Components of tomato leaf homogenate suppress responses from galeal chemoreceptors of the adult Colorado potato beetle

Effects of both potato and tomato residues (obtained following vacuum distillation of leaf homogenate) on responses to galeal chemosensilla of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), to trans-2-hexenol, one of the leaf alcohols that stimulate a highly uniform gustatory response in this system, are described. Tomato residue suppressed the response to hexenol in a dose-dependent manner whereas potato residue had no effect. Suppression was detectable 0.3 s after the first application began and the normal response to hexenol recovered within 2 min. Alkaloids from potato (solanine) and tomato (tomatine) also suppressed the response to hexenol but the characteristic actions of these compounds could not fully explain the activity of the tomato residue. Constituents of tomato residue, in addition to tomatine, are probably responsible for its significant effect on galeal chemosensory responses and these probably comprise a complex set of active compounds that allow the Colorado potato beetle to distinguish potato and tomato leaves.