Transgenic Bt (Ingard) cotton has been the biggest step achieved so farm reducing insecticide applications to cotton in Australia. In the past two years there has been a 50% reduction in applications of insecticide to Helicoverpa on Ingard compared with conventional cotton (Long et al 1997). The reduction in sprays has been especially so with endosulfan in the early part of the cropping season when Bt production and efficacy of Ingard plants has been best. The technology has disappointed many growers because of marginal and variable efficacy. Although the full reasons for variability are not well understood, better efficacy is required to continue advances in non-chemical pest control over a greater area