What does it look like?
Manchurian wild rice is a giant grass that grows up to 4m high. It has harsh, dull green leaves that are 1-2cm wide and grow in fans. The purplish or red-brown flower heads are 40-60cm long and are produced from November to December. Manchurian wild rice is often confused with native raupo and flax, but raupo is slightly smaller, has bluish-green leaves and dies back in winter. Flax leaves are much smoother and shinier.
In New Zealand, Manchurian wild rice has been recorded in lagoons, riverbanks, tidal flats, roadside ditches, damp pasture, and cropping land. It’s a relatively hardy plant that can grow in both fresh and salt water.
Why is it a problem?
Manchurian wild rice forms dense stands in aquatic or semi-terrestrial areas. It’s very invasive and quickly spreads on land that is not grazed. It’s tolerant of drought, frost and poor drainage, but does not tolerate shade. Regrowth from underground rhizomes occurs after physical damage like fire and grazing.
It spreads mainly by rhizome (underground stem) fragments on excavators and farm machinery. Eel nets, boats, and trailers also spread rhizome fragments. To prevent the spread, all potentially contaminated items should be checked, and all rhizome material removed before leaving an area where it’s present.
Manchurian wild rice reproduces through seed and through its rhizomes (roots), which spread slowly outwards.
Control methods
Infestations are regularly sprayed with herbicides until no further regrowth occurs, which can take several years. 10 years free of regrowth are required before elimination is declared at a site.
More information
Manchurian Wild Rice is not known to occur in Hawke’s Bay.
If you think you have found Manchurian Wild Rice, freephone MPI’s pest and disease hotline on 0800 809 966.
Related links
- https://www.mpi.govt.nz/biosecurity/exotic-pests-and-diseases-in-new-zealand/active-biosecurity-responses-to-pests-and-diseases/
- https://niwa.co.nz/sites/default/files/Freshwater%20invasive%20species%20of%20New%20Zealand%202020_1.pdf
- http://apps.mpi.govt.nz/applications/nzpests-view/Article/635/Manchurian-wild-rice
- http://www.nzpcn.org.nz/flora_details.aspx?ID=2657
- https://www.mpi.govt.nz/biosecurity/long-term-biosecurity-management-programmes/national-interest-pest-responses-programme
- http://www.nzflora.info/factsheet/Taxon/Zizania-latifolia.html
- https://www.thisisus.nz/assets/Resources/New-Zealand-freshwater-weed-and-pest-visual-guide.pdf
- https://www1.maf.govt.nz/uor-cgi/uor.pl/show?species_id=26148
- https://www.weedbusters.org.nz/what-are-weeds/weed-list/manchurian-rice-grass
- NPPA and the control of weeds | NZ Government
Notify Council
If you think you've found this pest, please get in touch with our Biosecurity Team at biosecurity@hbrc.govt.nz or call us on 0800 108 838.
Management Programme
National Pest Plant Accord (NPPA)
The NPPA is designed to prevent the sale, distribution and propagation of a set list of pest plants (the Accord list) within New Zealand. If allowed to spread further, these pest plants could seriously damage the New Zealand economy and environment.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
National Interest Pest Responses programme (NIPR)
Nine harmful weeds are managed under the National Interest Pest Responses (NIPR) programme. These pests could cause serious harm to New Zealand's environment and economy if they are allowed to spread.
More informationNotifiable Organism
Some organisms must be notified to MPI if they're spotted in New Zealand. These include serious pests and diseases like foot-and-mouth disease, the rabies virus, fruit fly and disease-carrying mosquitoes. If a notifiable organism established in New Zealand, it could severely affect our primary production or trade and market access. If you spot a notifiable organism, you have a legal obligation under section 44 of the Biosecurity Act 1993 to tell MPI. Call the pests-and-diseases hotline on 0800 80 99 66.
The Biosecurity (Notifiable Organisms) Order 2016 lists notifiable organisms. New additions can be made by the Governor-General and MPI periodically reviews the list to ensure it is up-to-date.
Taxonomies
FamilyPoaceae
TypePlants
GroupGrass
HabitatLand
Management ProgrammeNational Pest Plant Accord (NPPA)Unwanted OrganismNational Interest Pest Responses programme (NIPR)Notifiable Organism
