Elsinoë australis (citrus scab)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Plant Trade
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Elsinoë australis Bitanc. & Jenkins
Preferred Common Name
- citrus scab
Other Scientific Names
- Sphaceloma australis Bitanc. & Jenkins
- Sphaceloma fawcettii var. viscosa Jenkins
International Common Names
- English: sweet orange scab
- Spanish: antracnosis del naranjo; costra de los agrios; roña de la naranja dulce; sarna de la naranja dulce; sarna o roña del naranjo dulce
- French: anthracnose de l'oranger; gale des agrumes
- ELSIAU (Elsinoe australis)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Ascomycota
- Subphylum: Pezizomycotina
- Class: Dothideomycetes
- Subclass: Dothideomycetidae
- Order: Myriangiales
- Family: Elsinoaceae
- Genus: Elsinoë
- Species: Elsinoë australis
Notes on Taxonomy and NomenclatureTop of page The teleomorphs of the citrus scab pathogens Elsinöe fawcettii and E. australis are only known from Brazil, so most published information concerns the fungi identified as their anamorphs. The species are differentiated primarily by host range, tissues attacked and molecular markers (Tan et al., 1996; Timmer et al., 1996). Variety scabiosa, previously described by Jenkins (1936), is no longer considered valid. Four pathotypes of E. fawcettii are now recognized based on host range: Florida Broad Host Range, Florida Narrow Host Range, Tryon's and Lemon (Timmer et al., 1996).
DescriptionTop of page Teleomorph
Ascomata pulvinate, globose, dark, pseudoparenchymatous, multi-locular, up to 80-120 µm thick. Asci up to 20 per locule, subglobose or ovoid, bitunicate, inner wall thickened at the top, 12-16 µm diameter, eight-spored. Ascospores hyaline, ellipsoidal or oblong-ellipsoidal, with two to four cells, usually constricted at the central septum, 10-12 x 5-6 µm diameter (12-20 x 4-8 µm for E. australis). Only known from Brazil.
Acervuli intra-epidermal or sub-epidermal, scattered or confluent, pseudoparenchymatous. Conidiogenous cells originated from the upper cells of the pseudoparenchyma or from the hyaline or pale-brown phialidic conidiophores, which have two to four septa. Conidia hyaline, unicellular, ellipsoid, biguttulate, 4-8 x 2-3 µm. Mycelium hyaline, scanty, septate, short-branched. Colonies in culture very slow-growing, rose to purple, well raised above the agar surface and covered by tufts of short, erect hyphae. The anamorphs of E. fawcettii and E. australis are practically identical, except that E. fawcettii produces spindle-shaped conidia (10-15 x 2.5 -3.0 µm) on host tissue whereas E. australis does not.
For more information, see Bitancourt and Jenkins (1936), Sivanesan and Critchett (1974a,b,c), Holliday (1980) and Sivanesan (1984).
DistributionTop of page Ciccarone (1957) identified a scab on lemon fruits in Sicily as caused by E. australis but there have been no records in Italy since.
See also CABI/EPPO (1998, No. 198).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.Last updated: 23 Apr 2020
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Ethiopia||Absent, Invalid presence record(s)||EPPO (2020); CABI/EPPO (2012)|
|India||Absent, Invalid presence record(s)||EPPO (2020)|
|-Tamil Nadu||Absent, Invalid presence record(s)||EPPO (2020)|
|Japan||Present, Localized||EPPO (2020)|
|-Honshu||Present, Localized||EPPO (2020)|
|South Korea||Present||CABI/EPPO (2012); EPPO (2020)|
|Italy||Absent, Formerly present||1957||CABI/EPPO (2012); EPPO (2020)|
|-Sicily||Absent, Formerly present||CABI/EPPO (2012); EPPO (2020)|
|Netherlands||Absent, Confirmed absent by survey||EPPO (2020)|
|Dominican Republic||Absent, Invalid presence record(s)||EPPO (2020)|
|United States||Present, Localized||CABI/EPPO (2012); EPPO (2020)|
|-Arizona||Present, Few occurrences||NAPPO (2011); CABI/EPPO (2012); EPPO (2020)|
|-California||Present, Localized||NAPPO (2016); NAPPO (2013); EPPO (2020)|
