Effect of leaf condition on diapause induction of a Kanzawa spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) population on tea plants

Abstract

The effect of leaf condition on the diapause induction of Tetranychus kanzawai Kishida was investigated. Two leaf-condition treatments were prepared under a constant short daylength of 9L:15D. In the "refreshed" treatment, dietary bean leaves were renewed twice at the deutonymphal (pre-imaginal) and adult stages, while leaves were not renewed in the "non-refreshed" treatment. At the population level most females entered diapause at 15°C and 18°C under both leaf conditions, while a significantly lower proportion of females entered diapause at 20°C under both leaf conditions. The diapause incidence was consistently lower in the "refreshed" treatment, though the difference was not significant. When comparing each lineage initiated from one fertilized female at 20°C/9L:15D, lower diapause incidence was consistently found in the "refreshed" treatment than in the "non-refreshed" one. ANOVA showed a significant interaction between lineage and leaf condition. These results suggest that under moderate temperatures leaf condition acts as a secondary factor to enhance the primary diapause-inducing effects of short-day and temperature.