Technical Abstract: Phenylacetaldehyde is a flower volatile and attractant for many nectar-seeking moths. Acetic acid is a microbial fermentation product that is present in insect sweet baits. It is weakly attractive to some moths and other insects, but can be additive or synergistic with other compounds to make more powerful insect lures. Acetic acid and phenylacetaldehyde presented together in traps made a stronger lure than either chemical alone, for moths of the alfalfa looper, Autographa californica (Speyer), and the armyworm, Spodoptera albula (Walker). However, this combination of chemicals reduced captures of the cabbage looper moth Trichoplusia ni (Hubner), the silver Y moth Autographa gamma (L.), MacDunnoughia confusa (Stephens), and the soybean looper moth Chrysodeixis includens (Walker), compared to phenylacetaldehyde alone. These results indicate both positive and negative interactions of acetic acide, a sugar fermentation odor cue, and phenylacetaldehyde, a floral scent cue, in eliciting orientation responses of moths. This research provides a new 2-component lure for the alfalfa looper and for the armyworm S.albula, for potential use in pest management.