Sri Lankan researchers identify fungus causing the blight – By Arundathie Abeysinghe
A team of researchers at Sri Lanka Rubber Research Institute (RRISL) have identified the fungus causing the blight (Colletotrichum tropicale) for the first time in the world. The condition which affects rubber cultivation is a global phenomenon and retards the main function of the leaf producing food for the plant by photosynthesis, thus reducing output of latex. Rubber (Hevea brasiliensis) is one of the main cash crops in Sri Lanka and over 13,7000 hectares of rubber cultivation is a main source of foreign exchange earnings. Kegalle, Ratnapura, Monaragala, Kalutara, Galle and Matara districts are the main rubber producing areas in the country. Rubber cultivation in all these areas has been vulnerable to the blight.
Researchers conducted laboratory tests by causing the infection artificially to healthy leaves with the newly discovered fungi. The research team included Dr. Sarojini Fernando of the Plant Diseases and Microbiology Department of RRISL, Prof. Anupama Daranagama of Kelaniya University and Nadeeshani Abeyratne.
RRISL is the world’s first Rubber Research Institute dedicated to research on rubber and was established in 1909.
According to research conducted from 1905, “causes of this blight have been identified to have changed during different periods. In 1905, the fungi that caused this blight had been identified as Colletotrichum Gloeosporioides and in 1997 as Colletortrichumacutatum. Subsequently, it had been identified as Colletotrichum simmondsi, Colletotrichum citri, Colletotrichum nymphaeae, Colletrotrichum laticiphilum and Colletotrichum siamense. Researchers of RRISL who conducted the research have identified Colletotrichum tropicale as the main fungus causing the blight. They are optimistic that their discovery would be instrumental in future research to bring under control the Colletotrichum blight.
Scholars are of the view that “Colletotrichum tropicale was identified in 2010 as an endophyte in Theobroma cacao leaves in Panama. Currently, it is widely reported among Colletotrichum species causing anthracnose in several cultivated as well as native plants worldwide, in both tropical and temperate regions and have the capacity to grow within a temperature range of 10-35°C.”
“Colletotrichum tropicale is a fungal pathogen which causes a blight in rubber plants, affecting their ability to produce latex, the primary product of rubber trees. The fungus can significantly impact the leaves, reducing their photosynthetic efficiency and leading to a decline in rubber production. This blight is also known as anthracnose, a serious threat to the rubber industry worldwide. Severity of the disease is more in high rainfall areas. During the past three to four years, this situation seriously retarded the health and growth of rubber plants. It is a threat to rubber cultivations in the traditional rubber growing wet regions. To-date, there is no effective method developed by any country to control the disease and the disease prevails even under good agricultural practices. Current phenomenon is similar to the ‘coffee rust’ blight which wiped out Sri Lanka’s coffee plantations in the late 1800s. Hence, this needs to be immediately addressed as output has declined by nearly a third already in some rubber plantations and the industry is fast becoming unviable.”
According to a recent study carried out by researchers of several universities in Sri Lanka, it was revealed that “the rubber yields are significantly less in wet zone after the incidence of the new leaf disease. The yield drop in the wet zone estates after the incidence of the leaf disease is estimated to be around 40%. This yield drop could further escalate in the future, if the new leaf disease continues to infect the rubber plantations.”
