From Plant
Resources of South-East Asia (PROSEA)
by Ohler J. G., and S. S. Magat
Taxon
Cocos nucifera L.
Protologue
Sp. pl.: 1188 (1753).
Family
PALMAE
Chromosome
Numbers
2n = 32
Synonym
Cocos nana Griff. (1851).
Vernacular
Names
Coconut
(palm and fruit) (En). Cocotier (palm), coco (fruit) (Fr). Indonesia:
kelapa (general), nyiur (Malay), krambil (Javanese). Malaysia: kelapa.
Papua New Guinea: kokonas. Philippines: niyog (Pilipino, Tagalog),
iniug (Ibanag), lubi, ungut (Bisaya), laying (Manobo). Burma (Myanmar):
ong. Cambodia: doong. Laos: phaawz. Thailand: ma phrao (general),
kho-saa (Karen-Mae Hong Son), dung (Chong-Chanthaburi). Vietnam:
d[uwf]a.
Origin and
Geographic Distribution
Cocos nucifera
is native to the coastal regions of tropical Asia and the Pacific, but
its primary centre of origin is the subject of speculation. Fossil
coconuts have been found as far apart as India and New Zealand. The
ability of the thickly husked and slow germinating fruit of wild
coconut (called Niu Kafa type) to remain viable after floating long
distances at sea ensured wide natural dispersal in the Indo-Pacific
long before domestication may have started in Malesia. The domesticated
coconut (called Niu Vai type) has a robust stem and large fruits, which
however cannot survive long periods of floating at sea because of
thinner husks and shells and quicker germination. Initial dissemination
of the domesticated coconut coincided with migrations of Malesian
peoples to the Pacific and India, which started some 3000 years ago.
Where wild coconut already occurred, there was opportunity for
introgression with domesticated types, as both retained full
crosscompatibility. Polynesian, Malay and Arab navigators played an
important role in further dispersal of coconut into the Pacific, Asia
and East Africa. The coconut became truly pantropical in the 16th
Century after European explorers had taken it to West Africa, the
Caribbean and the Atlantic coast of tropical America.
Uses
The coconut palm has been
called the 'tree of life', the 'tree of heaven' and 'one of nature's
greatest gifts to man' because of its value as provider of so may
useful products. For domestic oil extraction the fresh endocarp of
mature fruits is grated and squeezed with hot water; for industrial
production the endosperm is dried to copra and taken to the mill for
oil extraction. High-grade oil is used for cooking or in the
manufacture of margarine, shortening, filled milk, ice-cream and
confectioneries. Oil of lower grades is processed into soap,
detergents, cosmetics, shampoos, paints, varnishes and pharmaceutical
products. Remnant fatty acids and alcohols and methyl esters find
application as components of emulsifiers and surfactants. The presscake
or copra meal is a good feed.
Coconut milk or cream
(Indonesia/Malaysia: 'santan'; Philippines: 'gata') pressed from
freshly grated endosperm mixed with water has been a traditional
ingredient in many Asian food and bakery products. It is now also
marketed in pasteurized and homogenized canned or powdered form. After
preparing coconut milk by boiling grated fresh coconut meat a presscake
remains. In Java it is considered a delicacy, named 'blondo' or
'galendo'. Skimmed milk powder, produced after boiling fresh coconut
milk and removing the floating oil, contains 25% hydrolyzed starch and
can be mixed with water to make a beverage. Protein can be separated by
ultrafiltration and spray-dried into a white powder, which is very
suitable for infant nutrition. Coconut skim milk is an essential
ingredient of a gelatinous delicacy ('nata de coco') in the Philippines
used in sweetened desserts, ice-cream and confectionery. Shredded or
thinly sliced and desiccated fresh coconut endosperm is a favourite
side-dish and ingredient in many confectionery, bakery and snack food
products. Ball copra is an Indian speciality produced by slow drying,
dehusking and shelling of the whole mature nut. It is used to prepare
sweets offered during religious and cultural rites and in traditional
medicine.
The nut cavity is filled with water that tastes sweet
when the coconut is young. Coconut water is now commercially preserved
without altering its typical flavour. It can also be used in the
production of 'nata de coco', which is a gelatinous dessert produced by
the action of bacteria on coconut water or diluted coconut milk,
developed in the Philippines. It is a source of inexpensive growth
hormone products for horticulture, such as the Cocogro developed in the
Philippines. The tender, jelly-like endosperm of young coconuts is a
delicacy consumed directly or grated and mixed with food. The
haustorium or apple of germinating coconuts can be eaten fresh.
The
shell of the nut can be made into household utensils and decorated
pots, converted into shell charcoal (suitable for activation) or used
as fuel. Finely ground coconut shell is used as filler for resin glues
and moulding powders. Green husks yield white coir (yellow fibres) for
making ropes, carpets, mats and geo-textiles. Brown coir from husks of
mature fruits is used in brushes (long bristle fibres), mattresses,
upholstery and particle board (short fibres). Coir dust or coco peat is
a component of potting mixtures (water-holding capacity of 700—900%),
light building materials, thermal insulation, adhesives and binders.
