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Agriculture > Plantation Crops > Coconut (Cocosnucifera)

Crop Management

Plant Protection

Diseases

Of the several maladies that confront coconut production in Kerala State, the coconut root (wilt) disease is of utmost concern. The palm is also affected by a number of other diseases like stem bleeding, bud rot, mahali, leaf rot, gray blight and Tanjavur wilt.

  1. Root (wilt) disease
  2. Stem bleeding
  3. Bud rot
  4. Mahali
  5. Leaf rot
  6. Gray blight
  7. Tanjavur wilt (Basal Stem Rot)
  8. Button shedding

Pests

The coconut palm is infected by a number of insect and non-insect pests inflicting heavy crop losses. The most devastating among them are rhinoceros beetle, red palm weevil, leaf eating caterpillar, coreid bug, cockchafer beetle, coconut eriophyid mite, mealy bug and rodents

  1. Rhinoceros beetle (Oryctes rhinoceros)
  2. Red palm weevil (Rhyncophorus ferreugineus)
  3. Leaf eating caterpillar (Opisina arenosella)
  4. Coreid bug (Paradasynus rostratus)
  5. Cockchafer beetle (Leucopholis coneophora)
  6. Coconut eriophyid mite (Aceria [Eriophyes] guerreronis)
  7. Mealy bug (Pseudococcus sp.)
  8. Termites
  9. Rodents

Root (wilt) disease

Occurance

First observation of the disease was in 1882 in three isolated pockets in Kerala, one at Erattupetta of Meenachil taluk of Kottayam district and other two at Kaviyoor and Kalloopara of Thiruvalla taluks in Pathanamthitta district. The disease has been spreading in all directions independently from the three foci of infection noticed. Disease noticed in all types of soils under varying ecological conditions from foothills to coastal sands. At present the disease occurs in a continuous manner in 4,10,000 ha in eight southern districts of Kerala stretching from Trivandrum in south to Thrissur in north. Lowest disease intensity of 1.52% observed in Trivandrum district followed by 2.6% in Thrissur district. Highest intensity is noticed in Kottayam district(75.63%) followed by Allepy district (70.69%) . Disease is debilitating in nature but not lethal.

Loss:

The loss in terms of nut yield is proportional to the intensity of the disease and generally varies from 10 to 80 per cent. The annual loss has been estimated to be approximately 968 million nuts in Kerala state.

Symptoms:

The characteristic symptom is the flaccidity of leaflets. Yellowing of older leaves, necrosis of leaflets and deterioration and decay of root system are other salient features of the disease. The leaflets curve inwardly to produce ribbing so that the whole frond develops a cup like appearance. Abnormal shedding of buttons and immature nuts are also noticed.

Management:

Coconut root (wilt) is a non-lethal debilitating disease and the affected palms survive for a long period giving a reasonably good yield. The root (wilt) affected palms are susceptible to diseases like leaf rot and pests like rhinoceros beetle and red palm weevil. So there is a chance of confusing the pest and disease symptoms with the root (wilt) disease.

Negligence on the management aspects aggravates the malady. Efficient management of palms suspected to be affected by coconut root (wilt) disease demands control of all pests and diseases and imparting natural resistance and health to the palms through proper manuring and agronomic practices. A package of management practices for the effective management of root (wilt) disease is given below:

  • Rogue out palms that are affected severely by root (wilt) and yield less than 10 nuts / palm / year and those, which have contracted the disease before flowering. Replant with disease tolerant material / high yielding hybrids (Chandrasankara).

  • Apply fertilizers for coconut palms as follows,

  • N P2O5 K2O
    palm/year
    Average management 0.34 kg 0.17 kg 0.68 kg
    Good management 0.5 kg 0.32 kg 1.2 kg
  • In addition to the above, apply 50 kg cattle manure or green manure and 1 kg of lime / palm / year. Magnesium may be supplied @ 500 g MgO per palm per year in the Onattukara region (sandy soil) and 100 g MgO in the remaining areas. The cheapest source of MgO is magnesite (MgCO3). The magnesium in magnesite is acid soluble. Hence it may be preferred in acid soils. Magnesium sulphate is the most common source of MgO.

