Parasitism of frozen Halyomorpha halys eggs by Trissolcus japonicus: applications for rearing and experimentation

An effective cold storage method for stockpilingHalyomorpha halyseggs for field surveys and laboratory rearing ofTrissolcus japonicus

“…On-demand production of parasitoids can be facilitated by stockpiling host material in cool or freezing temperatures, which may either extend or terminate host development (Mahmoud and Lim 2007;Ayvaz and Karabörklü 2008) depending on the temperature and the duration of storage. Different host insect life stages (Ayvaz and Karabörklü 2008;Tang et al 2014;Forouzan et al 2018) can be cold-stored across a range of temperatures, including above-freezing (hereafter, "refrigeration"; typically 2 -10°C) and sub-zero (hereafter "freezing"; as low as -80°C) temperatures (Mainali and Lim 2013;Spínola-Filho et al 2014;McIntosh et al 2019). Cold storage durations for host material in past studies have varied from relatively shortterm (less than 7 days), intermediate amounts of time (weeks to months) or much longer time frames (e.g.…”

“…Cold storage durations for host material in past studies have varied from relatively shortterm (less than 7 days), intermediate amounts of time (weeks to months) or much longer time frames (e.g. > 1 year) (Kivan and Kilic 2005;Spínola-Filho et al 2014;McIntosh et al 2019). In many cases, cold storage treatments are an effective strategy for extending the period of availability of host material for research or production of parasitoids for releases against pest insects (Orr 1988;Goldson et al 1993;Rathee and Ram 2018).…”

“…The consequences of reduced host suitability for parasitoids reared on cold-stored hosts can take the form of (i) reduced acceptance of cold-stored hosts by parasitoids, (ii) lethal effects on developing parasitoids in accepted host eggs, or (iii) sublethal effects on developing parasitoids in accepted host eggs. Lethal effects, whereby cold storage reduces parasitoid offspring emergence, are often due to reduced host quality caused by cold storage (Mahmoud and Lim 2007;Mainali and Lim 2013;McIntosh et al 2019). Sub-lethal effects of cold storage do not kill immature parasitoids, but subsequently cause changes in their physiology, morphology or behaviour (Mahmoud and Lim 2007;Mainali and Lim 2013;McIntosh et al 2019).…”

“…Lethal effects, whereby cold storage reduces parasitoid offspring emergence, are often due to reduced host quality caused by cold storage (Mahmoud and Lim 2007;Mainali and Lim 2013;McIntosh et al 2019). Sub-lethal effects of cold storage do not kill immature parasitoids, but subsequently cause changes in their physiology, morphology or behaviour (Mahmoud and Lim 2007;Mainali and Lim 2013;McIntosh et al 2019). Parasitoid traits that can be affected by cold storage of host material include development time, behaviours related to host acceptance (e.g.…”

“…A stockpiling technique for H. halys eggs for parasitism by T. japonicus would be useful for "sentinel egg mass" field studies investigating T. japonicus distribution and abundance, as well as laboratory colony maintenance and production of larger numbers of parasitoids for field releases. Currently, deep-freezing H. halys egg masses at -80°C is the main method used for stockpiling in support of laboratory and field studies (Abram et al 2017;McIntosh et al 2019). In some earlier studies, deep-freezing of H. halys eggs was observed to increase the development success of some native European and North American parasitoids, although effects were inconsistent across parasitoid species (Haye et al 2015;Herlihy et al 2016;Abram et al 2017).…”