Baseline studies and preliminary resistance survey of Australian populations of cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae)

Cotton aphids, Aphis gossypii, may be more troublesome in transgenic (Ingard(R)) cotton, because an overall reduction in pesticide use in transgenic cotton for the control of pests such as Helicoverpa spp., gives reduced control of concurrent aphids. Additionally, coincidental cotton aphid in conventional cotton is being exposed to an increasing number of organophosphate insecticides targeted against Helicoverpa spp. Resultant insecticide sprays targeted specifically at cotton aphid, are likely to increase and-must be managed to maintain insecticide susceptibility. As a first step to studying resistance in cotton aphid, two strains were collected from unsprayed sources and tested against 21 registered or experimental insecticides by laboratory bioassay, to establish baseline data for resistance monitoring. The LC99.9 of the more susceptible strain was used arbitrarily as a discriminating concentration to detect resistance in three populations of cotton aphid collected in cotton growing districts of New South Wales. In contrast to overseas studies, our results suggest that Australian cotton aphid was resistant to endosulfan and pyrethroids but not to carbamates or organophosphates.