A
sweet sap containing about 15% sucrose is tapped from unopened
inflorescences. It is a refreshing toddy when consumed fresh and it
transforms into a light alcoholic wine when fermented. A by-product of
palm wine is vinegar. Boiling fresh sap yields palm syrup and sugar.
Distillation of palm wine yields a potent arak.
The leaves are
used to thatch roofs (Indonesia: 'atap'); the leaflets are plaited into
mats, baskets, bags and hats; immature leaflets are made into
traditional decorations and small bags or containers for food; the
midribs of the leaflets are formed into brooms. The palm heart, which
consists of the white, tender tissues of the youngest, unopened leaves
at the stem apex, is considered a delicacy. Young palms (3—4 years)
have the heaviest palm heart, weighing 6—12 kg.
The wood of old
palms is very hard, but a freshly felled trunk can be sawn with a
special tungsten carbide-tipped saw blade. Preservative treatment of
sawn lumber is needed if it is to be used for construction or any
outdoor use. Coconut wood is also suitable for furniture, household
utensils and tool handles.
Medicinal uses have been attributed
to coconut. The roots are considered anti-pyretic and diuretic. Its
decoctions are used against venereal diseases in Malay Peninsula while
an infusion is used in Indonesia to treat dysentery. Milk of young
coconut is diuretic, laxative, anti-diarrhoeic and counteracts the
effects of poison. The oil is used to treat diseased skin and teeth and
mixed with other medicines to make embrocations. The kernel of young
fruit is mixed with other ingredients and rubbed on the stomach against
diarrhoea. The kernel is prepared in Indo-China as a potion to treat
ulcers of the skin and the nasal mucous membrane.
Coconut palm
has also an ornamental value. The palms' often slanting stems and
graceful crowns bordering a white beach along a blue sea are hallmarks
of the tropics which attract tourists.
Production and International Trade
Average
annual world production of copra in 1995—2000 was estimated at about
5.0 million t, equivalent to 3.1 million t oil and 1.7 million t
coconut meal. This may represent less than 55% of the actual production
from 11 million ha of coconut, owing to considerable home consumption
and sales of young coconuts for drinking. Coconut is mainly a
smallholder crop and less than 10% of the total area consists of
estates. Asia and the Pacific account for 89% of world production,
Latin America and the Caribbean for 5% and Africa for 3%.
The
major coconut producers are the Philippines (39% of world production),
Indonesia (24%), India (14%), Mexico (4%), Vietnam and Papua New Guinea
(each about 3%). Estimated areas (in million ha) planted with coconut
are: Indonesia 3.71, the Philippines 3.16, India 1.67, Sri Lanka 0.49,
Thailand 0.41, Malaysia 0.29, Papua New Guinea 0.21 and Vietnam 0.20.
With about 1.7 million t of oil traded annually, coconut is now the 7th
most important supplier of vegetable oil in the global market. However,
it has a special position in the market together with palm-kernel oil
as a major source of lauric oil. The Philippines and Papua New Guinea
export about 80% of their national coconut oil production in contrast
to Indonesia which exports only 20—30% and India which exports almost
none. About 50% of the coconut meal produced annually in the world is
exported, about 500 000 t by the Philippines and 300 000 t by Indonesia.
Properties
Fresh, mature
coconut fruits weigh 1.1—2.5 kg and consist of husk (exocarp and
mesocarp) 30—45%, shell (endocarp) 14—16%, endosperm 25—33% and free
water in the cavity 13—25%. The proximate composition of fresh
endosperm per 100 g edible portion is: water 35—52 g, oil 34—45 g,
protein 3—4 g, carbohydrates 9—11 g, fibre 2—3 g and ash 1—2 g. High
quality copra has 63—68% oil, no more than 6% water and less than 1%
free fatty acid. The fatty acid composition of coconut oil is: caproic
acid 0.3—0.5%, caprylic acid 6—8%, capric acid 5—8%, lauric acid
45—50%, myristic acid 15—19%, palmitic acid 8—12%, stearic acid 2—4%,
oleic acid 6—8%, linoleic acid 1—2% and arachidic acid 0.5%. More than
90% of the fatty acids are saturated. Lauric acid is an easily
digestible source of energy and a precursor of the anti-microbial lipid
mono-laurin, which enhances the human immune system. It is hardly
deposited at all in body tissues.
Coconut milk contains
approximately fat 15—35%, protein 3% and sugar 2%. Powdered coconut
milk has: fat 60%, protein 7% and carbohydrates 27%; dried and powdered
skim milk has fat 6%, protein 24% and carbohydrates 25%; spray-dried
coconut protein powder contains protein 59%. Desiccated coconut
contains fat 58%, protein 7% and carbohydrates 24%. Presscake contains
fat 6%, protein 21%, carbohydrates 49% and crude fibre 12%.
