Manchurian Wild Rice | Zizania latifolia

California Pest Rating  for
Machurian Wild Rice. Photo credit: National Institute of Water & Atmospheric Research (NIWA), New Zealand
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Manchurian Wild Rice | Zizania latifolia
Pest Rating: A | Proposed Seed Rating: R


Initiating Event:

This plant was been detected in California in 2017.

History & Status:

Zizania latifolia is a large perennial grass growing to 3.5 m.  It is hardy in warm temperate and subtropical areas. It flowers from July to September, and the seeds ripen soon thereafter. The flowers are bisexual. It is adaptable to many soil types and can even grow in shallow water once established. Z latifolia typically grows in dense, long-lived stands on land and water margins, overtopping other riparian species. It is extremely tolerant of damage, grazing, cold or heat, wind, fire, different soil types, moderate shade and moderate salinity.

Although Z. latifolia was once grown in China as a grain crop, it is now almost exclusively grown as a vegetable. The swollen stem bases, infected with the smut fungus Ustilago esculenta, are eaten as a vegetable by the Chinese. They must be harvested before the fungus starts to produce spores, as the stems deteriorate once the smut reaches reproductive maturity.

Official Control: Z. latifolia has been eradicated in California and other states as it serves as a host to a fungus that could infect North American native wild rice species (e.g., Z. aquatica). Importation of the stems to the United States is prohibited in order to protect the North American Zizania from the fungus. A small plot of smut-infested Z. latifolia was discovered growing near Modesto, CA in 1991; it was destroyed to prevent the spread of the smut.

California Distribution:  Z. latifolia is not known to be naturalized in California, but it is being cultivated in Riverside County.

California Interceptions: Z. latifolia was recently submitted to CDFA from a cultivated field in Riverside County.

Worldwide Distribution: Z. latifolia is native to China, Northeastern India, Japan, Korea, Myanmar, and southern Russia where is grown as a vegetable. It is cultivated in Southeast Asia as well. It is naturalized in several other areas. It is unknown whether it is not invasive in these areas despite naturalization, or its invasiveness is ignored due to its long cultivation. Z. latifolia was accidentally introduced into New Zealand where it has become a serious wetland weed in the coastal zone of the North Island. It was also introduced into Hawaii, where it may not have persisted.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. The risk is Medium (2), as the plant could occur in wetlands in warmer areas. Areas such as the Delta as well as irrigation canals and watering ponds might be potential habitat for this plant in California.

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Evaluate the host range of the pest. Score: 3 The risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.

Low (1) has a very limited host range.

Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential: Risk is High (3). The plant spreads vegetatively via rhizomes and produces numerous seeds. Under the right conditions it can spread rapidly in water. The seeds can spread on boats and equipment. Birds may also spread the seed.

Evaluate the natural and artificial dispersal potential of the pest:

Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

High (3) has both high reproduction and dispersal potential.

4) Economic Impact: If it invaded wet meadows (as in New Zealand) or rice fields, it could lower yields and choke out desired plants. It can grow in irrigation ditches and reduce water delivery and access. The swollen stem bases, infected with the smut fungus Ustilago esculenta, are eaten as a vegetable by the Chinese. There is concern that esculenta could spread from Z. latifolia to native North American species of Zizania (e.g., Z. aquatica) that produce commercial wild rice. Z. aquatica is not native to California, but over 16,000 acres of wild rice was grown in California in 2006, making it the largest producer of wild rice in the world.

Economic Impact 4: A, D, E, & G.

Evaluate the likely economic impacts of the pest to California using the criteria below.

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

The potential Economic Impact is High (3):

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact: Under favorable circumstances, latifolia forms permanent stands along water margins and moist meadows of nothing but Zizania latifolia, replacing all other species. It can increase siltation, altering water systems, increase the impact of flooding and destroying habitat for aquatic fauna and flora. The impact is potentially High (3).

Environmental Impact 3: A, C, & D

Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 3

Low (1) causes none of the above to occur.

Medium (2) causes one of the above to occur.

High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Zizania latifolia:

Add up the total score and include it here. High (14)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.
Score: 0

Not established (0) Pest never detected in California, or known only from incursions.

Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (14)


There is moderate uncertainty, as the plant has established and become invasive in New Zealand, but similar conditions occur in limited areas of California. It is native to eastern Asia and widely naturalized beyond its natural range, yet it is not cited as a weed of rice paddies despite being seemingly well adapted to these conditions.

