The Coconut Palm

CONTENT

THE COCONUT PALM

INTRODUCTION

DECRIPTION

THE BUD ROT DISEASE

INTRODUCTION

THE BUD ROT COMPLEX

PHYTOPHTHORA BUD ROT

SYMPTOMS

ETIOLOGY

EPIDEMIOLOGY

DISEASE CYCLE

VARIEATAL RESISTENCE

MANAGEMENT

THE COCONUT PALM

‘Cocos nucifera’

THE COCONUT PALM

Common names : Coconut Palm, Coco Palm, Coconut Tree

Scientific name : Cocos nucifera

Explanation of scientific name:   

Cocos     - Portuguese for monkey, in reference to the face that appears on the stripped nut.     

nucifera -  nut bearing  

Scientific classification

Kingdom: Plantae

(unranked): Angiosperms

(unranked): Monocots

(unranked): Commelinids

Order: Arecales

Family: Arecaceae

Subfamily: Arecoideae

Tribe: Cocoeae

Genus: Cocos

Species: C. nucifera'

Introduction

The coconut palm, Cocos nucifera, is a member of the family Arecaceae (palm family). It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word.

Found across much of the tropics, the coconut is known for its great versatility as seen in the many domestic, commercial, and industrial uses of its different parts. Coconuts are part of the daily diet of many people. Its endosperm is known as the edible "meat" of the coconut; when dried it is called copra. The oil and milk derived from it are commonly used in cooking and frying; coconut oil is also widely used in soaps and cosmetics. The clear liquid coconut water within is a refreshing drink and can be processed to create alcohol. The husks and leaves can be used as material to make a variety of products for furnishing and decorating. It also has cultural and religious significance in many societies that use it.

Of the more than 1500 species in the Palm family of plants (Palmaceae), the Coconut palm is the best known.  A unique tree, with no really close relatives (it is the only member of the genus Cocos), it is considered to be one of the most useful trees in the world.  A recent study reported 360 contemporary uses for this tree, half of which were for food.  Several Philippine proverbs demonstrate the usefulness of this species:

"If you could count the stars, then you could count all the ways the coconut serves us."

"He who plants a coconut tree, plants vessels and clothing, food and drink, a habitation for himself, and a heritage for his

children."

While the coconut can be found growing throughout the tropical regions of the world, its center of origin is not exactly known.  Fossilized coconuts have been found in New Zealand, and the trees have been cultivated for over 4,000 years in India.  This leads most botanists to believe that the species originated somewhere around the Indian Ocean.  The exceptionally wide distribution of coconuts today is due to the influence of humans, having been carried from place to place by explorers and immigrants.  Since the chief means of dispersal in nature is by the nuts floating in water to distant shores, the existence of all inland coconuts is undoubtedly the result of our actions.

Description

Plant

Cocos nucifera is a large palm, growing up to 30 metres (98 ft) tall, with pinnate leaves 4–6 metres (13–20 ft) long, and pinnae 60–90 cm long; old leaves break away cleanly, leaving the trunk smooth. On very fertile land a tall coconut palm tree can yield up to 75 fruits per year, but more often yields less than 30 mainly due to poor cultural practices.

Fruit

Botanically the coconut fruit is a drupe, not a true nut. Like other fruits it

has three layers: exocarp, mesocarp, and endocarp. The exocarp and

mesocarp make up the husk of the coconut. Coconuts sold in the shops of

non-tropical countries often have had the exocarp (outermost layer)

removed. The mesocarp or "shell" thus exposed is the hardest part of the

coconut, and is composed of fibers called coir which have many traditional

and commercial uses. The shell has three germination pores (stoma)

or eyes that are clearly visible on its outside surface once the husk is

removed.

A full-sized coconut weighs about 1.44 kilograms (3.2 lb). It takes around

6000 full-grown coconuts to produce a tonne of copra.

