More than 700,000 rubber smallholders including tappers rely on rubber farming as their main source of income in Mindanao. According to the Observatory of Economic Complexity, in the past year, rubber accounted for US$131-million export to Malaysia, China, South Korea, Indonesia, and Vietnam.
However, there is an emerging threat in the rubber plantations in Mindanao - the Pestalotiopsis Leaf Fall Disease (PLFD), a fungal disease that causes falling of rubber leaves, reduced rubber production, and eventually the death of the tree. In Mindanao, thousands of smallholders and tappers’ livelihoods were affected as more than 37,000 rubber tree plantations were infected with the disease.
To reinvigorate the rubber plantations in Mindanao, the Philippine Rubber Research Institute (PRRI), in collaboration with the University of Southern Mindanao, implemented the project, “Etiology, detection, and management strategies against Pestalotiopsis disease of rubber.” The project was funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development of the Department of Science and Technology (DOST-PCAARRD). The project was led by PRRI Executive Director Cheryl L. Eusala.
The project developed a DNA-based detection method for early diagnosis; identified effective chemical and biological treatments; identified three potential endophytes or fungi that live in plants that suppress the growth of the pathogen that causes PFLD, and strengthened disease assessment and management.
From these accomplishments, a protocol for the management of PLFD was developed and recommended to different local government units (LGUs). This protocol was applied by 3,452 rubber farmers and 6,504 rubber plantation owners in 54 municipalities of the six rubber-producing regions in Mindanao (Regions 9, 10, 11, 12, 13, and BARMM).
“Halos bumaba ng kalahati ang ani namin ng latex dahil sa sakit na ito [PLFD]. Napakahirap sa panahon na iyon, syempre, apektado ang pang-araw-araw naming kabuhayan [para sa] aming pamilya. Ngunit [noong] dumating ang PRRI at USM, unti-unting nagbago ang takbo ng aming kabuhayan,” said Wilfredo Alpuerto Jr., one of the rubber farmers that benefited from the project. “Muli naming naibalik sa normal ang ani. Sa katunayan, malaki ang naging pagtaas ng produksyon ng latex kumpara sa dati o higit pa.”
Assessment and field trials
To assess the severity of infection of the disease, six rubber-producing regions in Mindanao were surveyed. PLFD was confirmed in the provinces of Agusan Del Sur, Basilan, Bukidnon, Davao De Oro, North Cotabato, Sultan Kudarat, and Zamboanga Sibugay. From the survey, seven new species of Pestalotiopsis infecting rubber trees in Mindanao were identified.
Moreover, cross-infection was also studied in various plant species including guava, banana, peanut, cassava, okra, pummelo, mango, cacao, lanzones, coconut, durian, mangosteen, coffee, pineapple, sweetpotato, string beans, corn, and jackfruit. It was seen that banana, cassava, mango, cacao, lanzones, durian, coffee, coconut, and peanut were potential host plants of the Pestalotiopsis pathogen. This could mean that other than rubber trees, the productivity of fruit-bearing trees mentioned may also be affected.
Following the survey, different management strategies involving chemical and biological treatments were evaluated. Fungicides such as Carbendazim, Carbendazim+Mancozeb, Pyraclostrobin, Benomyl, Thiophanate Methyl, Difenoconazole, Tebuconazole+Trifloxystrobin, Trifloxystrobin, and Azoxystrobin were found effective against the pathogen in vitro. Also, organic-based treatments such as Probio Organic Microbials; marigold, and wild sunflower plants showed potential effects in controlling the pathogen, in vitro.
Moving forward, the project recommends the continuous monitoring and surveillance of the PLFD in Mindanao. Validation of the status of the disease can be done through the use of a DNA-based detection kit and long-term management can be implemented through chemical and organic-based recommended treatments.
This project was an entry for Best Research Paper Category during the National Symposium on Agriculture, Aquatic and Natural Resources Research and Development (NSAARRD) held on October 14, 2025. Winners of the award will be conferred during the DOST-PCAARRD’s 2025 S&T Recognition and Awarding Ceremony in celebration of the Council’s 53rd Founding Anniversary.
NSAARRD, annually spearheaded by DOST-PCAARRD, recognizes outstanding R&D contributions in the agriculture, aquatic, and natural resources sector in the country.