Conclusion and Rating Justification:

A potentially significant weed in CA of both natural wetlands, wet crop lands and irrigation canals. It is also a carrier of a fungus that could attack and seriously reduce productivity of wild rice. Despite some uncertainty, an A rating is justified given the potential risks.


Baldwin, B. G., D. H. Goldman, D. J. Keil, R. Patterson, T. J. Rosatti, and D. H. Wilken, editors. 2012. The Jepson manual: vascular plants of California, second edition. University of California Press, Berkeley.

CDFA Pest Damage Report 331PO6200067 dated 10/19/2017.

CDFA Pest Damage Report 331PO6200069 dated 10/20/2017.

Chen, S., Li, D., Zhu, G., Wu, Z., Lu, S., Liu, L., et al. 2006. Zizania in Flora of China, Vol. 22. Z. Y. Wu & P. H. Raven eds. Beijing; St. Louis, MO: Science Press, Missouri Botanical Garden Press. Pp. 186–187.

Duke, J. A. 1983. Handbook of Energy Crops: Zizania aquatica L. Accessed online 11/9/2017:

Larkcom J. Oriental Vegetables John Murray 1991 ISBN 0-7195-4781-4

Global Invasive Species Database. Species profile: Zizania latifolia. Accessed on on 11/8/2017:

Ohwi, J. 1984. Flora of Japan. F. G. Meyer & E. G. Walker, eds. Smithsonian Institution Press. Washington, D.C.

Tanaka. T. Tanaka’s Cyclopaedia of Edible Plants of the World. Keigaku Publishing 1976

Terrell, E. E. & L. R. Batra. 1982.  Zizania latifolia and Ustilago esculenta, a grass-fungus association. Economic Botany 36: 274–85.

Wagner, W. L. D. R Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i, Volume 1. University of Hawai’i and Bishop Museum Press. Honolulu, HI.

Weedbusters Plant Profile: Manchurian Wild Rice. Accessed 11/8/2017:

Photo credit: National Institute of Water & Atmospheric Research (NIWA), New Zealand

Responsible Party:

Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6650;[@]


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Pest Rating: A | Proposed Seed Rating: R

Posted by ls

11 thoughts on “Manchurian Wild Rice | Zizania latifolia”

  1. One can apply for a permit to do so and it will be evaluated by CDFA technical staff. However, CDFA generally does not grant permits for commercial production of actionable pests/weeds that are deemed high risk in California. When working with a fungal pathogen it is even more difficult to prevent unintended release.

  2. Consequences on worldwide distribution and official control.

    Worldwide Distribution:
    Zizania Latifolia is considered a native plant in Hawaii. Zizania Latifolia, which has been cultivated and prevalent at lakes and/or wetlands, is native to the regions of Southeast Asia, Japan, Korea, China (Guo et al. 2007; Xu et al. 2008; Zhang et al. 2014), Taiwan, North-eastern India (Jain et al. 2011 & 2012; Bor 1940 & 1960; Shukla 1996), Russia’s Far East (Agro Atlas 2008;Tzvelev 1989; Bor 1940 & 1960; Shukla 1996), Ukraine (Prokudin et al. 1977; Dubyna et al. 1996), Britain (Fern 1997), and Lithuanica (Liatukas et al. 2009) where are grown as a vegetable. It has been introduced into Hawaii (Lichvar et al. 2016).

    Zizania latifolia was introduced into New Zealand and was naturalized in 1906 (New Zealand plant conservation network, Zizania Latifolia (2013)).

    An illegal planting of Zizania Latifolia infected with smut fungus, Ustilago esculenta Henn., was discovered near Modesto, California in 1991 (APSnet: plant disease back issue abstracts). It was destroyed to prevent the spread of the smut that poses a threat to native wild rice.
    However, the only Zizania specie that grows in California is Zizania aquatica, and it is neither a threatened nor an endangered species in the state of California.

    Without further concrete evidence backed by scientific research, the posted score of 14 is not justified.

    1. Zizania latifolia is not native to Hawaii, Britain, or Lithuania. It is naturalized in these areas and considered invasive in some of its naturalized range (especially in New Zealand).

      In California, no native species of Zizania occur, but Z. palustris is widely grown for its grain. Therefore, any pest or disease that may threaten Zizania spp. must be viewed as high risk. Risk analysis is most useful in identifying potential risk. Once negative impacts appear, it may be too late to eradicate the organism of interest. Therefore, a score indicating high risk is appropriate for Zizania latifolia.

