Combined effects of temperature and population density of Myzus persicae (Hemiptera: Aphididae) on consumption by Harmonia conformis (Coleoptera: Coccinellidae)

BACKGROUND The green peach aphid Myzus persicae is a major pest of many crops around the world, causing direct damage and acting as a vector for several viruses. This species has developed resistance to several insecticides, resulting in a greater emphasis on nonchemical methods of control. The aphidophagous ladybird, Harmonia conformis, is one of several species to predate on this pest. H. conformis is native to Australia, but has been exported to New Zealand, the USA and Europe as a biological control agent for horticultural pests and has now become established in several regions. Despite these introductions, the ability of H. conformis to predate on M. persicae has not yet been quantified. To address this knowledge gap, we measured the potential success of this natural enemy and its functional response over a range of temperatures. RESULTS H. conformis displayed a Type II response over all temperatures assessed. The peak temperature for voracity was 32 degrees C, with a potential maximum daily predation rate of 204 aphids. Consumption of aphids by H. conformis on canola plants within a glasshouse was less than predicted from the laboratory-generated models. However, consumption increased significantly with increasing density of M. persicae. CONCLUSION H. conformis can contribute markedly to aphid suppression and could be incorporated into integrated pest management systems which rely on natural enemies, particularly during spring when temperatures increase above 25 degrees C. Furthermore, it would also be an ideal candidate for augmentative releases.

Automated summary

The ladybird Harmonia conformis has a significant impact on the suppression of the green peach aphid, especially at higher temperatures. The predation rate of H. conformis increases with the density of M. persicae, showing potential for inclusion in integrated pest management systems.