Major Coconut diseases are:-
1.Tanjore Wilt/ Basal Stem End Rot/ Ganoderma Wilt: Ganoderma lucidem and Ganoderma applanatum
Symptom:
- Initial symptoms of Tanjore wilt (Ganoderma wilt) start with 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 upwards.
- 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 discoloured, disintegrated and emitting a bad smell.
- Bracket formation at the base of the trunk during the rainy season. Ultimately the palm dies off.
Management:
Cultural method
- Remove and destroy all affected palms.
- Green manure crops must be raised and ploughed in situ before flowering.
Biological method
- Apply Pseudomonas fluorescens (Pf-1) @ 200g/palm + Trichoderma viride @ 200g/palm/year.
- Apply 200g photobacteria 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
- The bleeding patches in the stem may be chiselled and protected with tridemorph (5% calxin) and subsequently with hot coal tar.
- Aureofungin-sol 2 g +1 g Copper Sulphate in 100ml water applied as root feeding. (The active absorbing root of pencil thickness must be selected and a slanting cut is made. Keep the solution in a polythene bag or bottle and the cut end of the root should be dipped in the solution).
- Root feeding with Tridemorph 2ml or Hexaconazole 1 ml with 100 ml of water (3 times at 3 months interval).
- Forty litres of 1% Bordeaux mixture should be applied as a soil drench around the trunk in a radius of 1.5m.
2.Coconut Bud Rot: Phytophthora palmivora
Symptom:
- Palms of all age susceptible, but normally young palms are more susceptible, particularly during monsoon.
- In seedlings, the earlier symptom is the yellowing of one or two younger leaves. Basal tissues of the leaf rot quickly and can be easily pulled out 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 down and the palm dies
- 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 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.
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 drenching the crown with Copper oxychloride 0.25%. Apply Bordeaux paste and protect it from rain till normal shoot emerges. (Dissolve 100 gm of copper sulphate 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 or 1 % Bordeaux mixture on the crown of the neighbouring palms as a prophylactic measure before the onset of monsoon. 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 manage red palm weevil infestation of affected palms.
- Spray with Copper oxychloride 0.25% after the onset of Monsoon.
3.Coconut Leaf Blight: Lasiodiplodia theobromae
Symptom:
- Leaf blight causes serious damage in seedlings, leaves and nuts of adult palms.
- Generally, the adult leaves in the outer whorls are affected.
- The affected leaflets start drying from the tip downwards and exhibit a charred or burnt appearance.
- Dark grey 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, shrunken, deformed and dropped prematurely and resulting in nut yield loss up to 10 to 25%.
- The incidence was noticed throughout the year and 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.
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 3 months interval).
4.Coconut 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 inner portions of affected trunks are hollow due to the decay of inner 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. But fall is also noticed.
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 5ml in 100 ml water, thrice a year during April-May, September-October and January-February to prevent further spread of lesions.
5.Coconut Root Wilt or Kerela 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 is 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 front develops a cup like an appearance. Abnormal shedding of buttons and immature nuts are also noticed.
Management:
Cultural Method:
- Cut and remove disease advanced, uneconomical palms yielding less than 10 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.
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.
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
- To manage 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 place around the base of the spindle.
6.Leaf Rot disease: Colletotrichum gloeosporioides, Exserohilum rostratum and Fusarium spp.
Symptom:
- 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 wind, giving a “fan” shape to the leaves.
- Sometimes, the symptom becomes very acute and the spear fails to unfurl.
Management:
Physical method
- Remove the rotten portions from the spear and the two adjacent leaves.
Chemical method
- Pour fungicide solution of Hexaconazole – 2ml or Mancozeb – 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 the 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.
Source-
- TamilNadu Agritech Portal
