Comparison of Thermal Tolerance Between Spodoptera frugiperda and Spodoptera litura (Lepidoptera: Noctuidae)

Both Spodoptera frugiperda and Spodoptera litura are highly invasive pest species that can attack agricultural crops in new areas, causing high economic damage. The survival of invasive species is highly affected by their ability to adapt to new environments as well as climate change. Rapid cold hardening (RCH) and rapid heat hardening (RHH) play important roles in ecological adaptation and survival under fluctuating temperature conditions. To compare the rates of survival, development, and reproduction between S. frugiperda and S. litura, the effects of RCH (5°C for 12 h followed by -10°C for 2 h) and RHH (35°C for 12 h followed by 41°C for 2 h) treatments were determined on the 3rd or 6th instar larvae of both species. The results showed that treatments of CS (-10°C for 2 h) and RCH conditions into the 3rd instar larvae of both S. frugiperda and S. litura increased the survival rates at 23.2% and 24.0%, respectively. Treatments of HS (41°C for 2 h) and RHH conditions into the 3rd instar larvae of both species increased the survival rates at 30.6% and 26.7%, respectively. However, similar thermal hardening conditions treated into the 6th instar larvae did not increase the survival rates in both species. Thermal stress experienced at later larval instars negatively minimized the pupal weight and subsequent reproductive parameters of both species. The findings showed that S. frugiperda had a higher thermal plasticity set off by rapid thermal hardening than S. litura. Our results suggest that S. frugiperda retains the ability to enhance rapid thermal tolerance to cold winters and hot summers in the newly invaded habitats as well as climate change conditions.