A long and winding road – the process of importing a rust fungus Uromyces pencanus as a biocontrol agent of Chilean needle grass (Nassella neesiana) in New Zealand

Abstract

Chilean needle grass [CNG] (Nassella neesiana) is mostly a pasture weed in New Zealand where it outcompetes and displaces pasture species and can cause major damage to stock. Native to Agentina, CNG is widespread in Hawke’s Bay and Marlborough, with smaller sites in northern Canterbury and Auckland. A rust fungus, Uromyces pencanus, was identified as the most suitable biocontrol candidate against CNG, with strain UP27 shown to be highly host specific after extensive research undertaken in Argentina. In 2011, the New Zealand Environmental Protection Authority (EPA) granted permission to import Uromyces pencanus. Ten years on, a permission to export the rust from Argentina was finally approved during the Covid-19 pandemic, with a three-month export permit. During that time, additional host range testing were undertaken for Australia which resulted in the unexpected production of U. pencanus spores on two non-target Austrostipa species from Australia. The journey from finding a suitable biological control agent for CNG to getting a culture into New Zealand and the future outlook of this project are discussed.