82 38 24 31 95 54 18 - 29 104 28 37 35 105 52 20 8 111 29 24 23 116 44 10 16 122 39 22 18 123 36 19 18 130 35 18 17 *Figures show the number of lice seen in twenty wool partings.

Test 3 (varying solvent systems) Table 6 gives the results for formulations of deltamethrin in a variety of other solvent systems when applied to recently sheared merino sheep.

TABLE 6 Various Solvent Systems Body Pre Sheep wt Dose Treat- Week Week Week No. (kg) (ml) ment 4 6 8 Formulations 140 27 6 91 0 0 0 174 27 6 66 0 0 0 10 g/l deltamethrin in xylene system of Test 1 175 26 6 30 1 0 0 172 17 9 47 1 0 0 10 g/l deltamethrin 178 33 8 90 0 0 0 2,5 g/l BHT 180 34 8 47 0 0 0 to 1 litre with cyclohexanone containing 50 ppm SUDAN RED IV 131 25 6 51 0 0 0 10 g/l deltamethrin 132 29 6 34 0 0 0 2,5 g/l BHT 138 28 6 87 0 0 0 50 ppm SUDAN RED IV DGBE/cyclohexanone (65::35 w/w) to 1 litre 10 g/l deltamethrin 142 32 8 73 0 0 0 100 g/l mineral oil 149 24 8 47 0 0 0 2,5 g/l BHT 181 31 8 27 0 0 0 50 ppm SUDAN RED IV cyclohexanone to 1 litre 10 g/l deltamethrin 164 36 5 117 0 0 0 100 g/l mineral oil 165 33 8 47 0 0 0 2,5 g/l BHT 177 30 4 27 0 0 0 50 ppm SUDAN RED IV diethylene glykol mono-n-butylether (DGBE) to 1 litre 143 31 8 90 1 0 0 10 g/l deltamethrin 155 21 6 44 1 0 0 2.5 g/l BHT 162 25 6 75 1 0 0 50 ppm SUDAN RED IV dipropylene glycol monomethyl ether (DPM) to 1 litre 137 29 6 60 0 0 0 10 g/l deltamethrin 163 28 6 72 0 0 0 2.5 g/l BHT 169 21 6 39 0 0 0 100 g/l acetylated lanoline alcohols cyclohexanone to 1 litre TABLE 8 (Continued) Various Solvent Systems Body Pre Sheep wt Dose Treat- Week Week Week No. (kg) (ml) ment 4 6 8 Formulations 156 23 6 57 1 0 0 as for Example No. 10 176 31 8 180 2 0 0 129 29 - 14 14 8 17 130 23 - 18 28 14 22 154 25 - - 171 47 72 Controls 160 36 - 17 8 8 24 171 30 - 17 29 24 20 Test 4 (varying pyrethroids) The efficacy of a variety of different pyrethroids applied as liquid pour-on formulations to merino sheep was determined. The results are given in Table 7. A backline application was made within 24 hours of shearing. All formulations used the xylene-based solvent system given in Test 1, except flumethrin which was formulated as a miscible oil formulation but which was diluted with the xylenebased solvent to achieve the lower concentrations.

The results show all the pyrethroids tested to be effective, although at the dosages used phenothrin and flumethrin did not give complete eradication.

Test 5 (effect of deltamethrin against keds) The efficacy of deltamethrin against infestations of merino sheep with keds (Melophagus ovinus) was determined by applying 8 ml of deltamethrin in the xylene-based solvent system given in Test 1 as a backline treatment to twenty newly shorn sheep. Twenty further sheep were treated in the same way with deltamethrin in the DGBE-based solvent system given in Test 2. The concentration of deltamethrin was 10 g/l.

All forty sheep were re-examined 10 weeks after treatment and no live keds were found.

