Community action using ecologically based management reduces rodent damage

A 3.5-year study measuring the impact of community action using ecologically based management of the rice field rat, Rattus argentiventer, was conducted at a village scale in lowland irrigated rice monocultures in West Java, Indonesia, and in the Red River Delta in Vietnam. In this farmer participatory study, we examined the economic benefits at the village level of integrated rat management in terms of yields.

In each country, four villages (100–120 hectares) were selected. Ecologically based rodent management was conducted in two villages (treatments); traditional rat control was conducted in two other  villages (controls).

Farmers adopted the following integrated management:

1. Synchrony of planting within 2 weeks;
2. One trap-barrier system (TBS) for every 10 hectares, each 25 x 25 meters with a crop planted inside 3 weeks earlier;
3. A 2-week rat campaign 1 week before transplanting, or within 2 weeks of crop initiation around source habitats (village gardens and irrigation channels);
4. Reduction of secondary irrigation banks to less than 30 centimeters to prevent nesting by rats; and
5. Improved field sanitation and general hygiene around villages and gardens.

In Indonesia, there was a 50% reduction in rodenticide use. Also, for every 1% increase in tiller damage by rats, rice yield decreased by 58 kilograms per hectare. Wet-season crops benefited more from the TBS than did dry-season crops at the same rat abundance index. In one wet season, more than 14,000 rats were caught during a 2.5-week community campaign conducted during land preparation and after transplanting of the rice crop. The benefit-to-cost ratio for all seasons and years averaged 25:1 but varied considerably from year to year, from a low of –2:1 to a high of 63:1.

In Vietnam, there was a 75% reduction in the use of rodenticides and plastic fences on treated sites compared with control sites.  This translated into an 18:1 benefit-cost ratio on treated sites compared to 3:1 on untreated sites, mainly through the significant reduction in money required to buy rodenticides and plastic fences.

Communities conducting integrated rodent management increased rice yields more when rats were common in both dry- and wet-season crops. The economic benefit of integrated rodent management was equal to or better than that achieved by conventional management based on synthetic rodenticides, and without the associated environmental risks to nontarget species.

Further reading:

Singleton GR, Sudarmaji, Jacob J, Krebs CJ. 2005.  Integrated management to reduce rodent damage to lowland rice crops in Indonesia. Agric. Ecosyst. Environ. 107: 75-82.

Brown PR, Tuan NP, Singleton GR, Ha PTT, Hao PT, Tan TQ, Tuat NV, Jacobs J, Müller WJ. 2006. Ecologically based management of rodents in the real world: application to a mixed agro-ecosystem in Vietnam. Ecol. Appl. (in press)

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