Coconut
wood has a density of 400—600 kg/m3, the basal annular outer parts as
much as 850 kg/m3; it is suitable as timber for construction purposes
because of its moderate to high strength and lack of knots.
Description
An
unarmed, unbranched, pleonanthic, monoecious palm tree, with a terminal
crown of leaves, up to 20—30 m in tall cultivars, 10—15 m in dwarf
cultivars. Roots mostly in the top 1.5 m of soil, normally 6 m x 1 cm
but in optimum soil conditions up to 30 m long. Stem cylindrical,
erect, often curved or slanting, 20—40 cm in diameter but the swollen
base ('bole') up to 60 cm, light grey, becoming bare and conspicuously
ringed with scars of fallen leaves. Leaves sheathing, spirally
arranged, pinnate, 4.5—6(—7) m long, up to 60—70 per plant of which one
half still unfolded in the central spear; petiole stout with clasping,
fibrous sheath at base, about one quarter of total leaf length, grooved
above, rounded beneath; leaflets 200—250, linear-lanceolate, 50—120 cm
x 1.5—5 cm, single folded lengthwise at base, apex acute, regularly
arranged in one plane.
Inflorescence axillary, protandrous,
unopened (immature) looking like a spadix within a spathe, opened
(mature) about 1—2 m long, consisting of a central axis with up to 40
lateral, spirally arranged, spike-like rachillae (branches) each
bearing 200—300 male flowers and only one to few female flowers near
the bare basal part; male flowers 1—3 together, sessile, 0.7—1.3 cm x
0.5—0.7 cm, pale yellow, with 3 small sepals, 3 larger petals, 6
stamens in 2 whorls and a rudimentary pistil; female flowers solitary,
much larger than male flowers, globose in bud, ovoid at anthesis, 2—3
cm in diameter, enveloped by 2 small scaly bracteoles, sepals and
petals each 3, suborbicular, sub-equal, persistent and enlarging in
fruit, pistil with large 3-locular ovary, 3 sessile triangular stigmas
and 3 nectaries near ovary base.
Fruit a globose, ovoid or
ellipsoidal fibrous drupe, indistinctly 3-angled, 20—30 cm long,
weighing up to 2.5 kg; exocarp very thin, 0.1 mm thick, smooth, green,
brilliant orange, yellow to ivory-coloured when ripe, usually drying to
grey-brown in old fruits; mesocarp fibrous, 4—8 cm thick, pale brown;
endocarp (shell, together with its contents called the 'nut' of
commerce) ovoid, 10—15 cm in diameter, 3—6 mm thick, hard, stony, dark
brown, indistinctly 3-angled with 3 longitudinal ridges and 3 large,
slightly sunken pores ('eyes') at basal end, each with an operculum.
Seed only 1, very large, with a thin brown testa closely appressed to
endocarp and adhering firmly to endosperm ('meat') which is firm, 1—2
cm thick, white, oily; at basal end in endosperm a small peglike embryo
0.5—1 cm long is embedded (under one of the endocarp pores); in centre
of seed is a large central cavity, partially filled with coconut water
which is completely absorbed 6 months after harvesting.
Growth and Development
Mature
fruits of most coconut cultivars start germinating soon after harvest.
The embryo enlarges and the apical part emerges from the shell. At the
same time, the cotyledon develops into a haustorium. The primary root
emerges from the apical mass, followed by the plumule. As growth
continues they emerge at opposite sides through the husk. Shoot
emergence occurs about 8 weeks after placing coconuts in a germinating
bed and another 5 weeks later, the first leaf starts to unfold. The
leaves increase in size but remain entire until the seedling has 7—10
leaves, usually after one year's growth. Subsequent leaves become
progressively pinnate.
Tall cultivars produce about 10 leaves
during the first year, dwarf palms have 14. In subsequent years, larger
and more leaves are formed, until full leaf size is attained and annual
production levels off at 12—18 leaves for talls and hybrids and 20—22
leaves for dwarf palms. Since a leaf of a tall palm remains on the tree
for about 2.5 years after unfolding, the leaf number in the crown
levels off at 30—35 after 6 or 7 years. Leaf initiation until
senescence takes about 4 years.
The root system consists of
adventitious roots numbering 2000—4000 per palm. Decayed roots are
replaced regularly; new roots emerge from the upper part of the
thickened basal stem.
The regular development of both canopy and
root system is well adapted to the constant environment of the humid
lowland tropics. The long development periods of large organs give the
palm a certain inflexibility to short-term stress. Under adverse
conditions, flowering and fruiting are mainly affected, leading to
smaller inflorescences and fewer female flowers; abortion of
inflorescences; reduction in fruit set, nut size and filling; premature
nut fall and tapering of the stem. Thus, stress affects yield much more
than growth. The size of new leaves and roots has been fixed a long
time in advance and cannot be adjusted to short-term stress periods.
