Rodent Damage Control Research in the Philippines

Rodent Damage Control Research in the Philippines


NWRC's Field Station at the National Crop Protection Center, 1968-1983


photo of rice paddies in PhilippinesSoutheast Asian countries have a long history of serious rat damage to rice, coconut, and other staple crops. In the 1950s, extensive crop losses in the Philippines during rat population irruptions resulted in international relief efforts to prevent starvation in rural areas. Several U. S.-sponsored research and operational efforts provided insights and limited relief. Dry season, village-wide baiting programs with 1080 or zinc phosphide became the mainstay of rodent control efforts. In June 1968, the Denver Wildlife Research Center (now the National Wildlife Research Center, NWRC), with support from the U. S. Agency for International Development (for a cooperative program that lasted 25 years), established its first overseas field station., the Rodent Research Center (RRC), on the campus of the University of the Philippines College of Agriculture.

NWRC Staff Assigned to the Philippines

F. Nelson Swink 1968-1972
G. Keith LaVoie 1968-1970
Gerry A. Atwell 1969-1971
Richard R. West 1970-1973
Michael W. Fall 1971-1975
Russell F. Reidinger, Jr. 1974-1978
Lynwood A. Fiedler 1978-1983
Melvin G. Garrison 1980-1982

The Philippine staff of the RRC grew from 2 at its establishment in 1968 to more than 30 by the mid-1970s, to more than 100 after the development of its successor organization, the National Crop Protection Center and 7 Regional Crop Protection Centers in 1976.


The mission of the new institution was to develop more effective methods of rodent control in rice production, to identify safer rodenticides for agricultural use, and to assist the Philippine government in training wildlife damage specialists. The challenge was to coordinate a program across an agricultural archipelago (more than 7,000 islands spread across more than 1,000 photo of Rodent Research center, Philippinesmiles) with diverse culture and an established bureaucratic structure (more than 600 government employees involved in rodent control). In 1971, the research focus changed (tied to Green Revolution objectives) to determining what a small farmer with 1 or 2 hectares could do to protect his rice crop using locally available materials, regardless of activities on neighboring farms. In 1975, following success in achieving the initial objectives, the Center began to develop similar approaches to protect coconut, corn, and other crops from rodent damage and investigations of bird problems in Philippine agriculture.

Some Research Accomplishments

Rodent Identification: Several hundred rodent specimens were collected from agricultural areas on major islands among the country's 7,100 islands. Morphometric work, museum comparisons, and chromosome studies were conducted to identify species. Representative specimens were deposited in the Smithsonian Institution, including the major pest species: Rattus rattus mindanensis (now Rattus tanezumi), Rattus argentiventer, and Rattus exulans.

Damage Assessment: NWRC statisticians devised an index to assess rat damage to rice based on cut stems observed at harvest and a national sampling scheme was conducted in wet season and dry season crops over a 3-year period. About 90% of rice fields had measurable damage; about 7% had damage over 10%. Overall damage averaged 3.5% of cut stems at harvest.

Rodent Ecology and Behavior: Rattus tanezumi and Rattus argentiventer bred throughout the year in ricefield areas, whenever food and cover were available; peak reproduction occurred during the wet season - from May to December. Beginning in the 1960s, farmers changed from growing 1 annual rice crop that matured in 8 months to 2 or 3 crops of Green Revolution varieties that matured in 16 weeks or less. The high yielding rice varieties, responsive to fertilization, irrigation and pest control, produced both ecological and human social changes that had important effects on rodent population and damage patterns.

