Low Temperature Storage of Telenomus remus (Nixon) (Hymenoptera: Platygastridae) and its Factitious Host Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae)

Abstract

We conducted three bioassays to evaluate the effect of low-temperature storage of eggs (host) and pupae and adults (parasitoid) on the biology and parasitism capacity of the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). Viable stored Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs were parasitized to the same degree or even higher than fresh eggs when stored until 14 days at 5°C or until 21 days at 10°C. In contrast, the percentage of parasitized sterilized eggs was equal to the control only when stored for 7 and 14 days. Survival of T. remus pupae declined with storage time at both studied temperatures (5 and 10°C). However, after 7 days of storage, survival of pupae was still 86.3 and 64.9% at 10 and 5°C, respectively. The number of adult male survivors remained similar until the fourth storage day at both 5 and 10°C. In contrast, female survival did not differ until day 8 at 10°C or day 6 at 5°C. Parasitism capacity of stored adults was not altered by storage compared with the control. Therefore, we conclude that the maximal storage time at 10°C is 21 days for viable C. cephalonica eggs and 7 days for T. remus pupae, while parasitoid adults should not be stored for more than 4 days at either 5 or 10°C.

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

“…Our results showed that while the placement of viable H. halys egg masses at a relatively high average temperature (22.9ºC) for 4-7 days had a negative impact on parasitism levels and fitness parameters of emerging parasitoids, these reductions in parasitoid emergence and fitness were not observed for refrigerated eggs or in either treatment at a lower average temperature (13.4ºC). The decrease in T. japonicus emergence and body weight and the increase in development time with increasing physiological age of viable H. halys eggs is in agreement with results from other studies (Qiu 2007;Yang et al 2018). Since the H. halys embryo is developing in untreated eggs (and this progresses faster at warmer temperatures), host resources and quality for immature parasitoids are likely declining (Barrett and Schmidt 1991;Vinson 2010;Skillman et al 2017).…”

Use of Low Temperature Storage to Preserve Host and Parasitoid to Improve the Rearing of Telenomus podisi (Hymenoptera: Platygastridae) on Euschistus heros (Hemiptera: Pentatomidae) Eggs

“…An important finding of our study is that the sex ratio of T. podisi offspring was not affected by storage of E. heros eggs at any of the three tested temperatures and generally remained at 0.86 or higher, with a minimum of 0.72. Higher numbers of females are considered important in ABC because males do not contribute directly for parasitism-induced declines in pest populations (Navarro 1998;Queiroz et al 2017). A similar sex ratio was considered to be of acceptable quality in mass production of other egg parasitoids such as Trichogramma pratissolii (Querino & Zucchi) (Hymenoptera: Trichogrammatidae) (van Lenteren 2003).…”

“…Apart from host availability, one of the major difficulties in mass rearing of egg parasitoids in the laboratory is the necessity of releasing them immediately after adult emergence, due to the adults' short life span (Queiroz et al 2017). Although T. podisi has a longer life span than T. remus, this still applies to both species.…”

“…Low production costs are essential for making biological control agents including T. podisi economically viable tools in ABC (Bernardo et al 2008, Macedo et al 2006, Carvalho et al 2008, Colinet & Boivin 2011Queiroz et al 2017). Therefore, appropriate storage techniques are needed to increase the parasitoids' shelf life (Macedo et al 2006;Queiroz et al 2017). Shelf life increase is often inversely proportional to production costs and can therefore be decisive for the success or failure of ABC (Macedo et al 2006;Queiroz et al 2017).…”

“…Therefore, appropriate storage techniques are needed to increase the parasitoids' shelf life (Macedo et al 2006;Queiroz et al 2017). Shelf life increase is often inversely proportional to production costs and can therefore be decisive for the success or failure of ABC (Macedo et al 2006;Queiroz et al 2017).…”