After long-term stress leaf emergence slows down which further reduces
yield, since the emergence of inflorescences follows that of the
subtending leaves.
At the rosette stage, the growing point
continues to enlarge until the size of the leaf initials reflects the
prevailing growing conditions; then trunk formation starts. At close
spacing, height growth increases at the expense of flowering and
fruiting. Precocity and yield are positively correlated with annual
leaf formation, as an inflorescence appears in the axil of each leaf.
Hence, dwarf varieties yield earlier and more than tall varieties.
First flowering in tall varieties occurs at 5—7 years, in dwarf
varieties after 2 years and in dwarf x tall hybrids about 3—4 years
after germination. Growing conditions have great influence on these
aspects. Coconut palms can be more than 100 years old, but highest
yields are usually obtained between 10—20 years of age for talls and a
few years earlier in dwarfs and hybrids.
During the first phase
of anthesis which lasts 16—22 days, only male flowers open
progressively from the top to the base of the upper spikes and down to
the lowest spikes. Each male flower opens, sheds its pollen and
abscises within 2 days. The first female flower at the top of the
spadix becomes receptive about 3 weeks in tall or 1 week in dwarf palms
after the spathe has opened and the stigmas of the last female flower
at the bottom of the spadix turn brown 5—12 days later. Female flowers
are nectiferous and sweet-scented. Pollination is both by insects and
by wind (the pollen is dry). Each female flower remains receptive for
2—3 days.
Tall coconuts are generally allogamous because the
male and female phases do not overlap while in dwarfs, self-pollination
is common due to considerable overlap. Self-pollination can also occur
when the female phase of one inflorescence overlaps with the male phase
of a second inflorescence on the same tree. About 50—70% of the female
flowers abort during the first two months due to poor fertilization or
other physiological causes. Fruits are mature 11—12 months after
anthesis, but may not drop until 15 months old.
Other Botanical Information
Cocos nucifera is the only species of the genus Cocos
L. A generally accepted classification system for the wide variability
of coconut does not exist. Coconuts that are thought to be of natural
origin are said to be of the 'Niu kafa type' (fruits long, angular,
thick husked, floating easily, long lasting viability, slow
germination); those which are thought to be developed under cultivation
are of the 'Niu vai type' (fruits globose, thinner husk, not floating
easily, increased endosperm, earlier germination). Niu kafa and niu vai
are Polynesian words. Where these 2 types come into contact,
introgression takes place.
Up to now, cultivated coconuts have been classified into 2 groups: tall palms (sometimes referred to as var. typica Nar.) and dwarf palms (sometimes referred to as var. nana
(Griff.) Nar.). More than 95% of all cultivated coconuts are tall
palms. Examples of tall cultivars are: 'Malayan Tall', 'Rennell Island
Tall', 'Vanuatu Tall', 'Jamaican Tall' and 'West African Tall'. Dwarf
palms are rare, but can be found in different ecotypes. Characteristics
of dwarf palms are: weaker growth and slow height increment; slender
stem; smaller leaves, inflorescences and fruits; precocity and rapid
succession of inflorescences; high degree of self-pollination. The
inheritance of dwarfness is not well understood but hybrids are usually
intermediate in height increment and other characteristics to the tall
and dwarf parents. Three different types of dwarf cultivars exist: the
'Niu Leka' from Fiji which differs only from the talls by its very
short internodes and short rigid leaves, while it is also allogamous;
the medium-sized palms such as 'Malayan Dwarf' from Indonesia,
'Gangabondam' from India and 'King' from Sri Lanka; and the small dwarf
cultivars in various countries. Dwarfs are also differentiated based on
the colour of leaf petiole of young coconuts, into green, yellow and
red (orange or golden) dwarfs. In the Philippines, there are green
dwarfs with large fruits, such as 'Tacunan', 'Kinabalan' and 'Catigan'.
The
nuts of 'Makapuno' from the Philippines and the 'Kelapa Kopjor' from
Indonesia have endosperms that fill almost the entire cavity. The
endosperm is soft, has a peculiar taste and is considered a delicacy.
The nuts do not germinate but the embryos can be cultured in vitro.
This character may appear in any tall cultivar.
Classification in
cultivated coconuts can best be done by distinguishing cultivar groups
and cultivars. A promising classification system of coconut cultivars
is based on the degree of introgression, which can be expressed in
characteristics of the fruits: proportion of husk in the whole fruit,
proportions of water, meat and shell in the husked fruit.
