Effects of Dormancy and Photoperiod on Alfalfa Weevil (Coleoptera: Curculionidae) Reproductive Diapause

Alfalfa weevil, Hypera postica (Gyllenhal), adults reared as larvae in the laboratory under an 8-h photophase were subjected to three storage conditions and two photoperiods to determine their effects on female reproductive diapause and fecundity. Contrary to previous reports, weevils reared in the laboratory as larvae and adults under a short-day photoperiod remained in a partial reproductive diapause. Newly-emerged weevil adults subjected to a 5-wk dormant period followed by an 8-h photophase had a rate of oviposition nearly twice that of adults reared under an 8-h photophase without a dormant period. Adults reared under a 15-h photophase after the dormant period also remained in a partial reproductive diapause. Results demonstrate that alfalfa weevil reproductive diapause is influenced by dormancy (an inactive state) and photoperiod. This is the first report of an efficient method to break reproductive diapause in the alfalfa weevil which will enable continuous production of nondiapausing laboratory-reared weevils for research and mass production of predators and parasites for biological control.