Collar rot explained

Collar rot is a symptomatically described disease that is usually caused by any one of various fungal and oomycete plant pathogens. It is present where the pathogen causes a lesion localized at or about the collet between the stem and the root. The lesions develop around the stem eventually forming a "collar". Observationally, collar rot grades into "basal stem rot", and with some pathogens is the first phase of "basal stem rot" often followed by "root rot". Collar rot is most often observed in seedings grown in infected soil. The pathogens that cause collar rot may be species or genera specific. But generalist pathogens such as Agroathelia rolfsii (aka Sclerotium rolfsii or Athelia rolfsii) are known to attack over 200 different species.^[1] While bacteria caused collar rot is not common, trees infected with Fire blight (Erwinia amylovora) may develop collar rot.^[2] Non-parasitic collar rot may be caused by winter damage.The symptomatically described disease Southern blight is often the first observed precursor of the collar rot caused by the fungus Agroathelia rolfsii. Causally known as Sclerotial blight,^[3] Agroathelia rolfsii survives in the soil as sclerotia, and in infected decomposing plant material as mycelia.^[4]

Collar rot that is caused by the oomycete Phytophthora is causally called Phytophthora collar rot, and is a common disease of fruit and nut trees,^[5] as well as other flowers and crops.^{[6] [7]} Phytophthora species remain in the soil, as spores, and in infected plant tissue, as mycelia, so absent control measures (sterilization, toxic applications) the disease continues so long as susceptible plants are grown in that soil.^[8]

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Hosts and agents

• In carnations (Dianthus caryophyllus) by Alternaria dianthi,^[9]
• In chili (Capsicum) by Phytophthora,^[10]
• In cinchona (Cinchona officinalis) by Phytophthora quininea,^[11]
• In Chinese evergreens (Aglaonema) by Fusarium subgutinans,
• In coffee plants (Coffea) by Gibberella stilboides,^[12]
• In dogwoods (genus Cornus) by Phytophthora cactorum where the disease is also called "crown canker",^[13]
• In eggplant/brinjal (Solanum melongena) by Sclerotinia sclerotiorum and Sclerotium rolfsii,^[14]
• In elephant foot yams (Amorphophallus paeoniifolius) by Sclerotium rolfsii,^[15]
• In fruit and nut trees by a variety of pathogens including Sclerotium rolfsii, Alternaria^[16] and Phytophthora,
• In groundnut/peanut (Arachis hypogaea) by Aspergillus niger which also causes wilt and crown rot,^[17] and by Lasiodiplodia theobromae,
• In hardwoods and conifers by Phytophthora cinnamomi,
• In maize (corn, Zea mays) by Sclerotium rolfsii,
• In papaya by Calonectria,
• In pines by both Phytophthora and Diplodia pinastri,
• In rhododendron, China aster, marigold, gloxinia and zinnia by Phytophthora cryptogea,
• In sunflowers by Sclerotium rolfsii,^{[18] [19]} and by Phytophthora cryptogea.
• In sweet potatoes (Ipomoea batatas) by Sclerotium rolfsii,
• In tobacco by Sclerotinia sclerotiorum.^[20]
• In tomatoes (Solanum lycopersicum) by Alternaria solani,^[21]

