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 p otential 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 r ate. Host range was investigated in larval survival tests and adult ch oice tests under laboratory conditions. Larvae were successfully reare d on 8 of 11 indigenous Solanum species, on 4 of 5 exotic Solanum spec ies (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 occu rred on several of the indigenous Solanum species and on eggplant. The se trials were conducted under quarantine conditions with the potentia l for laboratory artifacts. The poor larval survival on nonhosts and t he inability of the agent to recognize nonhosts as oviposition sites s upported a request for release of this agent, which was subsequently g ranted. (C) 1995 Academic Press, Inc.