ECTOPARASITES OF LIVESTOCK IN NEW-ZEALAND

Ectoparasites (blowflies, lice, ticks, and mites) are not the main threat to farm production in New Zealand but are major concerns to the farmer and are a drain on resources. Lice and blowflies have been present from the earliest days of pastoral agriculture in New Zealand, as was the scab mite, Psoroptes ovis, supposedly extinct since the 1880s. The cattle tick, Haemaphysalis longicornis, was a later addition to New Zealand's arthropod pest fauna, which has been extended further by the relatively recent introduction of the Australian sheep blowfly, Lucilia cuprina. Lesser players such as the sheep ked (Melophagus ovinus), mange mites (Chorioptes spp., Psorergates ovis, Psoroptes spp., Demodex spp.), and a bot fly (Oestrus ovis) add their tiny din as background noise to the orchestrated effects of the main players. Estimates of the monetary losses due to ectoparasites can be computed, but their long-term value is doubtful - particularly when seen against a background of fluctuating world prices and occasional reversals of differential values between, say, carcase and by-products. Flystrike alone is estimated to cost >$30 million annually. To this can be added the losses due to other ectoparasites. In the light of these costs it is clear that the <$1 million currently spent annually on research demonstrates high cost-effectiveness. However, given the continuing application of pesticides (and the attendant drain on overseas funds to purchase them), plus the labour associated with preventing or alleviating ectoparasite damage, and the production losses or deaths that cannot be Prevented, a net loss to farming due to ectoparasites cannot be denied. This paper briefly examines the historical aspects of the ectoparasites of livestock in New Zealand, and follows with a view of their current prevalence, geographical distribution, and economics. Next there is a discussion of the management (''control'') methods currently employed, considering topics such as insecticide resistance, biological control, molecular biology, and rural sociology. Finally, I attempt a glimpse into the future, based on the assumption that unrestricted use of insecticides may no longer be an option for agriculture within the next 20 years, or sooner.