Population growth response of Tetranychus urticae to eggplant quality: application of female age-specific and age-stage, two-sex life tables

Abstract

The life table parameters of the two-spotted spider mite (TSSM), Tetranychus urticae Koch, were determined on seven eggplant cultivars (“Isfahan”, “Dezful”, “Shend-Abad”, “Neishabour”, “Bandar-Abbas”, “Jahrom” and “Borazjan”) at 25 ± 1°C, 60 ± 5% RH and a photoperiod of 16:8 (L:D) h. The age-stage, two-sex life table and the traditional female age-specific life table were constructed by using demographic data. There was a significant difference between the duration of different life stages of TSSM on different eggplant cultivars. Using the age-stage, two-sex life table, the intrinsic rate of increase (r) on the above-mentioned cultivars varied from 0.022 day−1 on “Neishabour” to 0.157 day−1 on “Isfahan”. The value of the net reproductive rate (R0) of TSSM on different eggplant cultivars varied from 1.425 offspring on “Neishabour” to 11.585 offspring on “Isfahan”. Furthermore, the values of the gross reproductive rate (GRR) were significantly different on the tested cultivars, and the lowest and highest values of this parameter were obtained on “Isfahan” (29.574 offspring) and “Neishabour” (2.867 offspring), respectively. The mean generation times (T) of TSSM on the above-mentioned cultivars were 15.415, 15.102, 14.191, 15.110, 16.117, 15.187 and 14.736 days, respectively. There was a little difference among the same life table parameters estimated by female-based and two-sex methods. These differences occurred because the traditional age-specific life table deals only with female populations. Comparison of TSSM life table parameters on different eggplant cultivars and cluster analysis of these parameters revealed that “Isfahan” and “Neishabour” were the most susceptible and resistant cultivars to this pest, respectively.