How an egg parasitoid responds to an unusual stinkbug oviposition behavior: the case of Gryon gonikopalense Sharma (Hymenoptera: Scelionidae) and Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae)

The phytophagous stinkbug pest Bagrada hilaris (Hemiptera: Pentatomidae) (= bagrada) buries single eggs in the ground, an exception among pentatomids. To investigate potential biological control strategies to mitigate the pest???s damages, an evaluation of the egg parasitoid Gryon gonikopalense (Hymenoptera: Scelionidae) as a biocontrol agent is ongoing. Its ability to detect and parasitize buried bagrada eggs could be a key factor in the short and long-term regulation of bagrada populations in the U.S. However, this foraging ability would be relevant only if bagrada mainly oviposits in the soil and if G. gonikopalense mainly parasitizes buried eggs, which is currently unknown. We assessed the oviposition pattern of bagrada in presence of three host plants (broccoli, white mustard and white rocket) and at three density levels (one, five or fifteen copulae). The prevalent oviposition site of bagrada was in the soil (92% of eggs) with no effect from the host plant neither the bagrada density. Eggs oviposited on mustard were mainly present on the top third, but no distribution pattern was observed on broccoli and white rocket. Gryon gonikopalense preferred parasitizing buried eggs (87% of total parasitism). It was also able to parasitize non-buried eggs whatever their location. Artificially increasing the number of non-buried eggs in the experimental design only resulted in a slight reduction in the parasitism of buried eggs (70%). As a result, this study highlights the relevance of using G. gonikopalense against bagrada as its specific foraging behaviour responds well to the main oviposition behaviour of its host.

Automated summary

This study evaluates the oviposition pattern of the phytophagous stinkbug pest Bagrada hilaris and the parasitism behavior of the egg parasitoid Gryon gonikopalense, highlighting the relevance of using G. gonikopalense as a biocontrol agent against B. hilaris based on its specific foraging behavior.