Judul: Pengamatan populasi Cylas formicarius (Fabr.) (Coleoptera : Brentidae) pada pertanaman ubi jalar (Ipomoea batatas (L.) Lamb.) di Desa Cikarawang, Kecamatan Dramaga, Kabupaten Bogor, Jawa Barat
Abstrak: Ubi jalar merupakan salah satu komoditas pangan penting di Indonesia. Kendala yang dihadapi dalam usaha tani ubi jalar di antaranya adalah kerusakan yang disebabkan oleh hama Cylas formicarius (Fabr.), yang dapat menyebabkan cetakan di lapang dan tempat penyimpanan. Penelitian ini bertujuan untuk mengetahui awal serangan hama di lapang dan laju peningkatan populasinya. Pengamatan keberadaan hama dilakukan dengan menggunakan perangkap pit fall, pengamatan langsung dan pengamatan di laboratorium. Sampel perangkap pit fall sebanyak 1/2 dari jumlah guludan di lahan. Perangkap berupa gelas plastik di beri larutan formalin 0.04% sebanyak 1/3 bagian gelas. Pengamatan dilakukan setiap hari. Pengamatan langsung dilakukan setiap hari pada 49 unit sampel dengan mengamati keseluruhan bagian tanaman sampel di atas permukaan tanah dan daerah sekitarnya dengan radius 20 cm. Sejak minggu ke-15 setelah. tanam,umbi sampel di bawa ke laboratorium untuk di amati kemunculan imago C. formicarius. Pengamatan pemunculan imago dilakukan selama delapan minggu kemadian. Hasil pengamatan visual langsung ke tanaman dan perangkap pit fall sampai dengan 99 hari setelah tanam (hst), menunjukan imago yang berada di lahan sangat sedikit (3 imago di pit fall dan 6 imago di pengamatan langsung). Setelah umbi terbentuk, pengamatan kemunculan imago dari umbi menunjukan bahwa populasi hama meningkat tajam pada 127 hst dan mencapai puncak pada 148 hst.
Keyword: Cylas formicarius, Fit fall, Ubi jalar

Judul: Damage Intensity of Sweet Potato weevil Cylas formicarius (Coleoptera: Brentidae) Cilembu Sweet Potato Plants in Sumedang
Abstrak: Ubi jalar merupakan tanaman pangan strategis sumber karbohidrat peringkat ke-4 setelah padi, jagung dan ubi kayu. Produksi ubi jalar tahun 2016-2020 menurun 34,77%. Kendala yang dihadapi salah satunya adalah serangan hama dan penyakit. Salah satu hama penting pada tanaman ubi jalar adalah hama Cylas formicarius. Penelitian ini bertujuan mendapatkan informasi mengenai tingkat serangan hama boleng pada pertanaman ubi jalar Cilembu di Kabupaten Sumedang. Penelitian dilakukan pada bulan Febuari‒Juni 2022. Pengamatan dilakukan pada 15 lahan petani di tiga desa yang telah ditentukan. Pengamatan struktur umur dan kerapatan populasi C. formicarius di masing-masing lahan petani dilakukan dengan cara mengambil 3 umbi yang menunjukkan gejala terserang berat. Tingkat populasi C. formicarius paling tinggi berada di Desa Cilopang dengan populasi larva 228 ekor, pupa167 ekor, dan imago 199 ekor. Tingkat serangan C. fromicarius paling tinggi mencapai 15.79% di Desa Cilopang., Sweet potato is a strategic food crop and the fourth-largest source of carbohydrates after rice, corn, and cassava. The production of sweet potatoes from 2016 to 2020 has decreased by 34.77%. One of the challenges faced is pest and disease infestation. One significant pest affecting sweet potato plants is the Cylas formicarius weevil. This research aims to gather information on the level of infestation of the sweet potato weevil in Cilembu sweet potato plantations in Sumedang Regency. The study was conducted from February to June 2022. Observations were made on 15 farmer fields in three designated villages. Observations on the age structure and population density of C. formicarius in each farmer's field were conducted by taking three tubers showing severe infestation symptoms. The highest population of C. formicarius was found in Cilopang Village, with a larval population of 228, pupal population of 167, and adult population of 199. The highest infestation rate of C. formicarius reached 15,79% in Cilopang Village.
Keyword: location, planting age, population

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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