New leaf blight disease in rubber plantations

Rubber growers should pay proper attention to the spread of a fungal disease associated with rubber cultivation which reduces the production of rubber latex by about 30%, Plantations State Minister Kanaka Herath stated.

Rubber Research Institute Deputy Director Dr. Priyani Seneviratne also said that rubber growers should be vigilant to prevent the spread of leaf blight fungal diseases due to the prevailing rainy weather.

This fungal disease was found in rubber plantations in the island in both 2019 and 2020. This year too, the disease is associated with rubber growing districts such as Kegalle, Kalutara and Ratnapura has been identified.

This fungal disease, also known as Pestalotiopsis, is also known as leaf blight due to the shedding of leaves in rubber plantations. Although the average annual leaf fall in rubber plantations occurs from February to April, the leaves fall even after the normal leaf fall period in rubber plantations where the fungal disease has spread, she said.

She added said that if any rubber plantation sheds leaves in or after May, it may be due to this new leaf fall disease. However, due to the current outbreak of COVID-19 disease and severe travel restrictions in the country, it is practically difficult to inspect these crops or to control the disease in any way.

“It has been noticed that the disease is spreading rapidly due to the prevailing monsoon and rainy weather. It is essential to know the extent of the affected areas to treat the disease and to prevent the further spread of the disease. We urge all rubber collectors to be vigilant about leaf fall during or after May. If a leaf fall has occurred on your rubber plantation during the month of May, please notify the Rubber Development Officer of the area where the rubber land belongs or call the following telephone number,” she stated.

Accordingly, the Rubber Research Institute requests rubber growers to send details such as a picture of a fallen leaf, the address of the land, telephone number, the clone belonging to the plantation, and the extent of the land to 0772419482 via WhatsApp.

The Minister pointed out that for the first time in Sri Lanka, a pilot project for spraying chemicals using drone technology was launched to control this disease. In the pilot project carried out at Panawatta Estate, Yatiyantota, the chemical was sprayed on the leaves of the rubber leaves under the guidance of Rubber Research Institute officials.

Fungicide spraying has long been practiced from the root of the tree. Applying the chemical in this way is practically impossible. As a solution to this situation, drones are used to apply chemicals directly on rubber leaves. The pilot project has proven that the application of the substance is more efficient and effective. Therefore, this fungal disease was successfully controlled using drones.

State Minister Herath said that in addition to drone technology, modern pest control methods would be used to control the spread of this fungal disease in rubber plantations and prevent its further spread.

The fungal disease, which affects rubber plantations, was first reported in the Kalawana area in Ratnapura in 2019 and has now spread to districts such as Kegalle and Kalutara.  Dr. Seneviratne said that there is a high probability of the spread of this fungal disease in areas with high rainfall.

The disease was reported from Indonesia in 2017 and Malaysia in 2018. It is estimated that production could be reduced by as much as 30%. This fungal disease causes damage not only for rubber cultivation but also for many plants including avocado.

“If the leaf shedding is more than 50%, the rubber tapping should not be carried out. This could reduce rubber production by as much as 30%. It can be observed that if one fungus infects one rubber variant, it is often resistant to the other variants. However, it is observed that the disease spreads to all species,” Dr. Seneviratne added.