Ushering in modern agroecological farming approaches that complement indigenous systems of sustainable natural resource management and environmental quality is part of our mission at the Center for Development Programs in the Cordillera (CDPC). Among our efforts in this mission is our continuing research on available biopesticides in the Cordillera region. One of these is our study on the Paswik plant as a biopesticide for rice production in the rice terraces. An endemic tree or shrub that can be found all over the Cordillera region, the paswik has been observed by farmers to kill snails and the earthworm locally known as pancit-pancitan in rice fields. Initial field trials by the Montanosa Research and Development Center using extracts from the plant’s leaves showed similar observations that the plant is toxic to earthworms and snails.
The Pancit-Pancitan
The pancit-pancitan are thread-like earthworms which are a recent occurrence in rice paddies in the Cordillera highlands. They are surface dwellers which farmers consider a pest as they reproduce very quickly, and with their large population they can cover and damage newly replanted rice seedlings. They are observed not to burrow and hence not considered by farmers to cause seepage or destruction to rice paddies, particularly terraced paddies. The worms disappear after the planting season or when the paddy soil hardens. Identification of the earthworms has yet to be confirmed, although the pancit-pacitan bears resemblance to the Sparganophilus cf. tamesis Benham, 1892 (Family: Sparganophilidae) as described by the International Rice Research Institute.[1]
To discourage the widespread use of chemicals to control the pancit-pancitan, CDPC continues its research project to explore the biopesticide potential of the paswik plant.
Laboratory Research
Prior to the COVID-19 pandemic in 2019, CDPC pitched the paswik plant as a research topic to senior high school students of the Philippine Science High School (PSHS) – Cordillera campus. The students conducted a crude phytochemical analysis of the plant and the results showed it contains the toxic bioactive element saponin, a known molluscicide. A bioassay was conducted with fresh worms. The paswik extract from dried leaves was observed to be toxic to the pancit-pancitan worm in three concentrations of 25ml extract/10ml water, 12.5 ml extract/10ml water and 6.25 ml extract/10 ml water. It took an hour for the worms to be paralyzed and two hours to die. The students inferred that it could have been the presence of saponin that caused the toxicity. The research initiative of the students was cut short when COVID-19 struck and a lockdown was imposed.
In 2023, CDPC resumed laboratory testing on the paswik. Fresh specimens of the plant were sent for another phytochemical screening to the Department of Science and Technology (DOST)-Cordillera Administrative Region which in turn brought the specimens to the Standards and Testing Division of the DOST–Industrial Technology Development Institute. The result on presence of saponin corroborated the findings of the PSHS students. The DOST phytochemical tests showed presence of sterols, triterpenes, alkaloids, glycosides and tannins in addition to the saponins.
Phytochemicals present in paswik
| saponins | the main elements causing toxicity of saponin-rich plant extracts. Worms and snails are the most sensitive species for all saponins[1] |
| sterols | precursors of plant hormones, brassinosteroids, regulating plant growth and development[2] |
| triterpenes | Triterpene glycosides have important ecological and agronomic functions, contributing to pest and pathogen resistance and to food quality in crop plants[3]
|
| alkaloids | naturally occurring toxic amines produced by plants mainly as a defense mechanism to protect themselves against herbivores[4] |
| glycosides | represent a large group of secondary metabolic products derived from plants, demonstrating several known functions, including growth regulation, allelopathy, and defense mechanism against damage induced by herbivores[5]
|
| tannins | such as accumulated tannins protect the vulnerable parts of the plants from microbial attack by inactivating viruses and invasive extracellular enzymes of microbes by direct tanning action[6] |
A bioassay (Brine Shrimp Lethality Test) will be conducted by professors of the Benguet State University to examine the efficacy of the chemicals present in the plant. An insecticidal bioassay will further be undertaken to find out the relationship between the amount of plant sample and the magnitude of response of the worms.
CDPC will continue to study the toxicity of paswik extracts considering that earthworms and snails are highly vulnerable to saponin-rich plants such as the paswik.
Community engagements
Gathering of the paswik plant
While laboratory tests on the paswik are being undertaken, field trials will also continue as a social process for Cordillera farmers to study the various forms of application (plain dried and pounded leaves, leaves extract, others), dosage/amount, timing of application to control the reproduction of the earthworms without killing or totally eliminating other field fauna. Field trials had been ongoing during the planting season in 2023 in Tadian and Sagada in Mountain Province and in the CDPC Lacnog farm in Tabuk, Kalinga.
