Rev 11/11/2024
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Nematode around 2 mm long.
Long overlap of esophagus over intestine.
Diovarial females, sexually reproducing.
Typical pratylenchid stylet.
Nematodes are unusually long for endoparasites, but inhabit air channels rather than an intracellular environment.
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Hirschmanniella oryzae is found throughout rice-growing regions, Asia, Japan, West Africa, South America, U.S. in Texas and Louisiana; but is thought not to be present in California. Sher found complexes of several species in collections from rice, including H. spinicaudata and H. belli. Literature prior to 1968 may deal with mixtures.
Many of the 29 currently recognized Hirschmanniella species are associated with rice (Sturhan and Hallmann,2010; Khun et al., 2015).
Zheng (in Davis as a visiting Chinese scholar in the early 1980s), surveyed 100 rice fields around Northern California and concluded all the Hirschmanniella populations that he found were H. belli. He concluded that populations of H. belli in California were much lower than those of H. oryzae in China. The nematodes identified as H. belli are commonly associated with sedges and common cattail (Typha latifolia) along streams and in wet ditches surrounding rice fields. It should be noted that the Zheng and other studies were based on morphometric and anatomical characters of the nematodes and did not employ molecular techniques.
Hirschmanniella species are widespread and are mainly in tropical and subtropical areas (Asia, Africa, the Americas, Oceania). They are adapted to an aquatic environment, and some are marine species whichs is rare among Tylenchid nematodes (Luc, 1987).
A-rated pest in California Nematode Pest Rating System (Martin, 2024).
Migratory endoparasite of roots. Juveniles and adults enter behind the root tip and move in air channels; can also migrate into older roots. Generally, they cause lesions in the root cortex while feeding with their stylets and can be classified as �lesion nematodes�.
Nematodes do not migrate up into stem.
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Rice, corn, sugarcane, grasses, sedges, and many others
Ecophysiological Parameters:
Eggs hatch occurs in 4-5 days in roots; and development to adult takes about 1 month.
Two or more generations are produced per growing season, with a 10- to 15-fold increase - up to 250/g root.
Nematodes are more common in damp paddy fields than drained and dried fields. It survives poorly in dry fields.
Nematode can survive without food for several weeks; may overwinter in dead roots as eggs (if kept moist), also as juveniles and adults.
There is a positive correlation between population densities and pH.
Weeds in and around rice paddies are iconsidered mportant survival hosts.
Infestation retards growth, decreases height, delays tillering, and reduces weight of dry matter.
Causes necrosis of penetrated epidermal cells, damage and destruction of cortical cells resulting in cavities in cortex, necrotic regions, and secondary invasion.
This nematode occurs with H. spinicaudata in West Africa and the combination reduces rice yields by 20%. In contrast to H. oryzae. H. spinicaudata survives well in dry soils.
Previously, H. oryzae was thought to cause a serious disease of rice called "Mentek."
Host Plant Resistance
There is no significant resistance in rice varieties to H. oryzae, although there is considerable tolerance due to repeated individual selection.
Host Plant Resistance, Non-hosts and Crop Rotation alternatives:
Soil Fumigation
Fumigant nematicides are effective in dry fields, but economically questionable.
In trials conducted by A.L. Taylor in Thailand, treatment of soil in rice seedbeds with nematicides (1,3-Dichloropropene (Telone) (then D-D mixture), DBCP, or methyl bromide) and treatment of paddy soil with either D-D or DBCP (both by injection and then flooding) or by flooding and then mixing in DBCP or D-D, increased rough rice yields by 24 to 37%. The weight of plants increased by as much as 95% and tillering increased as much as 43%.
Crop Rotation
Rotation to non-hosts for 1 year is effective, but may be impractical.
Cultural Methods
A prolonged dry period between crops is effective, but may also be difficult to achieve.
Heavy fertilization has been recommended to help offset reduced yields.
In West Africa, H. spinicaudata can reduce rice yields by 20%, and can survive the dry season well in root debris; however, if the fields are flooded between crops, causing the roots to decay, hydrogen sulfide is released and H. spinicaudata survives poorly (research by Fortuner in Senegal). But flooding may be difficult to achieve as river flow diminishes during the dry season, making water less available.
Babatola, J.O. and Bridge, J., 1979. Pathogenicity of Hirschmanniella oryzae, H. spinicaudata, and H. imamuri on rice. Journal of Nematology, 11:128-132.
Bridge, J., Plowright, R.A., and Peng, D., 2005. Nematode parasites of rice. In: Luc M, Sikora RA, Bridge J (eds.). Plant parasitic nematodes in subtropical and tropical agriculture, 2nd Edition. CABI Publishing, Wallingford, Oxfordshire, England. pp. 87-130
Fortuner, R., and Merny, G., 1979. Root-parasitic nematodes of rice. Revue de Nematologie., 2:79-102
Katsuta, A., Toyota, K., Min, Y.Y. and Maung, T.T. 2016 Development of real time PCR primers for the quantification of Meloidogyne graminicola, Hirschmanniella oryzae and Heterodera cajani, pests of the major crops in Myanmar. Nematology 18: 257- 263.
Khun, K., Decraemer, W., Couvreur, M., Karssen, G., Steel, H., and Bert, W., 2015. Deceptive morphological variation in Hirschmanniella mucronata (Nematoda: Pratylenchidae) and a polytomous key to the genus. Nematology, 17:377-400.
Luc, M., 1987. A reappraisal of Tylenchina (Nemata). 7. The family Pratylenchidae Thorne, 1949. Revue de Nematologie, 10: 203-218
Martin, H.J., 2024. California Pest Rating Proposal for Hirschmanniella oryzae (van Breda de Haan, 1902) Luc & Goodey,1964 rice root nematode. California Department of Food and Agriculture, Sacramento, California, USA.
Peng, D., Gaur, H. S., and Bridge, J. 2018. Nematode parasites of rice. In: Sikora, R. A., Coyne, D., Hallmann, J., and Timper, P. Eds. Plant parasitic nematodes in subtropical and tropical agriculture. 3rd Ed. CABI publishing, Wallingford, Oxfordshire, England Pg 120-163.
Prot, J.C., 1992. Rice-root nematodes. In: Webster, R.K. and Gunnell, P.S. (eds.). Compendium of rice diseases. APS Press, The American Phytopathological Society, University of California, Davis. pp. 48-49.
Sturhan, D., and Hallmann, J., 2010. The genus Hirschmanniella (Tylenchida: Pratylenchidae) in Europe, with description of H. halophila sp. n. from Germany and notes on H. caudacrena. Nematology, 12: 809-826.
Tandingan De Ley I, Mundo Ocampo M, Yoder M & De Ley P 2007. Nematodes from vernal pools in the Santa Rosa Plateau Ecological Reserve, California I. Hirschmanniella santarosae sp.n. (Nematode: Pratylenchidae), a cryptic sibling species of H. pomponiensis Abdel Rahman & Maggenti, 1987. Nematology 9: 405-429.
USDA Phytosanitary Certificate Issuance and Tracking System, Phytosanitary Export Database (PExD) Harmful Organisms Database Report. Hirschmanniella oryzae. Accessed 10/4/2024.
Whitehead, A.G., 1998. Migratory endoparasites of roots and tubers (Hirschmanniella, Pratylenchus, Radopholus and Scutellonema). Plant Nematode Control. CABI