Irradiation of Colorado potato beetle eggs - effect on parasitism by the wasp Edovum puttleri

In order to extend the period of time during which Colorado potato beetle ( CPB) eggs are suitable hosts for the parasitic wasp Edovum puttleri, CPB eg gs were subjected to various doses of gamma radiation between 2.5 x 10(4) a nd 5.0 x 10(6) rads prior to storage. For given storage times there were sp ecific doses of radiation that resulted in notably, but not significantly, higher percent absolute emergence (number of adult wasps that emerged/total number of CPB eggs exposed to E. putterli). After 7 days of storage, absol ute emergence was highest after exposure to 2.5 x 10(4), 4.4 x 10(5) and 1. 2 x 10(6) rads; and after 14 days of storage it was highest after exposure to 4.4 x 10(5) and 1.2 x 10(6) rads. For these doses of radiation and stora ge times, percent absolute emergence was equal to 40 +/- 8%, a value that o verlaps the range reported for CPB eggs that have not been irradiated. With increased storage time, absolute emergence dropped below 25%. While storag e of irradiated eggs had a negative effect on percent parasitization, it di d not affect the percentage of wasps that emerged (percent emergence = numb er of adult wasps that emerged/number of CPB eggs that were parasitized) fr om parasitized eggs. Percent emergence from non-irradiated eggs has been re ported to average 78%, while in these studies, percent emergence from irrad iated eggs typically was greater than 90%. Irradiation and storage of CPB e ggs had little effect on the weights of adult wasps, and these wasps appear ed to be active and in good condition. However, for unfed adult wasps, long evity decreased with increasing doses and storage times. Gamma irradiation of CPB eggs can be used to kill developing CPB embryos and to prevent deter ioration of the host eggs. Our results show that irradiation can increase t he period of time (from 72h to 14 days) in which CPB eggs are suitable host s for rearing E. puttleri.