Since the introduction of a resistance management program in 1983, frequencies of pyrethroid resistance in Helicoverpa armigera (Hiibner) in areas of the Namoi and Gwydir valleys, New South Wales, in which cotton is grown, have increased each summer then declined between autumn and late spring. We examined two possible causes for this decline-immigration of susceptible adults and selective mortality of resistant pupae. Diapausing pupae were collected during winter and spring, and larval populations were collected in spring 1987 and 1988, in and around the Namoi-Gwydir region. In winter 1987, large populations of pupae with resistant frequencies >53% were found under crop residues of cotton. Smaller populations of pupae were observed under maize and pigeon pea; the resistance frequencies were <55%. Selective mortality in pupae could not account for the presence of populations of larvae with resistant frequencies <35% in spring 1987. We propose that immigration of susceptible moths is the most likely cause in the annual decline in resistance frequencies. Results from the 1988 season are consistent with this hypothesis.
Document Type: Research Article
Publication date: October 1, 1990
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.