Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2008
Publication Date: 8/1/2008
Citation: Chen, W., Leopold, R.A., Harris, M.O. 2008. Cold Storage Effects on Maternal and Progeny Quality of Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae). Biological Control. 46(2):122-132. Interpretive Summary: Cold storage of insects is typically used for convenience and/or to economize when rearing them for either research for release in the control of other pests. It is imperative that the cold storage period be relatively innocuous to the insect because storage that is too long or at a temperature that is too low can cause damage to the parental and subsequent generations. Thus, this study quantified the length of time that could be used for cold storage of a parasitic wasp,Gonatocerus ashmeadi, when it was stored within its host, the eggs of the glassy-winged sharpshooter (GWSS). This egg parasitoid could be stored under a temperature regime that fluctuated daily from 4.5 to 7.5°C for 20 days without causing damage to wasps or to two subsequent generations of its progeny. If storage of the parents was 30 days or longer, survival, fertility and male sex ratio was adversely affected. Furthermore, parasitism and daily egg deposition by the first generation of female progeny was also reduced. These effects were not seen in the second generation, however. Our results indicate that this wasp can be stored for 20 days without loss of effectiveness or even longer during their mass propagation because wasps stored longer than 20 days do not transmit chilling damage to their progeny beyond the first generation. With these insects, the relatively short generation time of 10 days would allow for a fast elimination of the chilling-induced impairments.
Technical Abstract: This study determined the effects of cold storage on the survival and development of the mymarid wasp, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), when stored within host eggs of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) under a daily fluctuating temperature. The quality of the F1 and F2 generations of progeny derived from parents stored up to 50 d was also assessed by examining the incidence of parasitism and several reproductive and developmental parameters that indicate fitness. Parasitized eggs were stored for 20 d without detrimental affects on subsequent wasp survival, development or progeny quality. After 30 d of storage, wasp survival declined, developmental time was extended, and the fecundity of the F1 females decreased. Storage for 40 d severely damaged G. ashmeadi eggs because it not only yielded a 12% survival rate, 44% female sterility and increased the proportion of males by 155%, but also severely reduced parasitism and fecundity of the F1 females by 70% and 73%, respectively. No wasps emerged after 50 d of storage. Cold storage also affected the emergence pattern of the parental but not the F1 and F2 generations. Parental emergence was extended and the pattern consisted of two peaks after the initial onset. Analysis of several demographic parameters for the F1 and F2 populations further confirmed that the quality of the F1 progeny declined after 30 d of storage, and after 40 d it decreased significantly. The detrimental effects of cold storage on the parental and F1 generations do not extend to F2 generation. Our results indicate that short-term cold storage of parasitoid eggs could be used for maintaining and accumulating these parasitoids during mass propagation for release in a control program.