Leaf wilt disease threatens coconut plantations in the South

An estimated 100,000 coconut trees in southern Sri Lanka have been affected by a disease that is being termed “Weligama coconut leaf wilt disease”. The disease which was diagnosed in 2006 is transmitted mainly by insect vectors that absorb juice from an infected tree and then move on to another, thereby infecting many trees in the process.

The Institute of Bio-chemistry, Molecular Biology and Biotechnology University of Colombo (IBMBB) in collaboration with the Coconut Research Institute (CRI) and the National Research Council and the Sri Lankan Council for Agricultural Research Policy are conducting tests on how best to avoid the further spread of the disease.

A workshop was held in this regard on May 15 with Professor Matthew Dickinson of the University of Nottingham, who has been conducting experiments on a similar disease affecting palms in Ghana. Tests done so far have shown that the causing element is an organism known as phytoplasma. The disease has so far been contracted by trees in the Galle, Matara, Akuressa, Dikwella, Walasmulla and Kirinda areas. Dickinson, speaking at a recent press briefing, said that symptoms of the disease varied around the world.

Africa has been plagued with a severe version that kills the trees whereas the Indian sub continent has a milder strain which stunts growth but does not kill. In Sri Lanka various symptoms including misaligning of leaves, yellowing and eventually withering of leaves plus root rotting have been identified. Although no trees have died yet, the disease cripples the growth of the tree and also leaves it more vulnerable to other diseases. The speed at which the phytoplasma disease grows is said to be slow as the insect vectors which are the main carriers are not able to fly fast from tree to tree.

Dr. Priyanthi Fernando, Head of Crop Protection Division CRI, said, “At this stage it is difficult to tell what economic loss it will cause but if it spreads to the whole country it will have a high economic loss”.

To prevent this from happening, the authorities have demarcated the limits of the affected trees and established a three km safety zone within which no trees are affected. Fernando said that no palm trees are allowed out of the zone, and that any other plant life being taken out will have to be completely eliminated of disease using pesticides, etc. If it moves into the Coconut triangle it will cause a lot of damage”, said Deputy Director of Research CRI, Everard Jayamanne.