Double trouble for the stink bug Bagrada hilaris: Harnessing sterile eggs to enhance parasitoid efficacy in its biocontrol

Invasive agricultural pests such as Bagrada hilaris, a major pest of Brassicaceae crops, pose significant threats to global food security and require innovative management strategies. This study explored the potential application of the synergism between the Sterile Insect Technique (SIT) and Classical Biological Control (CBC) for the implementation of Area-Wide Integrated Pest Management to control this pest. SIT involves the release of sterilized males to reduce pest populations by producing nonviable offspring. Eggs produced by females mated with sterilized males (SIT eggs) serve as a novel substrate for parasitization by the oophagous parasitoid Gryon aetherium, thereby enhancing the effectiveness of CBC. Our findings demonstrated that these sterile eggs exhibit extended viability for parasitization maintaining their suitability for up to 15 days under laboratory conditions, compared with untreated eggs, which are available for parasitization for up to a maximum of 5 days. Parasitoid emergence rates from SIT eggs were comparable to those from control eggs, with no significant impact on the sex ratio and the longevity of offspring. These findings may suggest favorable ecological implications for the application of the two techniques by presenting a scenario in which the population of the harmful species is subject to demographic control through the combined release of sterile males and the biological control agent. SIT eggs also have the potential as “long-life sentinel eggs” for monitoring the parasitoid population and identifying natural enemies already present in the invaded areas.