Seed

Within the shell is a single seed. When the seed germinates, the root

(radicle) of its embryo pushes out through one of the eyes of the shell. The

outermost layer of the seed, the testa, adheres to the inside of the shell. In

a mature coconut, a thick albuminous endosperm adheres to the inside of

the testa. This endosperm or meat is the white and fleshy edible part of

the coconut. Although coconut meat contains less fat than

many oilseeds and nuts such as almonds, it is noted for its high amount of

medium-chain saturated fat. About 90% of the fat found in coconut meat

Layers of the coconut fruit (1) Exocarp / Epicarp(2) Mesocarp(3) Endocarp(4) Endosperm(5) Embryo

is saturated, a proportion exceeding that of foods such as lard, butter,

and tallow. There has been some debate as to whether or not the

saturated fat in coconuts is healthier than other forms of saturated fat

(see coconut oil). Like most nut meats, coconut meat contains

less sugar and more protein than popular fruits such as bananas, apples

and oranges. It is relatively high in minerals such

as iron, phosphorus and zinc. The endosperm surrounds a hollow interior

space, filled with air and often a liquid referred to as coconut

water (distinct from coconut milk). Immature coconuts are more likely to

contain coconut water and less meat. They are often sold with a small

portion of the husk cut away to allow access to the coconut water. Young

coconuts used for coconut water are called tender coconuts. The water of

a tender coconut is liquid endosperm. It is sweet (mild) with an aerated

feel when cut fresh. Depending on its size a tender contains 300 to 1,000

ml of coconut water.

The meat in a green young coconut is

softer and more gelatinous than that in a

mature coconut—so much so that it is

sometimes known as coconut jelly. When

the coconut has ripened and the outer

husk has turned brown, a few months

later, it will fall from the palm of its own

accord. At that time the endosperm has

thickened and hardened, while the

coconut water has become somewhat bitter.

When the coconut fruit is still green, the husk is very hard, but green

coconuts only fall if they have been attacked by molds or other blights. By

the time the coconut naturally falls, the husk has become brown, the coir

has become drier and softer, and the coconut is less likely to cause

damage when it drops, although there have been instances of coconuts

falling from palms and injuring people, and claims of some fatalities. This

was the subject of a paper published in 1984 that won the Ig Nobel Prize in

2001. Falling coconut deaths are often used as a comparison to shark

attacks; the claim is often made that a person is more likely to be killed by

a falling coconut than by a shark; yet, there is no evidence of people ever

being killed in this manner.

When viewed on end, the endocarp and germination pores give the fruit

the appearance of a coco (also Côca), a Portuguese word for a scary witch

from Portuguese folklore, that used to be represented as a carved

vegetable lantern, hence the name of the fruit. The specific

namenucifera is Latin for nut-bearing.

A small number of writings about coconut mention the existence of

the coconut pearl. This is generally considered a hoax. Professor

Armstrong, of Palomar College, says "most eyewitness records of coconut

pearls cited in the literature are secondhand accounts that were not

observed by the authors of these articles. There are a few firsthand,

published accounts of pearls observed inside coconuts, but these have

been shown to be fraudulent."

The shell composition is shown in the tables below.

Coconut shell compound (dry basis)

Compound Percent

Cellulose 33.61

Lignin 36.51

Pentosans 29.27

Ash 0.61

Source: Jasper Guy Woodroof (1979). "Coconuts: Production,

Processing, Products".2nd ed. AVI Publishing Co. Inc.

Coconut shell ash compound

Compound Percent

K2O 45.01

Na2O 15.42

CaO 6.26

MgO 1.32

Fe2O3 + Al2O3 1.39

P2O5 4.64

SO3 5.75

SiO2 4.64

Root

Unlike some other plants, the palm tree has neither tap root nor root hairs; but has a fibrous root system.

Inflorescence

On the same inflorescence, the palm produces both the female and male flowers; thus the palm is  monoecious.  Other sources use the term polygamomonoecious. The female flower is much larger than the male flower. Flowering occurs continuously. Coconut palms are believed to be largely cross-pollinated, although some dwarf varieties are self-pollinating.

THE “BUD ROT” (Phytophthora

palmivora) DISEASE

Introduction

Bud rot is a fatal disease of coconut palm, characterized by the rotting of the terminal bud and surrounding tissues. Even though it affects the palms of all ages, young palms in low lying and moist situations are more susceptible to the disease. It is generally a sporadic disease, but sometimes appears in epidemic forms. The disease commonly occurs in West and East coasts of India.

The “Bud Rot” Complex

The coconut palm is a monocotyledon and normally possesses only one vegetative bud. In all the several fatal disease to which the palm is subject the central spindle of leaves and the soft tissues immediately surrounding the bud tissues undergo a process of decay some weeks prior to the wilting of young expended leaves in the crown. This fact induced the earliest workers to focus their attention on the bud region of the coconut palm and, in several instances, to misinterpret the sequence of events which culminate in the rotting of the bud and the subsequent death of the whole plant. Thus the term “Bud Rot”, which, with one exception, is merely descriptive of a concomitant symptom of different kinds of diseases fatal to the coconut palm, has, in the past, lost its value as an eminently descriptive and popular name of a specific malady.