  • Growing green manure crops like sunn hemp, sesbania, cowpea and calapagonium in the coconut basin and their incorporation in situ is beneficial as the practice reduces the intensity of the root (wilt) and increases the nut yield. The ideal green manure crops for the sandy and alluvial soils are cowpea and sesbania, respectively.

  • Under rainfed conditions, apply fertilizers in two splits, 1/3rd at the time of early southwest monsoon and 2/3rd before the northeast monsoon. Under irrigated conditions apply fertilizers in three equal splits (April-May, August-September and December-January).

  • Apply fertilizers and manures in 10 cm deep circular basins at a radius of 2 m from the bole of the palm.

  • When the crop is grown under the bund and channel system, desilt the channel and strengthen the bunds during summer months.

  • Follow strictly all the prescribed prophylactic measures against leaf rot disease, red palm weevil, rhinoceros beetle etc. so as to ensure that the palms are not debilitated. To maintain the productivity of the palms, prophylactic measures are of great importance.

Diseases Menu

Stem bleeding

Symptoms:

Exudation of the reddish brown liquid through the growth cracks mostly at the basal part of the trunk and bleeding patches higher up in the trunk are characteristic symptoms. One or more lesions, lying close by, may coalesce to form large patches. The liquid that oozes out dries up and turns black. The tissues beneath the bleeding points decay and become yellowish. The lesions spread upwards as the disease progresses. In advanced stages, the leaf size reduces leading to reduction in crown size. The rate of leaf production slows down. The production of bunches is affected and nut shedding takes place. The trunk gradually tapers towards the apex. The progress of the disease is faster during July to November.

Causal organism:

The fungus, Thielaviopsis paradoxa is the causal agent. Growth cracks on the trunk, severe summer followed by heavy down pour, water stagnation, imbalance in nutrition, excess salinity and stress can act as predisposing / aggravating factors.

Management:

  1. Chisel out completely the affected tissues and paint the wound with Bordeaux paste.Apply coal tar after 1-2 days.

  2. Destroy the chiseled materials by burning. Avoid any mechanical injury to trunk.

  3. Apply neem cake @ 5 kg per palm in the basin along with other organics.

  4. Apply hexaconazole @ 25 ml in 250 litre of water as soil drenching once in four months.

  5. . Swabbing the lesions on the trunk with a paste of Trichoderma viridae talc based formulation (100 g /100ml) along with application of lime or dolomite @ 1 kg /palm during April-May and application of neem cake @ 5 kg /palm + organic manure enriched with (1%) during September- October.

Diseases Menu

Bud rot

This disease was reported as early as 1913 by Fletcher, Govt. Entomologist of Coimbatore. The causal organism was reported as Phytophthora palmivora (See image) by Shaw & Sundararaman 1914. Disease spread slowly, though persistently, by means of tappers, rhinoceros beetle and human agencies.

Symptoms

Palms of all age are liable to be attacked but normally young palms are more susceptible, particularly during monsoon when the temperature is low and humidity is very high. In seedlings, the spear leaf turns pale and comes off with a gentle pull. In adult palms, the first visible symptom is the colour change of the spear, which becomes pale and breaks at the base and hangs down. The tender leaf base and soft tissues of the crown rot into a slimy mass of decayed material emitting a foul smell. The rotting slowly progresses downwards, finally affecting the meristem and killing the palms. This is accompanied by drooping of successive leaves. Even then, nuts that are retained on the palm may grow to maturity. The disease proves fatal if not checked at the early stages, before damage of the bud.

Management:

  • In early stages of the disease (when the heartleaf starts withering) cut and remove all affected tissues of the crown. Apply Bordeaux paste and protect it from rain till normal shoot emerges.

  • Burn all disease-affected tissues removed from the palm.

  • Spray 1% Bordeaux mixture on spindle leaves and crown of disease affected as well as neighbouring palms, as a prophylactic measure. Palms that are sensitive to copper containing fungicides can be protected by mancozeb. Small, perforated sachets containing 2 g of mancozeb may be tied to the top of leaf axil. When it rains, a small quantity of the fungicide is released from the sachets to the leaf base, thus protecting the palm.

  • Adopt control measures for rhinoceros beetle.

