Overwintering ecology of two species of spider mites (Acari: Tetranychidae) on different host plants

The overwintering ecology of two species of spider mites was studied on three different host plants in central Wakayama Prefecture, southwestern Japan. Laboratory diapause-inducing experiments showed that populations of Tetranychus urticae on peas and chrysanthemums both had a very low inherent capacity for diapause, and the population on chrysanthemums continued development and reproduction throughout the winter. On the other hand, populations of T. kanzawai had a genetically strong diapause capacity, regardless of the host species on which they occurred. However, the proportion of field-induced diapause females was lower in the population occurring on Akebia qninata, an evergreen host that had ample fresh leaves throughout the winter, than the populations on peas and Clerodendrum trichotomum, a deciduous tree, the leaves of both of which deteriorated or defoliated in winter. The low incidence of diapause on A. quinata seemed due to weak diapause induction and/or earlier diapause termination in the plastic response to ample food conditions. On A. quinata, high proportions of eggs and immatures remained throughout the winter, suggesting that development acid reproduction are possible throughout the winter in this area under ample food conditions.