|-Florida||Present, Few occurrences||NAPPO (2011); CABI/EPPO (2012); EPPO (2020)|
|-Louisiana||Present, Few occurrences||NAPPO (2010a); CABI/EPPO (2012); EPPO (2020)|
|-Mississippi||Present, Few occurrences||NAPPO (2010); CABI/EPPO (2012); EPPO (2020)|
|-Texas||Present||NAPPO (2010a); CABI/EPPO (2012); EPPO (2020)|
|Australia||Present, Localized||CABI/EPPO (2012); EPPO (2020)|
|-New South Wales||Present, Localized||EPPO (2020); CABI/EPPO (2012)|
|-Queensland||Present, Localized||EPPO (2020); CABI/EPPO (2012)|
|Cook Islands||Present||CABI/EPPO (2012); EPPO (2020)|
|Fiji||Present||CABI/EPPO (2012); EPPO (2020)|
|New Caledonia||Absent, Invalid presence record(s)||EPPO (2020)|
|Niue||Present||CABI/EPPO (2012); EPPO (2020)|
|Samoa||Absent, Unconfirmed presence record(s)||CABI (Undated); CABI/EPPO (2012); EPPO (2020)||Original citation: South Pacific Commission, 2008, personal communication|
|Argentina||Present||CABI/EPPO (2012); EPPO (2020)|
|Bolivia||Present||CABI/EPPO (2012); EPPO (2020)|
|Brazil||Present||CABI/EPPO (2012); EPPO (2020)|
|-Goias||Present||CABI/EPPO (2012); EPPO (2020)|
|-Minas Gerais||Present||CABI/EPPO (2012); EPPO (2020)|
|-Rio de Janeiro||Present||CABI/EPPO (2012); EPPO (2020)|
|-Rio Grande do Sul||Present||CABI/EPPO (2012); EPPO (2020)|
|-Sao Paulo||Present||CABI/EPPO (2012); EPPO (2020)|
|Ecuador||Absent, Invalid presence record(s)||CABI/EPPO (2012); EPPO (2020)|
|Paraguay||Present||CABI/EPPO (2012); EPPO (2020)|
|Uruguay||Present||CABI/EPPO (2012); EPPO (2020)|
Risk of IntroductionTop of page The citrus scab pathogens E. fawcettii and E. australis are not listed as quarantine pests by any regional plant protection organization.
Hosts/Species AffectedTop of page E. australis is most important on orange (Citrus sinensis) and mandarin (C. reticulata) fruit. It also infects lemons (C. limon), satsumas (C. unshiu), limes (C. aurantifolia), Fortunella and fruit of many other citrus species, but is not known to affect leaves.
Host Plants and Other Plants AffectedTop of page
|Citrus aurantiifolia (lime)||Rutaceae||Other|
|Citrus limon (lemon)||Rutaceae||Other|
|Citrus reticulata (mandarin)||Rutaceae||Main|
|Citrus sinensis (navel orange)||Rutaceae||Main|
|Citrus unshiu (satsuma)||Rutaceae||Other|
|Fortunella margarita (oval kumquat)||Rutaceae||Other|
|Simmondsia chinensis (jojoba)||Simmondsiaceae||Other|
Growth StagesTop of page Flowering stage, Fruiting stage, Vegetative growing stage
SymptomsTop of page Fruits are infected in the early stages of their development, grow misshapen and are subject to premature fall. On the rind of developed fruits, raised lesions are formed with different shape, size and colour according to the species and cultivar affected. They appear as scattered protuberances, conical projections or crater-like outgrowths, or they coalesce to give scabby patches or extensive areas of fine eruptions. Scab lesions do not extend into the albedo. E. australis forms larger, smoother, more circular scabs than E. fawcettii scabs, which are typically irregular, warty and deeply fissured.
List of Symptoms/SignsTop of page
|Fruit / abnormal shape|
|Fruit / lesions: scab or pitting|
|Fruit / premature drop|
Biology and EcologyTop of page Inoculum for new infections consists of conidia, and possibly ascospores, from scabs formed on fruits. Conidia are formed abundantly on wet scabs, in a nearly saturated atmosphere, between 20 and 28°C.
Germination of conidia and infection do not require rainfall, both processes being possible in the presence of free water from dew or fog. A wet period of 2.5-3.5 h is needed for conidial infection. The temperature range required for germination of conidia is 13-32°C, but infection does not take place below 14°C or above 25°C (Whiteside, 1975). The incubation period is at least 5 days. The optimal temperature for disease development is 20-21°C. Fruits are infected when young, i.e. when not more than 20 mm across.
