Diapause characteristics of the Kanzawa spider mite, Tetranychus kanzawai Kishida, in pea fields of central Wakayama Prefecture, Japan

The diapause status was studied of the Kanzawa spider mite, Tetranychus kan zawai Kishida, occurring in pea fields and on non-cultivated hosts along th e field in central Wakayama Prefecture, Japan. The proportion of diapausing females on peas and the non-cultivated evergreen host, Akebia quinata (Thu nb.), increased through autumn, reaching a peak of 60% in December, but dec lined thereafter. In November, a higher proportion of diapausing females wa s found on another non-cultivated deciduous host, Clerodendrum trichotomum Thunb. than on the above two hosts. This earlier increase on C. trichotomum was due to the host defoliation. The diapause percentage of T. kanzawai at 16 degrees C and 20 degrees C was close to 100% at daylengths shorter than 10 h. The critical daylength for diapause induction was between 10 and 11 h.