EFFECTS OF USING CONSTANT AND CYCLICAL STEPWISE-INCREASING TEMPERATURES ON PARASITIZED AND UNPARASITZED EGGS OF THE GLASSY-WINGED SHARPSHOOTER DURING COLD STORAGE

• Author(s): Leopold, Roger; Chen, Wenlong; Yocum, George;
• Abstract: Glassy-winged Sharpshooter (GWSS) egg masses, deposited on Euonymus japonica cuttings, were stored 1d after oviposition at either a constant temperature of 12C or under a regime that cycled daily, stepwise, (10, 11, 12, 13C @ 6h intervals) under an 8L:16D photoperiod. After storage under the cycled temperature regime for 15 and 20d, the hatch was 74 and 63%, respectively. Control hatch at 20d was about 80% and 50% after storage at a constant 12C. 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 30 to 40% 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 12C during the egg stage was about onehalf that of the control group, while the values for the 20d cycled group are yet to be determined. The rates of parasitism and emergence by Gonatocerus ashmeadi decreased with the length of time that 1-d-old unparasitized GWSS eggs were stored under the cycled regime. When held up to 25d in storage, parasitism by wasps and emergence of their progeny remained statistically similar. After 50d of storage, parasitism and progeny emergence dropped 30% and 20%, respectively. After a storage period of 25d, parasitoid emergence from parasitized eggs stored at a constant 4.5C was significantly higher than those stored similarly at 4C. The cycled stepwise-increasing temperature regime of 4.5, 6.0, and 7.5C changing at 8h intervals yielded a significantly higher parasitoid emergence than a cycled regime of 4, 6, and 8C. When stored under the regime starting at 4.5C, for 10, 20 and 25d, the emergence of wasps was 66%, 59% and 59%, respectively. Parasitized eggs stored under this regime for 80d produced no wasps.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium