Judul: Pest attack rate and abundance of predator on shallot plants in Gebang, Pakel, Tulungagung
Abstrak: Bawang merah (Allium ascolonicum L.) merupakan komoditas hortikultura penting dan memiliki nilai ekonomi tinggi. Produktivitas bawang merah di Tulungagung berfluktuasi setiap tahunnya salah satunya disebabkan oleh adanya serangan hama dan penyakit. Penelitian ini bertujuan mengetahui tingkat serangan hama dan kelimpahan predator pada pertanaman bawang merah. Penelitian dilaksanakan pada bulan Januari sampai Mei 2022 menggunakan metode pengamatan langsung di lapangan dan wawancara kepada petani. Pengamatan dilakukan pada 3 petak pertanaman bawang merah milik petani. Setiap petak pertanaman diamati 200 tanaman contoh yang ditentukan secara sistematis. Pengamatan luas dan intensitas serangan hama serta kelimpahan populasi predator dilakukan setiap minggu mulai umur tanaman 1 minggu setelah tanam (MST) sampai 7 MST. Hasil penelitian menunjukkan bahwa hama yang menyerang pada pertanaman bawang merah yaitu Liriomyza chinensis dan Spodoptera exigua. Luas serangan L. chinensis berkisar antara 0–83% dan intensitas serangan berkisar antara 0–54% di ketiga lahan. Sedangkan luas serangan S. exigua berkisar antara 0–9,5% dan intensitas serangan berkisar antara 0–6,92%. Intensitas serangan L. chinensis ada hubungan dengan budi daya tiap lahannya dan intensitas serangan S. exigua tidak berhubungan dengan budi daya tiap lahannya karena jumlah serangan hama sangat rendah pada kategori tertentu. Kemudian predator yang ditemui di pertanaman bawang merah yaitu Pardosa psedoannulata, Menochilus sexmaculatus dan Solenopsis geminata., Shallots (Allium ascolonicum L.) is an important horticultural commodity and has high economic value. The productivity of shallots in Tulungagung fluctuates every year, one of the reason is caused by pests and diseases. This study aims to determine the level of pest attack and the abundance of predator in shallots plant. The research was conducted from January to May 2022 using direct observation in the field and interviews with farmers. The observation was carried out on 3 plots of shallots plant. In every plot 200 plant was sampled systematically. Observation of attack area and intensity of pest attacks and the abundance of natural enemy populations was observed weekly from 17 week after planting. The results showed that the pests in shallots are Liriomyza chinensis and Spodoptera exigua. The attack area and the intensity of L. chinensis ranged from 0-83% and 0-54% in the three plots. The intensity of attack L. chinensis was related to the cultivation of field and the intensity of attack S. exigua was not related to the cultivation of field because the pest attack was low in certain categories. Meanwhile, the attack area and the intensity of S. exigua ranged from 0-9,5% and 0-6,92%. The predators found in shallot are Pardosa psedoannulata, Menochilus sexmaculatus dan Solenopsis geminata.
Keyword: abundance, attack intensity, natural enemies, population

Judul: The Diversity of Arthropods and Flower-Visiting Activity of Tetragonula laeviceps in Shallots (Allium cepa L.).
Abstrak: Bawang merah (Allium cepa L.: Amaryllidaceae) merupakan komoditas nasional yang dapat menunjang perekonomian Indonesia. Kabupaten Brebes adalah salah satu daerah penghasil bawang merah di Indonesia. Petani di Kabupaten Brebes mengandalkan pestisida untuk mengendalikan hama yang dapat menurunkan keanekaragaman arthropoda. Penelitian bertujuan menganalisis keanekaragaman arthropoda pengunjung, dan mengukur aktivitas serta pollen load lebah T. laeviceps pada tanaman bawang merah. Pengamatan aktivitas kunjungan menggunakan metode focal sampling dan pengamatan keanekaragaman arthropoda pengunjung dengan scan sampling. Aktivitas kunjungan yang diamati adalah jumlah individu dan spesies arthropoda pengunjung, jumlah bunga dikunjungi per menit, dan durasi kunjungan per bunga. Hubungan faktor lingkungan dengan aktivitas kunjungan dianalisis dengan korelasi Pearson. Arthropoda pengunjung bunga bawang merah adalah Hesperiid sp. (Lepidoptera), Eurema sp. (Pieridae), Vespa sp. (Vespidae), Oxyopes sp. Araneae, Chrysopa sp., (Neuroptera), larva Lepidoptera dan nyamuk (Diptera). Durasi kunjungan T. laeviceps berkisar 58 – 88 detik per bunga dengan mengunjungi 1.1 – 1.3 bunga per menit. Pollen load T. laeviceps pada tanaman bawang merah dalam kurungan lebih banyak (78250 butir) dibandingkan di lahan terbuka (52500 butir). Kata Kunci : Bawang merah, aktivitas kunjungan, keanekaragaman, pollen load, stingless bee, Shallots (Allium cepa L.: Amaryllidaceae) is a national commodity that can support the Indonesian economy. Brebes Regency is one of the center production of shallots in Indonesia. Farmers in Brebes Regency use a pesticides to control pests that can reduce the diversity of arthropods. The aims of the study was to analyze the diversity of flower-visiting arthropods and to measure the visiting activity and pollen load of T. laeviceps on shallot. Observation of T. laeviceps visiting activity used focal sampling method and the diversity of arthropods was observed by using scan sampling. Visiting activities observed were the number of individuals and the species, the number of flowers visited per minute, and the duration of visits per flower. The relationship between environmental parameters and visiting activities was analyzed by Pearson correlation. Flower-visiting arthropods of shallot were Hesperiid sp. (Lepidoptera), Eurema sp. (Pieridae), Vespa sp. (Vespidae), Oxyopes sp., Araneae, Chrysopa sp. (Neuroptera), lepidopteran larvae and mosquitoes (Diptera). The visit duration of T. laeviceps ranged from 58 to 88 seconds per flower and the number of flowers visited was 1.1 – 1.3 flowers per minute. Pollen load of T. laeviceps in caged plants was higher (78250 pollen grains) than in open area (52500 pollen grains). Keywords: Diversity, pollen load, shallots, stingless bee, visiting activities
Keyword: Diversity, pollen load, shallots, stingless bee, visiting activities

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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