The pathogen is able to survive in scab pustules on fruits remaining on the tree, providing the inoculum for the next season. Even in resistant cultivars, the fungus can survive on diseased shoots from susceptible rootstocks (Whiteside, 1988). For more information, see Yamada (1961) and Whiteside (1975, 1988).
Dissemination of the pathogen is mostly by rain (or irrigation water), although insects and, to a certain extent, wind-carried water droplets containing spores may contribute to the spread of the pathogen. In international trade the pathogen can be carried on infected nursery stock, ornamental citrus plants, and fruits.
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Flowers/Inflorescences/Cones/Calyx||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Fruits (inc. pods)||hyphae; spores||Yes||Yes|
|Leaves||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Stems (above ground)/Shoots/Trunks/Branches||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Plant parts not known to carry the pest in trade/transport|
|Growing medium accompanying plants|
ImpactTop of page Of the two citrus scab pathogens, E. fawcettii is the more widespread but E. australis is more economically significant as it attacks species of citrus which are more widely grown.
In the field, E. fawcettii affects lemons, mandarins, tangelos and grapefruits, whereas most cultivars of oranges and limes are less or not affected. The disease may be serious in the nursery on susceptible rootstocks such as sour oranges, rough lemons, Poncirus trifoliata and Citrus limonia. It may stunt seedlings or make them bushy and difficult to bud. Scabs are present, particularly on the young growth. Infested nursery stock is the primary means by which scab is introduced into new plantings. Severely infected fruits are scarred and distorted and consequently unmarketable. E. australis differs in only causing fruit scab, mainly on oranges and mandarins.
Citrus scab is widespread in areas where suitable conditions of temperature and rainfall or high humidity prevail (wet subtropics and cooler tropics). Elsewhere, it occurs when new flush and fruit set coincide with spells of relatively warm, humid weather. It is also favoured by local conditions such as damp, low-lying areas and dense, shaded citrus groves. Citrus scab is important only in areas where susceptible species or cultivars of citrus fruit are grown for the fresh market and where young plants or new growth develop under favourable conditions of temperature, moisture and shade. Losses largely depend on seasonal and local variations in weather. The disease is not a problem in areas with a limited annual rainfall (less than 1300 mm), long-lasting hot seasons (mean monthly temperature above 24°C) or a dry summer. In the Mediterranean region and, more generally, in citrus-growing areas with a dry climate (e.g. California and Arizona in the USA, where the disease has never become established) scab, even if present, is rare or unimportant.
Detection and InspectionTop of page Semi-selective media containing antibiotics and fungicides (dodine) have been developed for isolating E. fawcettii from scab lesions (Whiteside, 1988). The possibility of using immunochemical methods for pathogen detection has been envisaged (Peláez Abellán et al., 1986). E. fawcettii and E. australis are readily distinguished using molecular techniques (Tan et al., 1996).
Similarities to Other Species/ConditionsTop of page E. fawcettii scabs are typically irregular, warty and deeply fissured, whereas E. australis forms larger, smoother, more circular scabs.
Citrus scab may be confused with other diseases, e.g. bacterial canker (Xanthomonas campestris pv. citri) and melanose (Diaporthe citri), or with injuries caused by various agents. For illustrations and further information, see Fawcett (1936), Brun (1971), Knorr (1973), Klotz (1978), Whiteside et al. (1988).
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.Citrus scab can be controlled using resistant cultivars (Ieki, 1982; Yoshida and Shichijo, 1984; Reddy et al., 1986) and by fungicide applications both in the nursery and in the orchard. Protectant fungicides may be applied (copper, ferbam, thiram, difenoconazole and chlorothalonil have been used), or systemic fungicides (benomyl, carbendazim) before flushing and after petal fall (see González, 1980; Rao, 1983; Reddy et al., 1983). Benomyl-tolerant strains of the pathogen have been found (Whiteside, 1980).
Crop sanitation, establishing citrus nurseries in dry areas or in greenhouses, and adoption of proper treatments, may help in production of rootstocks and budwood free from the pathogen. The usual procedures for importation of certified citrus planting material should be followed. For more information, see also Knorr (1977) and Roistacher et al. (1977).
ReferencesTop of page
Brun J, 1971. Les scab des agrumes. Fruits d'Outre Mer, 26:759-767.
Ciccarone A, 1957. Elsinoë australis Bitancourt et Jenkins, causing a citrus scab in Sicily. Rivista di Agrumicoltura, 2:1-36.
