Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Catch me if you can: novel foraging behavior of an egg parasitoid, Gryon gonikopalense, against the stinkbug pest, Bagrada hilaris.

Abstract

Host detection and parasitism by egg parasitoids involve host chemical recognition, spatial overlapping, and the ability to overcome physical barriers. Within the context of importation biological control, we examined the potential of Gryon gonikopalense (Hym.: Scelionidae), against the stinkbug pest, Bagrada hilaris (Hem.: Pentatomidae). Bagrada is invasive in the Americas where it negatively impacts cruciferous cropping systems. Within Pentatomidae, bagrada possesses a unique behavioral trait in that its eggs are oviposited buried. Our study aimed to evaluate the capacity of G. gonikopalense to respond to bagrada ovipositional behavior. We showed that G. gonikopalense exhibits a well-adapted foraging behavior observed by tracking and successfully parasitizing 2 mm-deep buried bagrada eggs, which was further supported by video recordings. Four conditions of egg detectability by parasitoids (free eggs, naturally buried eggs, and manually buried with disturbed or clean sand) and foraging durations were tested in Petri dishes. The parasitism rate of 100% was obtained after 72 hours for both free and naturally buried eggs; a rate of 71% was obtained after 2 h with free eggs. There was no significant difference concerning the parasitoid success rate (< 40%) with manually buried eggs. Our data suggested that host egg detection was based on chemical cues since parasitism success was reduced by up to 20% when eggs were manually buried under a clean substrate or a substrate previously used for oviposition but disturbed. Gryon gonikopalense can overcome both the egg detection and physical barrier constituted by the sand to parasitize the pest despite a reduced number of progeny produced.