An update on progress towards biological control of Nassella neesiana in Australia and New Zealand.

Nassella neesiana ( Chilean needle grass, Poaceae) is a Weed of National Significance in Australia and a declared pest plant in parts of New Zealand. Field observations and laboratory experiments have been undertaken in Argentina to identify fungal pathogens suitable as biocontrol agents. Three rust species have been selected for further study: Uromyces pencanus, Puccinia graminella and Puccinia nassellae. All three have been observed causing severe damage to N. neesiana in the field and are believed to be quite host specific. Attempts to elucidate their life-cycles experimentally have failed to-date and this is discussed. Uromyces pencanus is the most promising of the three because reliable methods have been developed for culturing and storing inoculum and applying it to plants. This paper outlines progress made towards assessing its host specificity and determining its life cycle and also discusses recent findings on P. graminella.