Ecology
Coconut palm is
essentially a crop of the humid tropics. It is fairly adaptable with
regard to temperature and water supply and so highly valued that it is
still common near the limits of its ecological zone. The annual
sunlight requirement is above 2000 hours, with a likely lower limit of
120 hours per month. The optimum mean annual temperature is estimated
at 27°C with average diurnal variation of 5—7°C. For good yields, a
minimum monthly mean temperature of 20°C is required. Temperatures
below 7°C may seriously damage young palms, but cultivars differ in
their tolerance of low temperature. While most coconuts are planted in
areas below 500 m, palms may thrive at altitudes up to 1000 m, although
low temperatures will affect growth and yield.
Generally, palms
grow in areas with evenly distributed annual rainfall of 1000—2000 mm
and high relative humidity, but they can still survive in drier regions
if there is adequate soil moisture. The semi-xerophytic leaves enable
the coconut palm to minimize water loss and withstand drought for
several months. In India, a monthly rainfall of 150 mm (with only a
3-month dry period) is enough, while in the Philippines, rainfall of
125—195 mm (1500—2300 mm annually) is ideal.
The coconut palm
thrives in a wide range of soils, from coarse sand to clay, if soils
have adequate drainage and aeration. Coconut palms are halophytic and
tolerate salt in the soil well. Coconut can grow in soils with a wide
range of pH but grows best at pH 5.5—7.
Propagation and planting
Coconut
palm is propagated by seed which is recalcitrant. The multiplication
factor is low, as one tall palm will in general not produce more than
100—200 seed-nuts per year. Although coconut plants can be regenerated
through somatic embryogenesis, genotypic differences in rate of embryo
formation and difficulties in hardening of in-vitro plants have been a
constraints to practical methods of large-scale clonal propagation so
far. However, a field of clonal coconuts may soon be planted in Mexico.
In vitro culture of excised embryos is also possible. It solves
problems of plant quarantine restrictions and finds application in the
international exchange of germplasm.
Seed-nuts are usually given
a resting period of one month after harvesting. They are kept in a
germination bed from where uniform seedlings can be transplanted to
polythene bags or to nursery beds. The polybag method and regular
fertilization have largely replaced the bare-root seedlings raised in
beds. Seedlings that are 3—8 months old are transplanted in the field.
They can be kept longer in the nursery bed but will then sustain a
greater transplanting shock. Coconut is planted mostly at spacings of
8—10 m x 8—10 m, in a triangular or square system. Dwarf cultivars are
planted at a spacing of 7.5 m x 7.5 m. Hedge planting may be used to
facilitate intercropping, but the radial symmetry of the leaf
arrangement does not tolerate extreme forms of row cropping.
Growers
prefer wider palm spacing to prevent inter-tree competition. As the
open crowns also transmit a fair portion of incident light coconut is
well suited to intercropping. Coconut is occasionally grown with cocoa
and coffee. Although this usually results in lower copra yields, the
combined income from well-fertilized coconut and intercrop is much
higher than that from coconut alone. In humid climates, cocoa is one of
the best intercrops. In Malaysia, more than 1000 kg/ha of dry beans
have been obtained from cocoa grown under coconuts. Coconut is also
grown in mixed cropping systems with other trees like rubber, mango,
cashew and banana. Under coconuts in the Philippines yields of bananas
of 40—60 t/ha have been obtained. Pastures are sometimes established
under the palms for use in mixed husbandry and green manures are
occasionally planted. However, pasture and cover crops can only be
grown and maintained when there is sufficient rain. Catch crops such as
rice, maize, finger millet, sweet potato, cassava, vegetables and
spices are often planted until the palms come into bearing. These crops
should not be planted closer than 2 m to the palms.
Husbandry
Weeding
is essential, especially for young coconut palms. Green manuring is
often practised to advantage. Fertilizing is required, especially on
soils that have been cultivated for many years, but smallholders seldom
apply fertilizers. If nutrient deficiencies largely limit growth and
yield, responses to fertilizer application and other cultural practices
can be observed within one year. Potassium and chloride are the major
nutrients needed by the palm, followed by nitrogen, phosphorous and
sulphur. Leaf analysis is an acceptable and quick guide to the
fertilizer requirements of the palm. The annual crop nutrient removal
of one hectare of coconuts, yielding 7000 nuts, is about: 49 kg N, 16
kg P2O5, 115 kg K2O, 5 kg Ca, 8 kg Mg, 11 kg Na, 64 kg Cl and 4 kg S.
An example of a yearly fertilizer recommendation per palm is a mixture
of 0.4 kg N, 0.3 kg P2O5, 1.2 kg K2O, 0.20 kg S and 0.90 kg Cl, applied
in split applications in a band around the palm (l.0—1.5 m from the
trunk) and split into 2 applications, at the beginning and end of the
rainy season. Fertilizer doses depend on local conditions. Foliar and
soil analyses help to determine the nutrient status of the palms. In
several countries in Asia sea salt (NaCl) is commonly applied to
coconut palms with positive effects on yields.
