Premature leaf abscission: an induced plant defense against gall aphids.

To the extent that premature leaf abscission reduces the pest population and is cost effective, it should be considered an induced plant defense. To test this hypothesis the authors examined patterns of abscission by 2 species of cottonwoods (Populus), quantified the impacts of abscission on the survival of 2 Pemphigus gall aphid species, and examined aphid behavioral and life history countermeasures to this host response. Premature leaf abscission is induced by gall aphid attack. -from Authors