Abstract
The annual life cycle and diapause characteristics of the Eotetranychus uncatus GARMAN population on white birch, Betula platyphylla var. japonica (MIQ). were studied Sapporo. The mite appeared on leaves in early May, and the occurrence ended in late September (1981) or in early November (1982) when leaves of white birch completely changed from green to yellow. The population passe through 4 or 5 generations during the season. Predators associated with this population were mainly phytoseiid mites. They appeared from mid-May to mid-September or late October, and their occurrence followed that of the mites, with a time lag of about 10 days.Photoperiodic response curve on diapause induction was the long day type, and its critical photoperiod was between 14.0 and 14.5 hr at 18°C. Diapause was induced in early September in the field. Part of the diapausing females collected in early October began to oviposit when incubated at 25°C and 15L-9D. The number of days required for the reactivation gradually decreased towards April. Proportion of laying females, on the contrary increased.
