Establishment, spread and initial impacts of Gratiana boliviana (Chrysomelidae) on Solanum viarum in Florida.
Solanum viarum Dunal (Solanaceae) is an invasive perennial shrub in southeastern USA. Native to South America, it was first found in Florida in 1988, and it has already invaded more than 400,000 ha of grasslands and conservation areas in 11 states. Currently recommended control tactics for this weed in pastures are based on herbicide applications combined with mechanical (mowing) practices. These control tactics provide a temporary solution and can cost as much as $188/ha for dense infestations of the weed. A biological control project against S. viarum was initiated in 1997. After 3 years of intensive host-specificity testing, the South American leaf beetle Gratiana boliviana was approved for field release by the United States Department of Agriculture (USDA)-Animal and Plant Health Inspection Service (APHIS)-Plant Protection and Quarantine (PPQ) in 2003, and its release in Florida began in summer 2003. Up to now, approximately 120,000 beetles have been released in 25 counties in Florida. The beetles established at virtually all the release sites in Florida. Beetle dispersal has been based on plant availability with annual dispersal from 1.6 to 16 km/year from the release sites. Initial impacts of the beetles range from 30% to 100% plant defoliation. The fruit production declined from 40 to 55 fruits per plant in summer 2003, when beetles were released, to zero or a few deformed fruits (one to four per plant) 2 years post release in five of the release sites monitored. Mass rearing, field release and post-release evaluation of G. boliviana and the target plant will continue during 2008.