Accumulation and excretion of cadmium in three successive generations of Spodoptera exigua (Lepidoptera: Noctuidae) and impact on the population increase.

Nowadays, heavy metal pollution has become more and more serious. Cadmium is one of the heavy metals that have caused serious pollution. Spodoptera exigua Hübner (Lepidoptera: Noctuidae), one of important agricultural pests, has broken out more frequently in recent years. In this study, accumulation at different developmental stages and excretion of Cd were detected, and effect of cadmium (Cd concentrations were 0.2, 0.8, 3.2, 12.8, and 51.2 mg/kg, respectively) on three successive generations of beet armyworm was also studied using life table in the laboratory. Results showed that Cd2+ contents were significantly different when S. exigua was reared under different Cd2+ concentrations in the same generation in a significant dose-dependent manner. The concentration of Cd2+ increased with extension of stress time. Cd2+ concentration at different developmental stages was different, that is, larvae > pupa > adult. After emergence, Cd2+ concentration in both females and males decreased gradually, but that in paired adults decreased to a greater extent than that in unpaired ones. Beet armyworm could excrete heavy metals by means of faeces, prepupa exuviate, and puparium. Life table of the laboratory population was constructed, which showed that low doses of cadmium promoted the increase of population, whereas high doses inhibited the increase, meanwhile, with the extension of exposure length, the index of population trend (I) declined more rapidly. The study might provide references for the long-term and objective assessment of heavy metal pollution and its effect on the populations of important agricultural pests.