Insect herbivores are confronted with a formidable and diverse array of naturally occurring plant toxins. We have shown that the corn earworm, Helicoverpa zea (Boddie), a polyphagous insect, is highly sensitive to the antimetabolic effects of 1-azetidene-2- carboxylic acid (AZC), a naturally occurring higher plant homolog of proline. Larvae reared on a diet containing AZC suffer developmental retardation and exhibit various developmental lesions. AZC toxicity is typically expressed during larval molts and it is particularly evident at the larval-pupal molt. If larval-pupal ecdysis occurs, the pupae are frequently deformed; often exhibiting large, nonsclerotized areas. The cellular and biochemical mechanisms for the toxicity of AZC and many allelochemicals are largely unknown. This study of the cell / tissue morphological and biochemical events that precede and / or accompany the symptoms of AZC toxins in H. zea will increase understanding of the protective role of allelochemicals in plant-herbivore interactions, and has the potential to further development of insect pest controls which do not require industrial pesticides.
