Coconut diseases spread in Southern province

By Dr. Chitranganie Jayasekara

The leaf rot-disease of coconut that was prevalent in the Matara district is now spreading to nearby areas of the Galle district. The 'leaf yellowing syndrome' is spreading at an alarming rate in the coconut plantations of the same area.

The leaf rot-disease was first reported in 2000 from the Weligama area. The disease had spread to Weligama, Matara, Kamburupitiya, Dikwella, Hakmana, Akuressa and Habaraduwa Divisional Secretariat regions. The Coconut Research Institute has found that the disease is caused by a complex of pathogenic fungi (mould) attacking the unopened bud leaves of the coconut crown.

Palms of all ages are susceptible to the disease. Due to the infection, the rotting of bud leaves occur and when these leaves unfold, dried and backened rotten portions of the leaves either fall off or stick together and remain on the crown. Such leaves appear as 'fishing rods'. When the disease progresses the crown diminishes, trunk tapers and flower, nut production reduces followed by complete cessation. Then, the crown is blown off. On an untreated palm, the full course of the disease takes about 3-5 years. It has been observed that the disease severity increases during the rainy season and reduces in the dry season.

As the disease was reported to the Coconut Research Institute, a full scale research program was initiated to determine the causal agent of the disease, effective fungicides for management of the disease and the factors predisposing the palms to the disease.

As a result few fungicides were recommended. It was revealed that drenching the fungicide solution to thoroughly wet the bud region, at 3-4 months intervals continuously reduces the disease. The program conducted to treat the palms in the Matara district reduced the disease incidence at the initial stages. Difficulties in finding climbers to treat large number of trees and cost of treatment are obstacles to continue the program causing resurgence of the disease.

Steps have been taken to identify the measures to control the disease conditions in the South. A two-pronged strategy prevent the spread to the unaffected areas and to reduce the spread in the affected areas and the crop loss will be implemented in this regard.

To check the spread the Coconut Cultivation Board has already closed the coconut nursery at Weligama and stopped collection of seed nuts from the affected areas. Since nut production is reduced by the leaf rot-disease, it is planned to conduct a program to supply fungicides and treat leaf rot-affected palms. The coconut growers will be encouraged to rehabilitate their palms by applying recommended dose of fertiliser, especially organic manure as the disease reduces the vigour of palms.

A joint programme by Coconut Research Institute and Coconut Cultivation Board will be commenced shortly to determine the affected areas and assess the number of diseased palms.

The writer is the Director, of the Coconut Research Institute