Context: Rattus tanezumi is a serious crop pest within the island of Luzon, Philippines. In intensive flood-irrigated rice field ecosystems of Luzon, female R. tanezumi are known to primarily nest within the tillers of ripening rice fields and along the banks of irrigation canals. The nesting habits of R. tanezumi in complex rice–coconut cropping systems are unknown.

Aims: To identify the natal nest locations of R. tanezumi females in rice–coconut systems of the Sierra Madre Biodiversity Corridor (SMBC), Luzon, during the main breeding season to develop a management strategy that specifically targets their nesting habitat.

Methods: When rice was at the booting to ripening stage, cage-traps were placed in rice fields adjacent to coconut habitat. Thirty breeding adult R. tanezumi females were fitted with radio-collars and successfully tracked to their nest sites.

Key results: Most R. tanezumi nests (66.7%) were located in coconut groves, five nests (16.7%) were located in rice fields and five nests (16.7%) were located on the rice field edge. All nests were located above ground level and seven nests were located in coconut tree crowns. The median distance of nest sites to the nearest rice field was 22.5 m. Most nest site locations had good cover of ground vegetation and understorey vegetation, but low canopy cover. Only one nest location had an understorey vegetation height of less than 20 cm.

Conclusions: In the coastal lowland rice–coconut cropping systems of the SMBC, female R. tanezumi showed a preference for nesting in adjacent coconut groves. This is contrary to previous studies in intensive flood-irrigated rice ecosystems of Luzon, where the species nests mainly in the banks of irrigation canals. It is important to understand rodent breeding ecology in a specific ecosystem before implementing appropriate management strategies.

Implications: In lowland rice–coconut cropping systems, coconut groves adjacent to rice fields should be targeted for the management of R. tanezumi nest sites during the main breeding season as part of an integrated ecologically based approach to rodent pest management.

Source: http://www.publish.csiro.au/?paper=WR11197

We investigated the species diversity and habitat use of rodents in the Ifugao Rice Terraces (IRT), Luzon, Philippines, as a first step in their assessment either as pest species of rice or as potential non-target species of rodent control practice. Trapping was carried out in caneland and forest habitats adjacent to rice cropland using trap lines of 10 – 15 cage-traps. Four trapping rounds, each consisting of 5 nights trapping, were replicated at two sites during the months of May and June. A diverse rodent fauna was recorded, including the non-native pest species, Rattus tanezumi, and the native species, Rattus everetti and Chrotomys mindorensis. Results from trapping and spool-and-line tracking suggested that these native species do not contribute to rice damage and that several may actually be beneficial in the ricefield ecosystem as vermivores that feed on invertebrate pests. Control should therefore be directed at the pest species, R. tanezumi, minimising non-target effects on the non-pest rodent species.

Source: http://www.tandfonline.com/doi/abs/10.1080/09670870701192433#.VPfrAnyUeSp

A sample of 10 Norway rats (Rattus norvegicus) was taken for DNA resistance testing from an agricultural site in Kent where applications of the anticoagulant rodenticide bromadiolone had been unsuccessful. All animals tested were homozygous for the single nucleotide VKORC1 polymorphism tyrosine139phenylalanine, or Y139F. This is a common resistance mutation found extensively in France and Belgium but not previously in the UK. Y139F confers a significant level of resistance to first-generation anticoagulants, such as chlorophacinone, and to the second-generation compound bromadiolone. Another compound widely used in the UK, difenacoum, is also thought to be partially resisted by rats which carry Y139F. A silent VKORC1 mutation was also found in all rats tested. The presence of a third important VKORC1 mutation which confers resistance to anticoagulant rodenticides in widespread use in the UK, the others being Y139C and L120Q, further threatens the ability of pest control practitioners to deliver effective rodent control.

Source: http://www.tandfonline.com/doi/abs/10.1080/09670874.2010.523124#.VPfqaHyUeSp

A survey of the knowledge, attitudes and practices (KAP) of 100 rice farmers and 50 coconut farmers was conducted in the coastal lowland agro-ecosystems of the Sierra Madre Biodiversity Corridor, Luzon, Philippines to identify current rodent management practices and to understand the extent of rat damage and the attitudes of farmers to community actions for rodent management. Pests were most commonly listed as one of the three most important rice and coconut production constraints. Other major crop production constraints were typhoons and insufficient water. Farmers consider rats to be the major pest of coconut and of rice during the wet season rice crop, with average yield losses of 3.0% and 13.2%, respectively. Rice and coconut farmers practised a wide range of rodent management techniques. These included scrub clearance, hunting and trapping. Of the 42 rice farmers and 3 coconut farmers that applied rodenticides to control rodents, all used the acute rodenticide, zinc phosphide. However, only ten rice farmers (23.8%) applied rodenticides prior to the booting stage and only seven farmers (15.6%) conducted pre-baiting before applying zinc phosphide. The majority of farmers belonged to farmer organisations and believed that rat control can only be done by farmers working together. However, during the last cropping season, less than a third of rice farmers (31.2%) applied rodent management as a group. In order to reduce the impact of rodents on the farmers of the coastal lowlands of the Sierra Madre Biodiversity Corridor, integrated management strategies need to be developed that specifically target the pest rodents in a sustainable manner, and community actions for rodent management should be promoted.

Source: http://www.sciencedirect.com/science/article/pii/S0261219410002991

BACKGROUND: Massive rodent population outbreaks occurred in the Ayeyarwady Delta, Myanmar, in July 2009, 15 months after cyclone Nargis. Satellite imagery with high temporal frequency was used to identify the area and planting time of rice at a landscape scale of > 80 000 ha, and household surveys of farmers were conducted to validate the mapping and to quantify losses.

RESULTS: Farmers did not have problems with rodents in 2007–2008; rodents were the principal problem in the 2009 summer and monsoon rice crops. The landscape scale modeling indicated that high rodent densities in 2009 were associated with extended or delayed cropping and harvesting time because of asynchronous planting, and with an increase in the amount of abandoned agricultural land after cyclone Nargis.

CONCLUSION: 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. 

Source: http://onlinelibrary.wiley.com/doi/10.1002/ps.3292/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+on+7th+March+from+10%3A00-13%3A00+GMT+%2806%3A00-09%3A00+EST%29+for+essential+maintenance.++Apologies+for+the+inconvenience.&userIsAuthenticated=false&deniedAccessCustomisedMessage=

Rodents are one of the major pests in lowland irrigated rice crops in the Philippines. Rattus tanezumi occurs throughout the Philippines, whereas Rattus argentiventer does not occur on the main island of Luzon. Little is known about the breeding ecology of R. argentiventer and R. tanezumi where they coexist in the Philippines. We hypothesised that R. tanezumi breeding occurs throughout the season whereas the breeding of R. argentiventer is strongly cued to the generative stage of rice crops. We examined the breeding ecology of the two species in San Jose, Mindoro, Philippines, for four rice cropping seasons (two dry and two wet) over two years, 2009–2010, as a basis to develop effective management. We found to our surprise that their breeding ecology was similar. For both species (i) the onset of the breeding season was at the tillering stage of the rice crop; (ii) conception of adult females was highest at booting and ripening of rice; (iii) the highest litter size occurred at the ripening and stubble stages, and the lowest at tillering. Based on their breeding ecology we recommend that the most effective strategy to reduce damage to rice crops is to prevent the development of high populations of both species of rice field rats. This goal requires coordinated community control at both the sowing/planting time and maximum tillering of rice, in combination with the synchronous planting of rice to limit the length of the main breeding season.

Source: http://www.sciencedirect.com/science/article/pii/S0167880912002836