Irrigation is
sometimes practised in dry areas where water is available and sea water
may be applied occasionally as long as the salt content in the soil
does not rise too high.
Diseases and Pests
Many
diseases affect coconut palm. Important are yellowing diseases, such as
lethal yellowing in the Caribbean, Cape St. Paul wilt, Kaincopé
disease, Kribi disease in West Africa and lethal disease in Tanzania.
These are caused by mycoplasma-like organisms. Generally, the symptoms
of yellowing diseases are browning and collapse of spear leaves,
yellowing of mature leaves, collapse of roots, premature nut fall,
death of bud and later, of the tree. 'Malayan Dwarf' is highly tolerant
of lethal yellowing but shows varying tolerance of other yellowing
diseases. Tall palms are more susceptible.
Similar diseases of
unknown etiology but suspected to be caused by mycoplasma-like
organisms are Malaysian wilt in Malaysia, stem necrosis in Malaysia and
Indonesia, Natuna wilt and leaf yellowing disease in Indonesia, Socorro
wilt in the Philippines and the New Hebrides disease in Vanuatu.
Malaysian wilt is characterized by premature nut fall; stiff, yellowish
and smaller new leaves; wilting and drying of old leaves and eventual
death of the palm. Palms with stem necrosis show shorter young leaves,
die-back of leaflets, necrosis in the leaflet midrib, internal
disorganization and necrosis of stem, bud, inflorescence and roots.
Natuna wilt causes leaf wilting and bending in both young and old trees
until leaves fall simultaneously with the nuts. Leaf yellowing disease
causes intensive yellowing of the older leaves and at the advanced
stage, the leaves are smaller and the whole crown is stunted. Symptoms
of Socorro wilt are premature senescence of the outer whorl of hanging
leaves or the drying of the leaves from the tip to the base until they
drop, premature falling of nuts, failure of inflorescence to develop,
and spathes becoming brown and dying. The few nuts that develop are
usually deformed, oblong, small and with damaged kernels.
Kerala
wilt, possibly caused by a virus, is an important disease in India.
Cadang-cadang, caused by the cadang-cadang viroid (CCVD) is a
devastating disease especially of flowering palms in the Philippines,
particularly in the Bicol region and adjacent provinces (estimates of
the affected area range from 250 000 ha to 400 000 ha). The symptoms
are yellow mottling on leaves, formation of small and stiff leaves that
usually break at the middle until only a group of small, erect and
yellowish-green leaves remain at the top of the stem and production of
fewer roots. The inflorescence is also affected; at the later stage of
the disease, only male flowers develop and nut production stops.
Although control methods are still unknown, the eradication of diseased
palms and sterilization of knives that are used on the farms may help
reduce the spread and incidence of cadang-cadang. Coconuts in Guam are
infected by a disease similar to cadang-cadang, also caused by a viroid.
Bud rot occurs worldwide and is caused by the soil-borne fungus Phytophthora palmivora
which is favoured by high humidity. It causes rotting of the spear and
the growing point. It can be controlled by wider plant spacing, better
aeration, drainage and weed control. Basal stem rot develops from an
infection by the fungus Ganoderma boninense.
The fungus first affects and destroys the roots and then the base of
the stem turns reddish-brown and releases a brown, gummy exudate.
Disease occurrence can be prevented through improved growing
conditions, production techniques and proper sanitation measures.
Control methods are eradication of affected palms and application of
fungicide. Stem bleeding or oozing of reddish-brown liquid from the
cracked stem is caused by Thielaviopsis paradoxa. Cultural management techniques and drenching the soil with fungicides effectively control the disease. Leaf blight caused by Pestalotia palmarum and leaf rot or leaf spot caused by Drechslera halodes (= Drechslera incurvata) are widespread fungal diseases, while leaf blight caused by Botryodiplodia theobromae
damages palms in Brazil, Malaysia, Sri Lanka and Trinidad especially
during months of high temperatures and low relative humidity and
rainfall.
Numerous insect pests attack coconut palms. The rhinoceros beetle (Oryctes rhinoceros)
is widespread in South-East Asia and the Pacific. Its larvae tunnel
through the apical bud leaving characteristic triangular cuts in opened
leaves. When the growing point is attacked, the palm dies. Control is
done by keeping the plantation clean and applying Baculovirus oryctes or the insect-pathogenic fungus Metarhizium anisopliaeto
breeding places. Recently, a male-produced aggregation pheromone was
discovered to be a powerful attractant in selective trapping to reduce
beetle populations. Different outbreak situations require specific
control approaches. Other Coleoptera that inflict serious damage to
coconut are Promecotheca spp. in Indonesia, Malaysia and the Philippines and Brontispa longissima in Indonesia, Malaysia and the Pacific. Larvae of Promecotheca spp. tunnel through foliar tissues while adults eat the underside of leaves. Brontispa longissima larvae and adults feed on leaflet tissues and may defoliate the whole crown in severe cases. The weevils Rhynchophorus ferrugineus and Rhynchophorus schach
in South Asia and Malaysia cause serious damage by their boring into
the coconut stem. Many caterpillars feed on coconut leaves, such as Hidari irava in Indonesia and Malaysia, Tirathaba spp. in South-East Asia and the Pacific, Setoria nitens in Burma (Myanmar), Indonesia, Malaysia and Vietnam, Parasa lepida in India, New Guinea, China and South-East Asia and Brachartona (Artona) catoxantha in Indonesia, Malaysia, New Guinea and the Philippines. The scale insect Aspidiotus destructor
is one of the most widespread pests of the coconut palm and can be
controlled by an emulsion of soft laundry soap and kerosene in water.