Related diseases

• Rootstock blight^[22]
• Stem rot

Notes and References

1. Ahmad, Yasmin . Mirza, M. Siddique . Aslan, M. . 1988. Collar Rot of Maize caused by Sclerotium rolfsii in Pakistan. Pakistan Journal of Agricultural Research. 9. 4. 604–605. https://web.archive.org/web/20141102214500/http://www.cabi.org/GARA/FullTextPDF/Pre2000/19901141977.pdf. 2 November 2014. live.
2. Book: Horst . R. Kenneth. 2008. Westcott's Plant Disease Handbook. seventh. Dordrecht. Springer Verlag. 105. 978-1-4020-5193-7.
3. Web site: Ames, Teresa . Sweetpotato Diagnotes: Sclerotial blight . Centre for Biological Information Technology (CBIT), The University of Queensland .
4. Web site: Hartman, John . Beale, Julie . Bachi, Paul . Plant Pathology Fact Sheet: Root and Collar Rots of Tree Fruits . College of Agriculture, University of Kentucky . https://web.archive.org/web/20081204190255/http://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-FR-T-10.pdf . 4 December 2008 . dead . 22 November 2014 .
5. Web site: Thomson, Sherman V.. Scott, C. Ockey. 1998. Utah Pests Fact Sheet: Phytophthora Crown and Collar Rot. Utah Plant Disease Control No. 6. Utah State University Extension and Utah Plant Pest Diagnostic Lab (UPPDL). https://web.archive.org/web/20120319093146/https://utahpests.usu.edu/IPM/htm/fruits/fruit-insect-disease/root-crown-rot/. 19 March 2012. dead. 22 November 2014.
6. Book: Erwin, D. C. . Bartnicki-Garcia, S. . Tsao, P. H. . 1983. Phytophthora, its Biology, Taxonomy and Pathology. The American Phytopathological Society. St. Paul, Minnesota. 978-0-89054-050-3.
7. Web site: Gulya, Thomas J.. 2012. Sunflower Diseases Remain Rare in California Seed Production Fields Compared to North Dakota . Plant Management Network. https://web.archive.org/web/20141121215841/http://www.plantmanagementnetwork.org/pub/php/research/2012/sunflower/ . 21 November 2014. live. etal.
8. Book: Agrios, George N.. 1988. Phytophthora Foot, Crown, Collar, Stem, or Trunk Rots . Plant Pathology. third. Burlington. Elsevier. 301–306. 978-0-323-13969-4.
9. Book: Horst, R. Kenneth. 2013. Field Manual of Diseases on Garden and Greenhouse Flowers. Dordrecht. Springer Verlag. 43. 978-94-007-6049-3. 10.1007/978-94-007-6049-3. 6747201.
10. Akter, M. K. . 2007 . Pathogenicity of Phytophthora capsici and possibilities of its biological and chemical control . Journal of Agroforestry and Environment . 1 . 2 . 81–84 . https://web.archive.org/web/20141121224346/http://www.cseas.kyoto-u.ac.jp/brahmaputra/JAE/ASFBpdf/2.AFSB1(2)pdf/18.%20Nahar%201.pdf . 21 November 2014 . dead. etal . 22 November 2014 .
11. Book: Crandall, Bowen S.. 1950. Cinchona root and collar rot in Peru and Bolivia. Circular no. 855. Washington, DC. United States Department of Agriculture.
12. Baker, Celia J.. 1970. Coffee bark disease in Kenya. Kenya Coffee. 35. 414. 226–228. subscription .
13. Web site: Snover-Clift, Karen . Jensen-Tracey, Sandra. 2011. Crown Canker of Dogwood, Phytophthora cactorum. Department of Plant Pathology and Plant-Microbe Biology, Cornell University. https://web.archive.org/web/20120614211406/http://plantclinic.cornell.edu/factsheets/dogwoodcrowncanker.pdf . 14 June 2012. live.
14. Book: Reddy, P. Parvatha. 2014. Solanaceous Vegetable Crops, 8.3.2 Collar Rot, Sclerotinia sclerotiorum, Sclerotium rolfsii. Plant Growth Promoting Rhizobacteria for Horticultural Crop Protection. New Delhi, India. Springer Verlag. 162–163. 978-81-322-1972-9. 10.1007/978-81-322-1973-6. 44837424.
15. Pravi, V. . Jeeva, M. L. . Archana, P. V. . 2014. Rapid and Sensitive Detection of Sclerotium rolfsii Associated with Collar Rot Disease of Amorphophallus paeoniifolius by Species-Specific Polymerase Chain Reaction Assay. Molecular Biotechnology . 56. 9. 787–794 . 24788585. 10.1007/s12033-014-9757-x . 10370740 .
16. Book: Khan, Aslam. 2001. Plant Diseases. Delhi, India. Kalpaz Publications. 99–102. 978-81-7835-052-3.
17. Kishore, G. Krishna . Pande, S. . Podile, A. R. . 2005. Biological control of collar rot disease with broad-spectrum antifungal bacteria associated with groundnut. Canadian Journal of Microbiology. 51. 2. 123–132. 10.1139/w04-119. 16091770 . 19249919 . https://web.archive.org/web/20141031174327/http://podilerao.tripod.com/ramu11.pdf. 31 October 2014. live.
18. Mizra, S. M. . Khokhar, L. K.. 1985. Occurrence of sunflower collar rot diseases caused by Sclerotium rolfsii in Pakistan. Helia. 8 . 41–43.
19. Book: Gulya, Thomas . Rashid, Khalid Y. . Masirevic, Stevan M. . 1997. Sunflower diseases. Schneiter, Albert A.. Sunflower technology and production. Madison, Wisconsin. Soil Science Society of America. 263–379. 978-0-89118-227-6. 10.2134/agronmonogr35.c6.
20. Web site: Virginia Polytechnic Institute. 31 December 2008. Disease Management Research for Virginia Tobacco. Research, Education & Economics Information System, United States Department of Agriculture.
21. Maiero, Marisa . Ng, Timothy J. . Barksdale, Thomas H. . 1990. Inheritance of Collar Rot Resistance in the Tomato Breeding Lines C 1943 and NC EBR-2. Phytopathology. 80. 12. 1365–1368. 10.1094/phyto-80-1365.
22. Symptoms of rootstock blight can be confused with Phytophthora collar rot. Johnson, Kenneth B.. 2005. Fire blight of apple and pear. The Plant Health Instructor . 10.1094/PHI-I-2000-0726-01 . https://web.archive.org/web/20120203212538/http://www.apsnet.org/edcenter/intropp/lessons/prokaryotes/Pages/FireBlight.aspx . 3 February 2012. live.