Preferred scientific name
Erythricium salmonicolor (Berk. & Broome) Burds. 1985
- Corticium salmonicolor Berk. & Broome 1873
- Pellicularia salmonicolor (Berk. & Broome) Dastur 1946
- Phanerochaete salmonicolor (Berk. & Broome) Jülich 1975
- Necator decretus Massee 1898
Preferred common name
Pink disease of citrus
Alternative common name
- Cobweb disease of citrus
- Pink limb blight
Common host plants
E. salmonicolor is present in many countries (CAB International 1996) where it can infect all citrus varieties and a wide range of other woody plants (Cooke et al. 2009; Food and Fertilizer Technology Center 2003; Timmer 2000). E. salmonicolor has been reported in eastern Australia on grapefruit (C. paradisi), lemon (C. limon), lime (C. aurantifolia), mandarin (C. reticulata) and orange (C. sinensis) and cited by New South Wales Department of Primary Industries (1951), Plant Health Australia (2001) and Simmonds (1966).
In eastern Australia this pathogen has also been reported in association with the following alternative hosts:
- African mahogany (Khaya senegalensis)
- apple (Malus X domestica)
- Cassia fistula
- Cassia fruticosa (=Senna fruticosa)
- Cassia nodosa
- chilli (Capsicum annuum)
- crab apple (Malus sylvestris)
- custard apple (Annona cherimoya X squamosa)
- drum-stick tree (Moringa oleifera)
- elm (Ulmus glabra)
- fig (Ficus carica)
- flooded gum (Eucalyptus grandis)
- holly (Ilex aquifolium)
- jackfruit (Artocarpus heterophyllus)
- loquat (Eriobotrya japonica)
- mango (Mangifera indica)
- nashi pear (Pyrus pyrifolia)
- pear (Pyrus communis)
- quince (Cydonia oblonga)
- Senna septemtrionalis
- sugar apple (Annona squamosa)
- tea (Camellia sinensis)
- Thai eggplant (Solanum undatum) [Plant Health Australia 2001, Farr and Rossman 2014].
In addition to these hosts other alternative hosts are known to occur in other countries (Farr and Rossman 2014). As for the many of the alternative hosts listed above, such hosts are distributed widely throughout Western Australia either as minor crops or in home gardens.
Plant part affected
Bark (periderm) tissues of stems and also of the limbs and trunks of mature trees
- New South Wales (New South Wales Department of Primary Industries 1951, Plant Health Australia 2001)
- Northern Territory (Plant Health Australia 2001)
- Queensland (Simmonds 1966, Plant Health Australia 2001)
Status in Western Australia
Erythricium salmonicolor (Berk. & Broome) Burds. 1985 is considered to be absent from Western Australia and is a quarantine pest. It is a prohibited organism under section 12 of the Biosecurity and Agriculture Management Act 2007.
To confirm the current status please check the Western Australian Organism List. For more information on prohibited organisms please see frequently asked questions about the BAM Act and WAOL.
Biology and ecology
When orchard conditions are humid or wet, E. salmonicolor can spread quickly along the outer woody tissues, and is observed as a smooth, white-pink-grey coloured encrusted hyphal mass (Cooke et al. 2009, Food and Fertilizer Technology Center 2003, Timmer 2000). Eventually the bark is penetrated by the fungus and dies, dries to a grey colour, and splits off the tree (Food and Fertilizer Technology Center 2003 Timmer 2000).
This can be associated with gumming in the infected branches (Timmer 2000, Cooke et al. 2009). Often infections result in the ringbarking or girdling and subsequent death of entire limbs or trees (Timmer 2000 Food and Fertilizer Technology Center 2003).
The mechanism of disease spread by E. salmonicolor is not well understood in citrus, and although basiodiospore formation on hyphal masses has been reported on alternative hosts, it had not been observed on citrus (Timmer 2000) until more recently (Timmer and Graham 2006).
Infected bark and wood within an orchard are thought to provide a source of inoculum for infection of nearby healthy trees (Food and Fertilizer Technology Center 2003, Timmer and Graham 2006). Hence, it is recommended that growers cut off infected branches and burn them (Timmer 2000, Cooke et al. 2009). Disease incidence is greater on trees that have dense canopies (Timmer and Graham 2006), presumably as they stay moist for longer.
Because the pathogen can infect multiple woody hosts, infection rates have been reported to be greater in citrus orchards located close to tropical forests (Food and Fertilizer Technology Center 2003, Cooke et al. 2009).
Yield losses are due to limb or tree decline caused by ringbarking or girdling by the fungus (Cooke et al. 2009; Food and Fertilizer Technology Center 2003; Timmer 2000).
Pink disease of citrus can be economically important where crops are grown in tropical wet regions (Timmer 2000, Timmer et al. 2003), and also in subtropical coastal regions of Australia, particularly where an orchard may be close to rainforest (Cooke et al. 2009).
Historically, E. salmonicolor was reported to cause severe damage to Washington navel and Valencia orange trees in the north coast of New South Wales under abnormally wet conditions that occurred over several years prior to 1951 (New South Wales Department of Primary Industries 1951).
What do I do if I find it?
Erythricium salmonicolor (Berk. & Broome) Burds. 1985 is a prohibited organism for Western Australia. It is important that suspected disease occurrence is reported. Its early detection and eradication will help protect the Western Australian citrus industry. Please contact the Pest and Disease Information Service (PaDIS) to report this pest.
CAB International 1996, 'Corticium salmonicolor', Distribution Map 122, 5th edn, CAB International, Wallingford.
Cooke T, Persley D, House S 2009, Diseases of Fruit Crops in Australia. CSIRO Publishing, Collingwood.
Farr DF, Rossman AY 2014, Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA, retrieved 2 May 2014, from http://nt.ars-grin.gov/fungaldatabases/.
Food and Fertilizer Technology Center 2003, 'Major Diseases of Citrus in Asia', Food and Fertilizer Technology Center Publication Database, accessed 2 May 2014, http://www.agnet.org/library.php?func=view&id=20110708000535.
New South Wales Department of Primary Industries 1951, 'Plant disease notes', Australian Plant Disease Recorder, vol. 3, no. 1, pp. 1-15.
Plant Health Australia 2001, Australian Plant Pest Database, online database, accessed 2 May 2014.
Simmonds JH 1966, Host Index of Plant Diseases in Queensland, Department of Primary Industries, Queensland.
Timmer LW 2000, 'Pink Disease and Thread Blight' in LW Timmer, SM Garnsey, JH Graham (eds), Compendium of Citrus Diseases, 2nd edn, The American Phytopathological Society, Minnesota, p. 35.
Timmer LW, Garnsey SW, Broadbent P 2003, 'Diseases of Citrus' in RC Ploetz (ed), Diseases of Tropical Fruit Crops. CABI Publishing, Wallingford, pp. 163-195.
Timmer LW, Graham JH 2006, Fungal Diseases of Citrus that Resemble Systemic, Graft-transmissible Diseases, viewed 2 May 2014, http://www.ivia.es/iocv/enfermedades/Fungal_diseases/Fungal_diseases.htm.