Biological Control of Tropical Soda Apple (Solanaceae) in Florida: Post-Release Evaluation

Abstract

Foreign exploration to search for natural enemies of the invasive plant tropical soda apple, Solarium viarum Dunal (Solanaceae) were conducted initially in 1994 by University of Florida researchers in collaboration with Universidade Estadual Paulista, Jaboticabal campus, Brazil. Sixteen species of insects were found associated with tropical soda apple in Brazil and Paraguay (Medal et al. 1996). A biological control program was initiated by the University of Florida in 1997 with funds provided by the United States Department of Agriculture, Animal and Plant Health Inspection Service, and the Florida Department of Agriculture & Consumer Services. Explorations in the place of origin (southern Brazil, northeast Argentina, south Paraguay, and Uruguay) of the target weed were conducted in collaboration with Brazilian university researchers, and the USDAAgriculture Research Service Biological Control Laboratory in Hurlingham, Argentina. During exploratory surveys, the leaf beetle Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) was found on tropical soda apple plants in southern Brazil. A high level of specificity and significant defoliation of tropical soda apple were demonstrated in host-specificity tests conducted at the Florida Biological Control Laboratory quarantine facilities in Gainesville, the USDA-ARS (Agriculture Research Service) South American Biological Control Laboratory in Argentina, and the USDAARS quarantine facilities in Stoneville, Mississippi, as well as in extensive field surveys and open-field tests conducted in South America. After five years of intensive plant feeding and oviposition tests, the South-American leaf beetle G.boliviana was the first biological control agent approved for field release (7 May 2003) by the USDA-APHIS-PPQ in the southeastern United States to join the battle against tropical soda apple also known by the nickname the 'plant from heir (Coile 1993). This exotic weed has invaded over half a million hectares of grasslands and natural areas in at least 6 states (Florida, Alabama, Georgia, Mississippi, South Carolina, and Texas). Intensive host-specificity tests including 126 plant species in 35 families were conducted with G. boliviana from 1998 to 2001 (Medal et al. 2002, 2003, 2004). Initial releases of G boliviana in Florida began in summer 2003, and currently approximately 200,000 G. boliviana immature and adults have been released in 37 Florida counties, 14,000 in 2 counties in Georgia, 18,000 in 3 counties in Alabama, and 825 in 1 county in Texas. In th s article we report the establishment, post-release monitoring, and initial impacts of G. boliviana on tropical soda apple plants in Sumter County, Florida. A field release of G. boliviana was made in a