Detrimental effect of the rust Uromyces pencanus on the invasive species Nassella neesiana (Chilean needle grass).
Nassella neesiana (Poaceae) is a perennial grass species indigenous to South America. While usually not troublesome and sometimes appreciated as a forage species within its native range, it is an unwanted species in other parts of the world, where it is considered a serious threat to native biodiversity and an important hindrance to agriculture. The difficulties encountered in controlling the species by chemical and cultural methods have led to investigate the feasibility of applying classical biological control in Australia and New Zealand. The rust Uromyces pencanus has been selected as a promising agent to this end. The effect of the disease caused by this fungus on growth of artificially inoculated N. neesiana plants was investigated. It was found that diseased plants incubated under controlled environmental conditions grew less, produced less green tissue and lost more aerial biomass than healthy control plants. The same tendency was observed under natural environmental conditions. Differences in growth pattern and resistance to disease were encountered between plants from different accessions reared under the same conditions during the experiments. The consequences such differences could have on the efficacy of the rust as a biological control agent are discussed.