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

Abstract

<p>For <i>Helicoverpa punctigera</i>(Wallengren), and to a lesser extent <i>Helicoverpa armigera</i>(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 <i>H. punctigera</i> and <i>H. armigera</i>, over about 2.4 million km2in inland Australia. Of 1976 samples, <i>H. punctigeralarvae</i> 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. <i>H. armigeralarvae</i> 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 <i>H. punctigera</i> samples. <i>H. punctigeralarvae</i> 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 <i>H. punctigera</i> 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.</p>