TABLE 7 Control of the Sheep-Biting Louse by a Number of Pyrethroids Sheep Result Compound/Dose/!Formulation No. (No. of Lice) CYPERMETHRIN 5 mg/kg 782 0 (1 ml/5 kg-25 g/l formulation) 767 7 732 26 756 0 50 mg/kg 746 0 (1 ml/5 kg-250 g/l formulation) 733 0 (14/10 - D) PHENOTHRIN 721 8 25 mg/kg 765 23 (1 ml/5 kg-125 g/l formulation) 727 - 3 724 8 400 mg/kg 779 6 (4 m1/5 k9-500 9/1 formulation) 753 18 FEN VALE RATE 744 9 10 mg/kg 740 3 (1 ml/5 kg-50 g/l formulation) 769 2 (14110 - D) 766 0 100 mg/kg 776 0 (2 ml/5 kg-250 gIl formulation) 730 0 FLUMETHRIN 783 21 0.5 mg/kg 725 10 (1 ml/5 kg-2.5 g/l formulation) 719 1 722 0 12-16 mg/kg 755 5 (25 ml/30-40 kg - 20 gIl formulation) 748 7 741 64 737 52 CONTROLS 764 83 754 53 no treatment 758 121 723 55 D = died between 14/10 and 21/10.

Test 6 (time to take effect) The time for the pyrethroid to fully clear the merino sheep following backline application of the liquid formulation was investigated and the results are shown in Table 8. These demonstrate that the pyrethroid takes a finite period to completely clear the sheep of lice. However, the sheep are substantially cleared within 15 days. The effect is also demonstrated in certain of the preceding Tables.

TABLE 8 Process of Reduction in Lice Numbers Following Pyrethroid Backline Treatment Lice Score Sheep Day Group No. 0 7 9 15 35 42 Cypermethrin 756 > 20 7 3 0 21 0 50 mg/kg 746 > 20 7 2 5 21 0 733 > 20 9 3 0 0 0 766 > 20 2 2 3 0 0 Fenvalerate 770 > 20 6 1 0 0 0 100 mg/kg 730. > 20 2 2 2 11 0 Flumethrin 722 > 20 10 - 8 41 0 755 > 20 19 - 10 181 31,2A 12-16 mg/kg 748 > 20 12 - 4 71,2A 41,3A 741 > 20- - - 14 - 64(18) 737 > 20 - - 15 - 52(18) Controls 767 > 20 - - 16 - 83(19) 754 > 20 - - 10 - 53(15) 758 > 20 - - 22 - 121(19) 723 > 20 - - 20 - 55(13) I = immature lice A= adult lice (|||) Formulations for use according to the present invention Suitable formulations are presented in the following Examples. In general, a suitable solvent system contains 0 to 100% by weight xylene, 0 to 100% by weight cylohexanone, and up to 20% by weight corn oil.

EXAMPLE 1 10.1 9 of technical deltamethrin (989 9 active per kg), was dissolved in a solvent consisting of: cyclohexanone Sudan Red IV (oil soluble dye) 50 ppm and the volume adjusted to one litre to give a solution containing 10 g/l deltamethrin.

EXAMPLE 2 51 g of technical deltamethrin (989 9 active constituent per kg) was dissolved in a solvent blend containing: xylene 55% by weight cyclohexanone 30% by weight corn oil 1 5% by weight Sudan Red IV 1000 ppm and the volune adjusted to one litre with the same solvent blend to give a solution containing 50 g/I deltamethrin.

EXAMPLE 3 10.1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent blend, containing: xylene 55% by weight cyclohexanone 30% by weight corn oil 15% by weight Sudan Red IV 50 ppm and the volume adjusted to one litre with the same solvent blend, to give a solution containing 10 g/I deltamethrin.

EXAMPLE 4 51 g of technical deltamethrin (989 g active per kg) was dissolved in the same solvent blend given in Example 3 and the volume adjusted to give a solution containing 50 g/l deltamethrin.

EXAMPLE 5 10.1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent consisting of: diethylene glycol monobutyl ether BHT antioxidant 2500 ppm Sudan Red IV 50 ppm and the volume adjusted to one litre with the same solvent to give a solution containing 10 g/l deltamethrin.

EXAMPLE 6 10.1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent blend containing: cyclohexanone 50% by weight diethylene glycol monobutyl ether 50% by weight BHT antioxidant 2500 ppm Solvent Blue No.36 50 ppm and the volume adjusted with the same solvent blend to give a solution containing 10 g/l deltamethrin.

