Two pronged strategy to overcome :

Weligama coconut leaf Wilt Disease

Weligama Coconut Leaf Wilt Disease (WCLWD), now confirmed as a phytoplasma-borne disease was first detected in the Weligama area in late 2006. The first suspicion of this disease arose when the scientists of Coconut Research Institute (CRI) were informed by officers of noted the appearance of a new coconut disorder in the Kamburugamuwa area which is in the vicinity of Weligama with symptoms characteristic of the phytoplasma-borne disease known as ‘Kerala Wilt’ in India.

Kerala Wilt disease is highly prevalent in coconut palms of the Kerala state of India and has been in existence for over 80 years.

The most notable symptom observed in palms suffering from the disorder in Weligama was the yellowing of leaves, which often falsely diagnoses as deficiency of Magnesium in the palm over a larger extent in the southern province extending from Weligama on all directions.

CRI has reacted immediately from the very outset by sending the Plant Pathologist of the institute to Kerala to familiarize with the symptoms of Kerala Wilt disease and study the disease management plan currently being practised in India.

This immediately helped in training staff of CRI and CCB, Agriculture Research and Production Assistants and GNN in the three districts, Matara, Galle and Hambantota to infected palms.

Identification of this disease requires a well trained eye since the early symptoms of the disease are difficult to distinguish from normal palm and an infected palm. Subsequently an initial suvery was conducted jointly by CRI and CCB to determine the extent of the disease.

The survery revealed that the extent of spread was around 40,000 ha encompassing the entire Matara District and bordering sections of Galle and Hambantota Districts.

Accurate

CRI by developing an accurate molecular diagnostic procedure has confirmed the casual agent of the disorder as a phytoplasma and named it as Weligama Coconut Leaf Wilt Disease (WCLWD). The Kerala Wilt disease in India is also believed to be caused by a phytoplasma though there is no conclusive evidence to say whether or not the two phytoplasmas are the same.

It may be speculated that both are the same and the disease may have come to Sri Lanka either by wind transmission of phytoplasma carrying insect vectors of illegal importation of infected palms from India.

Another possibility is evolving of a phytoplasma from other phytoplasmas already existing in the vicinity, for instance phytoplasmas causing grassy shoot or white leaf diseases in sugarcane.

Coconut Lethal Yellowing Disease (CLYD) is the most commonly known phytoplasma disease in the world which is widespread in the Caribbean region and some countries of Africa and Central America. CLYD is the most dreadful coconut disease known to date which kills an infected palm within a pace of two years.

The most dreadful consequence of phytoplasma-borne diseases is that so far no treatment is available for making an infected palm free from the pathogen because it is an undifferentiated bacterium, which in habits the phloem tissues of plants.

Only option available to eradicate a phytoplasma disease is to remove and dispose all infected individual plants. Such an action is impracticable for a crop of the nature of coconut which is so extensively planted and intrinsically bound with socioeconomic basis of the Sri Lankan culture.

Thus the only alternative is to manage the disease by taking maximum precautions to prevent it from being spread to other areas of the country while gradually diverting the farmers in the infected area for opting for alternative crops/livestock to compensate their loss of income diminishing from the coconut crop loss in the long run due to WCLWD.

Having known the gravity of this fearsome disease CRI had immediately come out with interim recommendations through consultations of scientists within the institute and outside organizations; CARP, Department of Agriculture, universities and other research institutes.

At the very outset a steering committee comprising members from CRI, CCB, CDA, DOA, RRI and Wayamba University of Sri Lanka was appointed to discuss, improve and approve immediate strategic actions. A two-prong strategy,

1. Immediate management plan to prevent the spread of disease to other coconut growing areas of the country by demarcating and maintaining a 3-km border as a disease free buffer zone and barring cross border movement of all kinds of palms through law enforcement,

2. Conduct a multidisciplinary research program and a survey to obtain detailed information on disease diagnosis, symptomology, epidemiology, modes of transmission, diesese and palm health association, alternative crops and livestock, crop loss and socio economic factors related to the disease for making much more commanding recommendations for disease management was formulated for immediate implementation.

