In New Zealand, farmers are being empowered to use rust fungus to kill an invasive weed threatening their livelihoods. Since first being detected in the 1920s, likely introduced from South America by way of contaminated wool, packing material, or desired seed stock, Chilean needle grass has spread quickly over the country, unhindered by any native biological agent able to control it. It has covered over 3700 hectares of land to date by being transported on vehicles, farm machinery, and the movement of animals and people.
This invasive species of grass is taking over valuable land, reducing the availability of useful grasses to feed livestock, and is unpalatable to grazing cows and sheep. Even more troubling, the sharp blade tips that inspired the name can penetrate animal skin and eyes and lead to serious infections or blindness in livestock and pets. Previous methods for managing infestations, including destroying infested stock and applying herbicides, have been challenging, expensive, and ultimately ineffectual. Having officially been declared as a pest in 2013 by the Regional Pest Management, agriculturalists are encouraged to take action against the propagation of Chilean needle grass through any effective means.
Enter rust fungus – particularly, the strain Uromyces pencanus – that has been recognized to be a successful biocontrol agent against Chilean needle grass. New Zealand’s Environmental Protection Authority approved the release of this fungus to combat the grass’s growth. The Manaaki Whenua Landcare Research facility was the first to seek permission from the EPA to use the rust fungus, which was granted in 2011.
A ten-year wait followed to get permission to export the rust fungus from Argentina due to the Convention on Biological Diversity (CBD). This treaty aims to protect biodiversity and ensure that benefits from genetic resources are shared fairly. Though biocontrol research institutions don’t profit financially, the CBD applies to biocontrol agents, and the Argentinian government was cautious because it had not exported a pathogen for biocontrol before.
The Landcare Research Facility finally received approval to export the fungus from Argentina in September 2021 but faced even more roadblocks due to the COVID-19 pandemic and accompanying restrictions. The rust fungus spores left Argentina in December 2021 but didn’t reach New Zealand for almost a month. Unfortunately, the fungus spores had not survived the long trip and were no longer viable by the time they reached New Zealand, further delaying the work of the facility. However, renewed approval from the EPA and the Argentinian government has given Landcare Research the opportunity to import another batch. In July 2024, the EPA allowed the release of the fungus to the public after an application from the Marlborough District Council.
According to Dr. Chris Hill, the General Manager of Hazardous Substances and New Organisms in the EPA, the Uromyces pencanus strain was tested and proven to be host-specific, meaning it will only kill and slow down the spread of the Chilean needle grass, not posing any threat to humans, animals, or any other plants, unlike many chemicals used for pest control that do not discriminate between weeds and beneficial plants. Extensive testing on native grasses in particular was conducted to ensure that no damage would be done.
Dr. Hill also stated, “We hope the introduction of this rust fungus will help slow the spread of this aggressive weed and reduce harm to livestock and other farm animals,” ensuring the public that “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 [Maori for power associated with possession and occupation of tribal land].”
