Testing semiochemicals from aphid,plant and conspecific: attraction of Harmonia axyridis

Abstract Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an invasive specie affecting the dynamics and composition of several guilds. Nowadays, no biological control method is available to reduce the populations of this harmful coccinellid. Attractants and semiochemicals seem to be the best alternative but only few studies have tested the impact of semiochemicals on this Asian lady beetle. In this work, through wind‐tunnel experiments, semiochemicals from aphids (Z,E‐nepetalactone, E]‐β‐farnesene, α‐pinene and β‐pinene), from coccinellids (‐]‐β‐caryophyllene) and from the nettle Urtica dioica L. were evaluated as potential attractants. The nettle volatile compounds (Z]‐3‐hexenol and E]‐2‐hexenal) were extracted using a Clevenger Apparatus^® and identified by headspace gas chromatography–mass spectroscopy. In the wind‐tunnel experiments, the main components of the aphid alarm pheromone as well as a component of the aphid sexual pheromone strongly attracted both sexes of the Asian lady beetle while (‐)‐β‐caryophyllene only attracted few individuals and had no impact on the males. The nettle extract as well as the (Z)‐3‐hexenol oriented both males and females to the odor source. The (E)‐2‐hexenal was shown to have no effect on females even if this green leaf volatile attracted males. Because Z,E‐nepetalactone was identified as the most efficient attractant in the wind‐tunnel experiments, this volatile was also tested in a potato field where H. axyridis has been showed to respond to this semiochemical. This study highlighted that Z,E‐nepetalactone orientated the Asian lady beetle H. axyridis under natural conditions, indicating that this volatile compound could certainly help for an efficient biological control approach against this invasive specie.