ABUNDANCE OF OVERWINTERING PUPAE AND THE SPRING GENERATION OF HELICOVERPA SPP, (LEPIDOPTERA, NOCTUIDAE) IN NORTHERN NEW-SOUTH-WALES, AUSTRALIA - IMPLICATIONS FOR PEST-MANAGEMENT

In 1987 cotton supported the highest densities of pupae with an estimated population of 556 million individuals, while <5 million in total were found under residues of sunflower, sorghum, and grain legumes. In 1988, the population of pupae under cotton (24 million) was only 5% of that in 1987, and more were found under sunflower residues (11 million). Levels of parasitism and other mortality were lower in pupae from under cotton than other crops, and a high proportion of pupae (40-50%) survived to emergence. Virtually all overwintering pupae located in the study area have been H. armigera. The regular spring reappearance of H. punctigera in the Namoi-Gwydir area, and possibly other Australian cropping areas, must therefore derive largely from immigrants. For H. armigera 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. -from Authors