Biological control of parthenium: progress on the redistribution of established agents to southern Queensland

Parthenium (Parthenium hysterophorus L.), a serious weed of grazing areas in central Queensland (Qld) and a Weed of National Significance in Australia, has spread into parts of southern Qld. The isolated nature of the southern Qld infestations, probably resulting from the movement of contaminated stock feed, livestock and machinery, has meant many of the effective biological control agents established in core infested areas of central Qld have not extended their distribution at the same pace as the weed. As a result, a program to redistribute these agents from central Qld to southern Qld was initiated. The seed-feeding weevil (Smicronyx lutulentus Dietz), the stem-boring weevil (Listronotus setosipennis (Hustache), and the root-boring moth (Carmenta nr. ithacae Beutenmuller), the winter rust (Puccinia abrupta var. partheniicola Dietel & Holway), and the summer rust (Puccinia xanthii var. parthenii-hysterophorae Seier, Evans & Romero) were prioritised for redistribution. Since late 2015, prioritised agents have either been bulk collected from central Qld, or reared in glasshouse facilities in Brisbane, and released at 19 sites across 10 geographically isolated areas in southern Qld. Periodic surveys of release sites have indicated strong evidence of establishment of the winter rust and the Smicronyx weevil at most of the sites and preliminary signs of establishment of the summer rust and the Listronotus weevil at a few sites. Redistribution of field-collected and glasshouse-reared agents and monitoring of their establishment status in the field will continue over the next year.