      1. Do you have concrete evidence back by scientific research that Ustilago esculenta will indeed attack Zizania palustris? Why can’t we do an experiment and introduce Ustilago esculenta to Zizania palustris in a closed environment and see if it does attack it? Without further tests, you are simply making assumptions.

        1. Credible assumptions are the basis of risk analysis, as they rely on the best available evidence. Zizania latifolia and Z. palustris are congeners and close relatives. Some of the worst environmental damage has been done to North American plants by fungi that evolved on congeners in Asia. These include Chestnut blight that caused the biological extinction of billions of American chestnuts that dominated many forests in the eastern U.S., Dutch elm disease that has destroyed billions of American elms, and beech scale (the vector of beech bark disease).

  3. Comments on consequences of introduction:
    1) Climate/host interaction; score: medium (2).
    The restriction of temperature for Zizania latifolia to grow is 68°F~86°F; it grows slow when temperature is lower than 59°F. Zizania latifolia stops growing when temperature is lower than 50°F or greater than 86°F. A land with pH 5.5~6.5 is suitable for this plant to grow. (李文汕 2001- published in Chinese).

    2) Known pest host range; score: low (1).
    Ustilago esculenta actively grows when temperature is about 77°F (李文汕 2001- published in Chinese). This species attacks Zizania latifolia, which has restricted host range and is the only known host (Chung et al. 2004), and it is transmitted in the rhizome (Chung et al. 2004). This fungus is not dangerous due to infection of other Oryzeae (Liatukas et al. 2009).

    3) Pest dispersal potential; score: low (1).
    Infection with Ustilago esculenta, spends its entire life cycle in the host plant (Chung et al. 2004), destroys the flowering structures of the plant and does not make seed; and the plant is propagated asexually by rhizome (Terrell et al. 1982; Chan et al. 1980). Without providing sufficient supply of water and without having moderate ambient temperature, the plant does not have high reproduction or dispersion.

    4) Economic impact; score: low (1) causes 0 or 1 (e.g., G) of the impacts.
    The studies of cytological and morphological suggested that the Asian Zizania latifolia is clearly differentiated from the North American species (Duvall, 1987; Terrell et aI., 1997), which was well proved by phylogenetic study (Xu et aI., 2010). It is a nutritious aquatic vegetable for growing Zizania latifolia rather than planting the native Zizania in North America for crops (Terrell et al. 1982; Kawagishi et al. 2006). When the supply of water is recirculated in a closed system, the impact of agricultural use for irrigation will be insignificant.

    5) Environment impact; score: medium (2) cause one of the above to occur (e.g., A). Zizania latifolia grows quickly when nitrogen and phosphorus are abundant in the environment (Lee et al. 2004). It is likely that polluted water saturated with nutrients from sewage waste was favorable for vegetative development of this plant. Research in New Zealand showed that Zizania latifolia was superior in cleaning of dairy farm wastewater than Phragmites australis (Tanner 1996). This plant can be grown in wetlands or shallow shores of water bodies as forage for cattle and horses (Pan et al. 1993; Zhai et al. 2001).
    It can cause land to become waterlogged and form swampy areas due to destroyed drainage systems. It can damage lakes and streamside plant communities by overtopping and suppressing the other plants (Liatukas et al. 2009).
    6) Post entry distribution and survey information; score: not established (0).
    Zizania latifolia has been planted in Riverside, California since 2015. Pest has never detected in California.

    Final score: Low (7).
    Conclusion and rating justification:
    The ambient temperature for Zizania latifolia to grow is 68°F~86°F; it grows slow when temperature is lower than 59°F. Zizania latifolia stops growing when temperature is lower than 50°F or greater than 86°F. A land with pH 5.5~6.5 is suitable for this plant to grow. Ustilago esculenta actively grows when temperature is about 77°F. Under these restrictions, Zizania latifolia can be cultivated in limited areas in California.

    When Ustilago esculenta invades Zizania latifolia, it prevents the plant from flowering and making seed so that the plant is spread asexually by rhizome. Zizania latifolia has been cultivated by G&M nursery in Riverside, California since 2015. Based on G&M’s experience, knowledge, and skills in growing Zizania latifolia, there are not any problems of reproduction or dispersion of Ustilago esculenta during these three years.

    Chan YS, Thrower LB (1980), The host-parasite relationship between Zizania caduciflora Trucz. And Ustilago esculenta P. Henn. Lv. Growth substances in the host-parasite combination, New Phytol. 85, 225-233.

