A PRELIMINARY INVESTIGATION INTO RESISTANCE TO SYNTHETIC PYRETHROIDS BY THE SHEEP BITING LOUSE (BOVICOLA-OVIS) IN NEW-ZEALAND

Increasing reports of failure of synthetic pyrethroids far the control of Bovicola ovis on sheep lead to a preliminary investigation into th e insecticide resistance status of this pest during 1994, Eighteen str ains of lice from North and South Island flocks experiencing failure o f synthetic pyrethroid treatments to control lice were exposed to cype rmethrin (high-cis) in a treated surface (contact) bioassay. Lice from a group of ''hermit'' sheep were chosen as a reference susceptible st rain against which resistance of field strains was measured and resist ance factors (RFs) calculated. Low to moderate resistance to cypermeth rin (high-cis) was demonstrated, with RFs ranging from 1.0 to 12.4.