The name was given, in the first instance, by Butler in 1906 to a specific disease the etiology of which had been studied by him in India. In his published description Butler attributed the disease to the fungus Pythium palmivora, but in1919 he renamed the casual organism Phytophthora palmivora, by which name it is known at the present time.

Stockdale, in 1906, was the first to separate into more than one disease those affections of the coconut palm in the West Indies which result in a soft-rotting of the bud. He stated that in a proportion of the death palms in Trinidad the rotting of the bud was purely secondary. Subsequent work has shown that he was justified and that still further sub-division was necessary.

In 1911 Johnston published a lengthy account of a so-called bacterial disease of coconut palms which he called Bud Rot and stated that it was caused by Bacillus coli. Johnston’s work was carried out in Cuba and other West Indian Islands, including Jamaica and Trinidad. Johnston seems to have been definitely of the opinion that any disease of the coconut palm which eventually resulted in a soft-rotting of the bud was due to B.coli.

At Imperial Botanical Conference in London in July, 1924, diseases of coconut palms which terminated in a rotting of the bud were fully

discussed. Five mycologists took part in the discussion-namely, Butler (India), Sharples (Malaya), Ashby (British West Indies), Dawson (East Africa), and Nowell (British West Indies). In the published proceedings Butler dealt with the bud rot which is now universally accepted as being caused by P.palmivora, criticized johnston’s methods of inoculation with more than one kind of bacterial organism, and expressed doubt as to whether there is any such thing as a primary bacterial bud rot of palms.

Phytophthora Bud Rot (Phytophthora palmivora Butler)

The first record of this disease in palms is by Butler, who, in 1906, found it attacking the tender tissues in the crown of three species in Mandras-namely, the palmyra palm (Borassus flabellifer), the coconut palm (Cocos nucifera) and the areca or betel-nut palm (Areca catechu). In 1910 Butler published the result of his further study describing successful infection experiments with fungus to which he had given the name Pythium palmivorum. In 1919 he renamed the fungus Phytophthora palmivora, by which name it has since been known. With the exception of Malaya, the disease has been recorded in almost every country in the world where the crop is grown. Since the publication of Butler’s work in 1906 and 1910, the fungus has been extensively studied by many workers in different parts of the world.

In 1929 Ashby showed that the fungus P.palmivora Butler is the same botanical species as P.faberi Maubl. and P.theobromæColem., though it exists as a number of distinguishable morphological and pathological strains. Thus P.palmivora is a species of very wide distribution in tropical countries. As an active parasite on the above mentioned palms, cacao, rubber and other economic crops, it ranks as one of the most important plant pathogen in the world. It is therefore well known to plant pathologist and planters throughout the Tropics. The symptoms are very characteristic, and the disease can be easily distinguished from any other.

Symptoms

Phytophthora palmivora, causal organism of Bud Rot

Palms of all ages are susceptible to the disease, but it is more frequent on young palms. Briton- Jones (1940) described the disease symptoms first. The first visible symptom is the withering of the spindle marked by pale color. The spear leaf or spindle turns brown and bends over. Basal tissues of the leaf rot quickly and can be easily separated from the crown. Spindle withers and droops down and one by one, the inner leaves also fall away, leaving only fully matured leaves in the crown. A foul smell is emitted by the rotting tissue. The palms succumb to the disease with the death of the spindle. Later, infection spreads to the older leaves, causing sunken leaf spots covering the entire leaf blade spreading both up and down. Spot margins are irregular and water soaked, and when the leaves are unfolded, the characteristic irregular spots are conspicuous on the blade. In severely affected trees, the entire crown may rot and in few months the trees wilt. Bud rot and premature nut fall diseases are produced on coconut. The heart leaf becomes chlorotic, wilts and collapses.

The disease may spread to older, adjacent leaves and spathes, producing a dead centre with a fringe of living leaves. Light brown to yellow, oily, sunken lesions may be found on leaf bases, stipules or pinnae. Internally, the tissues beneath the bud rot discolored pink to purple with a dark brown border. Infected nuts show brown to black necrotic areas with a yellow border developing on the surface. Internally, they have a mottled appearance. Young nuts are highly susceptible and fail to mature and then fall off from the tree. Older, infected nuts ripen normally. The disease is rampant during the monsoon when the atmospheric temperature is low and the humidity is high.

