Long-term changes in the numbers of Helicoverpa punctigera (Lepidoptera: Noctuidae) in a cotton production landscape in northern New South Wales, Australia

Two noctuid moths, Helicoverpa punctigera and Helicoverpa armigera, are pests of several agricultural crops inAustralia, most notably cotton. Cotton is a summer crop, grownpredominantly in easternAustralia. The use of transgenic (Bt) cottonhas reduced the damage caused by Helicoverpa spp., but the development of Bt resistance in these insects remains a threat. In the past, large populations of H. punctigera have built up in inland Australia, following autumn- winter rains. Moths have then migrated to the cropping regions in spring, when their inland host plants dried off. To determine if there have been any long- term changes in this pattern, pheromone trapswere set for H. punctigera throughout a cropping landscape in northernNewSouthWales from1992 to 2015. At least three generations of mothswere caught fromspring to autumn. The 1st generation (mostly spring migrants) was themost numerous. Trap captures varied between sites and decreased in time, especially for moths in the 1st generation. Nearby habitat type influenced the size of catch and there was some evidence that local weather also influenced the numbers of moths caught. There was no correlation between trap catches in the cropping region and rainfall in the inland. In addition, therewas little evidence that Bt cotton has reduced the abundance of H. punctigera at landscape scale. The apparent decline in the number of presumably Bt susceptiblemoths arriving each spring inthe cropping regions frominland habitats is of concern in relation to the management of Bt resistance.