|Chen, Wenlong - DEPT ENT, NORTH DAKOTA SU|
Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: November 12, 2004
Publication Date: December 1, 2004
Citation: Leopold, R.A., Chen, W., Yocum, G.D. 2004. Effects of using constant and cyclical stepwise-increasing temperatures on parasitized and unparasitzed eggs of the glassy-winged sharpshooter during cold storage. In: Proceedings of the CDFA Pierce's Disease Control Program Research Symposium, December 7-10, 2004, Coronado, California. p. 124-127. Technical Abstract: Glassy-winged sharpshooter (GWSS) egg masses, deposited on Euonymus japonica cuttings, were stored 1 day after oviposition at either a constant temperature of 12 deg. C or under a regime that cycled daily, stepwise, (10, 11, 12, 13 deg. C at 6h intervals) under an 8L:16D photoperiod. After storage under the cycled temperature regime for 15 and 20 days, the hatch was 74 and 63%, respectively. Control hatch at 20 d was about 80% and 50% after storage at a constant 12 deg. C. The survival to adulthood, length of the nymphal stage, and the fecundity of the adult females were all affected by cold storage during the egg stage, regardless whether the temperature was held constant or cycled. Survival to adulthood was reduced 40 to 50% and the time required to complete the nymphal stages was significantly longer than the control. The number of eggs oviposited by females and length of the ovipositional period after being held at 12 deg. C during the egg stage was about one-half that of the control group, while the 20d cycled group has yet to be determined. The rates of parasitism and emergence by Gonatocerus ashmeadi decreased with the length of time that 1-day-old GWSS eggs were stored under the cycled regime. When held up to 25 days in storage, parasitism by wasps and emergence of their progeny remained statistically similar. After 50 d of storage, parasitism and progeny emergence dropped 30% and 20%, respectively. After a storage period of 25 days, parasitoid emergence from the parasitized eggs stored at a constant 4.5 deg. C was significantly higher than those stored similarly at 4 deg. C. The cycled stepwise-increasing temperature regime of 4.5, 6.0, and 7.5 deg. C changing at 8h intervals yielded a significantly higher parasitoid emergence than a cycled regime of 4, 6, and 8 deg. C. When stored under the regime starting at 4.5 deg. C, for 10, 20 and 25 days, the emergence of wasps was 66%, 59% and 59%, respectively. Eggs stored 80 days produced no wasps.