Increased control of the sheep biting louse Bovicola (Damalinia) ovis with deltamethrin formulated in a fractionated wool grease carrier.
The synthetic pyrethroid deltamethrin (DM) containing a trace of [(14)C]-DM was formulated with non-oxidised sterol and wax ester fractions (F1) of wool grease and as the commercial preparation 'Clout-S'. These were applied as a 'backline' strip to sheep immediately after shearing and the concentration of [(14)C]-DM at meridians adjacent to the application strip and at 1/4 and 3/4 of the dorsal-ventral distance was determined. The F1 formulation resulted in significantly greater lateral spread of DM with less remaining at the application site (66+/-8% of dose) 98 days after treatment compared to 'Clout-S' (94+/-3% dose). Autoradiographic examination of treated wool demonstrated that there was more DM in the lower half of the wool staple when formulated in F1 compared to 'Clout-S'. Greater mortality occurred when sheep biting lice Bovicola (Damalinia) ovis were exposed in vitro to wool containing DM from F1 compared to 'Clout-S' treated sheep. In field trials there was increased efficacy against synthetic pyrethroid resistant B. ovis with F1 formulation than with 'Clout-S'. The study has demonstrated that synthetic pyrethroid availability, and therefore efficacy, can be significantly increased when the insecticide is formulated in a 'carrier' with the physicochemical characteristics of wool grease.
Hennessy
D R
DR
CSIRO Division of Animal Production, McMaster Laboratory, Private Bag, Delivery Centre, Blacktown, Australia. d.hennessy@anprod.csiro.au
Darwish
A
A
Maxwell
C A
CA
D000818:Animals; D002626:Chemistry, Pharmaceutical / Q000379:methods; D007300:Insect Control / Q000379:methods*; D007306:Insecticides; D010373:Lice Infestations / Q000517:prevention & control / Q000662:veterinary*; D009570:Nitriles; D009821:Oils; D008003:Phthiraptera; D011722:Pyrethrins; D012756:Sheep; D012757:Sheep Diseases / Q000517:prevention & control*; D014935:Wool
D007306:Insecticides; D009570:Nitriles; D009821:Oils; D011722:Pyrethrins; C017180:decamethrin