The white fly Aleurodicus destructor sometimes causes serious damage to coconut in Indonesia and the Philippines.
Harvesting
Coconut
fruits can be harvested about 11—12 months after flowering. The palm
can be harvested every 2—3 months but rapidly germinating types should
be harvested more frequently. Dwarf cultivars sprout in 45—60 days and
must be harvested monthly. Climbing the palms and cutting the ripe
bunches is still the harvesting method most practised. Gathering fallen
nuts is easier, but there are more losses due to rat attack and theft.
Some nuts may germinate on the tree and consequently, their kernel and
oil content may have started to deteriorate. In some countries bamboo
poles (up to 25 m long) with a knife attached to the top end are used
to cut the ripe bunches, elsewhere monkeys (Macacus nemestrina) are trained to harvest ripe nuts.
Yield
Smallholder
plantations usually yield between 0.5—1 t of copra/ha. In Malaysia,
average estate yields are about 1.5 t of copra/ha but the potential
yield is about 3.5 t/ha. Well-managed plantations of selected local
tall coconut palms in Indonesia yield 3.5—4.5 t copra /ha.
Rehabilitated and fertilized tall coconut palms in small farms in the
Philippines achieve an average annual yield of 2.8 t copra/ha or 83
nuts/tree per year.
Plantations of dwarf coconut palms in
Malaysia produce about 1.5—2 t/ha and even 3.5 t/ha under favourable
conditions. Dwarf x tall hybrids combine the high number of fruits
produced by the dwarf type with the larger size from the tall one and
usually have a higher yielding potential than the parents. Experimental
yields of more than 6—9 t/ha have been obtained in Ivory Coast and the
Philippines.
Handling After Harvest
Harvested
coconuts are stored in a protected place until the husks are completely
dry. Dried coconuts are dehusked manually by striking and twisting them
on a steel point that is placed firmly in the ground. Dehusking
machines have been developed but have not been a success. After
dehusking, nuts are split with a machete and the water is drained. The
nut halves are placed in a kiln dryer or an indirect hot air dryer for
1—2 days, after which the endosperm is scooped out from the shell and
dried further until its moisture content is less than 6%. Sun-drying is
also practised but there is a higher risk of product deterioration
especially during humid and rainy periods. Aflatoxin-producing moulds
may affect the quality when the moisture content of dried copra exceeds
12%.
Coconut oil can be extracted from the copra (yield about
60%) by dry processing methods such as mechanical pressing and by using
solvents. It can also be extracted from the fresh kernel through
several wet processes. In traditional extraction coconut cream or milk
is obtained from the grated fresh kernel by boiling it gently until the
oil floats to the surface.
Whole or dehusked coconuts are also
sold to coconut desiccation factories. To produce desiccated coconut,
the shell and the brown testa are pared off, the white endosperm
washed, steamed, pasteurized, shredded into small pieces of various
sizes and forms, dried and packed.
Genetic Resources
Local
coconut cultivars (ecotypes) are usually heterogeneous populations with
some predominating characteristics. Cultivars with different names and
growing in different areas are sometimes rather similar and maybe of
the same origin. Germplasm collections are found in several research
stations around the world. In 1978, the International Board for Plant
Genetic Resources (IBPGR, now IPGRI) adopted a minimum list of
descriptors to be used in collecting germplasm in the field. In 1980,
it supported the survey and collection of coconut germplasm in priority
areas in South-East Asia and provided funds for the collection of
coconuts in Indonesia, the establishment of a coconut germplasm centre
in the Philippines and collection of germplasm in the Pacific to be
planted on one of the Andaman Islands to screen for Kerala wilt disease
resistance for mainland India.
The Coconut Genetic Resources
Network (COGENT), with IPGRI's administrative support, coordinates the
conservation of more than 700 accessions in 15 countries. Major coconut
germplasm collections include those of the Philipine Coconut Authority
(PCA), the Research and Development Centre for Industrial Crops (RDCIC)
in Indonesia, IPGRI-Asia, the Pacific and Oceania at Serdang, Malaysia,
the Central Plantation Crop Institute (CPCRI) in India, the National
Centre for Agricultural Research (CNRA) in Ivory Coast and the National
Coconut Development Programme (NCDP) in Tanzania.