    Chung K, Tzeng DD (2004), Nutritional requirements of the edible gall-producing fungus Ustilago esculenta, Journal of Biological Sciences 4(2), 246-252.

    Duvall MR (1987), A systematic evaluation of the genus Zizania (Poaceae), Ph.D. dissertation, University of Minnesota} St. Paul.

    Kawagishi H, Hota K, Masuda K, Yamaguchi K, Yazawa K, Shibata K, et al. (2006), Osteoclast-forming suppressive compounds from makomotake, Zizania latifolia infected with Ustilago esculenta, Bioci Biotechnol Biochem., 70, 2800-2802.

    Lee DB, Lee KB, Kim CH, Na SY, (2004), Environmental assessment of water, sediment and plants in the Mankyeong river, ROK Environmental Geochemical Health, 26, 135-145.

    Liatukas Z, Stukonis V (2009), Zizania latifolia-a new alien plant in Lithusnia, Botanica Lithuanica 15(1), 17-24.

    Pan FS, He SL, Chen SL, (1993), A systematic and evolutionary study of Zizania L. (Gramineae)-chemical components of the herb. Bulletin of Botanical Research, 13, 399-403.

    Tanner CC (1996), Plants for constructed wetland treatment systems-a comparison of the growth and nutrient uptake of eight emergent species, Ecological Engineering, 7, 58-83.

    Terrell EE, Batra IR (1982), Zizania latifolia and Ustilago esculenta, a grass fungus association, Economic Botany 36(3), 274-285.

    Terrell EE, Peterson PM, Reveal JL, Duvall MP (1997), Taxonomy of north American species of Zizania (Poaceae), SIDA, 17, 533-549.

    Xu X, Walters C, Antolin MF, Alexander ML, Lutz S, Ge S, Wene J (2010), Phylogeny and biogeography of the eastern Asian-North America disjunct wild rice genus (Zizania L., Poaceae), Molecular Phylogenetics and Evolution, 55, 1008-1017.

    Zhai CK, Lu CM} Sun GJ, Lorenz KJ (2001), Comparative study on nutritional value of Chinese and North American wild rice, Journal of Food Compositions Analyses, 14, 371-382.

    李文汕 2001, 茭白筍的引進與種植, 台灣濕地90年8月號第27期,

    Responsible Party: Name, address, telephone number and email address of the rater.
    Name: Chia-Hung Liu, owner of G&M Nursery,
    Address: 10151 Cleveland Ave., Riverside, CA 92503,
    Telephone number: (714) 244-5980
    Email address:

    1. 1.)The temperature limits of optimal growth for Zizania esculenta is of little import for the purposes of assessing its risk of invasion. Many perennial plants stop or slow growth in cooler or hotter temperatures and resume growth when temperatures return to a more moderate range. Z. latifolia has invaded wetlands in habitats as distant as New Zealand and Lithuania; neither country is noted for being as warm as the core native habitat for Z. latifolia.

      2.) This comment refers to Ustilago esculenta, not Z. latifolia. Nevertheless, while Zizania latifolia is the only KNOWN host of Ustilago esculenta, it has never been tested whether it will also attack the main wild rice (Zizania palustris) that is native to North America and grown extensively in California. The possibility that U. esculenta may attack Z. palustris if given a chance is why Z. latifolia and Ustilago esculenta have been treated as pests by the USDA.

      3.) The commenter states that Z. latifolia stems infected with U. esculenta do not flower and grow slowly. That may be true, but not all stems are infected; in many cases parts of clumps may grow well and flower. Studies of biological control effectiveness have determined that, depending on the species, 65% to 95% reduction of seeds in invasive plants is needed to prevent spread. Prevention of flowering, if U. esculenta were to attack the annual native Z. palustris, might have a more devastating effect on the native annual than on the alien perennial.

      4.) There is no doubt that Z. latifolia and Z. palustris are distinct geographically, morphologically, and genetically. Nevertheless, the two species are close relatives and the possibility for sharing susceptibility to U. esculenta is real.

      5.) The effects described here in the PRP and by the commenter justify a (3), not a (2).

      The posted score of 14 (High Risk) is justified.

      1. You’re simply making assumptions without providing hard evidence backed by scientific research.

        1. In the absence of firm evidence of the host range of Ustilago esculenta, a conservative approach is justified to protect California agriculture and environment. Even if U. esculenta proves to have only one host, then there is still evidence that Zizania latifolia is invasive where it is adventive, and that it can outcompete native species.

          1. Is it an option to grow it in a controlled environment? Green house at a location that is away from water sources.

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