With the introduction of cotton containing the two Bollgard II® genes (Cry1Ac and CryIIAc), the need for cotton producers to spray their crops with pesticides to control Helicoverpa spp. has been greatly reduced (Fitt, 2000). This has made cotton more suitable to Integrated Pest Management (IPM) strategies that are an ever increasing economically and environmentally sound approach to the control of pests (Fitt et al 2004). IPM strategies have provided the grower with many benefits in terms of costs saved, and to the community in terms of lower levels of insecticide in the environment (Fitt, 2000). Most notably, there has been a marked reduction in pesticide use and a shift to using softer (target-specific) pesticides, as well as a greater interest in the management of beneficial invertebrates such as predators and parasitoids (Hoque et al 2000, Mansfield et al 2006).However the major challenge to the sustainable use of Bt cotton is the risk of Helicoverpa spp. developing resistance to the Cry toxins (Fitt, 2000). Resistance to conventional Bt sprays has evolved in field populations of another moth (Plutella xylostella), Bt resistant strains of H. armigera have been generated in the laboratory, and alleles that confer resistance have been isolated from field populations (Downes et al 2010; Mahon et al 2007; Baker et al 2008). Concerns for Bt resistance are well founded, and much effort is being applied to developing and implementing resistance management strategies.