Submitted to: Society for Cryobiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2005
Publication Date: 12/1/2005
Citation: Chen, W., Harris, M., Leopold, R.A. 2005. Refrigerated storage of glassy-winged sharpshooter eggs for use in the propagation of parasitoids [abstract]. Cryobiology. 51(3):406-407.
Technical Abstract: Releasing beneficial mass-reared insects as an alternative to using chemical pesticides or as an adjunct to chemical control can reduce environmental contamination and slow the progress of pesticide resistance. Having cold storage techniques to accumulate, store and ship beneficial insects is especially important when commercial entities are compelled to maintain production of insects as a profitable enterprise. We are developing cold storage methods to facilitate the mass-rearing of an egg parasitoid that attacks the glassy-winged sharpshooter (GWSS), an insect vector of Pierce’s Disease of plants. Currently, production of this parasitic wasp, Gonatocerus ashmeadi, also requires rearing the host pest insect since there is no artificial diet. Our previous study dealt with increasing the parasitoid shelf-life, by cycling the in-storage temperature for the parasitized GWSS eggs as opposed to holding it constant. When stored under the cycled regime of 4.5, 6.0, and 7.5ºC changing at 8 hr intervals for 10, 20 and 25 days, the emergence of wasps was 66%, 59% and 59%, respectively . However, the chilling sensitivity of the unparasitized GWSS eggs is significantly greater than that of the parasitoids. Holding GWSS eggs at 10ºC for 8 days is lethal, yet hatching occurs within 30 days if storage is at 13ºC . This study shows that killing eggs by placing at 2ºC for 5 days before storage at 10ºC is an acceptable means for preserving hosts for parasitism by the wasps. We determined parasitism rates and progeny emergence from GWSS eggs that developed 1, 3, 5, 7 or 9 days before storage up to 65 days and exposure to wasps. Parasitism and progeny emergence was highest for eggs stored as either 1- or 3-days-old. For these two groups, we also observed that there was a linear negative correlation between parasitism and progeny emergence vs. storage time. Parasitism and progeny emergence remained at acceptable levels for 1-day-old eggs up to 20 days in storage (90 and 76%) but after 65 days they fall to 45 and 28%, respectively. Preliminary quality assessment testing of wasps reared from 3-day-old eggs stored for 55 days showed that the lifespan and fecundity did not differ from that of wasps reared from untreated eggs. Complicating these studies is the situation that plants acceptable as egg-laying sites to the GWSS must be provided and that cuttings from these plants that hold the egg masses must remain viable throughout the cold storage period. Studies designed to determine whether the source of the reduction in host suitability occurring over time in storage is caused by plant or egg host deterioration are continuing. (Source of funding: USDA-APHIS and USDA-ARS, Conflict of interest: None declared)  R.A. Leopold, W. Chen, G.D. Yocum. In: M.A. Tariq et al. (Eds.) Proc. Pierce’s Disease Res. Symp. San Diego Dec.7- 10 (2004) 124.  R.A. Leopold, W. Chen, D.J.W. Morgan, G.D. Yocum. In: M.A. Tariq et al. (Eds.) Proc. Pierce’s Disease Res. Symp. San Diego Dec. 8-11 (2003) 221.