Evaluation of three cold storage methods of Bagrada hilaris (Hemiptera: Pentatomidae) and the effects of host deprivation for an optimized rearing of the biocontrol candidate Gryon gonikopalense (Hymenoptera: Scelionidae).
The cold storage of host eggs has been utilized in the production of egg parasitoids used in biological control programs. However, similar stockpiling methods can lead to various responses depending on the parasitoid species considered. Hence, standardization of storage methods is difficult. The egg parasitoid Gryon gonikopalense Sharma, is currently being evaluated as a biocontrol agent of Bagrada hilaris (Burmeister), an invasive pest on Brassicaceae crops in the Americas. In this study, we investigated cold storage methods and the effect of host deprivation on G. gonikopalense in order to optimize its rearing process. Laboratory tests were conducted with bagrada bug eggs stored under three temperature treatments (-20°C, 5°C, 13°C) and six durations (one week to three months). In addition, we assessed the effect of host deprivation on parasitoid fecundity and progeny development. Bagrada bug eggs stored at 5°C up to one month allowed three and nine times more parasitism than eggs stored at 13 and -20°C respectively. Progeny emergence rate was also the best with eggs stored at 5°C (94.1%) while eggs stored at 13 and -20°C led to 77.7 and 89.2% of emergence respectively. However, the different storage treatments led to similar longevities and body lengths for male and female progeny. In addition, G. gonikopalense did parasitize bagrada eggs after 60 days of host deprivation, but fecundity was reduced by 84%. The results can be used to optimize bagrada bug egg production for use in laboratory and/or field experiments and improve G. gonikopalense rearing and production.