Cotton aphid and two-spotted mite have the potential to cause dramatic reductions in the yield and fibre quality of cotton. Management of these pests is strongly dependent on insecticides and acaricides. Recent development of resistant in both species now threatens the sustainability of their control. This project will monitor resistance in mites and aphids to existing control options, and establish baseline resistance and cross resistance data for new chemistry. This will enable continued development of effective resistance management strategies and integration of new control options, thereby maintaining the sustainability of cotton production. This will be best achieved by pursuing an integrated approach, including monitoring, cross-resistance testing, mechanism elucidation, and the evaluation and the timely inclusion of new chemistry that is compatible with IPM. This project will monitor the resistance of mites and aphids to a wide range of current control options. For new options, biological and synthetic, a sound knowledge of the base-line (initial) resistance levels and cross resistance profiles will be developed so they can be effectively incorporated into resistance management strategies. Without this study Australia's capacity to manage these pests, and in particular our reputation as a producer of clean lint, uncontaminated with aphid honeydew, could be dramatically affected.