Published on: October 25, 2022

‘Invisible’ disease

‘Invisible’ disease Why in news?حوار-11-سبتمبر/ The threat to India’s pride, sandalwood, is increasing as the deadly sandalwood spike disease (SSD), which hitherto was confined mainly to forest areas, has started spreading to private fields where the cultivation of this aromatic tree has been taken up on a commercial basis.


  • A study has now shown that this ‘invisible’ disease, which is wiping out the sandalwood trees, can transmit through seeds of infected trees through the presence of disease-causing bacteria called Phytoplasma.
  • This phenomenon has been blamed for the spread of the SSD to commercial farms
  • A several sandalwood plants grown by sourcing seeds from nurseries had tested positive for SSD.
  • The study has recommended accreditation of commercial production of sandalwood seedlings through testing to ensure that the plants are free from SSD.
  • It has also called for a paradigm shift in policies handling sandalwood seedlings.
  • The phenomenon of SSD transmitting through seeds has posed a challenge to commercial cultivation as the farmer will not be able to know when his sapling would start showing symptoms of the disease. Some have shown symptoms four years after planting.

What is Phytoplasma ?

  • Phytoplasmas are phloem-limited pleomorphic bacteria lacking the cell wall, mainly transmitted through leafhoppers but also by plant propagation materials and seeds. Phytoplasma diseases of vegetable crops are characterized by symptoms such as little leaves, phyllody, flower virescence, big buds, and witches’ brooms.
  • They are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission.

Sandal wood Cultivation

  • It is a small tropical tree, and the traditional source of sandalwood oil. It is native to southern India and Southeast Asia.
  • High value of the species has caused over-exploitation, to the point where the wild population is vulnerable to extinction.
  • Indian sandalwood still commands high prices for its essential oil owing to its high alpha santalol content, but due to lack of sizable trees it is no longer used for fine woodworking as before.
  • The plant is long-lived, but harvest is only viable after many years.
  • Distribution : Indigenous to the tropical belt of the peninsular India, eastern Indonesia and northern Australia. It is now cultivated in India, Sri Lanka, Indonesia, Malaysia, the Philippines and Northern Australia.
  • Habitat: It normally grows in sandy or well drained stony red soils, but a wide range of soil types are inhabited.
  • IUCN status : Vulnerable
  • Karnataka had one of the richest sandalwood reserves largely in forests of Mysuru, Chamarajanagar and Mandya districts.