Abundance of Overwintering Pupae and the Spring Generation of Helicoverpa spp. (Lepidoptera: Noctuidae) in Northern New South Wales, Australia: Implications for Pest Management

Abstract

Helicoverpa armigera (Hübner) and H. punctigera (Wallengren) are major pests of cotton and other field crops in Australia. We measured the abundance, species composition, and survival of overwintering pupal populations under residues of autumn crops over two seasons (1987 and 1988) in the Namoi-Gwydir region, Australia. In 1987, cotton supported the highest densities of pupae with an estimated population of 556 million individuals, while H. armigera. The regular spring reappearance of H. punctigera in the Namoi-Gwydir area, and possiblyother eastern Australian cropping areas, must therefore derive largely from immigrants produced elsewhere. For H. armigera, the phenology of adult appearance in traps and emergence from diapause of local overwintering pupae suggest that spring populations consist of moths from local overwintering populations and from immigrant origin. This hypothesis is consistent with patterns of pyrethroid resistance measured in overwintering populations and during the spring of both seasons.