Effect of ingested soybean, ovomucoid and corn protease inhibitors on digestive processes of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae)

Abstract

European corn borer, Ostrinia nubilalis, were fed artificial diet containing either 1% (w/v) soybean, 2% (w/v) chicken ovomucoid or 1% (w/v) corn trypsin inhibitor and effect on digestive protease activity, larval weight and midgut protein were determined either 2 or 5–9 days later. The three different inhibitors used in this study appear to produce three different results. Soybean inhibitor inhibits corn borer trypsin, chymotrypsin and total proteolysis by midgut preparations. Ingested soybean inhibitor resulted in decreased larval growth, increased tryptic and decreased chymotryptic activity. Ovomucoid inhibitor neither inhibited corn borer proteases nor decreased digestive enzyme activity and had an effect similar to an increase in dietary protein. Corn inhibitor, which inhibits vertebrate proteases, does not inhibit corn borer proteases. Ingested corn inhibitor resulted in increased protease activity in the alimentary tract without a decrease in larval weight. The different results may be related to the source of each inhibitor. Corn is a host plant for the corn borer, soybean is not frequently fed on and chicken ovomucoid inhibitor is never consumed by the insect.