Integrated management to reduce rodent damage to lowland rice crops in Indonesia

Benefits and costs of an integrated management system coordinated at the community level to reduce rodent damage to lowland irrigated rice were measured in West Java, Indonesia, from 1999 to 2002. Four villages, each of 120 ha (70-80 families per village), were involved in the study, two being allocated as treatments and two as controls following a randomised block design. The emphasis was on integrated rodent management with the overall aim of reducing the need for toxic chemicals in rice fields. Rodent damage to rice can be measured at several stages of crop growth. In West Java, monocultures of lowland irrigated rice, cumulative damage to rice during the dry season was 54% at the primordial stage, 32% at the booting stage, but only 16% at the ripening stage. If measured at the ripening stage, the measured value ought to be multiplied by approximately 6.5 to obtain cumulative damage to the rice crop or by 4.2 for an estimate of yield loss. Rice yield can be estimated by farmers directly or by quadrat samples, the former being on average 20% lower than the actual yield. Integrated rodent management increased rice yields more when rats were common, in both dry and wet season crops. For every 1% increase in tiller damage by rats, there was a decrease of 58 kg/ha in rice yield. Wet season crops benefited more from a trap-barrier system (TBS) than dry season crops at the same rat abundance index. The benefit-to-cost ratio for all seasons and years averaged 25:1 but varied considerably from year to year between a low of -2:1 to a high of 63:1. The economic benefit of integrated rodent management was equal to or better than that achieved by conventional management based on synthetic rodenticides. (c) 2004 Elsevier B.V. All rights reserved.