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Rice as a trap crop for the rice field rat in Malaysia

Abstract

The potential of rice as a trap crop for the rice field rat, Rattus argentiventer, was clearly illustrated by the studies conducted in 60.7 ha of newly rehabilitated rice land in Permatang Pauh and in the MARDI Research Centre's rice fields in Bumbong Lima. The rice crop was very attractive to the rats, especially at the reproductive phase. The combination of a physical barrier and traps was very effective in exploiting rice as a trap crop for rice field rats. The trapping patterns indicated a massive influx of rats from the surroundings for a period of three weeks in Permatang Pauh and of a lesser degree in Bumbong Lima. In Permatang Pauh, adult male rats caught ranged in weights of 116-293 g and females 85-230 g. Very few subadults were caught, only 2.3% or 35/1550 measured, whereas in rice fields cultivated continuously, young and adult rats were caught (84 adults to 116 young, or 58 % of the rats caught were subadults and juveniles) as in the case of the population in Bumbong Lima. The sex ratio in the Permatang Pauh population showed a preponderance of males in the first two weeks but eventually more females appeared in the 4th and 5th week. The overall sex ratio was 1236 males to 1107 females (a ratio of 1.12:1), which did not depart from the expected ratio of 1:1. The total number of rats caught was 2343 in the first season but in the second season only 24 rats, 22 R. argentiventer (16 males and 6 females; sex ratio of 2.7:1) and a pair of Rattus rattus diardii were caught in Permatang Pauh. In the Bumbong Lima population, the sex ratio for adults was 37 males to 4 7 females (0.7:1) and in the young 75 males to 41 females (1.8:1). Rats were attracted to the crop only when the adjacent areas were harvested and, as the crop in the surrounding areas matured, the number of rats caught declined and reached zero at the booting phase. Rice at the early reproductive phase is an effective lure for the rice field rats and thus could be used as an efficient trap crop for its control.

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