Host plants for Helicoverpa spp. in inland Australia: Impacts of the Millennium Drought

As part of a thirty year study of the ecology of Helicoverpa spp. in inland Australia (see abstract for the presentation by Peter Gregg) we have recorded several characteristics of the vegetation, including the presence or absence of known host plants for Helicoverpa spp. at over 3,300 randomly selected sites in inland Australia. This has provided a comprehensive picture of short and long term changes in host plant abundance in different habitats (floodplains, grasslands, acacia shrublands, chenopod shrublands, sandy deserts and stony downs). The Millenium Drought (2001-2009) severely affected southeast Australia where it was the worst drought in recorded history (Van Dijk et al. 2013; Water Resour. Res. 49, 1040-1057). It significantly affected host plant abundance in the acacia shrublands and to a lesser extent in the grasslands. Floodplains, sandy deserts, stony downs and chenopod shrublands were not affected. Of the sites surveyed in the acacia shrublands, about 61% supported host plants pre-drought compared with about 28% post-drought (P<0.001). In the grasslands, significantly more sites with host plants were also recorded (49%) before the drought than after the drought (35%) (P=0.018). In addition, the abundance of hosts was reduced at many sites, and good host plants were often replaced by plants which supported fewer larvae. This presentation will illustrate the impact of a major medium-term climate change (the Millenium Drought) on the host plants, and how those impacts may affect pest management.