Germplasm
conservation by field collections requires considerable resources of
land, staff and upkeep and remains vulnerable to natural disasters and
diseases. The cryopreservation of coconut embryos and pollen will
enable the safe and inexpensive long-term storage of coconut genetic
resources.
Breeding
Breeding
methods common to cross-pollinating species are applied to coconut
palm. The long duration of one breeding generation (more than 10
years), low multiplication rate (1 : 50/100), recalcitrant and large
'seed' and the large areas of land required for field testing, are
major obstacles to rapid selection progress. About 95% of all planted
coconut palms in the world are open-pollinated progenies after mass
selection within local ecotypes, often informally applied by the
growers themselves.
Important selection criteria in coconut are:
yield (kg copra per ha) and its components (number of nuts, copra
content per nut), early production, disease resistance and drought
tolerance. Selection for endosperm thickness is a minor factor of
selection; oil content and quality are fairly constant; length of husk
fibres is a selection criterion in Sri Lanka only. The flavour of
immature coconut water varies with ecotypes, but has not been a
criterion for formal selection as yet.
The genetic variance in
coconut yield and its components is mainly due to additive genetic
effects and the superior hybrids are the result of the general
combining ability of the parents. Methods of (reciprocal) recurrent
selection with genetically diverse subpopulations (dwarfs and talls)
are now used in some coconut breeding programmes to increase
substantial transgressive hybrid vigour for yield in new cultivars.
Chemical and more recently, molecular markers are applied in coconut
breeding to measure genetic divergence between sub-populations.
Dwarf
x tall hybrids have considerable heterosis for yield and precocity,
hence the focus of breeding programmes of several coconut research
centres on such hybrids since 1960. Some 400 hybrids have been tested
worldwide during the last 35 years; about 10 of these internationally
at several locations. The coconut research centre at Port Bouet in
Ivory Coast tested 123 hybrids, of which 35 produced 65% more than the
'West African Tall' standard cultivar. Four hybrids yielded even more
than twice as much (3.4—4.5 t/ha copra), including PB121 ('Malayan
Yellow Dwarf' x 'West African Tall') which has been planted widely also
in South-East Asia. Host resistance to major diseases has high priority
in some areas, but sources of resistance are not always available in
the coconut, e.g. against Cadang-cadang disease in the Philippines.
Crosses
for breeding purposes are made by hand pollination after emasculation
and bagging of inflorescences. Pollen collected from the male parent
can be stored (dry and under vacuum) for a considerable
period. Large-scale seed production is based on pollination of
previously emasculated inflorescences (not bagged) in isolated seed
gardens planted solely with the female parent of the hybrid cultivar
(usually a dwarf type). One hectare of seed garden produces yearly
enough 'seed' for planting 50—60 ha only. Hybrid seed production is
rather expensive and requires large land areas. An estimated 15% of all
coconut palms planted during the last decade are hybrids. Examples of
widely planted hybrid cultivars are: KB and KHINA series in Indonesia;
the PCA 15 series in the Philippines; Sawi-1 (= PB121) and Chumphon 60
in Thailand and PB series (e.g. PB121) from Ivory Coast.
In some
areas of the Philippines, the more robust tall palms are preferred as
planting material. In 1992, a programme of 15 crosses between 6 tall
types was carried out and best selected F1 was planted in a seed garden
to produce open-pollinated F2 seeds with similar qualities as a
synthetic (hybrid) cultivar. Cost of seed production is much lower, as
no emasculation or artificial pollination are involved.
Prospects
Some of the
latest dwarf x tall hybrid cultivars of coconut palms can potentially
yield more than 6 t/ha of copra per year (3.7 t of oil), but coconut
palm does not appear to have a bright future as a plantation crop in
the long term. Coconut oil already faces increasing competition in the
world market from palm-kernel oil and both may eventually also be
partly replaced by lauric oils produced by genetically transformed soya
bean and brassica oilseed. On the other hand, as a smallholder crop in
the coastal areas of the tropics, coconut will continue to be a very
important supplier of multifunctional food and other products.
Sometimes, it is practically the only crop that can be grown in the
prevailing ecosystem (e.g. some Pacific Islands). A quickly growing
world market for healthy and environmentally friendly products should
offer new opportunities for the coconut export trade. However, this
will require astute marketing, more research into the economic
viability of smallholder coconut production systems (e.g. replanting,
mixed intercropping and biological control of diseases and pests) and
into novel processing technologies for local industries to manufacture
diversified coconut products suitable for the international market.
Literature
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& Rao, V.R. (Editors), 1994. Coconut breeding. Workshop on
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Malaysia 150 pp.
Bourdeix, R., Baudouin, L., Billotte, N., Labouise,
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