Biosecurity: Rust fungus approved to control Chilean needle grass in Marlborough

Chilean needle grass is harmful to animals and could cost farmers millions of dollars in lost production.

The Environmental Protection Authority has approved the release of a rust fungus to control the spread of Chilean needle grass.

Chilean needle grass (Nassella neesiana) is an invasive weed that harms animals and could cost farmers millions of dollars in lost production.

Marlborough District Council applied to use a strain of rust fungus (Uromyces pencanus) as a biocontrol agent against the grass in New Zealand.

Dr Chris Hill, the authority’s general manager, hazardous substances and new organisms, said he hoped rust fungus would slow the aggressive weed’s spread and reduce harm to livestock and other farm animals.

“Testing shows this rust fungus can successfully slow infestations, killing the foliage of the Chilean needle grass, as well as reducing its growth and seed production.

“This rust fungus is highly host-specific, meaning it only lives on Chilean needle grass.”

Hill said testing results showed rust fungus was “highly unlikely” to harm native plants or animals.

“There is also no risk to people.”

Chilean needle grass is a perennial grass from South America and was first identified in New Zealand in the 1920s.

The seeds have sharp tips that can bore into the eyelids and pelts of animals, resulting in severe animal welfare issues, including blindness.

Plants form dense clumps, which exclude pasture species and are less palatable to stock, reducing farm productivity.

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Methods for managing Chilean needle grass infestations on farms, such as destocking for the three months the seeds are present, or applying herbicide, can be difficult and expensive.

One study estimates that, across the sector, the potential cost of lost production could reach as much as $1.16 billion if the weed is left unchecked.

Chilean needle grass is well established in some regions, particularly Hawke’s Bay, Marlborough, Auckland and Canterbury

“Our panel of independent experts approved this release following a rigorous, evidence-based investigative process which included the consideration of public submissions, international best practice and engagement with mana whenua,” Hill said.

In recent years the authority has approved other biocontrol agents for weeds such as old man’s beard, Sydney golden wattle and moth plant, among others.