Disease : Basal Stem Rot (Thanjavur wilt)

The basal stem rot disease of coconut is known as Thanjavur wilt in Tamil Nadu, Anaberoga in Karnataka and Ganoderma wilt in Andhra Pradesh. This disease usually attacks old or weak palms under stress condition.

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Symptoms

  • The outer leaves wither and droop and usually remain suspended for a long time around the stem.
  • The leaves break or buckle very close to their bases.
  • Successively produced leaves are smaller and the crown is reduced to a mere handful of short erect yellow leaves.
  • Apex of the trunk show a tapering pattern.
  • As the disease advance drooped leaves fall off one by one leaving only a few smaller leaves at the apex.
  • Roots as well as basal portion of the stem of the infected palm show varying degrees of discolouration and disintegration.
  • In most of the cases, the roots became brittle.
  • At the base of the stem a characteristic reddish brown discolouration develops from which brown viscous gummy substance oozes out.
  • These bleeding patches coalesce forming discoloured band around the trunk, which extended up to one meter from ground level.
  • The bark turns brittle and often gets pealed off in flakes leaving open cracks and crevices.
  • The internal tissues are discoloured and disintegrate emitting a bad smell.
  • The tissues on the bleeding spots are soft to touch.
  • The bole decays rapidly resulting in the formation of large cavities.
  • The fruiting body of the pathogen appear as brackets at the base of the trunk or occasionally just above the soil level.
  • Frequently the palms break off at the base and collapse.
  • Production of female flowers are arrested or poorly developed in severely affected palms.
  • Similarly necrosis of the male flowers are also noticed.

Procedure for Observation

Look for the incidence of the disease in the garden.

ETL

Mere presence

Epidemiology

The spread of the disease is more rapid in dry areas and slow in wet areas. The disease is prevalent in sandy or sandy loam soils in coastal areas where coconut is grown under rainfed conditions and in neglected gardens. Soil moisture stress during summer months, water stagnation during rainy season and presence of old infected stumps in the garden are found to favour the spread of the disease. This disease is mostly observed in old palms of 20-60 years.

Control Measures

  • Remove and destroy palms in the advanced stages of infection.
  • Burn the bole portion along with the roots Isolate diseased palms from healthy palms by digging isolation trenches of 1 m deep and 50cm wide.
  • Regular basin irrigation during summer months.
  • Avoid flood irrigation to prevent the possible spread of the pathogen through soil.
  • Apply50 kg farmyard manure and 5 kg neem cake per palm per year.
  • Appy Trichoderma harzianum fortified in neem cake/compost/organic matter Reduce the fertilizer application to one fourth of the recommended dose.
  • Soil drenching with 40 L of 1% Bordeaux mixture thrice a year.
  • Root feeding with 2 g aureofungin sol + 1g of copper sulphate in 100ml of water three times a year or alternatively with tridemorph (Calixin) 2 ml in 100ml water.