INDUCTION OF REPRODUCTIVE DIAPAUSE IN EMPOASCA-FABAE (HOMOPTERA, CICADELLIDAE) AND ITS IMPLICATIONS REGARDING SOUTHWARD MIGRATION

To determine if the phenology of Empoasca fabae (Harris) includes reproductive diapause, the progeny of females collected in Louisiana were reared under various conditions of photoperiod and temperature. Adults were paired, and the oviposition of each female was recorded for 40 d at 4-d intervals. Short day le resulted in a lower proportion of E. fabae ovipositing, a longer preoviposition period, decreased rate of oviposition. These responses constitute evidence for the induction of reproductive diapause. To determine whether reproductive diapause is expressed in northern populations in the field, 4th and 5th instars from New York state were reared at intervals through summer and fall, and tested for response to photoperiod. The proportion of E. fabae females becoming reproductively mature decreased as the season progressed. Less than 50% of field-reared females became gravid after mid-July. In the laboratory reproductive maturation in held-reared females was retarded by short day lengths, but not by long day lengths. The induction of reproductive diapause in late summer supports the hypothesis that E, fabae engages in a diapause-mediated southward migration to its overwintering area.