Zizania latifolia (Griseb.) Hance ex F.Muell

Preferred name: Zizania latifolia

Other scientific names: Hydropyrum latifolium Griseb., Zizania dahurica Turcz. ex Steud., Zizania aquatica var. latifolia (Griseb.) Kom., Zizania mezii Prodoehl, Zizania caduciflora Hand. Mazz., Zizania latifolia (Griseb.) Turcz. ex Stapf

Taxonomic position: Phylum Magnoliophyta, Class: Monocotyledoneae, Order: Poales, Family: Poaceae

Common names: Manchurian wild rice

EPPO Code: ZIZLA

Phytosanitary categorization: EPPO A2 List no. 461.

EPPO region: Azerbaijan, Belarus, Belgium, Estonia, France, Germany, Georgia, Ireland, Italy, Kazakhstan, Lithuania, Russia (non-native: Central Russia, European Russia, Southern Russia; native: Russian Far East and Eastern Siberia), Switzerland, Ukraine, United Kingdom,

Asia: Armenia, China (native: Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Shaanxi, Shandong, Sichuan, Yunnan, Zhejiang), India (Assam, Manipur), Indonesia (Java), Japan (Hokkaido, Honshu, Shikoku, Kyushu, Okinawa), Malaysia (Borneo), Mongolia, Korea (Democratic Peoples Republic of and Republic of), Singapore, Taiwan, Vietnam.

North America: Canada (British Columbia), USA (Hawaii).

Oceania: New Zealand.

Zizania latifolia is native to Eastern Siberia, and the Russian Far East (Afonin et al., 2008; Komarov, 1934; Tzvelev, 1976; Tzvelev & Probatova, 2019). In these areas, the species is distributed sporadically in the natural environment. Native populations of Z. latifolia are also distributed in the east of China along a wide stretch of latitudinal zones (21–50° N). The species can be found in the river basins of the Heilongjiang, Liaohe, Huanghe and Yangtze Rivers (Chen et al., 2017; Wagutu et al., 2022; Yang et al., 2020; Zhang et al., 2016). Z. latifolia has been domesticated and is cultivated in China as an aquatic vegetable (Guo et al., 2007). At present, in China, Z. latifolia is cultivated on more than 60 000 ha (Xie et al., 2023).

In the invasive range, Z. latifolia is locally established in New Zealand in the North Island, namely in Northland, Auckland, Waikato, and Wellington (Freshwater Pests of New Zealand, 2020; New Zealand Plant Conservation Network, 2023). In North America, Z. latifolia is considered established in Hawaii on the islands of Kauai, likely on Oahu, and Hawaii Island. One location has been detected in Canada, British Columbia in 2004 where it is locally abundant in shallow tidal water along the edges of Widgeon Slough on Siwash Island (https://search.museums.ualberta.ca/12-116227).

In the EPPO region, Z. latifolia has been intentionally introduced as an aquatic ornamental since the turn of the 20th century. It was also intentionally introduced from the 1930s onwards in water reservoirs in countries of the former Soviet Union to provide habitat for biota in managed waterbodies (Dubyna et al., 2017). Zizania latifolia was reported in Belarus for the first time in 1966 (Dubovik et al., 2021). Zizania latifolia was planted in Lake Endla (Central Estonia) between 1953 and 1955 (Kuusk et al., 2003). This population is still present in this area (eElurikkus, 2023). In Lithuania, Z. latifolia was recorded in the Dotnuvėlė stream near the Akademija lake in the city of Akademija in 2006 (Liatukas & Stukonis, 2009). It is reported in other countries, e.g. Azerbaijan and Kazakhstan, though the status of the species is unclear.

Zizania latifolia was first introduced in 1934 into the European part of Russia to provide habitat for biota in managed waterbodies (Maltseva & Bobrov, 2017; Morozova, 2014). The introduction of Z. latifolia into the Rybinsk Reservoir started in the late 1950s and in the Middle Volga region in 1957. At present, Z. latifolia can be found along a wide stretch of latitudinal zones (45–60° N). The species can be found in nine regions (oblasts) according to Vinogradova et al. (2018): Bryansk, Vladimir, Kaluga, Kostroma, Moscow, Yaroslavl, Krasnodar, Astrakhan and Volgograd. Starodubtseva et al. (2017) published a record of the species also in the Voronezh oblast region in a protected area (State federal level nature sanctuary Voronezhsky). Z. latifolia occurs e.g., in water reservoirs along the Volga River (Maltseva & Bobrov, 2017) and in lakes, such as Velikoe, Parovoe and Vashutinskoye (Belyakov et al., 2020; Belyakov & Garin, 2018). Z. latifolia is recorded in the Astrakhan State Biosphere Reserve (Afanasiev & Laktionov, 2008).

