Dietary Protein and Carbohydrate Levels Affect Performance and Digestive Physiology of Plodia interpunctella (Lepidoptera: Pyralidae)

In this study, life history and nutritional indices of Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae) was evaluated on six food commodities: dried fig, dried wheat germ, dried white mulberry, groundnut, pistachio, and raisin, compared with artificial diet. The influence of dietary macronutrient content on digestive alpha-amylase was also assessed. A delay in the developmental time of P. interpunctella immature stages was detected when larvae were fed on raisin. The highest survival rate of immature stages was on the artificial diet, and the lowest was on raisin. The highest realized fecundity and fertility were recorded for the females reared on artificial diet. Overall, fourth instar P. interpunctella reared on artificial diet had the highest relative consumed and growth rate, and lowest rates were observed in larvae fed raisin. Amylolytic activity and isoform patterns varied depending on larval instar and diets, but were higher for larvae fed artificial diet with moderate carbohydrate and protein. Zymograms showed the presence of three isoforms of alpha-amylase in midgut extracts of P. interpunctella fed different diets. Larvae fed dried white mulberry, fig, and raisin had one (A2) alpha-amylase isoform. The data suggest that dietary carbohydrate and protein content induce changes in nutritional efficiency, development, and alpha-amylase activity. A survey of the differences in digestive enzyme activity in response to macronutrient balance and imbalance highlight their importance in the nutrition of insects.