Diaz LE; Gimenez G; Zefferino E; Cerdeiras JT, 1992. Relevamiento de especies y biotipos de sarnas de los citrus en Uruguay. (Abstr.) Fitopatol. Bras., 17:165.
EPPO, 2012. EPPO Reporting Service. EPPO Reporting Service. Paris, France: EPPO. http://archives.eppo.org/EPPOReporting/Reporting_Archives.htm
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
IPPC, 2010. Detection of sweet orange scab (Elsinoë australis) in Texas and Louisiana, United States. IPPC Official Pest Report, No. USA-11/1. Rome, Italy: FAO. https://www.ippc.int/
Jenkins AE, 1936. Australian citrus scab caused by Saphaceloma fawcettii scabiosa. Phytopathology, 26:195-196.
Klotz LJ, 1978. Fungal, bacterial, and nonparasitic diseases and injuries originating in the seedbed, nursery, and orchard. In: Reuther W, Calavan EC, Carman GE, eds. The Citrus Industry. Vol. IV. Berkeley, USA: University of California.
Knorr LC, 1977. Citrus. In: Hewitt WB, Chiarappa L, eds. Plant health and quarantine in international transfer of genetic resources. Cleveland, USA: CRC Press, 111-117.
Kunta M; Rascoe J; Sa PBde; Timmer LW; Palm ME; Graça JVda; Mangan RL; Malik NSA; Salas B; Satpute A; Sétamou M; Skaria M, 2013. Sweet orange scab with a new scab disease "syndrome" of citrus in the USA associated with Elsinoë australis. Tropical Plant Pathology, 38(3):203-212. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1982-56762013000300004&lng=en&nrm=iso&tlng=en
NAPPO, 2010. Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Mississippi. NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=470
NAPPO, 2011. Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Florida and Arizona. NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=475
NAPPO, 2013. Phytosanitary Alert System: Sweet Orange Scab (Elsinoë australis) detected in California. NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=571
NAPPO, 2016. Phytosanitary Alert System: Elsinoë australis (Sweet Orange Scab) - APHIS Establishes Quarantined Areas in California for Sweet Orange Scab and Revises the Conditions for Movement of Regulated Fruit and Nursery Stock under the SOS Quarantine. NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=683
Pelaez Abellan AI; Fernandez Martinez AI; Garcia C, 1986. Antigenic detection of the fungus Sphaceloma fawcettii. Ciencias de la Agricultura, 26:3-8.
Rao NNR, 1983. Efficacy of two copper-based fungicides in the control of citrus scab. Pesticides, 17: 31-33.
Roistacher CN; Calavan EC; Navarro L, 1977. Concepts and procedures for importation of citrus budwood. Proceedings of the International Society of Citriculture, 1:133-136.
Tan MK; Timmer LW; Broadbent P; Priest M; Cain P, 1996. Differentiation by molecular analysis of Elsinoe spp. causing scab diseases of citrus and its epidemiological implications. Phytopathology, 86(10):1039-1044; 19 ref.
Yamada S, 1961. Epidemiological studies on the scab disease of Satsuma orange caused by Elsinoë fawcettii Bitancourt et Jenkins and its control. Tokai-Kinki National Agricultural Experiment Station, Horticultural Station, Special Bulletin No. 2.
Yoshida T; Shichijo T, 1984. Testing for resistance of citrus cultivars to Elsinoe fawcettii and segregation of resistance on hybrid seedlings. Bulletin, Fruit Tree Research Station, Japan, B (Okitsu), No. 11:9-16
CABI, Undated. Compendium record. Wallingford, UK: CABI
CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI
NAPPO, 2010. Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Texas and Louisiana. In: Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Texas and Louisiana. USA: NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=451
NAPPO, 2010a. Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Mississippi., NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=470
NAPPO, 2011. Phytosanitary Alert System: Detection of Sweet Orange Scab (Elsinoë australis) in Florida and Arizona., NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=475
NAPPO, 2013. Phytosanitary Alert System: Sweet Orange Scab (Elsinoë australis) detected in California., NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=571
NAPPO, 2016. Phytosanitary Alert System: Elsinoë australis (Sweet Orange Scab) - APHIS Establishes Quarantined Areas in California for Sweet Orange Scab and Revises the Conditions for Movement of Regulated Fruit and Nursery Stock under the SOS Quarantine., NAPPO. http://www.pestalert.org/oprDetail.cfm?oprID=683
Distribution MapsTop of page
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