Behavioural responses of the egg parasitoid Trissolcus mitsukurii to the footprints of Halyomorpha halys and Nezara viridula

Abstract: Trissolcus mitsukurii is Asian egg parasitoids associated to different pentatomids
such as Halyomorpha halys. Adventive populations of T. mitsukurii were found in Northern
Italy showing a great impact on this pest, suggesting its exploitation as a biological control
agent (BCA) against H. halys. Releasing an exotic parasitoid requires investigating the
interaction BCA/environment, to avoid negative impacts on the entomofauna of the new
habitat. Trissolcus mitsukurii is mainly associated to Nezara viridula in its native area, hence, we investigated the female parasitoid’s ability to distinguish between naturally released cues of H. halys and N. viridula and compared it with the foraging behaviour of Trissolcus japonicus. A single female parasitoid was exposed to contact kairomones of both pests, to evaluate its modifications in orthokinetic and locomotory behaviour. Additionally, for T. mitsukurii, synthetic compounds simulating the cues of the two pentatomids were used. The results confirmed the preference of T. japonicus for H. halys while T. mitsukurii preferred N. viridula’s cues. The significance and consequences of these results in the biological control of H. halys in invaded areas are discussed.