【目的】 观察取食人工饲料和3种寄主植物的甜菜夜蛾Spodoptera exigua 3龄幼虫感染核型多角体病毒后，其中肠组织的病理变化。【方法】 核型多角体病毒感染甜菜夜蛾后，剖取围食膜观察在不同时间点围食膜的变化，以及采用组织切片法探究取食人工饲料和不同寄主植物的甜菜夜蛾感染病毒前后其中肠组织的病理变化。【结果】 幼虫感毒后的围食膜首先由无色透明、具有弹性的圆桶状结构，变成乳白色、弹性降低的单片状结构，随着感毒后时间的推移，围食膜破坏严重，变成无弹性的碎片状。取食不同寄主植物和人工饲料的甜菜夜蛾在未感染病毒时其中肠组织都没有明显的变化，而感染病毒后甜菜夜蛾中肠组织围食膜被破坏或消失；中肠柱状细胞伸长、变形，细胞间隙变大，排列混乱，细胞脱落，肠壁变厚。此外，核型多角体病毒对取食人工饲料和不同寄主植物的甜菜夜蛾中肠组织的影响也存在差异，对取食人工饲料和黄豆的影响类似且最大、甘蓝次之，蕹菜最小。【结论】 核型多角体病毒对甜菜夜蛾中肠组织具有显著的影响，且取食不同寄主植物时其影响存在明显差异。

[Objectives]  To investigate the effects of infection with the nucleopolyhedrovirus (NPV) and diet on the midgut of beet armyworm (Spodoptera exigua) larvae. [Methods]  Peritrophic matrices (PMs) were dissected from larvae at different times post-infection so that change in this tissue could be observed over time. Pathological changes in midgut tissues of NPV-infected and non-infected larvae feeding on artificial diets and different plants were revealed by making histological sections. [Results]  Infection with NPV caused the PM to change from a transparent, flexible, cylindrical structure to an opalescent, sheet-like structure with reduced elasticity, and ultimately, a group of inelastic fragments with no structural integrity. Diet had no significant effect on the midgut tissues of uninfected larvae. However, diet had obvious effects on the midguts of infected larvae. In some diet treatment groups intestinal epithelial cells became elongate and then irregular, the intestinal wall thickened, intercellular spaces became larger, the cellular arrangement became disordered with cells detaching, ultimately causing the structure of the PM was to be seriously damaged or even disappear. There was a significant interaction between NPV infection and diet with NPV having the greatest effect on the midgut tissue of larvae that were fed artificial diets and soybeans (Glycine max), followed by those fed collards (Brassica oleracea), and the least effect on those fed water spinach (Ipomoea aquatica). [Conclusion]  NPV had significant adverse effects the midgut tissue of beet armyworm larvae but the severity of these effects varied with diet.