Minimising damage of invertebrate pests in canola through a better understanding of the impact of beneficial insects

Natural enemies suppress populations of a wide range of insect herbivores thus most of the potential pest species are managed to below outbreak levels in field crops. The value of the ecosystem service of pest control is estimated at more than US$400 billion per annum worldwide (Costanza et al. 1997), but there is only limited quantitative information for the Australian situation. Despite interest, agricultural industries reporting to have adopted Integrated Pest Management strategies rarely utilise natural enemies. Furthermore, relatively few research studies examining the role of predators and parasitoids in cropping systems measure their impact. Most studies examine species presence and/or abundance and then qualitatively infer impact. This means it is difficult to make informed pest control decisions incorporating natural enemy activity in absence of ‘real’ evidence of their impact.