斜紋夜蛾(Spodoptera litura)在甘藍、芋頭及田菁上的族群介量與取食量

Abstract

Spodoptera litura (Fabricius) is a polyphagous insect that can damage numerous hosts. Investigations of their life history traits, life table, and food consumption can offer a comprehensive understanding of the population growth potential of S. litura on different plant species. In this study, the performance of S. litura reared on cabbage, taro, and sesbania was investigated in a walk-in growth chamber at 25 ± 1oC, 60 ± 10% RH, and a photoperiod of 12:12 (L:D). The water, protein, nitrogen, and non-structural carbohydrate contents of these three hosts were analyzed. The nutrient analysis revealed that the protein, nitrogen, and total non-structural carbohydrate contents were much lower on cabbage, though the water content was not. However, the net consumption rate on cabbage was 439.1 cm2 and was 2 to 3 times higher than that for those fed on sesbania (207.8 cm2) and taro (141.7 cm2). Therefore, it might be due to the compensation effect that the results showed the largest head capsule width and heaviest body weight of larvae when the insects were reared on cabbage. The results of the age-stage, two-sex life table showed that the population parameters of net reproductive rate, intrinsic rate of increase, and finite rate of increase were all significantly highest on cabbage (1893.1 offsprings, 0.2374 d-1, 1.2679 d-1), followed by sesbania (1420.1 offspring, 0.2331 d-1, 1.2624 d-1), and lowest on taro (1361.0 offsprings, 0.2298 d-1, 1.2584 d-1). The mean generation time was the shortest on sesbania (31.2 d) and the longest on cabbage (31.8 d). S. litura showed the ability to adapt to varied nutrient contents in different hosts. Cabbage, taro, and sesbania were all suitable hosts for S. litura, but they performed the best on cabbage. S. litura also showed a high population potential on sesbania, which is a major green manure crop in the summer in Taiwan. Because sesbania is widely planted and S. litura can migrate long distances, an efficient pest management program aimed at S. litura in sesbania fields is necessary; otherwise, S. litura can build their population on sesbania and then migrate to adjacent economic crops or weeds, and increase the difficulty in pest management.