Heavy metal exposure through artificial diet reduces growth and survival of Spodoptera litura (Lepidoptera: Noctuidae).

Abstract

Insect physiology is affected by the presence of toxins in the surrounding environment of insects as well as their food sources. The objective of this study was to determine the effect of heavy metal exposure to two low concentrations (50μg/g and 150μg/g) of lead (Pb) and zinc (Zn) through artificial diet to the larvae on biological parameters of Asian armyworm (Spodoptera litura Fabricius) (Lepidoptera: Noctuidae). Both Pb and Zn, even at low concentrations, had relatively high toxic effects on S. litura larvae (P < 0.01). S. litura larval weight and length suffered the maximum reduction when the larvae were fed on diet mixed with the high Pb concentration (150μg/g) tested compared to the other treatments. At the same Pb concentration (150μg/g), values of larva growth index, pupa growth index, immature growth index, standardized growth index, and fitness index were 4.66, 7.33, 7.82, 5.35, and 10.00 times lower, respectively, than those of control. At the same Zn concentration (150μg/g), values of larval growth index, pupal growth index, immature growth index, standardized growth index, and fitness index were 5.61, 3.00, 3.04, 3.23, and 9.24 times lower, respectively, than those of control. The survival rate of S. litura larvae was also lower (12.5%) when the larvae were fed on diet mixed with Pb at 150μg/g after 10days of observation. Overall, the presence of those heavy metals in the environment, even at low concentrations, would exert an adverse impact on larvae development of this insect. From this point of view, findings could provide a basis for long-term evaluation of heavy metal risk and its impact on populations of important agricultural pests.