The disease is called nut fall or Mahali in Kerala. The fungus also infects nuts, causing decay of immature nuts and their fall during the rainy season. Water soaked grayish green area develops at the stalk end of the

nuts against dark green healthy area around. The lesions later turn brown and become sunken due to decay of underlying tissues. The rot extends into the husk and sometimes deep into the endosperm cavity.

Etiology

The diesease is caused by fungus, Phytophthora palmivora is a Butler. The fungus mycelium is typically non-septate and hyaline, intercellular in the tissue drawing its nutrients through haustoria. It develops rapidly to cover the host tissue with a cottony growth, especially during highly humid conditions. The sporongiophores are simple or branched and the sporangia are pear-shaped, with prominent papillae. They are formed singly at the tips of conidiophores and are hyaline and thin-walled, measuring 38-72 x 33-42m. they germinate by releasing motile zoospores through the papillar opening. The zoospores are reniform, with two flagella and they swim for a while in water and come to rest, losing the flagella. The resting zoospores are spherical and thin walled, measuring 8-10m in diameter. Later in the advance stages of fungal growth, oogonia and antheridia are produced, which copulate to produce oospores. The thick walled oospores are formed inside the oogonium surrounded by its persistent wall. They are spherical and measure 35-45m in diameter, and germinate by short germ tubes bearing sporangia at the tips. The fungus also produced thick walled intercalary or terminal chalamydospores.

No significant differences in mycelia growth were recorded in three different media over a range pH tested (4.0-8.0). Light had no influence on palpillate sporangia formation.

Epidemiology

Both the relative humidity and rainfall are related to infection and disease development. It was found that minimum temperature is also an important factor in disease incidence, in addition to humidity. Duration of ‘favorable days’ having high humidity and low temperature for extended periods determined disease development. The period elapsing between the first infection and the withering of the heart may vary from there to nine month or longer, depending on relative humidity.

The fungus might remain dormant in the leaf base during the dry season. Insect attack is considered a predisposing factor for the fungal infection. Rainfall might aggravate infection when the spotting appears on the pinae, since the fungus will be washed down into the bud, mortality is heavier in cold weather. Phytophthora propagules were isolated from crown debris of dead trees even after one year. This shows the potential hazard exerted by diseased trees as a source of inoculums in subsequent season.

A disease forecasting equation has been developed for predicting bud rot disease in Kerala. This would help to forewarn the farmers for taking plant protection measures to check bud rot incidence. In Philippines, Rillo & Paloma (1989) observed higher incidence of Phytophthora which was always preceded by high rainfall during the previous months. The fungus was found to survive in the frond base or basal part of the crown or on roots. The favorable period of infection is when relative humidity is above 94% and temperature is below 24°c. This disease is primarily spread by wind and windblown rain.

Bud rot disease incidence on coconut palm was low (1.6%) in sandy soils than black soils (25%).

Disease cycle

The fungus may perpetuate in the form of oospores or chlamydospores, formed late in the season and carried over the summer months on the host debris, in crevices and natural opening of the dead tissue. With the onset of monsoon rains and favorable atmospheric temperature (18-20°c), the fungus become active, producing the cottony mycelium that infects the tender host tissue. With continuing favorable weather the fungus produces sporangia and numerous zoospores, which spread rapidly in the rain water falling on the tree to cause new infections. Thus, the fungus multiplies rapidly in its asexual stage, later forming the sexual oospores and asexual chlamydospores, which enable it survive and adverse climatic condition.

Differentiation of fungus into + and – strains has been demonstrated, showing that union of antheridia and oogonia can result in the formation of oospores, a process that can give rise to new strains. However, more studies on the strain variations of this species are needed.

Varietal resistance

The hybrid was less sensitive than West African Tall. The Phytophthora incidence was higher in Cameroon Red Dwarf and MYD as compares to Catigan. In Indonesian dwarf selections such as Jombang & Raji appeared to be more resistant to nut fall in inoculation trials. For avoiding economic loss, it is recommended that the choice of planting material should be done by taking into account the environmental condition.

Management

In regard to controlling Phytophthora bud rot, Butler made extensive field trials which involved the cutting down of affected palms at the soft region of the trunk just below the crown, destroying the crown by fire and coupled with these operations the applications of Bordeaux Mixture to the bases of young leaves of all palms within 25 yards of the ones affected. Owing to cases of what he describes as dormant infections, which are said to extend over a period of two years, he discontinued the preventive or protective application of Bordeaux Mixture to surrounding palms and concentrated on the cutting down of obviously diseased crowns and burning them on the spot. In the British West Indies it has been recommended to prevent infection by the application of Bordeaux Mixture, and mixtures of lime and salt or lime and copper sulphate, coupled with the cutting down of affected palms at the base of the trunks, stacking up the material, and burning. The preventive application of fungicides has given inconclusive result, and the cutting down and destruction by fire is claimed by some to have given good results.

