Effects of photoperiod and temperature on pupal diapause induction of grape berry moth Lobesia botrana

The grape berry moth, Lobesia botrana Derm. & Sciff. (Lepidoptera: Tortricidae), one of the most injurious pest of grape berries in Greece, is a multivoltine species that overwinters as diapausing pupae. The effects of several diel and non-diel photoperiods and of temperature, experienced by eggs and larvae, on pupal diapause induction were investigated. The diapause response curve was of Type I (long day type) and the determining factor was the duration of scotophase (> 11 h), regardless of the duration of photophase. However, at very short (< 4 h) photoperiods, the incidence of diapause was also high. Diapause was positively and significantly correlated with the egg-larval developmental time, pupal mortality and the duration of the pupal stage. Eggs and larvae reared under LD 12 : 12 h photoperiod and various temperatures (from 12 to 30 <degrees>C) produced diapausing pupae (almost 100%), but the duration of the pupal stage (intensity of diapause) increased with increasing temperature. Under continuous darkness, however, the percentage diapause decreased with increasing temperature. Single and double 1-h light pulses were applied systematically at various times during the scotophase of six diapause-inducing diel photoperiods. Two photosensitive points in time (called A and B) were revealed, during which illumination resulted in a significant decrease of diapause induction. The decrease was much greater during the first sensitive period (early in scotophase) rather than in the second (late in the scotophase).