EXAMPLE 7 10.1 g of technical deltamethrin (989 g active per kg) was dissolved in a variety of solvent blends containing:

diethylene glycol monobutyl ether or 85-90% by weight ethylene glycol monobutyl ether acetate isopropyl myristate 1 0-1 5% by weight BHT antioxidant 2500 ppm Sudan Red IV 50 ppm and the volume adjusted with the respective solvent blend to give a solution containing 1 0 g/l deltamethrin.

EXAMPLE 8 Amounts of 2.6, 10.5, 42.5 and 84.2 g of technical cypermethrin (950 g active per kg) were dissolved in a solvent blend containing: xylene 55% by weight cyclohexanone 30% by weight corn oil 1 5% by weight and the volume adjusted to one litre with the same solvent blend to give solutions containing 2.5 g, 10 g, 40 g and 80 g per litre respectively of cypermethrin.

EXAMPLE 9 103 g of technical permethrin (970 g active per kg) in which the cis:trans isomer (arising from the two asymmetric carbon atoms in the cyclopropane ring) ratio was 25:75, was dissolved in a solvent blend containing: xylene 55% by weight cyclohexanone 30% by weight corn oil 1 5% by weight and the volume adjusted to one litre with the same solvent blend to give a solution containing 100 g/l permethrin.

EXAMPLE 10 An aqueous suspension of deltamethrin was prepared by suspending 10.1 g of technical deitamethrin of average particle size 2 to 5 microns in an aqueous formulation containing:

non-ionic wetting agent 1.5 g 1 mole nonylphenol condensed # with 15 moles of ethylene oxide fumed silicon dioxide 5.0 g xantham gum 4.0 g propylene glycol 60.0 g formaldehyde 1.0 g silicone oil (antifoaming agent) 1.0 g water to one litre.

Various other deltamethrin suspensions in the range 1 to 500 g/l deltamethrin were also prepared.

Claims

1. A method of controlling sheep ectoparasites which comprises the application onto a localised region of the skin or fleece of a sheep of a pyrethroid of the formula

wherein M is

and wherein X1 to X4 are independently selected from halo, C,C4 alkyl, halogen-substituted C,C4 alkyl, and halogen-substituted phenyl; X5 is-H or halo; R, is -H or cyano; and R2 is halogen-substituted phenyl.

2. A method according to claim 1 wherein the pyrethroid is selected from permethrin, phenothrin, deltamethrin, cypermethrin, cyhalothrin, flumethrin, cyfluthrin, cyphenothrin, tralomethrin, tralocythrin and fenvalerate (all as herein defined).

3. A method according to any preceding claim wherein the pyrethroid is applied to a substantially full-wooled sheep.

4. A method according to any preceding claim wherein the sheep is a merino sheep.

5. A method according to any preceding claim wherein the pyrethroid is applied at a rate of from 1 to 500 mg per kilogram sheep body weight.

6. A method according to any preceding claim wherein a pour-on application of from 2 to 1 5 ml of a liquid formulation comprising the pyrethroid is made.

7. A method according to any preceding claim wherein a liquid formulation is applied which comprises the pyrethroid dissolved in a solvent system comprising 30-70 wt % xylene, 20-40 wt % cyclohexanone and 5-25 wt % vegetable oil.

8. A method according to any one of claims 1 to 6 wherein a liquid formulation is applied which comprises the pyrethroid dissolved in a solvent system comprising a major proportion of diethylene glycol mono-n-butyl ether.

9. A method according to claim 8 wherein the solvent system further comprises a minor proportion of isopropyl myristate.

10. A method according to any one of claims 1 to 6 wherein a liquid formulation is applied which comprises a suspension or emulsion of the pyrethroid in an aqueous liquid.

11. A method according to any one of claims 1 to 5 wherein the pyrethroid is applied in the form of an aerosol.

1 2. A method according to any preceding claim wherein the sheep is infested with lice.

1 3. A method according to any preceding claim wherein the sheep is infested with keds.

14. A method of controlling sheep lice which comprises the application of a formulation substantially as disclosed in any Example.