Using regression analysis the early season dynamics of Helicoverpa punctigera (Wallengren) were determined from long series of light trap catches (10–19 years) from three sites in Australia (Narrabri and Trangie in New South Wales, and Turretfield in South Australia). The size of the second spring generation (G2, the one causing major pest problems in summer cropping regions) was strongly related to the size of the first spring generation (G1). In most cases, rainfall in early winter had a positive influence on the size of G2, whereas rainfall in spring had a negative effect. Regressions were found to account for 49 to 93% of the annual variation in G2, depending on site. The use of light trap catches and weather data to forecast pest levels from a few months to a few weeks in advance is discussed, along with the improved understanding of early season H. punctigera dynamics.
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Maelzer et al. (1996) studied this question.