  • Provide adequate drainage in gardens.

  • Adopt proper spacing and avoid over crowding in bud rot prone gardens.

Diseases Menu

Mahali

Shedding of female flowers (buttons) and immature nuts occur in coconut due to various reasons. The problem was reported in 1922 from Perumbilav and Chalissery areas of Palakkad district of Kerala. Since it resembled the mahali disease of arecanut in several respects, it was called as mahali disease. The disease is caused by Phytophthora spp.

Symptoms:

Shedding of female flowers and immature nuts are the common symptoms of the disease. Lesions appear on the young fruits or buttons near the stalk, which later lead to the decay of the underlying tissues and endosperm. Newly fallen nuts show a whitish growth of the fungus over the brown patches. This growth consists of the mycelium and sporangia of the causal fungus.

Management:

Spray 1% Bordeaux mixture or copper oxychloride preparation (0.2%) on the crown of palms, once before the monsoon and once or twice later on at intervals of 40 days.

Diseases Menu

Leaf rot


It is a common observation that leaf rot is often super-imposed on root (wilt) affected coconut palms. Leaf rot, in fact, worsens the condition of the root (wilt) affected palm very seriously.

Symptoms:

The first symptom is the appearance of water-soaked brown lesions in the spear leave of root (wilt) affected palms. Gradually these spots enlarge and coalesce resulting in extensive rotting. As the leaf unfurls, the rotten portions of the lamina dry and get blown off in wind, giving a 'fan' shape to the leaves. Some times, the symptom becomes very acute and the spear fails to unfurl.

This disease is a fungal complex initiated predominantly by Colletotrichum gloeosporioides, Exserohilum rostratum (See image) and Fusarium spp .

Management:

  1. Remove the rotten portions from the spear and the two adjacent leaves.

  2. Pour 300 ml of fungicidal solution at the base of the spear. This can be prepared by mixing hexaconazole 5EC 2 ml or mancozeb 3 g in 300 ml water.

  3. Treat the top two leaf axils with insecticide preparation. This can be prepared by mixing cartap hydrochloride 20 g with 200 g sand.

  4. Spray crowns and leaves with 1% Bordeaux mixture or 0.2% copper oxychloride formulations or 0.3% mancozeb in January, April-May and September. While spraying, care has to be taken to spray the spindle leaf

  5. After crown cleaning, (removal and destruction of affected parts) in coconut palms pour 300 ml of any of the following bio- control agent at the base of the spear leaves twice a year (April-May and September-October)

  1. Pseudomonas fluorescence (20g/l)

  2. PGPRmix 11 (20 g/l)

Diseases Menu

Grey blight

This is caused by the fungus Pestalotia palmarum .

Symptoms:

Symptoms appear in the mature leaves of the outer whorl as yellow specks encircled by a greyish band which later becomes greyish white. The spots coalesce into irregular necrotic patches causing extensive leaf blight. In advanced stages, the tips and margins of the leaflets dry and shrivel giving a burnt appearance.

Management:

Remove severely affected older leaves and burn. Spray the trees with 1% Bordeaux mixture or propiconazole 1 ml/l. .

Diseases Menu

Tanjore wilt (Basal Stem Rot)

Causal Organism : Ganoderma lucidum

Symptoms:

This disease is of recent occurrence in many parts of Kerala, especially in the districts of Palakkad, Malappuram, Thrissur, Kollam, Thiruvananthapuram and Wayanad. Middle aged palms were seen fatally affected. The characteristic symptom of the disease is the rotting of the basal portion of the stem. The bark turns brittle and often gets peeled off in flakes, leaving open cracks and crevices. The internal tissues are discoloured and disintegrated, emitting a bad smell. Mild bleeding occurs on the basal region. The tissues on the bleeding spots are soft to touch. Extensive damage of the root system following root rotting has been observed. Ultimately the palm dies off.

Management:

  • Apply organic manure @ 50 kg / palm.

  • Apply neem cake @ 5 kg / palm / year.

  • Reduce fertilizer application to one-fourth of the recommended dose.

  • Drench the basin with 40 litres of 1% Bordeaux mixture or tridemorph 0.1% or any other copper fungicide to soak soil up to 15 cm depth at quarterly intervals.

