Reproductive diapause in annual bluegrass weevil Listronotus maculicolis (Coleoptera: Curculionidae)

The annual bluegrass weevil, Listronotus maculicolis, is a destructive golf turfgrass pest in the northeastern US and Eastern Canada. The weevils overwinter as adults in leaf litters underneath trees and shrubs adjacent to the active area, and move to the nearest short mown turf to feed and lay eggs in spring. When they overwinter, they undergo reproductive diapause, during which the development of reproductive organs ceases until the diapause terminates. Understanding the factors triggering diapause termination is critical to the timely management of this pest. For this purpose, we tested the response to food and investigated the effect of temperature, food and cooling period on the development of reproductive organs in L. maculicolis. The weevils were dissected weekly for 4 weeks to measure the length of ovary and width of germaria in female adults, and widths of seminal vesicle and accessary gland and diameter of prostate gland in male adults. Food was essential to the organ development, and the weevil started to feed within 3 days after being transferred from 6/4 °C (Day/night: LD 10:14) to room temperature (22 °C). However, temperature played a more important role in triggering the termination of reproductive diapause, whereas a cooling period during diapause accelerated and synchronized the diapause termination process. Oviposition also significantly differed under various temperature and photoperiod regimes.