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Since 2007, a spate of rodent outbreaks has led to severe food shortages in Asia, affecting highly vulnerable and food-insecure families. Little has been documented about wildlife-management issues associated with these outbreaks. The aims of the present study were to synthesise what we know about rodent outbreaks in Asia, and identify important gaps in our knowledge. We compiled information from agencies of the United Nations, non-government organisations and the authors. The authors conducted site visits to areas affected by outbreaks of rodent populations, and convened an international conference in October 2009 to share knowledge. Bamboo masting is clearly implicated as the primary cause of the rodent-population outbreaks that led to severe food shortages in Mizoram (India), Chin State (Myanmar), Chittagong Hill Tracts (Bangladesh) and upland provinces of Lao PDR. In Laos, emergency food assistance was required for 85 000–145 000 people. In 2009, high rodent losses occurred also in lowland irrigated rice-based systems in the Philippines, Myanmar and Indonesia, not related to bamboo masting. Asynchronous or aseasonal growing of rice crops was a common element in these outbreaks. In the Ayeyarwaddy delta, Myanmar, 2.6 million rats were collected in 3 months through community activities; this outbreak appeared to be related to an extreme climatic event, Cyclone Nargis. There are two key features of rodent outbreaks that make the future uncertain. First, climate change and extreme climatic events will increase impacts of rodents on agricultural production. Second, there is food-security pressure in some countries to grow three crops per year. Increased cropping intensity will reduce fallow periods and create ideal conditions for rodents to breed nearly continuously. Implications of the research are as follows: (i) rodent outbreaks are a consequence of enhanced reproduction and natural mortality is of minor importance, particularly with rapidly increasing populations; therefore, we need to focus more on methods for disrupting reproduction; (ii) a stronger understanding of the ecology of pest species and community dynamics will enable ecologically sustainable management; (iii) we need landscape approaches that focus on crop synchrony, and timely coordinated community action to manage pest species and conserve desirable species; and (iv) a simple monitoring system can help implement ecologically based rodent management.

Context. Post-harvest losses by rodents have traditionally been calculated by estimates of consumption determined in the laboratory. Methods for assessing storage losses by rodents under small-holder conditions will help farmers and policy makers understand the impact rodents may have on food security, nutrition and health. Stored product loss assessment methods could also be used to monitor the effects of rodent control in villages.Aims. The present study examined a method to measure the amount of rice eaten by rodents in household granaries. The effects of trapping and better hygiene around granaries to reduce rodent populations were investigated using the post-harvest monitoring method to determine whether the programme was successful in lowering rodent numbers sufficiently to reduce post-harvest losses.Methods. Baskets with known quantities of rice were placed within household granaries and periodically monitored for moisture content, weight loss, faecal contamination and percentage of rodent-damaged grains. Using an empirical treatment-control study, rodent management was carried out at the community level through daily trapping in two Bangladesh villages and in Myanmar at the granary storehouse level. Post-harvest losses were monitored in villages/granaries with rodent management and in similar villages/granaries where there was no management. Key results.Estimates of household losses in the absence of rodent control were 2.5% in Bangladesh and 17% in Myanmar. These losses were reduced when rodent control was implemented, down to 0.5% in Bangladesh and 5% in Myanmar.Conclusions. The impact of rodents on small-holder storage can be accurately assessed in the field under realistic conditions. Intensive daily trapping at the community level together with improved hygiene practices can successfully reduce rodent numbers and this can significantly reduce stored grain losses and rodent contamination and damage levels.Implications. In addition to the threat of rodent pests during crop production, rodents are a major threat to food security after harvest and have, as of yet, unquantified impacts on household nutrition and health through potential transmission of gastro-enteric diseases and zoonoses to householders 2 and domestic livestock. Trapping and environmental management are affordable and effective tools to reduce rodent impacts on stored grain within communities and are viable alternatives to rodenticides.

Rodents present a major problem for food security in Asia where smallholder farming families are particularly vulnerable. We review here recent developments in the biology and management of rodent pests in cereal cropping systems in Asia. The past decade has seen a strong focus on ecologically‐based rodent management (EBRM), its adoption in field studies significantly increased rice yields (6–15%) and income (>15%) in seven Asian countries. EBRM principles have also been successfully applied to maize in China. We provide case studies on EBRM in Cambodia, on interactions between rodent pests and weeds, and on the importance of modified wetlands for biodiversity and rodent pest management. Knowledge on post‐harvest impacts of rodents is increasing. One research gap is the assessment of human health impacts from a reduction of rodent densities in and around houses. We identify 10 challenges for the next decade. For example, the need for population modelling, a valuable tool missing from our toolbox to manage rodent pests in cereal systems. We also need to understand better the interactive effects of cropping intensification, conservation agriculture and climate change. Finally, new management approaches such as fertility control are on the horizon and need to be considered in the context of smallholder cereal farming systems and mitigating health risks from zoonotic diseases associated with rodents. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A survey of 350 farmers was conducted in the lowland rainfed agricultural system of central Myanmar (Burma) to examine the importance of rodents, farmers' perception of the causes of yield loss, and their beliefs as to why they undertake rodent management. Farmers grew monsoon rice, summer rice and mungbeans with the major constraints upon production identified as pests (29.4% of respondents), followed by insufficient water (19.4%). The main pests were insects (48.6%), followed by rats (40.9%); however, farmers thought that rats caused most damage to their crops (47.7% of respondents; insects 30.3%), and were the most important pest to control. Farmers estimated that rodents caused 13% yield loss. Most farmers believed they could increase yields if they were to work together to control rats, but 61.1% applied rodent control individually. Most farmers (81%) thought that rodenticides were not safe despite 33% using them. Rodents were clearly identified as a significant problem by farmers. With an understanding of the main rodent pest species, ecology and crop damage, ecologically based management strategies for the lowland rainfed rice system in Myanmar can be developed.

Asynchronous planting following cyclone Nargis provided abundant high-quality food for an extended period, which in turn led to a lengthened breeding season of rodents. The outbreak of populations 15 months after cyclone Nargis is consistent with the time it would take rodent populations to build from a low base after a major flooding event. To prevent rodent outbreaks effectively, synchronous planting, use of rice varieties with a similar maturation date and good field sanitation are important actions for subsequent rice crops after a major weather event.

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