Current Status of Parthenium ( Parthenium hysterophorus Linn.) Biological Control in Australia

Current status of Parthenium (Parthenium hysterophorus Linn.) biological control in Australia Parthenium (Parthenium hysterophorus Linn.), an annual herbaceous plant native to the tropical Americas, is a weed of national significance in Australia. A major biological control program against parthenium in Australia commenced in 1977 and since then nine insect species and two rust fungi have been introduced into Australia. The stem-galling weevil, Conotrachelus albocinereus Deejan, the ischolar_main-feeding clear-wing moth, Carmenta near ithacae, and the summer rust Puccinia xanthii var. parthenii hysterophorae were the last three agents released. All agents established at some localities and seven are now widespread. Only the stem-galling moth Epiblema strenuana (Walker) is both widespread and damaging, occurring in all parthenium-infested areas in Australia at high population levels. In central Queensland the leaf-feeding beetle, Zygogramma bicolorata Pallister and stem-boring weevil, Listronotus setosipennis (Hustache) are also widespread and effective, while C. sp. nr. ithacae is at the early stages of field establishment and dispersal. In northern Queensland, E. strenuana and P. xanthii var. parthenii-hysterophorae are the only prominent agents. The combined impact of these agents has resulted in significant reductions in the abundance and impact of parthenium in most situations and seasons, though serious infestations can still occur. Not all potential agents have been properly investigated, and some additional agents known to be host specific in the native range warrant further investigation.