Pestalotiopsis leaf disease, a new threat to rubber trees across the whole world, has now become a grave threat to the sustainability of the rubber plantation industry in Sri Lanka, Colombo Rubber Traders’ Association (CRTA) said yesterday in a media statement.

“Although this fungus was reported in early 20th century in the country, it was considered a mild pathogen until recently. It reached epidemic proportions during the monsoon period of 2019 affecting plantations in Kalutara, Ratnapura and Galle districts. Unfortunately, almost all clones are susceptible for this disease.

“High humidity favours the spread of the disease causing defoliation and a considerable yield loss and ultimately the death of the tree, they said Unlike in the case of Corynespora leaf disease affecting young leaves at the apple green stage soon after wintering period, this new disease affects even mature leaves in the last quarter of the year.

“Other countries affected by this leaf disease are Malaysia, India, Thailand, Cameroon and Papua New Guinea, CRTA said. In all these countries there had been an alarming yield loss.

“As no resistant clone to this disease is identified to date, the only hope in managing the disease is by the use of fungicides. However, haphazard application of fungicides is of no use to control the disease. Chemical spraying should be done at the early stages of development of the disease. Unfortunately, proper protocol for fungicides spraying has not been developed yet.

“The disease may reach epidemic proportions in the coming monsoon period of this year starting from mid-April and hence all stakeholders are requested to be vigilant about this threat to the rubber plantation and they are strongly advised to get the assistance of scientists of the RRI in any emergency.”