MAJOR DISEASES AFFECTING COCONUT

DISEASES OF COCONUT

Root(wilt)

The symptoms of Root (wilt) disease are flaccidity, foliar yellowing and marginal necrosis. Research conducted at CPCRI Regional Station, Kayamkulam using electron microscope revealed the causal organism as Phytoplasma. The disease is spread through insects like lace bug and / or plant hopper.

The strategy comprises eradication of disease advanced palms, gap filling with elite disease tolerant seedlings, adoption of mixed farming/intercropping, organic recycling, providing summer irrigation, application of Mg SO4 along with fertilizer, control of leaf rot etc. CPCRI identified disease tolerant palms, among Chowghat Green Dwarf and local talls. Progenies of crosses involving CGD x WCT have been found to be promising.

Thanjavur wilt

In Tamil Nadu and Andhra Pradesh, Thanjavur wilt, otherwise called Ganoderma wilt is a serious problem. The symptoms are, presence of bleeding patches at the stem base, premature yellowing and drooping of outer whorl of leaves and gradual drying of spindle. The disease is caused by Ganoderma lucidum and G.applanatum. Fructification of the fungus can be seen on stumps of infected palms.

Integrated control measures include Phytosanitation, digging isolation trenches around diseased palms, root feeding of Calyxin, drenching the basin with 1% Bordeaux mixture and application of 5 kg neem cake. Raise banana in diseased garden, since banana is resistant to the pathogen.

Bud rot

Bud rot disease of coconut is characterised by withering, rotting of spindle leaf and foul smell. The disease is caused by a fungus. Phytophthora palmivora To control this disease remove decayed tissues and dress with 10% Bordeaux paste. The disease can be prevented by taking up pro-phylactic spraying of 1% Bordeaux mixture during the pre monsoon season.

Stem bleeding

The characteristic symptom of stem bleeding is the dark gummy exudation from the trunk. The causal organism is a fungus Thilaviopsis paradoxa. Control measures include chipping off the infected tissues, wound dressing and root feeding with 5% Calyxin and application of neem cake along with antagonistic fungi 1ike Trichoderma.

Mahali or fruit rot

Shedding of female flowers (buttons) and immature nuts are the symptoms of the disease. Water soaked lesions appear on the young fruits or buttons near the stalk which later develop and result in the decay of the under lying tissues. Caused by the fungus Phytophthora palmivora. The pathogen is more active during rainy season.

Pre-monsoon spraying the crown with 1% Bordeaux mixture (or any other copper fungicide such as Fytolan 0.5%) will control the disease. One or two spraying at intervals of 40 days is also advised. The shed nuts should be collected and burnt.

Crown chocking

This disease is commonly observed in Assam and West Bengal. It is characterised by emergence of shorter leaves with fascinated and crinkled leaves. The leaflets show severe tip necrosis and fail to unfurl. In many cases, it gives a choked appearance to the frond. Ultimately the affected palm dies.
Application of 50 g Borax at half-yearly intervals (Feb-Mar and Sept-Oct) along with recommended fertilizer in the basins will control the disease when it is in the early stage.

Tatipaka disease

First appeared in Tatipaka village of East Godavari district of Andhra Pradesh, following a cyclone in 1949. Palms in the age group of 25 to 60 years are more susceptible. Development of an abnormally large crown with dark green inner leaves and higher yield is the precursor of disease incidence. Subsequently the crown becomes smaller in size producing progressively shorter leaves. The stem begins to taper. The leaves give a fascinated appearance due to improper unfolding of leaflets. The affected tree produces smaller bunches with atrophied barren nuts. The causal agent is suspected to be Phytoplasma.

Leaf rot disease

A fungal disease seen in palms affected by root (wilt) disease. Caused by Colletotrichum gloeosporioides and Exerohilum rostratum. The first visible symptom is blackening and shrivelling up of the distal ends of the leaflets in the spindle. Later the affected portion breaks off in bits giving the infected leaves a fan-like appearance. If not controlled, subsequent spindles also get infected.