Combined effects of temperature and population density ofMyzus persicae(Hemiptera: Aphididae)on consumption byHarmonia conformis(Coleoptera: Coccinellidae)

Abstract

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 °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 °C. Furthermore, it would also be an ideal candidate for augmentative releases.

Functional response of larval and adult Coccinella septempunctata to eggs and larvae of Plutella xylostella on canola

“…Invertebrate predators play an important role in regulating the densities of insect pest populations in agroecosystems (Smout et al, 2010). Several factors, like variation in temperature (Holloway et al, 2021) In crop agroecosystems, densities of major pest species determine the consumption patterns and rates of generalist predators (Smout et al, 2010). Our study sheds light on the interactions between a commonly encountered predator in canola, C. septempunctata, and the invasive pest P. xylostella.…”

“…Invertebrate predators play an important role in regulating the densities of insect pest populations in agroecosystems (Smout et al., 2010). Several factors, like variation in temperature (Holloway et al., 2021) and prey stage preferences (de Oliveira Pimenta et al., 2020), can impact the functional response of insect predators. The results of our study indicate that both adults and larvae of the predaceous beetle C. septempunctata have specific preferences for P. xylostella life stages.…”

“…Other P. xylostella predators, including earwigs, E. annulipes (Nunes et al., 2020) and the nabid bug, N. kinbergii (Ma et al., 2005) show similar patterns of increased attack and consumption of larvae as temperatures rise between 20 and 35 °C. The common spotted ladybird beetle, Harmonia conformis (Boisduval) consumes more Myzus persicae (Sulzer) aphids at temperatures over 25 °C, and consumption peaks at 32 °C (Holloway et al., 2021).…”