Digestive proteolytic and amylolytic activities in Helicoverpa armigera (Lep.: Noctuidae) larvae fed on five host plants

The cotton bollworm, Helicoverpa armigera (Hübner), is a serious pest on a wide range of economic crops in many parts of the world. In this study, digestive proteolytic and amylolytic activities of H. armigera larvae (3rd to 5th instars) were evaluated on five main host plants including chickpea (cv Hashem), cowpea (cv Mashhad), soybean (cv 033), navybean (cv Dehghan), and corn (cv SC 704) at 25 ± 1 °C, relative humidity of 65 ± 5% and a photoperiod of 16: 8 (L: D) hours. The results indicated that the highest enzyme activity was in 5th instar. The highest general protease activity of 3rd, 4th and 5thinstar larvae was found on corn. The larvae fed on corn had the lowest trypsin activity. This leads to hyperproduction of chymotrypsin and elastase-like enzymes to compensate the inhibition of trypsin. The larvae of H. armigera reared on cowpea had the highest level of amylase activity, and the lowest activity was in the larvae fed on corn. The results revealed that among host plants tested, corn was more resistant (unsuitable) to H. armigera. Study on digestive proteolytic and amylolytic activities of H. armigera can be used in identifying the antidigestive or antifeedent compounds, which will help us to design appropriate management programs.