Biological control of parthenium weed: field collection and redistribution of established biological control agents.
Parthenium (Parthenium hysterophorus L.), a noxious weed of grazing areas in Queensland (Qld), is a Weed of National Significance in Australia. Eleven biological control agents (nine insect species and two rust pathogens) have been released against parthenium in Australia. The majority of these agents have become established and have proven effective against the weed in central Qld. Parthenium is spreading further into southern Qld, where many of the widespread and effective biological control agents in central Qld are not present. Hence, a program to redistribute these agents from central Qld to the south and south east of the state has been initiated. The seed-feeding weevil (Smicronyx lutulentus Dietz), the stem-boring weevil (Listronotus setosipennis (Hustache)), and the root-boring moth (Carmenta nr. ithacae Beutenmüller), the winter rust (Puccinia abrupta var. partheniicola Dietel & Holway), and the summer rust (Puccinia xanthii var. parthenii-hysterophorae Seier, Evans & Romero) have been identified as priority agents for redistribution. So far, field collected winter rust, the Listronotus weevil, the Smicronyx weevil, the Carmenta moth and the leaf-feeding beetle (Zygogramma bicolorata Pallister) have been field released at ten sites in south and south east Qld. Field releases of the winter rust from glasshouse cultures were also made at several sites. So far there is evidence of field establishment of the winter rust and the Smicronyx weevil in some of the release sites. Cultures of the summer rust and Listronotus weevil have recently been established at the Ecosciences Precinct for future mass rearing and field releases. Redistribution of field collected and glasshouse cultured biological control agents and monitoring their establishment status in the field will continue over the next three years.