HYPERSENSITIVITY - A NEGLECTED PLANT-RESISTANCE MECHANISM AGAINST INSECT HERBIVORES

Despite many examples of plants' hypersensitive reaction against pathogens, there are exceedingly few examples of hypersensitive reactions having any importance against insect herbivores. However, such plant defense mechanisms may be widespread among more sedentary insect herbivores. The examples in which a hypersensitive reaction was elicited against insect herbivores were against galling insects, bark beetles, adelgids, and siricids. The intimate and sessile interactions during insects' egg and larval stages may have selected more specific and more complex defenses, because of the greater and more varied opportunities that the host plant has for regulating the lives of its intimate associates. Thus, it is argued that the intimate association of these herbivores during egg and larval stages set the scenario for the evolution of this plant defense mechanism. The dearth of accepted examples of hypersensitive reaction against insect herbivores may not reflect its actual frequency and occurrence in nature. Further investigation on plants' hypersensitive reaction against insect herbivores may shed light on the ecology and evolution of insect-host plant association. © 1990 Entomological Society of America.