Development and reproduction of five Tetranychus species (Acari: Tetranychidae): Do they all have the potential to become major pests?

The objective of this study was to investigate whether four spider mite species, Tetranychus ludeni, T. phaselus, T. piercei and T. truncatus, currently with insignificant economic impact, have the potential to achieve the same status as T. urticae, which until now has been considered as the most serious tetranychid pest species in orchards and greenhouses. We investigated the effect of temperature on development, survival and oviposition at 11 constant temperatures ranging from 15 to 40 °C at intervals of 2.5 °C and estimated demographic parameters, such as the intrinsic rate of natural increase (rm), for these five species at five constant temperatures. Developmental time from egg to adult (female and male) decreased with increasing temperature from 15 to 32.5 °C in all five species, but increased slightly at 35 °C or higher, especially in T. ludeni and T. urticae. Using linear and non-linear developmental rate models, the lower thermal thresholds for egg-to-adult (female and male) and egg-to-egg development were found to range from 9.8 to 11.7 and from 9.8 to 11.4 °C, respectively. The intrinsic optimal temperature (TΦ) ranged from 18.0 to 27.4 °C for egg-to-female adult and from 23.9 to 27.2 °C for egg-to-egg development. The oviposition period and adult longevity were strongly affected by temperature. The rm-values increased with increasing temperature from 15 to 30 or 35 °C in all five species. The highest rm-values at each temperature were 0.114 day(-1) at 15 °C for T. ludeni, 0.199 day(-1) at 20 °C for T. urticae, 0.314 day(-1) at 25 °C for T. ludeni, 0.451 day(-1) at 30 °C for T. ludeni and 0.433 day(-1) at 35 °C for T. truncatus. The total fecundity, net reproductive rate (R0) and rm of T. ludeni were higher than those of T. urticae at all temperatures. T. piercei and T. truncatus showed higher rm-values at 30 and 35 °C than T. urticae. The results indicate that the former three species are better adapted to hot weather than T. urticae and have a high potential to become serious pests.