The prospects for cryopreservation of noctuid eggs in the mass production of Trichogramma spp.

Successful long-term cryopreservation of lepidopteran eggs for the mass production of parasitoids of the genus Trichogramma Westwood (Hymenoptera: Trichogrammatidae) requires a more tolerant species to withstand ultra-low temperatures. We compared the viability of eggs of Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae) and Mythimna sequax Franclemont (Lepidoptera: Noctuidae), cryopreserved in liquid nitrogen, and evaluated the viability of M. sequax eggs to support the large-scale production of high-quality Trichogramma species. The presence of anti-freezing metabolites in lepidopteran eggs was detected and quantified by ¹H nuclear magnetic resonance (NMR) spectroscopy. Parasitism by Trichogramma pretiosum Riley of M. sequax eggs stored for 30 days was significantly higher (84.2%) in comparison to A. gemmatalis (6.7%). The ¹H NMR spectrum showed that the amounts of anti-freezing metabolites maltodextrin and trehalose were greater in M. sequax eggs, a possible explanation for their suitability to cryopreservation in comparison to A. gemmatalis. Eggs of M. sequax cryopreserved for up to 12 months maintained a mean rate of parasitism between 80 and 90% by Trichogramma atopovirilia Oatman and Platner and T. pretiosum, the latter declining to 79% after 12 months. Both Trichogramma species can exploit long-term storage of M. sequax eggs at ultra-low temperatures, without any apparent fitness penalty to the first generation. This is the first record of eggs of a noctuid species being cryopreserved for up to one year and remaining susceptible to parasitism by Trichogramma species. This procedure should enable large-scale production of hosts with high nutritional quality, and the production of parasitoids that is synchronized better with their use as biological control agents in annual crops.