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

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 15degreesC and 18degreesC under both leaf conditions, while a significantly lower proportion of females entered diapause at 20degreesC 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 20degreesC/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.