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Occurrence - Natuna Wilt, Kalimantan Wilt, Samuda Wilt and a leaf yellowing in Sulawesi are coconut diseases of uncertain etiology reported from Indonesia. Since the first reports, these diseases continue to spread round the primary foci and to surrounding areas. They cause great loss of yield forcing some farmers to abandon their plantations or switch to other crops. This is largely due to the fact that there are no effective controls available as the causal agents are still not known. Natuna Wilt and Kalimantan Wilt have very similar symptoms and disease progressions. The period from first symptom to palm death of Natuna and Kalimantan Wilt is 3-9 months. For Samuda Wilt, this period is much longer, around 5-6 years. The leaf yellowing syndrome does not kill the tree, only reduces the yield. The causal agents of the diseases are still unknown but examination of diseased samples by DNA amplification using the polymerase chain reaction gave evidence of an association between phytoplasma and the diseases (Allorerung et al, 1999).
Prior to the investigations of Sitepu in Riau province in Sumatra (Sitepu et al, 1978) and in the Natuna islands (Sitepu, 1979), similar symptoms of disease had been reported from the main island of Borneo (Kalimantan) by Leefmans (1933) and by Muller (1935). Muller described a serious outbreak of a wilt disease of coconut in West Kalimantan, near Pontianak which killed 30,000 palms. He mentioned similar symptoms of wilting and frond breaking and attributed the outbreak to a combination of poor drainage, infection of the bole by Ganoderma lucidum and attack of the fronds by Oxydothis maculosa. Slightly earlier the general annual report of pests and diseases of crops (Leefmans, 1933) mentions a coconut disease from the southeast coast of Borneo from Bij Pegatan and Sampit. It is possible that a similar wilt disease was already present in Samuda, Sampit at that time.
Based on interviews with coconut farmers in the Natuna Islands in 1980 it was indicated that the wilt disease has existed since 1942 in Cemaga Village, in the sub-district of Bunguran Timur. Another incidence was also found in Kelanya village in 1955 and the spread became wider in 1960. The local community calls this disease Awa/Bala disease meaning that the disease is created by God for them as a result of making a sin to bury a dead person without Islamic procedure (Military occupation of these strategic islands in 1942 might account for this).
Infected tissues from coconut stem necrosis, reported by Turner et al (1978) in hybrid and Malayan Dwarf coconuts in North Sumatra (and also in Peninsular Malysia), were seen under electron microscopy to contain MLO but no association with LY was proposed at that time.
At the 4th ICLY Meeting, Hunt (1979) reported on diseased coconut palms near Pekan Baru in Riau province (eastern part of Sumatra) and about 100Km south of Medan in North Sumatra. This followed his inability to visit Natuna where the (then) current outbreak sounded very like LY according to Sitepu, who had been sent there by LPTI, the Industrial Crops Research Institute. The palms that Hunt saw were scattered, not more than about 20 affected and were not part of any major LY-like outbreak. However, individually, the symptoms were not too dissimilar from LY, particularly if one bore in mind that they were not Jamaica Tall. Samples were taken for EM studies by Jones at Rothamsted.
Reports of a visit made in 1999 ( Burotrop bulletin No 14, April 2001) by Warokka and by Jones state that some tress have a natural tolerance to Natuna Wilt and that resistance screening plots should be established.
Key to disease stages of Natuna Wilt of coconut palm (from http://groups.yahoo.com/group/CICLY/message/903)
Stage 0 Healthy palm.
Stage 1 All fronds still appear green but lower fronds droop more heavily, giving a top / bottom effect.
Stage 2 Lower fronds have pronounced droop but less than 5 fronds are drying or have turned brown and are hanging against trunk. Brown leaves are still firmly attached to crown and cannot he easily pulled away.
Stage 3 As in 2 but more than 5 and less than 15 fronds are hanging brown and dry Crown begins to appear thin.
Stage 4 As in 3 but more than 10 fronds remain green in the crown.
Stage 5 Palm has only 5- 1 0 green fronds in poor state, spear is shortened, 'gloss' of health fronds has gone.
Stage 6 Palm has less than 5 green fronds in crown.
Stage 7 Palm is dead, no fronds are green, any fronds remaining will be dry and withered.
Spread - dates and places of subsequent outbreaks (ditto)
Currently active areas - dates and places (seek information/confirmation)
Suspected new outbreaks - specify whether confirmed or unconfirmed (reference)
Other palm/plant hosts
New hosts, new vectors, new strains or suspected loss of resistance - confirmed or unconfirmed
Research projects - proposed research into Natuna Wilt can be found in the BuroTrop Bulletin No 14 for April 2001 and at http://groups.yahoo.com/group/CICLY/files/Natuna%20Wilt/
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