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Coconut diseases and their management – Kisan Suvidha
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Coconut diseases and their management

coconut tree cultivation

Coconut diseases and their management

Major Coconut diseases are given below:-

1.TANJARE WILT/BASAL STEM-END ROT/GANODERMA WILT: Ganoderma lucidem and Ganoderma applanatum

Symptom:

  • Initial symptoms of Thanjore wilt (Ganoderma wilt) start with withering, yellowing, and drooping of the outer whorl of leaves.
  • This is followed by exudation of reddish brown liquid through cracks at the base of the trunk and oozing spread upward. The tissues on the bleeding spots are soft to touch.
  • Decaying of tissues at bleeding point and 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 discolored and disintegrated, emitting a bad smell.

Bracket formation at the base of the trunk. Ganoderma appears at the base of the trunk. Ultimately the palm dies off.

Identification of pathogen:

This is a fungal disease. Causal organism is Ganoderma lucidem and Ganoderma applanatum

Management:

 Cultural method
  • Remove and destroy all affected palms.
  • Green manure crops must be raised and ploughed at the time of flowering.
Biological method
  • Apply Pseudomonas fluorescens (Pf1) @ 200g/palm + Trichoderma viride @ 200g/palm/year.
  •  Also, apply 200g Phosphobacteria and 200 g Azotobactor mixed with 50kg of FYM/palm.
  • Apply FYM 50kg + neem cake 5 Kg once in 6 months along with fertilizers.
Chemical method
  • Isolation of trench around the tree, 4 feet away from the base of the trunk. Apply Sulphur dust inside the trench.
  • The bleeding patches in the stem may be chiseled and protected with tridemorph (5% calxin) and subsequently with hot coal tar.
  • Aureofungin-sol 2 g +1 g Copper Sulphate in 100ml water or 2 ml of Tridemorph in 100 ml water applied as root feeding. (The active absorbing root of pencil thickness must be selected, and a slanting and a slanting cut is made. The solution to be taken in a polythene bag or bottle and the cut end of the root should be dipped in the solution).
  • Trunk injection/root feeding with Calixin 3 ml/tree.
  • Forty litres of 1% Bordeaux mixture should be applied as a soil drench around the trunk in a radius of 1.5m.

2.BUD ROT: Phytophthora palmivora

Symptom:

  • 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.
  • The earlier symptom is the yellowing of one or two younger leaves. Black spots appear on spindle leaves. Basal tissues of the leaf rot quickly and can be easily separated from the crown.
  • In the later stages the spindle withers and drops down.
  • The tender leaf base and soft tissues of the crown rot into a slimy mass of decayed material emitting a foul smell.
  • Ultimately the entire crown falls, and the palm dies

In adult palms, the first visible symptom is the color change of the spear, which becomes pale and breaks at the base and hangs down. 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.

Identification of pathogen:

This is a fungal disease. Causal organism is Phytophthora  palmivora

Management:

Cultural method
  • Provide adequate drainage in gardens.
  • Adopt proper spacing and avoid over crowding in bud rot prone gardens.
Chemical method
  • Remove all the affected tissue of the crown region and crown drenching with Copper Oxychloride 0.25%. (Apply Bordeaux paste and protect it from rain till normal shoot emerges. (Dissolve 100 gm of copper sulfate and 100 gm of quick lime each in 500ml. water separately and mix to form 1 litre of Bordeaux paste).
  • Spray 0.25% Copper oxychloride on the crown of the neighboring Palms as a prophylactic measure before the onset of monsoon. (Spray 1% Bordeaux mixture on spindle leaves and crown of disease affected as well as neighboring palms, as a prophylactic measure. Palms that are sensitive (Dwarf palms) 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.
  • The infected tissues from the crown region should be removed and dressed with Bordeaux paste sprayed with 1% Bordeaux mixture as pre-monsoon spray (May and September).
  • Leaf axil filling with Sevidol 8G, 25 g mixed with 200g sand is recommended to red palm weevil infestation of affected palms.

Spray with Copper Oxychloride 0.25% after the onset of Monsoon.

