An effective cold storage method for stockpiling Halyomorpha halys (Hemiptera: Pentatomidae) eggs for field surveys and laboratory rearing of Trissolcus japonicus (Hymenoptera: Scelionidae).
An effective stockpiling method for egg masses of the invasive brown marmorated stink bug (Halyomorpha halys [Stål]; Hemiptera: Pentatomidae) would be useful for rearing and field studies of its egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae). The current method of stockpiling H. halys egg masses at subzero temperatures has lethal and sublethal fitness consequences for T. japonicus. Our goal was to test the efficacy of refrigeration as an alternative method for stockpiling H. halys eggs. We show that parasitoid emergence from egg masses refrigerated at 8°C for up to two months before parasitism is higher than from frozen egg masses. In addition, 8°C cold storage usually had minimal or no sublethal fitness effects on emerging T. japonicus. Only after two months of host egg refrigeration did the emergence of T. japonicus begin to decrease significantly (by ~10% relative to untreated viable egg masses), whereas egg masses previously frozen at -80°C had a ~59% reduction in parasitoid emergence after 14 d of storage. Refrigerated egg masses that were subsequently exposed to a range of field-realistic average temperatures were still suitable for T. japonicus parasitism after 7 d. Our results demonstrate that refrigeration at 8°C, while resulting in complete mortality of H. halys embryos after 10 d, are more suitable for T. japonicus parasitism than those stored at -80°C. The quantity and quality of H. halys eggs that can be stockpiled with this method could facilitate T. japonicus laboratory colony maintenance, field monitoring, and releases.