Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2009
Publication Date: 7/1/2009
Citation: Overholt, W.A., Diaz, R., Hibbard, K., Roda, A., Amalin, D., Fox, A., Hight, S.D., Medal, J., Stansly, P., Carlisle, B., Walter, J., Hogue, P., Gary, L., Wiggens, L., Kirby, C., Crawford, S. 2009. Releases, distribution and abundance of Gratiana boliviana (Coleoptera:Chrysomelidae), a biological control agent of tropical soda apple (Solanum viarum, Solanaceae), in Florida. Florida Entomologist. 92(3):450-457. Interpretive Summary: Tropical soda apple (TSA) is native to South America and was first found in Florida in 1988. The plant spread and has become a problem in pastures throughout the southeastern U.S. from Texas to the Carolinas. Cattle avoid the spiny leaves and stems of TSA and the weed can take over a pasture. Scientists with USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Tallahassee, FL, along with University researchers and Florida Extension Agents, are studying a leaf-feeding beetle from Argentina that eats nothing but TSA. Thousands of these beetles were reared and released in Florida from 2003 to 2008. We conducted a state wide survey to find where the beetles now occur and to evaluate whether the beetles are causing damage to TSA plants. Our survey found that beetles were successful in establishing and spreading from release sites in central and south Florida, but were not found near release sites in north Florida. The absence of beetles in the north is due to the combination of fewer number released in the north and cooler temperatures that frost-kill the leaves of TSA when the beetles are beginning and ending their winter hibernation. Where beetles were present, TSA plants were smaller and produced fewer fruit as the number of beetles increased, clearly suggesting that beetles are having a negative impact on TSA plants. Next year releases of this insect will be focused in the northern parts of Florida to increase the likelihood of establishment and obtain the benefits of this beetle impacting this weed.
Technical Abstract: A biological control program against tropical soda apple (TSA) (Solanum viarum Dunal (Solanaceae)) released 176,643 Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) in Florida from 2003 to 2008. The spatial distribution of releases was clustered with more beetles released in south/central Florida than further north. A survey conducted in the fall of 2008 found G. bolviana present at > 70% of randomly selected locations between 26o and 29o latitude, but no beetles were found at sites further north. The presence of beetles and beetle damage were associated with smaller TSA plants and fewer fruit per plant. The absence of beetles in northern Florida may be due to the fewer number released in that area, but could also be influenced by land cover and climate.