Insecticides and acaricides: resistance and environmental impact.

Insecticides continue to be the primary means of control for ectoparasites on livestock. Intensive use of these materials has led to resistance to organochlorines, organophosphates and pyrethroids among populations of Haematobia irritans irritans, H. irritans exigua and Lucilia cuprina. Similarly, use of acaricides has led to resistance in one-host Boophilus ticks to all currently-used organophosphate-carbamates, synthetic pyrethroids and amidines. Resistance in multi-host ticks is less widespread. New chemicals are available for the control of resistant ectoparasites, but there are concerns over resistance and residues problems, which prompt the authors to discuss new pest management strategies. Environmental concerns are raised regarding the use of pesticides on livestock.