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Context. Overabundant rodents cause considerable crop damage and, in developing countries of South-east Asia, rodents can be an obstacle to attempts at alleviating poverty. Management is often based on the use of chemicals that can harm non-target species. Therefore, an effective and environmentally benign management approach such as ecologically based rodent management (EBRM) is desirable. Aims. We compared the effectiveness of EBRM to that of conventional management on populations of rice-field rats (Rattus argentiventer). Methods. The study was conducted as a large-scale replicated field trial in lowland irrigated rice fields in West Java, Indonesia. EBRM actions included habitat manipulations, removal of rats with trap barrier systems, coordinated rat-control campaigns and synchrony of cropping on the village level. We measured abundance, population structure, and breeding of rice-field rats as well as rice production and crop damage caused by rats. Key results.Although there was no overall effect of the EBRM treatment on rat abundance, we found decreasing rat abundance in rice-field habitats at the late cropping stage in treated villages and a decrease in body size of rats. In addition, we found fewer reproducing females when EBRM was applied than with the application of conventional methods, whereas male reproductive condition did not decrease. Overall, there was a reduction in mean crop damage when EBRM was applied (4.4 ± 0.4% in treatments v. 2.5 ± 0.4% in experimental controls), which translated into 6% higher rice production. Conclusions. The results demonstrated that EBRM is an appropriate approach to manage overabundant rodents in irrigated lowland rice-based agro-ecosystems and possibly in other agro-ecosystems. This will provide substantial benefits for smallholder farming communities in developing countries and most likely benefits for ecosystem health. Implications. The EBRM approach should be used routinely in irrigated lowland rice crops that are at risk of damage by rice-field rats.

Sublethal dose effect of imidacloprid on the survival of brown planthoppers on resistant and susceptible rice varieties.Imidacloprid insecticides and resistant rice varieties are commonly used to control the the rice brown planthopper (BPH) Nilaparvata lugens in the field. The aim of this research was to evaluate the resistance of N. lugens to imidacloprid and the influence of sublethal dose of the insecticide applied to a certain resistant rice varieties on the survival of BPH. The experiment was conducted in a greenhouse trial at Indonesian Center for Rice Research, Sukamandi, West Java. Each pair of adult BPH were infested on three rice varieties Ciherang, Inpari 13, and Pelita, and then followed by spraying five doses of imidacloprid. The the effective dose rate of imidacloprid on BPH was determined by the value of LD 95 compared with the recommended dose (20 g a.i. ha -1 ). The nymphal survival was concidered as a result of the applied sublethal doses. The numbers of nymphal progenies were observed until two peaks populations of both first and second generations. The insecticide then was applied at LD 50 dose equivalent on adult BPH of the second generation. The number of laid eggs and the abnormal egg shapes were counted. Imidacloprid doses that were unefffective against BPH showed by the values of LD 95 were 1224.3, 2799.0, dan 4692.8 g a.i. ha -1 at Ciherang, Inpari 13 dan Pelita rice varieties, respectively. Seven days after application of imidacoprid, about 70-90% of adult BPH still survived. Sublethal dosages of imidacloprid tended to increase the survival of BPH on a resistant rice variety of Inpari 13, as reflected by the number of nymphal progeny of 156-169 BPH/plant at the first population peak. Imidacloprid treatment increased the number of laid egg, but had no effect on the egg sterility.Key words: effectiveness, Nilaparvata lugens, oviposition, population survival ABSTRAK Pengaruh dosis subletal imidakloprid terhadap kesintasan populasi wereng coklat pada varietas padi rentan dan tahan. Insektisida imidakloprid dan varietas padi tahan wereng sering digunakan untuk mengendalikan populasi hama wereng batang coklat (WBC) Nilaparvata lugens di lapangan. Penelitian ini bertujuan menguji tingkat ketahanan WBC terhadap insektisida imidakloprid dan pengaruh dosis subletal terhadap sintasan populasi WBC pada varietas padi yang telah diketahui tipe ketahanannya. Penelitian dilaksanakan di rumah kaca Pusat Penelitian Padi Indonesia, Sukamandi. Sepasang imago WBC diinfestasikan pada tiga varietas padi (Ciherang, Inpari 13, dan Pelita), kemudian diberi lima dosis perlakuan imidakloprid. Keefektifan imidakloprid terhadap WBC ditentukan dari nilai LD 95 relatif terhadap dosis anjuran penggunan di lapangan 20 g b.a./ha. Nimfa yang lolos hidup dari pengujian ini dianggap sebagai perlakuan dosis subletal pada pengujian selanjutnya. Jumlah nimfa diamati hingga dua puncak populasi generasi ke-1 dan ke-2. Dosis perlakuan LD 50 diujikan kembali pada imago WBC generasi ke-2. Jumlah telur yang diletakkan dan ...

Nanoemulsions are gaining considerable interest for use in delivery of essential oil-based pesticides. Evaluation in the laboratory have shown promising efficacy of nanobiopesticides, and further development in nanoemulsion production at larger scale is needed for a wider application in the field. This study aimed to evaluate the changes in droplet size characteristics of citronella oil nanoemulsions produced using spontaneous emulsification at increased scales. The preparation of nanoemulsion was carried out in two stages of scale-up, namely the laboratory scale (200–1000 mL) and the larger scale (10–50 L). The process variables included stirring speed and time. Characterization was done on the oil droplet size, polydispersity index (PDI), zeta potential and microscopic structure. The oil droplet size, PDi and zeta potential varied with the emulsification process conditions and the production scale. In general, increasing mixing speed and time tended to decrease droplet size and PDI, and increase zeta potential. The changes in characteristics of nanoemulsion were minor at the higher production scales. Relatively small droplet sizes were found in the whole experiment (90–160 nm) with PDI of 0.2 – 0.4 and zeta potential of -28 to -8.8 mV. These results are useful for the design of nanoemulsion production at practical application scale.