Image: rust spores for release on a Chilean needle grass leaf.
The Environmental Protection Authority approved the release of the rust fungus in early July, and we’ve since been culturing it in containment to get ready for the first release. In October the Chilean needle grass rust was released at three sites near Blenheim in Marlborough and one site near Spotswood in Canterbury. We selected sites with high densities of Chilean needle grass plants, which were then sheltered to retain moisture. These sites will be left undisturbed for years to come, without spraying, grazing, or mowing, which would hinder establishment.
Luise Schulte, who led the rust release, explained that spores produced by the rust will disperse by wind to spread and infect other Chilean needle grass plants. “The rust infects and grows inside Chilean needle grass leaves and then bursts through the leaf surface, producing dark brown powdery rust pustules. The rust drains energy from infected plants and is most damaging in dry weather since the broken leaf surfaces cause increased water loss. When the wind-dispersed spores land on a Chilean needle grass leaf and are combined with some moisture, they germinate and infect again.”
Image: the release site in Marlborough.
Brent Holmes (Marlborough District Council) assisted us in the field, helping to scope potential release sites and gather baseline data. Warwick Lissaman, from the Chilean Needle Grass Action Group, and Tim Struthers, one of the site landowners, were also present on the day. For the North Canterbury release we had assistance from Morgan Shields (Environment Canterbury).
But the hard work isn’t over yet. Luise will go back to Marlborough in autumn to check for establishment of the rust at the release sites. Also, the strain of rust we released only infects South Island populations of Chilean needle grass, so we will still need to find effective strains for the Hawke’s Bay populations.
The journey to approval for release of the Chilean needle grass rust took about 30 years, involving collaborations with Argentina and Australia and multiple rounds of host range testing. We are very grateful to our international collaborators and everyone who supported this project over the decades.
This work is funded by the National Biocontrol Collective and the Ministry for Primary Industries’ Sustainable Food and Fibre Futures Fund [Grant #20095] on multi-weed biocontrol.
