Biology and Host Range of Gratiana spadicea (Klug, 1829) (Coleoptera: Chrysomelidae: Cassidinae), a Potential Biological Control Agent for the Weed Solanum sisymbriifolium Lamarck (Solanaceae) in South Africa

A leaf-feeding tortoise beetle (Gratiana spadicea) was screened as a potential biological control agent for the invasive exotic weed Solanum sisymbriifolium in South Africa. Favorable biological characteristics of G. spadicea include a high rate of increase, long-lived and mobile adults, several generations per year, and a high per capita feeding rate. Host range was investigated in larval survival tests and adult choice tests under laboratory conditions. Larvae were successfully reared on 8 of 11 indigenous Solanum species, on 4 of 5 exotic Solanum species (apart from S. sisymbriifolium), and on economically important S. melongena (eggplant) but not on any of the species of Datura, Nicandra, and Physalis tested. Very limited adult feeding and oviposition occurred on several of the indigenous Solanum species and on eggplant. These trials were conducted under quarantine conditions with the potential for laboratory artifacts. The poor larval survival on nonhosts and the inability of the agent to recognize nonhosts as oviposition sites supported a request for release of this agent, which was subsequently granted.