Volatiles Mediating Parasitism of Acrosternum arabicum Eggs by Psix saccharicola

Egg parasitoids have evolved various strategies to overcome the reliability-detectability problem and efficiently parasitize host eggs. Identifying what cues egg parasitiods use is important to increase their efficiency as biocontrol agents. In this study, we investigated the role of chemical cues from eggs and defensive compounds of the pistachio green stink bug (PGSB), Acrosternum arabicum (Wagner) (Hemiptera: Pentatomidae), on the foraging behavior and adult sex discrimination by the egg parasitoid Psix saccharicola (Mani) (Hymenoptera: Scelionidae). Parasitoid responses to volatiles from PGSB egg masses and sex-specific metathoracic gland (MTG) extracts were evaluated using a Y-tube olfactometer. We found that P. saccharicola was significantly attracted to volatiles emitted by egg masses and to MTG extracts from both sexes, but not to air or n-hexane controls. The parasitoids did not distinguish between male and female extracts or between clean air and n-hexane. Gas chromatography analysis revealed that the major components of MTG and egg masses extracts included various alkanes, aldehydes and esters. The compounds tridecane, ( E )-2-decenal, and ( E )-2-decenyl acetate, were identified as major components of the defensive secretions and eggs of PGSB. These findings suggest that PGSB volatile compounds influence parasitoid foraging behavior and offer insights into semiochemical-based biological control strategies against PGSB.