Are sterile eggs a suitable substrate for the egg parasitoid Trissolcus japonicus?
Halyomorpha halys (Hemiptera: Pentatomidae – formerly EPPO Alert List) originates from Asia and has emerged as an invasive pest in North America and Europe in the 1990s and 2000s, respectively. Management of this pest is mainly by chemical insecticides however this is not very effective because of the high mobility of the pest and its ability to develop resistance to synthetic insecticides. Classical biological control of H. halys has been researched using the egg parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae). T. japonicus completes its larval development within a single egg. In the pests native range, the use of sentinel fertile egg masses to detect egg parasitoids is a useful method, however applying this method in the invasive range could lead to spread of the pest species. Using sterile sentinel eggs to record indigenous egg parasitoids is a potential alternative. The study used sterile eggs of H. halys obtained in three ways: (1) irradiation of fresh eggs with gamma rays (irradiated eggs), (2) eggs obtained by mating H. halys fertile females with irradiated males (sterile insect technique (SIT) eggs) and (3) refrigeration of fresh H. halys eggs at 8° C for a minimum of 14 days (refrigerated eggs, control). The proportion of emergence of parasitoids was different for the three egg types. The 1-day-old SIT eggs tested had parasitoid emergence rates above 90 % and had similar values for eggs tested which were up to 10 days old. For the eggs tested which were 20 days old, the proportion of emerged insects dropped to 75 %. In contrast, irradiated and refrigerated eggs had lower emergence of parasitoids from 1-day-old eggs tested (84 % and 78 %), while values were higher for 4 day old eggs tested and similar values for 7 day old eggs. For the eggs tested which were 20 days old, the proportion of emergence for both the irradiated and the refrigerated eggs dropped significantly compared to the SIT eggs. The results suggest that SIT and biological control could be combined for the biological control of H. halys.
Sources
Roselli G, Anfora G, Sasso R, Zapponi L, Musmeci S, Cemmi A, Suckling DM, Hoelmer KA, Ioriatti C, Cristofaro M (2023) Combining irradiation and biological control against Brown Marmorated Stink Bug: are sterile eggs a suitable substrate for the egg parasitoid Trissolcus japonicus? Insects 14, 654. https://doi.org/10.3390/insects14070654