Inhibitory Effect of Goebelia alopecuroides L. and Vicia ervilia L. Extracts on Cotton Bollworm, Helicoverpa armigera Hb., Digestive Trypsin and Chymotrypsin Activity

During evolution, various compounds against herbivors were developed in plant species. Disturbance in digestive system by plant enzyme inhibitors is one of the effective methods in integrated pest managment programs. In this study, the effects of total Goebelia alopecuroides and Vicia ervilia seed extracts and their fractions were assessed against proteolytic activity of cotton bollworm. Total extracts of G. alopecuroides was effectively inhibited digestive proteinase of cotton bollworm compared with that of V. ervilia. The inhibitory effect of G. alopecuroides on Bovine trypsin and chymotrypsin as well as insects’ trypsin and chymotrypsin was higher than that of V. ervilia. Total seed extracts of V. ervilia significantly decreased digestive chymotrypsin activity. Ammonium sulfate precipitation of seed extract also showed significant inhibitory effect among the fractions. The fifth fraction of G. alopecuroides showed the highest inhibititory efect agianst digestive proteolytic activity of cotton bollworm and bovine trypsin. The first fraction of V. ervilia significantly inhibited total proteolytic activity.The first fraction of both plants seed extracts inhibited digestive trypsin of cotton bollworm compared to the other fractions. The third fraction of V. ervilia and the forth fraction of G. alopecuroides showed higher inhibitory effect on digestive chymotrypsin of cotton bollworm comperd with the other fractions. Comparing crude extracts effects of both plant species on laboratory and wild populations of cotton bollworm showed that wild ones was susseptible compared with the laboratory population.