  • Root feed with tridemorph 2 ml mixed with 100 ml water at quarterly intervals.

  • Avoid flood irrigation in order to prevent the possible spread of the pathogen through soil.

  • Isolate the affected palm from the healthy ones by digging a trench of size 1 m deep and 50 cm wide, 1.5 m away from the bole of the infected palm.

  • Avoid growing leguminous crops in and around the garden

Diseases Menu

Button shedding

The shedding of buttons in the coconut is attributed to the following reasons.

  1. Pathological conditions

  2. Attack of insect pests

  3. Nutritional deficiencies

  4. Soil and climatic variations

  5. Defects in pollination and fertilization

  6. Structural defects in the flower

  7. Abortion of embryos

  8. Limited capacity of the tree to bear fruits

  9. Unfavourable conditions such as deficit of moisture, water logging and lack of aeration.

The causes of button shedding may be identified and appropriate remedial measures adopted.

Diseases Menu

PLANT PROTECTION: PESTS

Rhinoceros beetle (Oryctes rhinoceros)

Occurrence and symptoms:

It is a very common destructive pest in coconut. The adult beetle bores through the unopened fronds and spathes hampering the growth of the palm and predisposing the palm to infestation by red palm weevil and bud rot. The attacked frond when fully opened shows characteristic triangular cuts. The beetle attack is maximum during summer months from March to June and minimum in September-October.

Management:

  1. Provide field sanitation to prevent breeding of beetles.

  2. Hook out the beetles from the attacked palms by using beetle hook.

  3. The topmost three leaf axils around the spindle may be filled with any of the following mixtures as a prophylactic measure:

    1. Application of 250g neem cake or marotti (Hydnocarpus wightina) cake mixed with equal volume of sand in the innermost 2-3 leaf axils. This treatment is to be done twice, ie, during April-May before the onset of south-west monsoon and during September-October after the south-west monsoon.

    2. Naphthalene balls 12.0 g (approx. 4 nos.) in the innermost 2 leaf axils and covered with fine sand, once in 45 days.

    3. Incorporation of Clerodendron infortunatum @ 10 per cent w/w basis in the cowdung pit and/or manure pits.

    Crown cleaning followed by application of 20 g Cartap hydrochloride 4G or Fipronil 0.3G or carbosulfan 6G mixed with 200 g sand in the innermost 2-3 laef axils. This treatment has to be done thrice during January, May and September.

  4. Release Baculovirus oryctes infected adults @ of 10-15 / ha to bring down the pest population.

  5. Inoculation of breeding sites with entomopathogenic fungus Metarrhizium anisopliae (@ 5 x 1011 spores / m3) var major causes mortality to the grubs.

Pests Menu

Red palm weevil (Rhyncophorus ferreugineus)

Occurrence and symptoms:

This weevil worst affects relatively young palms of age group between 5 to 10 years. The mode of entry, nature of infestation and colonization of this pest go unnoticed, defeating the normal pest management strategies. The diagnostic symptoms are the presence of holes on the stem, oozing out of a viscous brown fluid and extrusion of chewed up fibrous matter through the hole, longitudinal splitting of leaf base and wilting of central shoot. Sometimes the gnawing sound produced by the feeding grubs inside will also be audible.

Management:

  • Field sanitation should be given prime importance.

  • Avoid making steps or any other injury on the tree trunks to reduce the loci of infestation.

  • Leaf axil filling as suggested in the case of rhinoceros beetle will be useful against the red palm weevil also.

  • When green leaves are cut from the palms, stumps of not less than 120 cm may be left on the trees in order to prevent successful inward movement of the grubs through the cut end.

  • In attacked palms, observe for the bore-holes and seal them except the top most one. Through the top most hole, pour 1% carbaryl or 0.5% trichlorphon suspension @ one litre per palm, using a funnel.

  • When the pest infestation is through the crown, clean the crown and slowly pour the insecticide suspension.

  • As an alternative, apply 1% DDVP as a curative measure.

  • Coconut log traps with fermenting toddy or pineapple or sugarcane activated with yeast or molasses can be set in coconut plantation to attract and trap the free floating population of red palm weevil. Incorporate any of the insecticide to each trap to kill the weevils trapped.

