【目的】 为明确南方根结线虫 Meloidogyne incognita 侵染对斜纹夜蛾Spodoptera litura 幼虫的影响是否因幼虫的龄期而异。【方法】 采用被南方根结线虫侵染和未被侵染的乌桕叶片饲喂斜纹夜蛾幼虫，并测定不同龄期幼虫的生长（幼虫体重、发育历期、相对生长率）和营养利用（取食量、近似消化率、食物转化率）情况。【结果】 随着幼虫龄期的增加，斜纹夜蛾幼虫的取食量及发育历期呈上升趋势，幼虫体重、相对生长率和食物转化率先上升后下降，而近似消化率则先下降后上升。与饲喂未侵染南方根结线虫的乌桕叶片相比，取食线虫侵染的乌桕叶片的斜纹夜蛾2龄幼虫近似消化率（0.78±0.07）%显著增加了约30%，但斜纹夜蛾的4龄幼虫体重（0.12±0.04）g、相对生长率（0.20±0.06）g·g^－1·d^－1和食物转化率（0.54±0.18）%分别降低了61%、36%和73%。线虫侵染处理与龄期互作对斜纹夜蛾的发育历期和取食量无显著影响。【结论】 根结线虫侵染对斜纹夜蛾幼虫生长及其营养利用的影响因龄期而异，线虫侵染处理虽显著增加了斜纹夜蛾2龄幼虫的近似消化率，但却抑制了其4龄幼虫的生长及其营养利用。

[Objectives]  To examine whether the effects of the root-knot nematode, Meloidogyne incognita, infestation on Spodoptera litura larvae vary anoung different S. litura instars. [Methods]  S. litura larvae were randomly assigned to one of two treatment groups; one that was fed leaves of the Chinese tallow tree, Triadica sebifera, that were infested with M. incognita, and one that was fed nematode-free leaves, and differences in the growth (larval weight, development period, relative growth rate) and digestive ability (food intake, approximate digestibility, and food conversion rate) of these groups were measured and compared. [Results]  In general, food consumption and developmental period of S. litura gradually increased with larval development. Relative growth rate, larval weight, and food conversion rate first increased then decreased with larval development, whereas approximate digestibility first decreased, then increased, as larvae developed. The approximate digestibility of 2nd-instar larvae fed nematode infested leaves (0.78 ± 0.07) % was significantly higher (30%) than that of those fed nematode-free leaves. However, the larval weight (0.12 ± 0.04) g, relative growth rate (0.20 ± 0.06)   g·g^－1·d^－1, and food conversion rate (0.54 ± 0.18) % of 4th-instar larvae fed nematode infested leaves was significantly lower (61%, 36% and 73%, respectively), compared to larvae fed nematode-free leaves. There was no significant interaction effect between nematode infestation and instar on developmental duration or food consumption. [Conclusion]  Effects of root-knot nematode infestation on the growth and digestive ability of S. litura larvae varied with larval instar. Although nematode infestation significantly increased the approximate digestibility of 2nd-instar larvae, it greatly inhibited the growth and the digestive ability of 4th-instar larvae.