Cercospora janseana: addition to the EPPO Alert List
Why: Cercospora janseana (syn. Sphaerulina oryzina) is a fungal pathogen that causes narrow brown leaf spot (NBLS) of rice. Historically, narrow brown leaf spot was considered to be a sporadic and minor disease, but more recently it has reemerged as a problem for rice growers in the Southern USA, especially where rice is grown in ratoon cropping systems. Yield losses up to 40% have been reported. C. janseana is seedborne and infected rice seed may provide a pathway for long-distance spread. Considering its increased impact, the NPPO of Spain suggested that C. janseana could be usefully added to the Alert List.
Where: C. janseana is reported from tropical and subtropical rice-growing regions in Africa, Asia, the Americas and Oceania.
In the EPPO region, record of the presence of C. janseana exists in the Russian Federation in the Far East and Southern Russia in the 1990s. However, no recent records were found.
Africa: Angola, Chad, Congo (Democratic Republic of the), Gabon, Gambia, Ghana, Kenya, Madagascar, Malawi, Mozambique, Niger, Nigeria, Somalia, South Africa, Sudan, Tanzania (United Republic of), Togo, Zambia, Zimbabwe.
Asia: Afghanistan, Bangladesh, Brunei Darussalam, Cambodia, China (Guangxi, Hebei, Hubei, Hunan, Jiangsu, Jilin, Liaoning, Sichuan, Yunnan, Zhejiang), India (Haryana, Karnataka, Mizoram, Tamil Nadu, Uttar Pradesh), Indonesia (Java, Sumatra), Japan, Korea, Republic of, Lao People's Democratic Republic, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Sri Lanka, Syrian Arab Republic, Taiwan, Thailand, Vietnam
North America: Mexico, USA (Alabama, Arkansas, Florida, Louisiana, South Carolina, Texas)
Central America and the Caribbean: Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, Nicaragua, Panama, Puerto Rico, Trinidad and Tobago, Virgin Islands.
South America: Argentina, Bolivia, Brazil (Amazonas, Minas Gerais, Rio Grande do Sul, Santa Catarina, Sao Paulo), Colombia, Guyana, Suriname, Venezuela.
Oceania: Australia, Fiji, Papua New Guinea, Solomon Islands.
On which plants: The main host of C. janseana is rice, Oryza sativa. It has also been reported on other Oryza species, including O. barthii, O. latifolia, and O. rufipogon. It is unclear if historical records on other Poaceae hosts, which may act as alternative hosts, were misidentified and instead are different Cercospora species.
Damage: On rice, C. janseana affects leaves, sheaths, panicles and grains. Initial symptoms include narrow reddish-brown spots on leaves and sheaths. On susceptible cultivars this can develop into chlorosis and necrosis and early senescence. In severe infections, lesions can extend to panicles and glumes causing grain discolouration, poor grain filling, premature kernel ripening and reduced milling quality. In severe cases, plant lodging has been reported. C. janseana predominantly affects rice late in the growing season with peak host vulnerability occurring between heading and maturity. Rice grown in ratoon cropping systems are particularly susceptible due to greater inoculum build-up. In the USA, narrow brown leaf spot disease has been historically considered as a minor disease before 1950s. However, severe outbreaks have been reported since the 2010s despite the use of resistant cultivars.
Panicle disease symptoms from C. janseana can be misidentified as neck blast (caused by Pyricularia grisea), so identification from symptoms alone can be unreliable.
Dissemination: C. janseana overwinters on rice straw and stubble. Conidia (asexual spores) are released from infected hosts under high humidity and temperatures ranging from 20 to 28°C, and are dispersed by wind, rain splash and agricultural machinery. C. janseana is known to be seedborne which can facilitate long distance spread. It is suggested that C. janseana can also survive in volunteer rice and alternative grass hosts although it is not yet clear how alternative hosts contribute to disease development in rice.
Pathways: Seeds of host plants from countries where C. janseana is known to occur. Contaminated crop residues
Possible risks: Rice is an economically important crop grown in the southern part of Europe, Türkiye and around the Black Sea. C. janseana requires warm and humid conditions. It is not clear what impact C. janseana would have on rice crops grown in the EPPO region if it was established. A range of control strategies are available to control the spread of C. janseana including cultural practices such as crop rotation (to reduce inoculum buildup) and early planting of rice, chemical control measures and planting resistant varieties. C. janseana has multiple races which has contributed to overcoming host resistance.
The EPPO Secretariat considered that the attention of NPPOs of the EPPO region should be drawn to this reemerging disease which is not present in the EPPO region but could be introduced with infected seeds.
Sources
Agroatlas (2004). Distribution of the Cercospora Leaf Spot (Cercospora oryzae Miyake). https://agroatlas.ru/en/content/diseases/Oryzae/Oryzae_Cercospora_oryzae/map/index.html
Braun U, Crous PW, Nakashima C (2015) Cercosporoid fungi (Mycosphaerellaceae) 3. species on monocots (Poaceae, true grasses). IMA fungus 6(1), 25-98. https://doi.org/10.5598/imafungus.2015.06.01.03
CABI Compendium (2021) Sphaerulina oryzina (narrow brown leaf spot) Datasheet. Accessed at: https://doi.org/10.1079/cabicompendium.12254
INTERNET
- Interactive Agricultural Ecological Atlas of Russia and Neighbouring Countries. Diseases: Cercospora oryzae Miyake (teleomorpha Sphaerulina oryzina Hara) – Cercospora leaf spot, narrow brown leaf spot. Accessed at: https://agroatlas.ru/en/content/diseases/Oryzae/Oryzae_Cercospora_oryzae/index.html
NPPO of Spain (2026-09).
Pedrozo R, de Paula S, Flasco M, Dalla Lana F, Jia Y, Nicolli C (2025) New threats to rice production: emerging pathogens and their impact. Rice Production Strategies-Addressing Abiotic and Biotic Stresses and Socioeconomic Changes. https://doi.org/10.5772/intechopen.1011393
Searight J, Famoso AN, Zhou XG, Doyle VP, Richards JK (2023) A high-quality genome assembly for Cercospora janseana, causal agent of narrow brown leaf spot of rice. Molecular Plant-Microbe Interactions 36(10), 666-669. https://doi.org/10.1094/MPMI-10-22-0222-A
Searight J, Doyle VP, Famoso AN, Zhou X-G, Richards JK (2025) A population genomics approach to understand the diversity, migration, and reproduction of the rice pathogen Cercospora janseana. Molecular Plant-Microbe Interactions 38(6), 949–959. https://doi.org/10.1094/MPMI-03-25-0031-R
Uppala S, Zhou X, Chapala M, Vineela D, Sompalli S, Kotamraju V (2026) Narrow brown leaf spot of rice. The Plant Health Instructor. 26 http://doi.org/10.1094/PHI-P-2025-07-0003