3. LEAF BLIGHT (LB):  Lasiodiplodia theobromae

Symptom:

  • Leaf blight causes serious damage in seedlings and adult palms.
  • The pathogen causes damage in leaf and nuts.
  • The adult leaves in the lower 3 to 4 whorls are affected.
  • The affected leaflets start drying from the tip downwards and exhibit a charred or burnt appearance.
  • Dark gray to brown lesions with wavy to undulated margins appears from the apex of the nuts.
  • The fungus entered into the kernel through mesocarp, resulting in a decay of the endosperm.
  • The affected nuts were desiccated, shrunk, deformed and dropped prematurely and resulting in nut yield loss up to 10 to 25%.
  • The incidence was noticed through out the year. Maximum incidence was observed during summer months.

Spores and the resting structures on the affected portion of the leaves served as inoculum for further spread through the wind.

Identification of pathogen:

  • The leaf blight disease of coconut caused by the fungus Lasiodiplodia (Botryodiplodiatheobromae (Pat.) Griffon and Maubl.is an emerging serious problem in Pollachi tract of Tamil Nadu. At present, the disease is spreading at a faster rate in Coimbatore, Erode, Dindigul, Tirunelveli, Kanyakumari and other districts of Tamil Nadu and causing 10 – 25 per cent yield loss.

Management:

Cultural method
  • Remove and burn the severely affected leaves to avoid further spread.
Biological method
  • Application of 200g Pseudomonas fluorescens along with 50 kg of FYM+ 5 kg of Neem cake/ palm/ year.
Chemical method
  • Spray 1.0 per cent Bordeaux mixture or 0.25 percent Copper oxychloride (2 times at 45 days interval during summer months).
  • Root feeding of Carbendazim 2 g or Hexaconazole/ Tridemorph 2 ml + 100 ml water (3 times at three months interval).

Application of an additional quantity of 2 kgs of MOP.

4. LEAF ROT DISEASE: Colletotrichum gloeosporioides, Exserohilum rostratum and Fusarium spp.

Symptom:

  • Leaf rot disease commonly occurs on coconut palms already affected by root wilt disease especially in 8 southern districts of Kerala, namely Thiruvananthapuram, Kollam, Alappuzha, Pathanamthitta, Kottayam, Ernakulam, Idukki, and Thrissur, besides Theni, Tirunelveli, Coimbatore and Kanyakumari districts of Tamil Nadu.
  • The first symptom is the appearance of water-soaked brown lesions in the spear leaves 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 gets blown off in the wind, giving a “fan” shape to the leaves.

Sometimes, the symptom becomes very acute, and the spear fails to unfurl.

Identification of pathogen:

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

Management:

Physical method
  • Remove the rotten portions from the spear and the two adjacent leaves.
Chemical method
  • Pour fungicide solution of Hexaconazole (Contact 5E) – 2ml or Mancozeb (Indifil M45) – 3g in 300ml water per palm to the base of spindle leaf. 2-3 rounds of spraying are sufficient in the case of mild infection.

Spray crowns and leaves with 1% Bordeaux mixture or 0.5% copper oxychloride formulations or 0.4% mancozeb in January, April-May and September. While spraying, care has to be taken to spray the spindle leaf.

5.ROOT WILT (OR) KERALA WILT DISEASE: Phytoplasma

Symptom:

  • Tapering of the terminal portion of the trunk.
  • Reduction of leaf size
  • Abnormal bending or Ribbing of leaf lets termed as flaccidity.
  • Flowering is delayed and also yield considerably reduced.

The characteristic symptom is the flaccidity of leaflets. This is the earliest visual symptom. In the beginning, yellowing is restricted from the leaf tips to the middle of the 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.

Identification of pathogen:

  • Causal Organism is Phytoplasma.

The disease is transmitted by lace bug Stephanitis typica and the plant hopper Proutis tamoesta.

