Impact of trap barrier systems on rodent damage to upland rice cropping systems during bamboo masting events

Abstract

Synchronous bamboo masting events are well-known to cause rodent population outbreaks. In South Asia, Melocanna baccifera undergoes semelparous masting every 58 years leading to large rodent outbreaks and nearly 100% crop losses. Current crop protection methods used to control rodent outbreaks are largely based on large-scale use of chronic and acute poisons. Non-chemical control methods, such as the use of trap barrier systems (TBS), could be effective in such outbreak situations. However, TBS is currently used in lowland irrigated rice cropping systems, and thus would need to be evaluated and adapted to the upland rice production systems commonly found in the areas affected by bamboo masting induced rodent outbreaks. In this study we carried out field trials over two cropping seasons (2009 and 2010) in the Ruma area of the Chittagong Hill Tracts, Bangladesh during an on going bamboo masting event. Rodent activity was measured through active burrow counting in TBS fenced and unfenced rice crop fields. No rodent activity was found in TBS fenced fields in 2009, with some limited activity in TBS fenced fields in 2010. In 2010, the mean number of active burrows in unfenced fields was 8.66/ha, compared to 1.8/ha in the TBS sites. Rodent damage was measured by counting rice tillers cut by rodents, with no damage observed in TBS fenced fields in 2009, with some limited damage in TBS fenced fields in 2010 (0.26% damage), whilst unfenced field tiller damage was 3.2% during 2009 and 1.77% during 2010. The main rodent species captured by multi-capture traps in the TBS fences were Rattus rattus (70%), Mus musculus (19%), Rattus nitidus (5%) and Cannomys badius (5%). Rodent capture rates and crop damage were much lower than expected, which is arguably explained by an absence of rodent outbreaks in the selected communities, despite bamboo masting occurring in the surrounding forests around the rice fields. The using of TBS during the rodent outbreaks followed by Melocanna bamboo flowering is discussed in terms of the cost-benefits to prevent rodent damage in upland rice cropping systems.