Zizania latifolia locally established in Belgium where it has been planted as a marsh plant along ponds and lakes (Verloove, 2011). It was first observed in 2009 on the margins of a pond near La Hulpe (https://waarnemingen.be/observation/44769819/), probably as a relic of former cultivation (ornamental use). There are few other observations thereafter (Verloove, 2011). Recently, there have been numerous reports of the species throughout Belgium, probably as a result of the species being included in the alert list of the LIFE RIPARIAS project (https://alert.riparias.be/) and an extensive population was recorded in 2023 along the River Leie near Ghent (pers. comm. I. Jacobs, 2024).

In France, Z. latifolia was introduced in the botanical garden of Paris (Jardin des Plantes). In 1914 it was grown in the Allier Department (Thiollets, Gorbier-Peublanc, near Jaligny) close to the bank of a lake. In 1919, it invaded all the surroundings of the lake, covering an area of 300 m in length and 3–4 m wide. Z. latifolia has been first recorded in the wild in October 2016 in the Pyrenees. Zizania latifolia was detected for the first time in Germany in Freiburg in Breisgau in 2018 on the shore of the lake Opfinger (Amarell, 2020). It is not known how this population was first introduced into the area. In 2023, the species covered at least 200 m of shoreline of this lake (pers. obs. S. Follak, 2023).

The history of introduction into other EPPO countries is less well detailed.

Control of the species is difficult, because of the large annual accumulation of biomass, its extensive underground root/rhizome system, and its ability to grow from small rhizome fragments and the inaccessibility of most populations.

In New Zealand, successful eradication of small to medium (~100 ha in area) populations has been achieved using the grass-specific herbicides (pers. comm. P. Champion, 2024).

Raising water levels in spring (March–May) during the species' germination period could be successful in reducing the area colonized within lakes (Jia et al., 2017; Zhang et al., 2016).

Physical control can be effective at specific times (1) during the period when substantial self-thinning of shoots occurs (June–July) and (2) when the plant is mature but before senescence (September–October) Chandra and Tanaka (2006). However, this is a labour intensive and costly (Jia et al., 2017).

Mechanical diggers can be used to remove the plant from ditches, drainage channels and waterlogged riverbanks, but there is a high risk of transferring rhizome fragments to new sites (https://www.weedbusters.org.nz/what-are-weeds/weed-list/manchurian-rice-grass).

In the EPPO region, Z. latifolia is included on the EPPO A2 list of pests recommended for regulation as a quarantine pest.

In New Zealand, Z. latifolia is a ‘Pest of concern to New Zealand’ (Quarantine pest) (Ministry for Primary Industries, 2023). The species is an unwanted organism and notifiable organism under the Biosecurity Act 1993: propagation, spread, display and sale are prohibited. Z. latifolia is one of nine weed species managed by central government for national eradication under the National Interest Pest Response programme (https://www.mpi.govt.nz/biosecurity/exotic-pests-and-diseases-in-new-zealand/long-term-biosecurity-management-programmes/national-interest-pest-responses-programme/).

In Australia, Z. latifolia is on the National Priority List of Exotic Environmental Pests, Weeds and Diseases. Thus, it is considered as a species of ‘significant environmental and social amenity risk to Australia’ (https://www.agriculture.gov.au/biosecurity-trade/policy/environmental/priority-list). In Western Australia, Z. latifolia is a ‘Declared Pest, Prohibited - s12’. Prohibited organisms are declared pests by virtue of section 22(1) and may only be imported and kept subject to permits (https://www.agric.wa.gov.au/organisms/128909).

EPPO (2024b) recommends that Z. latifolia should be recommended for regulation as a quarantine pest and Z. latifolia should be banned for sale in the EPPO region. Plants for planting (horticulture) should be prohibition for import into the EPPO region.