The effects of herbivory by a weevil species, acting alone and unrestrained by natural enemies, on growth and phenology of the weed Sesbania punicea.
An apionid weevil, Trichapion lativentre [Apion lativentre] has been introduced into South Africa where it is the only herbivore of any consequence on the South American legume S. punicea. Plant growth at weevil-free sites was compared to that at sites colonized by weevils for one and for two seasons. Relative growth curves are used to describe the effects of weevil feeding on above-ground productivity and phenology of the host-plant. Feeding by adult weevils suppressed leaf-set, caused premature abscission of leaflets, and reduced stem growth. Larval feeding destroyed most buds and greatly reduced flowering and seed production. Mean mass of individual seeds increased as a consequence of weevil herbivory. These effects were exacerbated at sites that had been colonized by weevils for two seasons. It has yet to be established whether herbivory by A. lativentre will reduce density and spread of S. punicea and result in successful biological control.