 Preparation of 1 per cent Bordeaux Mixture

1. Dissolve one kilogram of Copper Sulphate in fifty litres of water.2. Dissolve one kilogram of Quick Lime in fifty litres of water

seperately.3. Pour Copper Sulphate solution into the Lime water slowly with

constant stirring.4. To check the quality of the mixture, dip a polished knife in the

solution for two minutes. If the knife gets a reddish stain, then the mixture is acidic and harmful to the plant, if sprayed. To neutralize the mixture, add more limewater, till the non-deposition of the red-dish stain on the knife.

 Preparation of 10 per cent Bordeaux paste

1. Dissolve one kilogram of copper sulphate in five litres of water.2. Dissolve one kilogram of Quick lime in another five litres of water

seperately.3. Mix the above two solutions to get the Bordeaux paste.

 Cares to be taken 

1. Use only wooden. earthen or plastic vessels, to avoid the corrotion of the metal vessels by the mixture.

2. Always spray freshly prepared mixture for effective management.

The disease occurs in both wet and dry season in Trinidad, and in either season the main portions of the crown and trunks are full of moisture, and effective early burning is, as personal observation has shown, in the majority of cases an expensive and difficult operation. Effective charring has been observed on estates where the managers have the faith and ability to enforce their orders. But in majority of cases the attempts have been ineffectual and just so much waste of time and money; and the writer would add that even when the fire has been effective it is his opinion that is money ill-spent on commercial plantations in the Western Tropics. In the Eastern Tropics the expense is justifiable only if such rotting tissue is known to harbor insects noxious to the coconut palm or other crops of economic value. The rhinoceros beetle grubs found in rotting tissues of the coconut palm are purely secondary and do not attack healthy crowns.

In the West Indies the writer recommends the cutting down of the palm at ground level, since there is no point in leaving a bare trunk standing, and making a pile of the sectioned stem and the crown in such a manner that the soft rotting tissue of the cabbage and young leaves is lowermost in the pile. An effective screening off of the spore-bearing fungous material, which, as already stated, has the tendency to fall rather than rise, thus is assured. Moreover, active saprophytic bacteria, and fungi will soon overrun the Phytophthora in the disintegrating tissue.

It was stated above that total recovery are rare in India. But it is interesting to note that in young palms up to five years old neither little leaf nor total recovery from Phytophthora bud rot has ever been seen. A possible explanation of this apparent discrepancy lies in the fact that young palms in Trinidad are generally given cultivation and manure when established in

sugar-cane, and in any case cultivation, by merely digging of the plant hole. For the first few years, therefore, the palms grow tolerably well, whereas in older palms the leaves do not reach proportional size because the roots spread to uncultivated soil, or to soil on which cultivation has been discontinued contemporaneously with the removal of the sugar-cane. It is well known that all the above ground tissue of well cultivated and rapidly growing palms are softer than those slow growing palms, and since the fungus confines its activities to soft tissues, it follows that tougher tissues of poorly grown palms offer more resistance to the invading mycelium. Many hundreds of acres of coconut palms are growing on poor soils entirely unsuited to the crop: hence the prevalence of bronze leaf wilt and possibly the more frequent occurrence of little leaf and total recovery from Phytophthora bud rot.

If the foregoing explanations is true, it follows on the same line of thought that there may be within coconut plantations on good soils palms whose normally produced young tissues are more rigid and tougher than others. Cytological studies of the tissues of different kinds of palms might lead to a quick method of selecting resistant varieties against Phytophthora bud rot. This could be done concurrently with mass selection for high yielding as well as for resistance to dieses in general. Selection work along similar lines might be done with a view to extracting varieties which can withstand extreme fluctuations of soil moisture, which is most important.

REFFERENCE

Books

Briton-Jones, H.R., 1940, The Diseases Of Coconut Palm, The Bud Rot Disease, Bailliere, Tindall And Cox, London

Srinivasulu, B. & Rao, D.V.R.,2007, Coconut Diseases, Bud Rot Disease, International Book Distributing Co., India

Websites

The coconut palm. Retrieved from http://www.thewisegardener.com/ Articles/palmofthemonth/coconut.htm

Coconut. Retrieved from en.wikipedia.org/wiki/coconut

APPANDICES