Temperature-dependent development and reproduction of rice leaffolder, Marasmia exigua (Lepidoptera: Pyralidae).

Marasmia exigua (Butler) (Lepidoptera: Pyralidae) is one of the major rice leaffolders negatively affecting the rice production in the world. The growth and development of M. exigua was studied at seven constant temperatures (10, 15, 20, 25, 27, 30 and 35°C). The results showed that M. exigua eggs failed to hatch at 10°C and the larvae could not complete development at 15 and 35°C. The developmental times of each stage, survival rates of pre-adult, adult longevity, fecundities and oviposition days of M. exigua at 20, 25, 27 and 30°C were investigated using age-stage, two-sex life table. The total pre-adult development time decreased with the increase in temperature decreasing from 61.58 days at 20°C to 28.94 days at 30°C. The highest survival rate was observed at 25°C (73%). Male adult longevities were generally longer than that of females, except at 30°C. The highest mean fecundity, age-stage specific fecundity and age-specific fecundity peak values were all observed at 27°C. The maximum intrinsic rate of increase r and finite rate of increase λ were observed at 27°C, while the maximum net reproduction rate R0 was observed at 25°C. The longest mean generation time occurred at 20°C and the shortest at 27°C. These results provide better understanding on the development, reproduction and dynamic of M. exigua populations, their distribution, and might be utilized to forecast and manage M. exigua outbreaks in China.