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Candidatus Phytoplasma palmae (Lethal Yellowing)
General information
Phytoplasmas are associated with many serious diseases of coconut including lethal yellowing- like diseases (LYDs) [1]. Candidatus Phytoplasma palmae is one of the LYDs which is reported to attack 37 species of palms. It is highly destructive and has destroyed a majority of the coconut palms on the Caribbean coast since the 1980s. In Florida, the LYD has also infected the ornamental palms [2]. LYDs are potential threats to the coconut production and yield losses can be significant [3].
The International Board for Plant Genetic Resources (IBPGR) has developed a technical guideline to avoid spread of LYDs by introducing safe movement of plant materials between areas [4].
Symptoms
LYD symptoms are similar in different parts of the world but the progression of symptoms and the susceptibility of different varieties can vary [1]. The typical development of symptoms can help to identify LYD and distinguish it from other diseases [5].
Symptoms observed in mature palms include [3]:
- Early nutfall
- Calyx end of the fallen nuts are observed to be blackened or water-soaked
- Necrosis of newly emerging inflorescences
- The flower spikelets usually blackened
- Foliar discoloration
- Unopened leaves fall off
- Crown withers
Taxonomic information
Category - Bacteria
Domain - Bacteria
Phylum - Firmicutes
Class - Mollicutes
Order - Acholeplasmatales
Family - Acholeplasmataceae
Genus - Candidatus Phytoplasma
Species - palmae
Distribution
LYD has been reported in Florida (US); Central America and Caribbean (Antigua, Bahamas, Belize, Cayman Islands, Cuba, Dominican Republic, Guatemala, Haiti, Honduras, Jamaica, Mexico, St. Kitts & Nevis) [1].
Prevention and Control
- Eradication of infected palms in areas of susceptible germplasm in newly infected areas [3].
- Planting of groundcover crops can reduce the reproductive potential of insect vector H. crudus [3] (e.g. tropical forage grasses such as Brachiara brizantha, Chloris gayana or Hemarthria altissima).
- The use of insecticides helps to reduce the vector population [13].
References
- Gurr, G.M., Johnson, A.C., Ash, G.J., Wilson B.A. L., Ero, M.M., Pilotti, C.A., Dewhurst, C.F. & You, M.S. (2016). Coconut Lethal Yellowing Diseases: A Phytoplasma threat to palms of global economic and social significance. Frontiers Plant Sci, 7(1521).
- CABI CPC (2019a). Datasheet on Haplaxius crudus (American palm cixiid). Retrieved from https://www.cabi.org/cpc/datasheet/35465.
- CABI CPC (2019b). Datasheet on Candidatus Phytoplasma palmae. Retrieved from https://www.cabi.org/cpc/datasheet/38647.
- Frison, E.A, Putter, C.A.J. & Diekmann, M. eds. (1993). FAO/IBPGR technical guidelines for the safe movement of coconut germplasm. Rome, Italy: FAO/IBPGR, 48 pp.
- Sullivan, M. & Harrison, N. (2013). CPHST Pest Datasheet for ‘Candidatus Phytoplasma palmae’ and related strains. USDA-APHIS-PPQ-CPHST.
- Howard, F.W. (1981). Pigment migration in the eye of Myndus crudus (Homoptera: Cixiidae) and its relation to day and night activity. Insect Sci Appl, 2 (3):129-133.
- Howard, F.W., Wilson, M.R. (2001). Hemiptera: Auchenorrhyncha. In F.W. Howard, D. Moore, R.M. Giblin-Davis & R.G. Abad (eds.), Insects on Palms (pp. 128-160). Wallingford, UK: CABI Publishing.
- Molet, T. (2013). CPHST pest datasheet for Haplaxius crudus. USDA-APHIS-PPQ-CPHST.
- EPPO/CABI (1997). Palm lethal yellowing phytoplasma. In I. Smith, D. McNamara, P. Scott & M. Holderness (eds.), Quarantine Pests for Europe (pp. 745-748). Wallingford, UK: CABI Publishing.
- Woodiel, N.L. & Tsai, J.H. (1978). A rotary flight trap used for sampling Haplaxius crudus (Homoptera: Cixiidae) in coconut groves. JNY Entomol Soc, 86 (1):37-44.
- Harrison, N.A. & Elliott, M.L. (2008). Lethal Yellowing of Palms. Plant Health Instr, 714 (1).
- Harries, H.C. (1978). The evolution, dissemination and classification of Cocos nucifera. Bot Rev, 44, 265-320.
- Anon (unknown). Caribbean Plant Health Directors: Priority pest threats to the region - Lethal Yellowing of Coconut.
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