Intraguild predation of non-coccinellid aphid natural enemies by Harmonia axyridis: prey range and factors influencing intraguild predation

Although Harmonia axyridis has been recorded as an intraguild predator of various aphidiophagous coccinellids, little is known about its interactions with other aphid natural enemies. We assessed the intraguild interactions between H. axyridis and four non-coccinellid aphid natural enemies (two species of parasitoid plus a lacewing and hoverfly). Petri dish trials showed that H. axyridis is an intraguild predator of 2nd instar lacewing (Chrysoperla carnea) larvae but not 3rd instar larvae . Predation of developing Aphidius ervi and Praon volucre parasitoid mummies was only observed occasionally. Experiments at a larger spatial scale and in more complex environments are needed to determine whether these interactions are ecologically important. The effect of alternative prey density, prey species and host plant species on intraguild predation was assessed. Preliminary results suggest that the density of alternative prey (pea aphid) does not affect predation of 2nd instar C. carnea by H. axyridis on single bean plants. Field sampling is being done to investigate the effect of habitat and season on the interactions between aphids, their native natural enemies and H. axyridis.