Abstract
The annual life cycles and diapause regulation of the multivoltine mites, Schizotetranychus schizopus (ZACHER), S. cercidiphylli EHARA and S. leguminosus EHARA were studied in Sapporo, northern Japan. Female adults fed on intact leaves responded to short photoperiod by laying diapause eggs with a critical photoperiod of about 14.0 hr at 18°C and between 13.0 and 14.0 hr at 25°C. However, even at long photoperiod mites laid diapause eggs if they had been reared on infested leaves. In the field, females started laying diapause eggs in early July. The time when 50% of females started laying diapause eggs varied between years in all the species studied. This variation was directly correlated with temperature and abundance of the mites, and these conditions are likely to have influenced the timing of diapause egg induction indirectly by affecting food quality of the host plants.
