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Last modified: 10 January 2007
Contacts or sources of information - National Institute of Agronomic Investigation (INIA); Moçambique Industrial
Occurrence & Spread - Carvalho and
Mendes (1958) reported for the first time the occurrence of an
unknown disease of coconut palm in northern Mozambique.
Plumb-Dhindsa and Mondjane (1984) considered such a disease to be
lethal yellowing and associated it with a phytoplasma.
Following an earlier report by Rao et al. (1995) a survey was jointly
conducted by the Department of Plant Protection of the Ministry of
Agriculture & Rural Development of Mozambique (DSV) and National
Coconut Development Programme of Tanzania (NCDP) to investigate the
etiology of the then unknown destructive disease. Using both
polymerase chain reaction (PCR) and hybridization techniques, Mpunami
and Seguni (1996) confirmed the occurrence of lethal yellowing
disease (LYD) of coconut palm in Cabo Delgado, caused by a
phytoplasma similar to that found in Tanzania and Kenya. The
disease was confined to Cabo Delgado, with highest incidence in the
districts of Palma and Mocímboa-da-Pra
Typical symptoms of LYD observed include premature
nut fall, followed by necrosis of the inflorescence, yellowing and
browning of leaves starting from the base of the crown. In
advanced stage, the leaves fall down leaving only the trunk,
resembling a telephone post. Infected plants die within 4-6 months
from first symptoms. Within Zambézia provice, the disease was
found in Chinde, Inhassunge, Nicoadala, Namacurra and
Within Cabo Delgado provide, LYD is found in Palma,
(Reproduced from the paper presented by B.S. Nuvanga and J.S. Cumbi at the 2nd International Coconut Workshop for Africa, Mombasa, Kenya, 8 - 12 May 2000)
Currently active areas & Suspected new outbreaks - There has been continued active spread of LYD in the coastal coconut belt to SW and NE of Quelimane, but substantial areas still remain free of the disease including the Malayan Dwarf seed garden at Macuse. At least two new districts have been affected since 2000 and there are many new foci in previously-affected districts. Despite this, the overall percentage losses by district are still low. Disease foci are known to have been present in Moma Sede and Larde since 2001 but probably became established earlier. There is no precise information on the extent of disease but 11,761 diseased palms have already been cut down in Moma Sede under a PROAGRI programme (which currently operates only in Moma); 12,500 palms (about half) have been affected by disease in one block on Boror estate at Ligonha (this probably includes palms damaged by rhinoceros beetle). New foci are reported at the bay of Angoche (Sicupire), 13km from Angoche at Mamaripe, and at Sangage (Nantapa, Mulaenda and Topa, 43km from Angoche). The disease is thought to be present in the plantation at Mogincual district and there are hearsay reports from the plantation at Quinga. Major epidemics were reported from Mocimba da Praia and Pemba regions in late 1990s and investigated by Mozambique authorities working with NCDP (Tanzania) scientists. Satellite photographs (Google Earth) suggest only a few mainly scattered coconuts remain along coastline; however, high resolution images are lacking for parts of area including offshore islands. The owner of the plantation on Quirimba Island (800ha mature coconuts, about 8km offshore) reports sporadic cases attributed to LYD (about 2-3 palms per annum) and considers that the low incidence is maintained through prompt removals. No LYD has been reported so far from Inhambane or other provinces. Quarantine measures, including checkpoints at key roadside locations, are in place to restrict movement of coconut planting materials from north to south.
(Extracted from consultancy report by Eden-Green (2006) commissioned by Millennium Challenge Corporation).
Other palm/plant hosts
New hosts, new vectors, new strains or suspected loss of resistance - confirmed or unconfirmed
99/109 Genetic diversity in coconut lethal yellow disease phytoplasmas in East Africa
Lethal diseases of palms occur in several parts of the world. Palm lethal yellowing phytoplasma (EPPO A1 quarantine pest) occurs in the Caribbean, Mexico, Belize and Honduras. Similar phytoplasma diseases are observed in West Africa (Cameroon, Ghana, Nigeria, Togo) and in East Africa (Kenya, Mozambique, Tanzania). Similarities between diseases have led to the assumption that palm lethal yellowing in the Americas and the African lethal diseases were similar. However, important difference in epidemiology and varietal susceptibility suggested differences between pathogens on each continent and also between East and West Africa. Genetic comparisons have previously shown that phytoplasma isolates from East Africa were related but distinct from those in West Africa and the Caribbean (see EPPO RS 97/222, 94/223).
Further genetic comparison have been made between isolates from East Africa. In Tanzania, 22 million coconut trees (Cocos nucifera) are planted along the mainland coast and in the islands of Zanzibar, Pemba and Mafia. The lethal disease was first reported in coconut trees near Bagamoyo (region of Dar es Salaam) at the beginning of this century. The disease has caused extensive damage on the mainland for the last 30 years and now also occurs in Mafia island. However, disease incidence is not identical in all affected regions. In southern regions, it is estimated that 56% palm trees have been killed since 1965 whereas only 8.5% have been affected in northern regions. Using PCR, RFLP and rDNA sequencing, genetic comparison were made between several Tanzanian isolates from regions with low, medium and high disease incidence. Phytoplasma isolates from Kenya (neighbouring region, north of Tanzania) and from Mozambique (neighbouring region, south of Tanzania) were also studied. Phytoplasmas were detected in all diseased samples. Results showed that phytoplasma isolates from Kenya and Tanzania are similar. But they are both distinct from Mozambique isolates, the later being related to West African isolates. No distinction could be made between Tanzanian isolates despite the fact that differences are observed in disease incidence. Differences in disease severity observed in Tanzania cannot be explained by the occurrence of different pathogens, but perhaps by genetic variability in palm tree populations or different insect vectors but more studies are needed.
Source: Mpunami, A.A.; Tymon, A.; Jones, P.; Dickinson, M.J. (1999) Genetic diversity in the coconut lethal yellowing disease phytoplasmas of East Africa. Plant Pathology, 48(1), 109-114.
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