Parthenium hysterophorus L. (Asteraceae)

Parthenium is a serious problem in several tropical and sub-tropical areas around the world and particularly an emerging problem in southern Africa. It is a Weed of National Significance in Australia. The chapter summarises current knowledge about the taxonomy, biology, distribution, ecology, impacts and biological control of the weed worldwide. Queensland has led attempts to achieve biological control of parthenium since it first began foreign exploration in 1977. Since then nine insects and two rusts have been released in Queensland. Some of these have since been, or will be, used by other countries. The program has brought significant benefits to Queensland through an increase in grass biomass in some areas. Instances of non-target attack by one agent, particularly in India, are discussed with the conclusion that the effects were ultimately negligible and possibly due to parthenium pollen lodging on the leaves of non-target plants. The insects introduced for parthenium have also given a measure of control for the very closely related weeds, ragweed and Noogoora burr. The paper draws a conclusion that local climatic conditions are very important when considering whether a successful agent in one country will be useful in a second country.