  • Use of pheromone trap for attracting and killing adult weevils @ one trap per 2 ha.

Pests Menu

Leaf eating caterpillar (Opisina arenosella)

Occurrence and symptoms:

This is an endemic pest of coconut palm especially in the coastal tract of Kerala. During epidemic of this pest, the palms often have a desolate look, the entire foliage being eaten by the caterpillar. Severity of attack is seen during the months from January to May. The caterpillar feeds on green matter from the lower leaf surface, remaining within galleries of silk and frass.

Lifecycle of Opisina Arenosella & infected leaf

Management:

  1. As a prophylactic measure, the first affected leaves may be cut and burnt during the beginning of the summer season.

  2. Arrange for the release of larval / pupal parasitoids, Goniozus nephantidis, Elasmus nephantidis (brown species) and Brachymeria nosatoi.

  3. Trunk release of G.nephantidis @ 10 nos/plam (4 to 6 releases) is effective for the management of leaf eating caterpillar.

  4. When infestation is very severe and if the biocontrol is not likely to be effective, spray the undersurface of the fronds with dichlorvos 0.05 per cent, malathion 0.1 per cent, quinalphos 0.05 per cent, or phosalone 0.07 per cent- Flubendiamide 39.35% SC (0.2%), Chlorantraniliprole 18.5% SC (0.5%) or Spinosad 45 SC (0.4 ml/l) are effective.

Note: Application of the insecticides should be followed by liberation of larval and pupal parasites from the 21st day.

Pests Menu

Coreid bug (Paradasynus rostratus)

Occurrence and symptoms:

The attacked buttons become deformed with characteristic crevices on the husk below the perianth with gum exudations and the tender nuts become barren. The attacked buttons do not develop resulting in immature nut fall.

Management:

Pesticide application is necessary if infection is severe. Spraying has to be done three times a year. Apply 0.1% carbaryl on the newly opened inflorescence after the receptive phase of the female flowers and spray the entire crown excluding the leaves and older bunches. Destruction of pollinating insects can be avoided if spraying is done in the afternoon hours.

Note: The insecticide may be applied according to the severity of infection in a need-based manner.

Pests Menu

Cockchafer beetle (Leucopholis coneophora)

Occurrence and symptoms:

The white grubs are mostly found in sandy loam tracts of Kerala and Karnataka. It damages the roots. In seedling, it tunnels into the bole and collar region. It has an annual life cycle with a grub period of 8 months. Peak grub population is observed from September to October. Adult beetles emerge out of the soil after pre-monsoon showers in May-June during sunset hours. The infested palms turn pale yellow and there will be considerable reduction in yield.

Management:

  1. Collection and destruction of adults during the monsoon period from adjacent vegetation (in the evening).
  2. Plough or dig the infested soil synchronizing with pre-monsoon showers.
  3. Drench the soil with chlorpyrifos 0.04 per cent suspension. The treatment should be given twice, first during April-May after the receipt of pre-monsoon showers and second during the month of September.

Note: Note: wherever possible, light traps may be set up to attract and trap adult beetles.

Pests Menu

Coconut eriophyid mite (Aceria [Eriophyes] guerreronis)

Occurrence and symptoms:

The eriophyid mite, which was a minor pest of coconut in India, has become a major pest on coconut recently. The mites are very minute in size and are not visible by naked eye. It measures 200-250 microns in length and 20-30 microns in width. The life cycle of this mite is completed in 10-12 days. It remains underneath the perianth (cap) of the developing nuts (buttons) and causes injury by feeding on the soft paranchymatic

tissues. Though the mites are microscopic, their damage is enormous and hundreds of mites could be seen in each infested button and tender nut. The earliest symptom on 2-3 month old buttons is pale yellow triangular patches seen below the perianth. Later, these patches become brown. Severely affected buttons may fall. As the buttons grow, brown patches lead to black necrotic lesions with longitudinal fissures on the husk. Uneven growth results in distortion and stunting of nuts leading to reduction in copra yield. In severe cases, the losses are compounded because the quality of fibre is reduced and distorted nuts increase the labour requirement for dehusking. The mites spread through wind and its multiplication is at a high rate. Though this pest was noticed only in a limited area during 1998, it has become a major pest of coconut in India.

