Integration of a predator and a pathogen with transgenic Bt cotton in controlling 'Helicoverpa armigera'

Abstract

Transgenic Bt ('Bacillus thuringiensis' Kurstaki) cotton (Bollgard II®) was introduced in Australia against two major lepidopteran insect pests of cotton, 'Helicoverpa armigera' (Hübner) and 'Helicoverpa punctigera' (Wallengren) (Lepidoptera: Noctuidae). This reduced the use of synthetic insecticides substantially. However, there are reports of surviving 'Helicoverpa' spp. on Bollgard II® cotton in Australia. Although surviving larvae did not have a greater incidence of alleles conferring resistance to the Cry toxins in Bollgard II® cotton, there have been significant changes in the frequency of these alleles. Bollgard II® cotton therefore should be regarded as a component of IPM rather than a tactic upon which the growers can rely solely. Numerous natural enemies of insect pests are present in Australian cotton fields. To use them successfully, we need to understand how they interact with Bt cotton. In this PhD project one predator, green lacewing ('Mallada signatus' Schneider (Neuroptera: Chrysopidae)) and a novel entomopathogenic fungus were tested for their ability to reduce survival of 'H. armigera' on Bollgard II® cotton.