Pseudocercospora purpurea explained

Pseudocercospora purpurea is a fungal plant pathogen that causes a leaf spot on the avocado.Species Cercospora purpurea was originally found on the leaves of Persea species in Georgia, USA in 1878.[1] before the species was transferred to the Pseudocercospora genus in 1976.

It is also found in New Zealand and Australia,[2] [3] and Tolima, Colombia.[4]

It is also found in Mexico, Martinique, Cameroon, South Africa and in the French West Indies (Gustafson, 1976;[5] Willis and Mavuso, 2007;[6] Everett and Siebert, 2018).[7] In Mexico, it had become the second most common disease in avocados (Turu, 1969). In South Africa, black spots on the leaves causing crop losses of up to 69% have been reported, in fruits used for export from orchards planted in a highly susceptible cultivar without suitable disease management (Darvas et al., 1987; Crous and Braun, 2003).[8]

It can cause significant losses (up to 48%) in commercial avocado production in Columbia by causing poor fruit quality and making fruits unacceptable for export (Lonsdale, 1991;[9] Reina-Noreña et al., 2015).[10]

The symptoms of this disease can be found in leaves, fruit, and stems during all parts of the growth stages. Small angular lesions are seen first, approximately 2.5 mm in diameter. They have a brown to purple coloration which is surrounded by a yellowish halo. As the disease progresses, the spots on the fruit begin to sink (into the skin), forming cracks without causing internal damage (Darvas, 1982; Dann et al., 2013).[11] These cracks, become target entry points for other pathogens, such as fungi (e.g., Colletotrichum gloeosporioides) that cause anthracnose (cankers) (Tamayo, 2004).

The spread of the fungal spores can be helped by wind, rain, and insects. High relative humidity and high temperatures also help in the development and spread of the pathogen (Darvas et al., 1987).[12] Usually, the fungus can remain dormant in the leaves for a period of about three months, becoming a source of inoculum for the infection of new fruits (Darvas, 1982).[13]

External links

Notes and References

  1. Web site: Species Fungorum - Names Record . www.speciesfungorum.org . 18 September 2023.
  2. Book: Peterson . R. . Grice . K. . Cercospora spot of avocado. In: Proceedings of the Australian Avocado Growers' Federation Conference, 1992. . 1992 . The Australian Avocado Growers' Federation . Brisbane, Australia . 8–9..
  3. Web site: Cercospora leaf spot . www.business.qld.gov.au . Agriculture and Fisheries Dept. . 18 September 2023 . en-AU . 19 October 2022.
  4. Rodríguez . Eleonora . Reina-Noreña . Julian Alberto . Tamayo-Molano . Pablo Julian . Rodríguez-Polanco . Luz Astrid . Validation of black spot [(''Pseudocercospora purpurea'' (Cooke) Deighton] management strategies in avocado crops in northern Tolima . Revista Colombiana de Ciencias Hortícolas . June 2020 . 14 . 2 . 10.17584/rcch.2020v14i2.10169. free .
  5. Book: Gustafson . D. . Avocado Society Yearbook . 1976 . Avocado Society . Miami, FL . 74–90. . World avocado production..
  6. Book: Willis . A. . Mavuso . Z. . Proc. 6th World Avocado Congress. . 2007 . Viña del Mar, Chile . 8 . Evaluation of alternative fungicides for control of Cercospora spot on ‘Fuerte’..
  7. Everett . K. . Siebert . B. . Exotic plant disease threats to the New Zealand avocado industry and climatic suitability: A review. . N. Z. Plant Prot. . 2018 . 71 . 25–38. . 10.30843/nzpp.2018.71.140. free .
  8. Book: Crous . P. . Braun . U. . Mycosphaerella and its anamorphs: 1. Names published in Cercospora and Passalora. . 2003 . CBS Biodiversity Series . Utrecht, The Netherlands.
  9. Lonsdale . J. . Control of preharvest fruit diseases of avocado. Part I: Efficacy of various Triazole fungicides against Cercospora spot and sooty blotch. . S. Afr. Avocado Grow. Assoc. Yearb. . 1991 . 14 . 61–62..
  10. Reina-Noreña . J. . Mayorga-Cobos . M. . Caldas-Herrera . S. . Rodríguez-Valenzuela . J. . Varón-Devia . E. . El problema de la peca en cultivos de aguacate (Persea americana Mill.) del norte del Tolima, Colombia. . Corpoica Cienc. Tecnol. Agropecu. . 2015 . 16 . 2 . 265–278..
  11. Book: Dann . E. . Ploetz . R. . Coates . L. . Pegg . K. . The avocado: botany, production and uses. . 2013 . CABI . Wallingford, UK . 380–422. . 2nd . Foliar, fruit and soilborne diseases..
  12. Darvas . J. . Kotzé . J. . Wehner . F. . Pathogenicity of fungi causing pre- and post-harvest diseases of avocado fruit. . Phytophylactica . 1987 . 19 . 4 . 489–493.
  13. Darvas, J. 1982. Etiology and control of some fruit diseases of avocado (Persea americana Mill.). PhD thesis. University of Pretoria. Westfalia Estate, South Africa.

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