In the community of Ankileng in Sagada where the plant grows, CDPC staff together with members of the Ankileng peoples’ organizations started field trial of the paswik as botanical pesticide. Paswik leaves were harvested and boiled, after which their juice was extracted and used as a form of application. Three liters of water are required for every kilo of paswik leaves and boiled for thirty minutes before the juice is extracted. The CDPC and community members used twelve kilos of paswik leaves and generated a total of 16 liters of paswik juice. The farmers applied the juice on a 300 square-meter farm land; observations are still ongoing on the paswik extract’s effect on the pancit-pancitan
Paswik: Features
To identify the plant’s taxonomy, we requested the assistance of the Bureau of Plant Industry and the Saint Louis University but they were not able to provide information. We were referred to the office of the City Environment and Natural Resources Office – Baguio City, which in turn referred us to the Watershed and Water Resources, Research and Development Extension Center of the Ecosystems Research and Development Bureau of the Department of Environment and Natural Resources (DENR). The office speedily identified paswik as Mamalis – Pittosporum pentandrum (Blanco) Merr belonging to the family Pittosporaceae.[8]
Reproduction of the plant in the highland Cordillera has yet to be observed. While we have observed profuse seeds below the canopy of some paswik plants, we have not seen seedlings growing. Some plants are described by the Useful Tropical Plant to bear flowers with male and female parts. In this case, the seeds can grow even in isolation. Some species bear flowers with only one sex. In this case, fertilization becomes a function of insects and birds that cross pollinate the flowers from male bearing plant to female bearing plant. It makes sense to protect the paswik plant that bears flower with both male and female parts. Similarly, birds and insects need to be protected to perform their role in nature’s propagation.
Identifying various species of the paswik thriving in the Cordillera and understanding their reproduction will form part of the farmers’ social practice, and CDPC will be part of this effort. This will include studying the plant’s reproduction to ensure sustainability and to prevent any ecological adverse impacts especially on other good organisms.
Known Uses of Paswik Plant
Several authors and studies have identified various benefits of the paswik plant. Vargas-Zamora cited several authors that established paswik as potential source of energy as it contains elements similar to the components of gasoline. Other citations noted its anti-bacterial property. Given the intricate natural reproduction of paswik, Vargas-Zamora concluded that the plant can be propagated through tissue culture in laboratory settings.[9]
(authors: PIC and Sustainable Agriculture staff)
[1] Joshi, RC, Aspe NM, Cope AE. ‘Field Guide: Earthworms in Heirloom Rice Fields of the Philippine Cordillera and Their Integrated Management’. International Rice Research Institute. 2020.http://books.irri.org/Field-Guide-Earthworms-in-Heirloom-Rice-Fields-of-the-Philippine-Cordillera.pdf
[2] Jiang, Xiaogang et.al. ‘What is the aquatic toxicity of saponin-rich plant extracts used as biopesticides?’ 2018. https://www.sciencedirect.com/science/article/abs/pii/S0269749117318985.
[3] Valitova, J. N., Sulkarnayeva, A. G., & Minibayeva, F. V. ’Plant sterols: Diversity, biosynthesis, and physiological functions. Biochemistry’. 2016 (Moscow), 81(8), 819–834. doi:10.1134/s0006297916080046
[4] Thimmappa, Ramesha et. al. ‘Triterpene Biosynthesis in Plants’. Annual Review of Plant biology. 2014. https://www.annualreviews.org/doi/10.1146/annurev-arplant-050312-120229.
[5] Mohan, V.R. ‘Encyclopedia of Food and Health Antinutritional Factors in Legume Seeds: Characteristics and Determination’.2016. doi:10.1016/b978-0-12-384947-2.00036-2
[6] Sotto-Blanco, Benito. ‘Chapter 12 – Herbal glycosides in healthcare’. 2022. https://www.sciencedirect.com/science/article/pii/B9780323858526000214
[7] Lekha, P. K., & Lonsane, B. K. (1997). ‘Production and Application of Tannin Acyl Hydrolase: State of the Art. Advances in Applied Microbiology’. 1997. doi:10.1016/s0065-2164(08)70463-5
[8] Global Biodiversity Information Facility (GBIF). ‘Pittosporum pentandrum (Blanco) Merr. n.d. https://www.gbif.org/species/2986294
[9] Vargas-Zamora, Cecilia.’In Vitro Culture of Pttosporum Pentandrum (Bl.)Merr’. 1992. https://www.journals.upd.edu.ph/index.php/sciencediliman/article/download/329/355
CDPC acknowledges the following individuals for their expertise and assistance in the research of the Paswik plant:
Mary Ann Awisan
DOST-Cordillera Administrative Region
Regional Standards and Testing Laboratory
BSU Compound, Km6 La Trinidad, Benguet
Helen A Maddumba, Center Head
Department of Environment and Natural Resources
Ecosystem Research and Development Bureau
Watershed and Water Resources Research, Development and Extension Center
Loakan Road, Baguio City
Ms. Maritess Alimurung
Bureau of Plant Industry (BPI), Baguio City
Alma Cruz
ORGANIC CHEMISTRY SECTION, CHEMISTRY LABORATORY
Standards and Testing Division Industrial Technology Development Institute
Department of Science and Technology
Bicutan, Taguig City 1631 Philippines
Arnobit, Maquier Hans
Cabfit, Melecio
Gonzales, Paolo
Students from the Philippine Science High School-Cordillera Administrative Region Campus
Science, Technology, Engineering and Mathematics Research 2