Effect of the secondary substances from wheat on the growth and digestive physiology of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae)

Three secondary compounds, pyrocatechol, gramine and ferulic acid from wheat were separately incorporated into artificial diets and fed to cotton bollworm Helicoverpa armigera (HĂźbner) larvae to determine their effects on larval and pupal weights and the nutritional indices of the larvae. The results show that these three secondary compounds can decrease the mean larval and pupal weights of cotton bollworm, with the mean larvae weights differing significantly between treatments. Mean pupal weight was only significantly reduced by ferulic acid and gramine, but not pyrocatechol. There were significant correlations between mean larval weight and concentration of the three secondary compounds tested, and between mean pupal weight and concentration of ferulic acid and gramine. The three secondary compounds tested affected the nutritional indices of cotton bollworm larvae differently. Compared with the control, ferulic acid and gramine significantly decreased RGR (the relative growth rate), AD (approximate digestibility) and ECD (conversion efficiency) of cotton bollworm larvae, and pyrocatechol only reduced ECD. All three indices were the lowest for cotton bollworm larvae fed on the diet with gramine (0.0984 ± 0.0114 g/g/day, 14.2670 ± 1.1541% and 31.1337 ± 1.1213%).