Since the first reported control failures at Emerald during the 1998-99 cotton season, insecticide resistance in cotton aphid, has emerged as a significant threat to the Australian cotton industry. Although once considered a late season pest, aphid populations now require targetted control earlier, resulting in increased aphicide sprays and consequent selection for resistance.

Previously, the cotton aphid had been readily controlled with the IPM compatible carbamate, pirimicarb. However, by 1999-2000 pirimicarb resistance was common in the southeast of Queensland and New South Wales. Pirimicarb also conferred cross-resistance to the unrelated organophosphate compounds dimethoate and omethoate rendering them useless. Efficacy of the remaining organophosphates is variable with some aphids also resistant to pyrethoids and endosulfan. These multiple resistant aphids can only be controlled by newer products such as diafenthiuron. The effects of resistance can be reduced with effective resistance management. Management in part requires an understanding of the underlying resistance mechanisms, however, this is not well understood in Australian A. gossypii populations.

Consequently, the objective of this project was to better understand the underlying resistance mechanisms used by A. gossypii. That information will then be used to develop more robust control strategies including a field based kit to detect pirimicarb resistance.