The Asian corn borer (ACB), Ostrinia furnacalis Guenee (Lepidoptera: Pyralideae), is a major insect pest of corn and damage resulting from this pest can reduce yield by 20–80% (Sanchez 1971). In the Philippines, the chemical ecology of O. furnacalis behavior, as affected by Ipomoea triloba L., a weed closely associated with corn, was studied extensively (Calumpang et al. 2000; Calumpang et al. 1994; Magsino 1995). Corn borer egg masses, larvae, pupae and feeding tunnels were reduced in the unweeded plots compared with the selectively-weeded and weed-free plots (Magalit 1983). I. triloba as a border for sweet corn also reduced damage by the Asian corn borer (Magsino 1995). Oviposition preference tests in the laboratory showed reduced number of egg masses when corn was entwined by I. triloba, when corn was grown beside it or when corn was entwined by wire. The presence of a repellent volatile chemical was demonstrated from the weed and from corn, the emission of which increased when corn was entwined by I. triloba (Calumpang et al. 2000).