Sustained Baiting with Anticoagulant Rodenticides in Rice and Corn: A highly effective technique, devised and tested extensively on small rice farms, involved a self-monitoring system of weekly adjustment of bait station numbers in relation to bait consumption by rats. Bait made from locally available anticoagulant rodenticide concentrates, such as warfarin, diphacinone, or racumin, could be prepared on farm with broken rice. Baiting started shortly after planting and continued until grain heads began to harden; rodenticide use was minimized by bait placement in relation to bait consumption. Damage by Rattus tanezumi and Rattus argentiventer, even in areas where crops could not previously be grown, could be held to less than 1%. These recommendations were incorporated in a Green Revolution rice production program that allowed farmers to avail of low cost rice production loans.

photo of rodent baiting in coconut treesCrown baiting to Control Rodent Damage to Coconut: Anticoagulant rodenticide baits prepared on farms in 100 g packs and placed monthly in the crowns of every 10th coconut tree proved highly effective in reducing rat damage maintaining it at low levels indefinitely. In test plots, yield increases averaged more than 2-fold over a 3-year period. Reductions in fallen maturing nuts, which had long been used to estimate rat damage, accounted for only about 5% of the overall yield increases, suggesting rats also affected flowers or setting of young fruits. The method required less than one-fourth the amount of bait needed for intensive ground baiting in coconut groves and has been applied worldwide.

Institutional Development

The Rodent Research Center (RRC) was originally administered by a Board of Directors composed of more than 20 U. S. and Philippine agency representatives. After 3 building cycles to expand facilities and construct faculty housing on the Los Baños campus, it ultimately became an administrative unit within the College of Agriculture at the University of the Philippines in Los Baños. In 1976, RRC was succeeded by a new institution, the National Crop Protection Center (NCPC), with initial funding arranged through a long-term, low interest loan from the United States. A new headquarters building, pens and support structures, two additional faculty houses, and a dormitory for trainees were constructed. Seven regional crop protection centers were also established to work with scientists at NCPC.


Staff members assisted the University of the Philippines in establishing an inter-disciplinary wildlife management program and a graduate program in vertebrate pest management that served students from the Philippines and a number of other countries. More than 30 graduate students were supported through the NWRCprogram. A 10-month certificate program for training of mid-career government pest control personnel in crop protection technology became a model for establishing mid-career training programs at the university. Research workshops and U. S.-supported commodity packages helped to establish rodent control research programs in government agencies Korea, Thailand, Indonesia, Malaysia, Laos, Cambodia, Vietnam, and Nepal. Rodent control training for 2,000 agricultural technicians, other workshops, multi-media packages, and training materials brought rodent control information directly to farm families.

Additional Information

For more information on work of NWRC's Philippine Field Station and its 25-year association with the U. S. Agency for International Development, search the NWRC catalog for published and unpublished progress reports and see:

FALL, M. W. 1977. Rodents in tropical rice. College of Agriculture, Technical Bulletin No. 36, University of the Philippines at Los Baños, College, Laguna, Philippines.

FALL, M. W. AND J. P. SUMANGIL. l980. National rat control program in the Philippines. Pages 9 15 in Small mammals: problems and control. BIOTROP Special Publication No. 12 (Bogor, Indonesia).

FIEDLER, L. A., M. W. FALL, AND R. F. REIDINGER, JR. 1982. Development and evaluation of methods to reduce rat damage to coconut in the Philippines. Proceedings of the Vertebrate Pest Conference 10:73 79.

W. H. Ressig, E. A. Heinrichs, J. A. Litsinger, K. Moody, L. A. Fiedler, T. W. Mew, and A. T. Barron. 1986. Illustrated guide to integrated pest management in rice in tropical Asia. International Rice Research Institute, Los Baños, Laguna, Philippines.

FALL, M. W. 1991. Controlling rice losses to rodents in rural communities. 1991. Pages 7-16 in G. R. Quick, editor. Report of the International Rice Research Institute Expert Panel Meeting on Rice Rodent Control, International Rice Research Institute, Los Baños, Laguna, Philippines.

FIEDLER, L. A., M. W. FALL, R. L. BRUGGERS AND J. W. DE GRAZIO. 1991. Rodent and bird problems in agriculture and their management in developing countries. Pages 65-73 in E. D. Magallona, editor. Proceedings of the 11th Int. Congr. Plant Protection Vol. 1, Manila, Philippines.

Philippine National Crop Protection Center website:



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