Establishment and Initial Impact of the Leaf-Beetle <I>Gratiana boliviana</I> (Chrysomelidae), First Biocontrol Agent Released Against Tropical Soda Apple in Florida

Abstract

Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae), the first biocontrol agent introduced against tropical soda apple, Solanum viarum Dunal (Solanaceae), was released in Florida in the summer 2003. Post-release evaluations have focused on insect population changes and the impact of insect feeding damage on the plant defoliation and fruit production of the target weed. Gratiana boliviana quickly established in the release sites, and dispersed causing extensive defoliations to tropical soda apple plants and significant reduction of fruit production. Plant defoliation during the first growing season was directly associated with the increase in number of beetles observed on the tropical soda apple plants. Beetles showed a dispersal ability from the release sites of 1.6 km per year. Two years after the beetle release, most of the tropical soda apple plants at the 3-ha release site in Polk County and at the release site in Okeechobee County, Florida have been replaced by other plant species, resulting in improved pastures. No negative non-target effects have been observed, even in plants closely related, such as the non-natives Solanum capsicoides Allioni and Solanum torvum Swartz that were growing in the proximity or mixed with tropical soda apple in the monitored sites.

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