The progress of actions taken date are as follows:

1. An immediate suvery was conducted and the boundary of the infected area was identified. A 3-km buffer zone was demarcated for maintaining a disease free boundary.

The border of the diseased area identified was A 17 road from Galle to Akuressa, Akuressa to Kirinda-Puhulwella through Kamburupitiya, Kirinda-Puhulwella to Walasmulla, Walasmulla to Beliatta and Beliatta Tangalle. The 3km width buffer zone was demarcated with 1 km outside and 2 km inside from the bordering roads.

2. Action was taken in collaboration with DOA to declare the pest as a quarantine pest and legislation was made for barring cross boundary transport of any plant material with the risk of carrying the disease.

A gazette notification No. 1542/7 of 24th March 2008 was issued giving provisions to carry out actions to control and prevent spread of the diseases and authorized officers were appointed for the task.

3. In order to maintain the disease free buffer zone a ‘Project Team’ was established under CCB by appointing a leader and a group of three Coconut Development Officers stationed in the area.

So far an approximately 20,000 coconut plantations in the boundary zone have been inspected and action has been taken to remove 1,237 palms from a total of 1,715 diseased palms detected. A relief payment of around Rs. 1,500,000 was paid for affected growers.

4. In order to assist growers badly affected by WCLWD and the Leaf Rot disease in areas inside the border, financial assistance was provided for uprooting around 1,000 unproductive palms amounting to approximately Rs. 400,000. Three hundred bottles of 100 ml ‘Folicur’ (fungicide) were issued at half rate to around 200 coconut growers to treat leaf rot affected palms.

As an incentive to carry out proper agronomic practices to enhance palm vigour around, 11,000 kg of Urea, 15,000 kg of IRP and 23,000 kg of MOP fertilizer were issued for around 200 growers at a subsidized rate.

5. Public awareness: Several publications and media materials were produced and awareness programmes were conducted jointly by CRI and CCB to make the coconut growers and general public aware of the disease and recommended management strategies.

The grass roots level officers in Agrarian Services Department, Samurdhi GSS etc., were given a through training on the disease to carry the message to growers. Several publications and media materials were produced and awareness programs were conducted to make the coconut growers and general public aware of the disease and recommended management strategies.

6. A field laboratory was set up and a multidisciplinary research program was commenced to study all aspects of the disease; diagnosis, symptomology, epidemiology, modes of transmission, disease and palm health association, alternative crops and live stock, crop loss and socio - economic factors related to the disease.

Plant Pathologist and an Agricultural Economist of CRI were stationed at the CCB Regional Office, Matara with three contracted Research Assistants to carry out these studies.

Further scientists of CRI in other disciplines, Physiology, Agronomy, Soils and Plant Nutrition, Breeding and Biometry have also commenced studies in their disciplines and are frequently visiting the area to strengthen the research efforts.

7. A detail survey was commenced and data collection was completed with the assistance of Agriculture Research and Production Assistants of the Department of Agrarian Services to obtain detailed information on disease incidence, extent, damage, crop loss, environmental and socio - economic issues, alternative farming strategies and farmer perceptions.

Efforts

In general the progress of the consorted efforts of CRI, CCB and other organization to date have been successful in developing and implementing the strategies developed for managing the WCLWD despite the tremendous pressure from the community to implement the disease free buffer zone where all infected palms have to be uprooted.

The research program is also making a good progress because of the multidisciplinary approach and the involvement of scientists from many organizations.

WCLWD should be dealt as a national priority since it is the most serious threat for coconut the country has ever faced since coconut became a commercial crop. If this disease spreads islandwide there would not be any solution for salvaging the country’s coconut industry.

The crop loss would become enormous leading to serious consequences for all people in the country who depend on coconut for more than 20% of their caloric requirement. In addition the loss of employment and economic repercussions in bridging the foreign trade balance could not be underestimated.

Therefore, a consorted effort from all relevant sectors of the coconut industry and the cooperation of the public are very much anticipated to manage the disease in the infested area and prevent spread of the disease to other coconut growing areas in the country.

- Dr. Priyanthi Fernando Head Crop Protection Division, CRI and Everard Jayamanne, Deputy Director (Research), CRI.