Effect of environmental variables on the bionomics of Telenomus remus (Hymenoptera: Scelionidae) against Spodoptera frugiperda (Lepidoptera: Noctuidae)
摘要
Telenomus remus has emerged as a sustainable alternative for managing Spodoptera frugiperda because it can overcome some limitation of conventional control methods. However, it is necessary to optimize rearing and release protocols and to understand how certain environmental variables affect the biological attributes of T. remus when parasitizing S. frugiperda. The present study evaluated the effect of different host densities (40, 80 and 120), temperature (16, 20, 24, 30 and 32°C ± 1 °C), relative humidity levels (45%, 65%, 85% ± 5% RH), photoperiod (16:8 and 8:16 Light: Dark) and supplementary food sources on the biological performance of T. remus. Among these, the highest parasitism rate of 92.9% ± 0.526% was recorded at 28°C ± 1 °C, while the lowest parasitism rate of 19.0% ± 2.56% was recorded at 16 °C. Even though the thermal performance curve suggested the Topt of 28.14 ˚C for fecundity, yet T. remus also managed to lay 188 ± 2.56 eggs/female at 24 °C which suggests that lowering temperature to 24 ˚C did not attenuated the reproductive capacity. Considering humidity levels, the highest parasitism of 93.5% ± 0.45% and fecundity of 247 ± 1.53 eggs/female were indicated at 65% RH, respectively. On the contrary, the fecundity decreased to 172 ± 1.23 when the relative humidity was raised to 85%. The results of photoperiod showed no significant difference in parasitism rate, adult emergence, and female offspring ratio, but female longevity decreased from 4.9 ± 0.05 days to 3.47 ± 0.09 days when the light period was reduced from 16 to 8 h. The provision of different supplementary food sources was also compared for their effect on the parasitism rate and adult longevity, among which fructose indicated an 87.1% parasitism rate, while male and females survived 4.87 ± 0.133 days and 5.7 ± 0.128 days, respectively. Overall, results of this study indicated that the optimal rearing performance of T. remus against S. frugiperda can be achieved at 28°C ± 1 °C, 65% RH, 16 h of light, and by using fructose as a food source.