Host plants and habitats of Helicoverpa punctigera and H. armigera (Lepidoptera: Noctuidae) in inland Australia

For Helicoverpa punctigera(Wallengren), and to a lesser extent Helicoverpa armigera(Hübner), native hostplants in non-cropping regions of inland Australia are believed to be contributors to populations which migratein spring to infest cropping regions of south-east Australia, and southwestern Australia. Non-crop hosts were sam-pled using sweep nets in 71 survey trips in 19 years between 1987 and 2017 for larvae of H. punctigera and H. armigera, over about 2.4 million km2in inland Australia. Of 1976 samples, H. punctigeralarvae were presentin 50.5%, distributed throughout the study area. Larvae were found on 106 host plant species in 24 families, in-cluding 61 new host records. H. armigeralarvae were found on 33 plant species from eight families, including1 4 new host records. However, only 4.3% of samples were positive for this species, and they were mostly inthe east of the study area and had fewer larvae than the positive H. punctigera samples. H. punctigeralarvae were found in each of six habitats, being, in order of mean numbers per sample: sandy deserts> flood plains > mulga,grasslands and salt bush > stony downs. Host status was determined for both species by plotting relative incidence against relative abundance, and the good hosts for H. punctigera differed between habitats. We discuss the value and limitations of this approach for identifying key hosts in broad scale population dynamics, and primary hostswhich may have close co-evolutionary histories with the insects.