Pestalotiopsis leaf disease of rubber is a new thread to the rubber plantation industry of the whole world. Pestalotiopsis leaf fall, caused by the fungal pathogen pestalotiopsis, has now become a grave threat to the sustainability of the rubber plantation industry in Sri Lanka.
Though this fungus has been reported far back in early 20th century in the country, it was considered as a mild pathogen until recent times. 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 unlike Corynespora leaf disease, which was affecting the clone RRIC 103 at the start and later spread to few other clones grown in the country as well. High humidity favours the spread of the disease causing defoliation and a considerable yield loss and ultimately the death of the tree.
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.
Further RRI scientists have observed the higher tendency of Pestalotiopsis fungus to attack leaves already slightly affected by Glyosporium affected leaves.
Disease can be easily identified as it produces circular patches on affected leaves. Sometimes these lesions coalesce to form necrotic areas on leaf surfaces and causing the fall of leaves. This unusual leaf fall should not be mistaken as late wintering and neglected.
Presently the other countries affected by this leaf disease are Malaysia, India, Thailand, Cameroon and Papua New Guinea. In these countries, the disease is spreading at an alarming rate causing a considerable 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. 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. Trials are being carried out to use Drawns for spraying fungicides from a height 5 meters above the canopy of trees to introduce an economical and effective chemical control system.
The disease may reach epidemic proportions in 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. They will help plantations to correctly identify the Pestalotiopsis affected trees from trees defoliated due to wintering.
