Sources of volatiles mediating host location behaviour of Glypta haesitator, a larval parasitoid of Cydia nigricana

Abstract The pea moth Cydia nigricana Fabricius (Lepidoptera: Tortricidae) is a major pest of pea, and one of its natural enemies is the parasitoid wasp Glypta haesitator Gravenhorst (Hymenoptera: Ichneumonidae). This study aimed to identify semiochemical sources exploited by G. haesitator females in their search for an oviposition site. Observations in a wind tunnel demonstrated that G. haesitator females were attracted by larval frass of C. nigricana , wing scales of adult pea moths, and herbivore-induced plant volatiles of pea plants (HIPVs). Twenty-four volatiles emitted by those sources were identified, eight of which elicited antennal responses in the female wasps. Behavioural importance of these eight compounds was verified in the wind tunnel testing a synthetic blend for G. haesitator attraction. We also evaluated parasitoid species and rates of parasitism on overwintered pea moth cocoons in two pea-growing regions in Germany and Norway. The parasitism rates were as high as 29% for G. haesitator , showing that this species is an important biological control agent of pea moth. Total parasitism in the regions was up to 71%. The overall results are discussed considering applied aspects of pea moth management combining semiochemicals and conservation biological control strategies related to natural parasitoid populations.