Management:

  1. Collect and destroy all the fallen buttons of the affected palm.

  2. Apply 2% neem oil + garlic emulsion or commercial neem formulation of azadirachtin 0.004% (Neemazal T/S 1% @ 4 ml per litre of water) or micronized wettable sulphur 0.4% in the crown on young bunches. In large coconut plantations, dicofol 0.1% can be applied after taking adequate precautions. However, spraying of dicofol should be avoided in homesteads. When rocker sprayer is used 1.0 to 1.5 litre of spray fluid per palm is required. If a hand sprayer is used, the spray solution required may be about 500 to 750 ml. Spraying has to be done on second to seventh bunches from top avoiding unpollinated inflorescence. Care should be taken to see that spray fluid reaches the perianth region of third, fourth and fifth bunches since these bunches harbour maximum number of mites. Three rounds of spraying are recommended in a year viz., March-April before the onset of southwest monsoon, in August-September during the dry spell between the southwest and northeast monsoons and in December-January after the northeast monsoon so that all the emerging bunches in the vulnerable stage receive one round of spraying. Rational rotation of the above pesticides may be adopted to avoid chances of resistance.

Preparation of neem oil + garlic emulsion (2%)

To prepare 10 litres of 2% neem oil + garlic emulsion, 200 ml neem oil, 200 g garlic and 50 g ordinary bar soap are required. Slice the bar soap and dissolve in 500 ml lukewarm water. Grind 200 g of garlic and take the extract in 300 ml of water. Pour the 500 ml soap solution in 200 ml neem oil slowly and stir vigorously to get a good emulsion. Mix the garlic extract in the neem oil + soap emulsion. Dilute this 1 litre stock solution by adding 9 litres of water to get 10 litres of 2 % neem oil + garlic emulsion.

As per the recommendation of the National Level Steering Committee, a holistic approach has to be adopted in the management of the coconut eriophyid mite. Hence, in addition to the plant protection measures mentioned above, the following measures can be adopted:

  1. Improving nutrient status by applying organic manure at the rate of 50 kg and neem cake 5 kg per palm per year. Also apply the recommended dose of fertilizers in two split applications.

  2. Growing compatible intercrops / mixed crops.

  3. Providing adequate irrigation.

Pests Menu

Mealy bug (Pseudococcus sp.)

Occurrence and symptoms:

The mealy bugs are widely distributed and are usually implicated in various disease conditions of coconut. During summer months, mealy bugs cause damage to spindle leaves, spathes and the buttons. Mealy bugs infest the unopened heartleaf and inflorescence. As a result, the leaves become highly stunted, suppressed, deformed and present a crinkled appearance. It is often confused with the leaf rot symptoms. The affected inflorescences are malformed and do not open. Even if they open, they do not bear nuts. Button mealy bugs colonize under the perianth lobes of

tender nuts. Infested nuts harbouring gravid mealy bugs remain on the spadix, which serve as inoculum for further spread.

Management:

Remove and destroy all dried up inflorescence and unproductive buttons. Apply non-residual phosphatic insecticides like dimethoate 0.05% or quinalphos 0.05 % at the site of infestation. Neem garlic emulsion 2% applied on infested bunches checks button mealy bugs.

Pests Menu

Termites

Occurrence and symptoms:

It is estimated that nearly 20% of the coconut seedlings are damaged by termites particularly in laterite soil.

Management:

  • Adopt field sanitation by avoiding organic matter residues in nursery soil and covering germinating nuts with a layer of river sand.

  • Drench the nursery with 0.05% chlorpyriphos twice at 20-25 days interval.

  • Swab the affected trunk with the same chemical.

Pests Menu

Rodents

Occurrence and symptoms:

Among the non-insect pests, rodents are the most important group causing severe crop damage to coconut, and damage is estimated as 20 per cent of the total production of nut in India. Rats damage tender nuts by forming characteristic holes. Shed nuts can be seen at the base of the palm.

Management:

  1. Place wax blocks of 0.005% bromadiolone in coconut crown of the infested palms at 3 to 4 days interval till the bait is no more consumed.

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