Control of headfly on sheep.

Eighteen different treatments against sheep headfly (Hydrotaea irritans) were tested on Scottish blackface and Swaledale ewes and lambs. Gamma-HCH + paradichlorobenzene gave consistently better control than crotoxyphos cream. Pyrethroids in sprays or incorporated into eartags were relatively ineffective. Pyrethroid pour-ons gave good control, but in a year of low headfly attack they were not as effective as HCH + paradichlorobenzene. Liveweight gain was improved by treatment with HCH + paradichlorobenzene and significantly improved by treatment with deltamethrin pour-on.