Management:

Cultural Method:
  • Cut and remove disease advanced, uneconomical palms yielding less than ten nuts per palm per year
  • Grow green manure crops – cowpea, sunhemp (Crotalaria juncea), Mimosa invisa, Calapagonium mucanoides, Pueraria phaseoloides, etc. may be sown in coconut basins during April-May and incorporated during September-October.
  • Irrigate coconut palms with at least 250-litre water in a week.
  • Adopt suitable inter/mixed cropping in coconut gardens.
  • Provide adequate drainage facilities.
Water Management (Irrigated) of Root Wilt affected Garden:
Age of Palm Basin Drip Perfo/Sprinkler (HDMSCS)
1-2 years old 25-30litres once in 2 days 10 lit per day, two emitters 50 cm from base  –
3-4 years old 75-80 litres once in 4 days 20lit per day, three emitters 75 cm from base  –
Adult Palm 200-250 litres once in 4 days 30-35 lit per day, four emitters 1 m away
(in laterite); 6 emitters (literal sandy soil)
Pit size for emitters – 25cm3
Irrigate to a depth of 20 mm once in 4 days
Biological method:
  • In addition to the above, apply 50 kg FYM or green manure and 5 kg of neem cake/palm / year.
  • 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.
  • Apply manures in 10 cm deep circular basins at a radius of 2 m from the bole of the palm.
Chemical Method:
  • Apply fertilizers for coconut palms in average management at the rate of 1.3 kg urea, 2.00 kg super phosphate and 3.5 kg potash (MOP) / palm/year in the form of urea, rock phosphate and muriate of potash, respectively.
  • Magnesium may be supplied @ 500 g MgO per palm per year in the (sandy soil) area. The cheapest source of MgO is magnesite (MgCO3). The magnesium in magnesite is acid soluble. Hence it may be preferred in acid soils.

To maintain the insect vectors, treat the top tow leaf axils with insecticide preparation. This can be prepared by mixing phorate 10 G with 200 g sand or powdered neem cake 250 g. Mix equal quantity of sand around the base of the spindle.

6.STEM BLEEDING DISEASE: Thielaviopsis paradoxa

Symptom:

  • The progress of the disease is faster during July to November.
  • Stem Bleeding is characterized by the exudation of a dark reddish brown liquid from the longitudinal cracks in the bark and wounds on the stem trickling down for a distance of several inches to several feet.
  • The lesions spread upwards as the disease progresses.
  • The liquid oozing out dries up and turns black. The tissues below the lesions become rotten and turn yellow first and later black.
  • In advanced cases, the interior of affected trunks is hollow due to the decay of interior tissues.

As a result of extensive damage to the stem tissue, the outer whorl of the leaves turn yellow, dry and shed prematurely. The production of bunches is affected adversely. Nut fall is also noticed.

Identification of pathogen:

The fungus, Thielaviopsis paradoxa is the causal agent of the disease. The progress of the disease was faster during July to November. The increase in growth cracks on the trunk, severe summer followed by sudden wetting, imbalanced nutrition, excessive salinity, etc. aggravates the disease. The fungus has also been found sometimes to attack leaves, petioles, and nuts.

Management:


Cultural Method:
  • Destroy the chiseled materials by burning. Avoid any mechanical injury to the trunk.
  • Along with 50kg FYM, apply 5kg neem cake containing the antagonistic fungi, Trichoderma@ 200g/palm/year culture to the basin during September.
  • Provide adequate irrigation during summer and drainage during rainy season along with recommended fertilizer.
Chemical Method:
  • Chisel out completely the affected tissues and paint the wound with tridemorph 5% or Bordeaux paste. Apply coal tar after 1-2 days on the treated portion. Burn off chiseled pieces.

Root feed with tridemorph  (5% Calixin) 5ml in 100 ml water, thrice a year during April-May, September-October, and January-February to prevent further spread of lesions.

 

Source-

Tamil Nadu Agriculture University.

MLA

“TNAU Agritech Portal :: Crop Protection.”TNAU AGRITECH PORTAL. N.p., n.d. Web. 07 May. 2017 <http://agritech.tnau.ac.in/crop_protection/coconut_diseases_1.html>.

APA

TNAU Agritech Portal :: Crop Protection. (n.d.). Retrieved from http://agritech.tnau.ac.in/crop_protection/coconut_diseases_1.html

Chicago

TNAU Agritech Portal :: Crop Protection, http://agritech.tnau.ac.in/crop_protection/coconut_diseases_1.html (accessed May 07, 2017).

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