Organisms with potential to assist in the control of Helicoverpa armigera in Australian cotton production systems

Abstract

Helicoverpa armigera was once considered the most important insect pest to Australian cotton production. The introduction of genetically modified cotton altered this status and made this insect pest control less chemically dependent, but resistance to the insecticidal compounds expressed in genetically modified cotton has evolved in laboratory-reared H. armigera populations and is shown to exist in natural populations. Preventing the development of resistance in field populations is complicated by the over wintering of potentially resistant individuals in the soil. Biocontrol may assist in reducing the population of resistant individuals. Several projects investigating the ecology of Australian cotton highlighted the existence of several native organisms with ability to limit the growth or utilise H. armigera as a host. The work reported here set about establishing the presence of such organisms in Australian cotton soils by recovering them from soil and farm-collected H. armigera that exhibited abnormal growth, disease or death. The recovered organisms were identified as the fungi Lecanicillium lecanii, Actinomucor elegans and several Aspergillus species. L. lecanii was subsequently shown to reduce moth emergence to 56% of the larvae to which it was applied. We also identified a species of Rhabditis nematode, which killed 34% of the larvae to which it was applied and reduced moth emergence to 28%. In light of these observations these organisms are reported as potential candidates for biological control of H. armigera.