Interactions between rodents and weeds in a lowland rice agro‐ecosystem: the need for an integrated approach to management

Abstract

Rodents and weeds are important pests to rice crops in Southeast Asia. The interaction between these 2 major pests is poorly documented. In temperate cereal systems, seeds of grass weeds can be an important food source for rodents and weed cover along crop margins provides important refuge for rodents. In 2012 and 2013, a replicated study (n = 4) in Bago, Myanmar compared 4 treatments (rodents and weeds; no rodents and weeds; rodents and no weeds; no rodents and no weeds) each of 0.25 ha in transplanted rice. Weeds were managed with hand weeding in the wet season, and hand weeding and herbicides in the dry season. Plastic fences were installed to exclude rodents. We examined the weed cover and relative abundance of weed species, rodent damage, rodent population dynamics and rice yield loss caused by rodents and weeds. The dominant rodent species was Bandicota bengalensis. In the dry season, Cyperus difformis was dominant at the tillering stage and Echinochloa crus‐galli was the dominant weed species at the booting stage. In the wet season E. crus‐galli was a dominant weed throughout the season. Damage by rodents was higher in the dry season. There were larger economic benefits for best weed management and effective rodent control in the dry season (258 US$/ha) than in the wet season (30 US$/ha). Concurrent control of weeds in and around rice fields combined with coordinated community trapping of rodents during the early tillering stage and ripening stage of rice are recommended management options.

Rodent damage to rice crops is not affected by the water-saving technique, alternate wetting and drying

“…Given that the landscape of fear seems to be what influences habitat use whilst rice is in its growing stages (Jones et al 2017), refuge habitats for rats such as dense vegetation near rice fields should be cleared and sanitation around the rice field maintained regularly to minimize rodent activity in the rice field. Regular weeding of fields reduces cover and alternate food source for rodents (Drost and Moody 1982;Htwe et al 2019;Puan et al 2011). The timing of control, i.e.…”

“…The timing of control, i.e. prior to the onset of breeding, is also critical (Brown et al 2011;Htwe et al 2019;Stuart et al 2015).…”

Rodent management and cereal production in Asia: Balancing food security and conservation

“…The study reported additive negative effects of rodent and weeds on crop yield, with the combined effect highest in the dry season. A clear recommendation from these findings is the need for concurrent weed and rodent management, especially during the early crop stages of rice production 28 . Such an interaction between weeds and rodents may not be unexpected but prior to this study, quantitative data were lacking.…”

“…Intensification of annual cropping by transitioning from one crop of rice to two crops, two crops to three crops, or two crops of rice followed by a non‐rice crop ( e.g ., maize or pulses), are all likely to increase the impacts of rodent populations on crop yields given the ability of the major rodent pest species in Asia to increase their annual breeding output when high quality food is available for more of the year. This includes Rattus argentiventer (most SE Asian countries), 19–22 Rattus tanezumi (Philippines) 23–27 and Bandicota bengalensis (Myanmar and South Asia) 28–32 …”

“…Each of the 16 plots (4 treatments x 4 replicates) were 0.25 ha. The study was conducted across both dry and wet cropping seasons 28 . The study reported additive negative effects of rodent and weeds on crop yield, with the combined effect highest in the dry season.…”