Manchurian Wild Rice


General description

Very tall, perennial grass <3m high, forms dense rhizome mats. Similar to raupo but taller. Leaves usually erect, may bend at top without twisting, (raupo leaves twist, don’t bend). Coarse, light-green leaves with prominent lines, tapering to sharp point. Flowers (Nov-Dec) 40-60cm long, purplish or chestnut brown. Large numbers of seed in some seasons.

Fresh or saline water, on margins, in swamps, adjacent pasture. Tolerates wide range of conditions.

Seed dispersed via birds, water. Rhizome fragments in water, machinery, nets, boats.

Dense growth blocks waterways, impeding drainage, disrupting recreational activities. Out-competes native water species. Invades pasture, causing land to become waterlogged. Causes flooding. Rhizomes penetrate stopbanks.

Site management

Resource consent usually required. Always begin control at top of catchment. For herbicide treatment, budget for 50-70% regrowth after first 1-2 treatments, 10% thereafter. Usually need 5-10 treatments over 6-8 years for eradication. Burn-off of initial spray trash OK if dense, not needed thereafter.

Recommended approaches

1. This species is managed by MAF Biosecurity NZ as a "National Interest Pest" with the aim to contain it within the Kaipara District and eradicate everywhere else in NZ. Please contact MAF Biosecurity on 0800 80 99 662 to report any sites.
2. Dig out very small sites.
3. Weed wipe small sites (terrestial sites only) Sep - Apr (300ml haloxyfop + 5ml crop oil/1L).
4. Spray (terrestial sites) Sep - Apr (100ml haloxyfop + 50ml crop oil/10L).
Follow up 6-8 monthly (not in winter) before regrowth reaches 1m, to prevent rhizome recovery.

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

RPMS status

Total Control - Whole Region
National Pest Plant Accord species - nationwide
Manchurian wild rice - Main species image