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Onion thrips, Thrips tabaci Lindeman, is a major pest of Australian field onion Allium cepa Linnaeus with their control heavily reliant on a few insecticides. An earlier study after grower complaints of control failures did not detect resistance in three populations. After testing an additional nine populations via a Potter spray tower laboratory bioassay unequally against a-cypermethrin, diazinon, dimethoate, l-cyhalothrin, malathion and methidathion, we document resistance in T. tabaci for the first time in Australia. The maximum difference in response (resistance) for each insecticide was detected by dividing the most resistant LC50 response by the least resistant LC50 response. Comparison of the most susceptible to the least susceptible population tested produced a-cypermethrin and l-cyhalothrin resistance at 164-and 606-fold, respectively. Diazinon and dimethoate resistance was also detected at 27-fold and 5.2-fold respectively although omethoate, malathion and methidathion resistance were not detected.

Populations of cotton aphid, Aphis gossypii Glover, were surveyed for insecticide resistance. Pirimicarb, organophosphate, endosulfan and pyrethroid resistance was identified. Aphis gossypii from New South Wales cotton‐growing districts were organophosphate and pirimicarb susceptible, whereas populations from similar districts in Western Australia, Queensland and Northern Territory displayed high to extreme resistance that was linked to control failure. New South Wales populations, however, were often endosulfan and pyrethroid resistant. Resistant A. gossypii have the potential to seriously impact on the Australian cotton industry and their resistance management is now incorporated into the resistance management strategy for Australian cotton.

Two field collected strains of western flower thrips, Frankliniella occidentalis, were tested against proprietary and experimental formulations of insecticide. Thrips were tested using a novel method whereby thrips were confined in testing units throughout all stages of the bioassay procedure. The bioassay technique proved to be quick and robust. Of the chemicals tested, the two non-registered compounds chlorfenopyr and fipronil were most active against field-collected F. occidentalis. The field-collected strains were tolerant to a range of organophosphate, carbamate and pyrethroid chemicals. Comparisons of dose-response curves with established field-use-rates indicate that only methiocarb and methamidophos are likely to be completely effective in the field. The theoretical implications of the data for management of F. occidentalis in Australia is discussed.