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Plantwise Technical Factsheet

yellow mottle decline (Coconut tinangaja viroid)

Host plants / species affected
Cocos nucifera (coconut)
List of symptoms/signs
Fruit  -  abnormal patterns
Fruit  -  abnormal shape
Fruit  -  reduced size
Growing point  -  dwarfing; stunting
Inflorescence  -  blight; necrosis
Inflorescence  -  discoloration panicle
Inflorescence  -  dwarfing; stunting
Leaves  -  abnormal colours
Leaves  -  abnormal leaf fall
Seeds  -  distortion
Seeds  -  empty grains
Seeds  -  shrivelled
Stems  -  stunting or rosetting
Whole plant  -  dwarfing
Whole plant  -  early senescence
Whole plant  -  plant dead; dieback
Symptoms
In nature, the first symptom is a progressive thinning of the crown, caused by a reduction in the number of fronds. The size and number of fruit are also reduced, with the fruit becoming rounded in alate varieties. A fine stippling of the leaves can also be seen; minute chlorotic spots appear on leaf lamina. As the disease progresses, fruit become deformed and shrivelled (See Pictures). Infected trees then cease to produce nuts, but may continue to produce inflorescences, which become increasingly smaller, may have necrotic tips and fail to set fruit. Eventually the tree stops producing inflorescences altogether as it loses more and more of its crown, which looks ragged and tattered (See Pictures). The fronds remaining on the tree have persistent stipules at their base. As the disease progresses and the tree loses more fronds, the trunk of the tree is tapered like a pencil tip. Eventually the crown becomes extremely thin with only a few tattered fronds. The infected tree is eventually so weakened that a storm usually blows off its top, finally killing the palm. The entire process may take up to 15 years.
Prevention and control
Cultural Control

The use of cutting and pruning tools without proper precautions should be avoided to prevent mechanical transmission. Tools should be disinfected by wiping with 10% bleach solution plus 1% mineral or vegetable oil between trees. Seed should be collected and selected from areas known to be free, or have very low incidence, of Tinangaja disease.

Mechanical Control

The removal and destruction of infected trees is recommended; infected trees should be replaced with healthy seedlings (or healthy mature transplants).
Impact
Tinangaja disease has caused a great deal of damage and continues to do so in coconut populations on Guam, where this tree is a dominant component of the island's flora. It has, therefore, negative ecological, environmental and economic impact.

For the landscape industry, Tinangaja disease adds to the cost of transplanting, establishing or maintaining coconut trees. New plantings must be tested for the disease. Infected trees must be removed and replaced.

For the grower and homeowner, CTiVd reduces the number of productive coconut trees and so makes fresh coconuts more scarce. The alternative, processed coconut, is much more expensive.
Related treatment support
 
External factsheets
Pestnet Factsheets, Pestnet, English language
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