Judul: Inventory Pests and Diseases of Peanut in Candiareng
Village, Batang Regency, Central Java
Abstrak: Jawa Tengah merupakan provinsi penghasil kacang tanah tertinggi kedua di Indonesia. Salah satu masalah potensial dalam budi daya kacang tanah adalah adanya hama dan penyakit. Inventarisasi hama dan penyakit kacang tanah spesifik lokasi di Jawa Tengah belum banyak dilakukan. Informasi mengenai hama dan penyakit spesifik lokasi penting diketahui sebagai acuan dasar dalam menentukan strategi pengendalian di lokasi tersebut. Tujuan dari penelitian ini adalah menginventarisasi hama dan penyakit pada pertanaman kacang tanah di Desa Candiareng, Kabupaten Batang, Jawa Tengah. Pengamatan hama dan penyakit dilakukan setiap minggu sebanyak empat kali dengan inventarisasi hama dan populasinya, gejala visual, intensitas penyakit, dan hasil panen. Wereng hijau (Empoasca facialis Jacobi), kutudaun (Aphis craccivora Koch), trips (Megalurothrips usitatus Bagnall), ulat grayak (Spodoptera litura Fabricius), dan ulat jengkal (Chrysodeixis chalcites Esper) ditemukan di lapangan dengan populasi berturut-turut 5.2-64.04 ekor/10 kali ayunan ganda, 1.22-2.63 ekor/tanaman, 0.69- 1.85 ekor/tanaman, 0.03-0.17 ekor/tanaman, dan 0.03-0.08 ekor/tanaman. Hama lain seperti belalang (Valanga nigricornis Burmeister), kepik penghisap pucuk (Anoplocnemis phasiana Fabricius ), dan ulat penjalin daun (Homona coffearia Nietner) juga dijumpai di lokasi pengamatan. Penyakit bercak daun (Cercospora arachidicola dan C. personata) dan belang daun (Peanut mottle virus) merupakan penyakit utama dengan insidensi berkisar 98-100% dan 20-48%, sementara keparahan berkisar 54-82.6% dan 5.4-28.2%. Penyakit bercak dan belang daun di lokasi pengamatan menyebabkan penurunan hasil panen sekitar 58 dan 47%. Penyakit sapu oleh fitoplasma juga ditemukan dengan insidensi yang sangat rendah.
Keyword: Central Java, inventory, peanut, pest and disease

Judul: Incidence and Severity of Corn Diseases in Cindaga Village, Kebasen District, Banyumas Regency, Central Java
Abstrak: Jagung (Zea mays L.) merupakan salah satu bahan makanan pokok di beberapa daerah di Indonesia. Penyakit jagung dapat menghambat pertumbuhan tanaman yang menyebabkan penurunan hasil. Penelitian ini bertujuan menginventarisasi, mengidentifikasi, serta mengukur tingkat insidensi dan keparahan penyakit pada tanaman jagung di Desa Cindaga, Kecamatan Kebasen, Kabupaten Banyumas, Jawa Tengah. Penelitian dilaksanakan dalam enam tahap, yaitu penentuan lokasi penelitian, penentuan tanaman contoh, identifikasi penyakit, pengamatan insidensi dan keparahan penyakit, wawancara petani, dan analisis data. Pengamatan penyakit dilakukan pada tiga lahan jagung dengan luas masing-masing 350 m2. Sebanyak 40 tanaman contoh setiap lahan diamati secara sistematik. Wawancara dilakukan untuk memperoleh informasi teknik budi daya petani. Berdasarkan gejala penyakit, tiga penyakit jagung yang berhasil diidentifikasi adalah bercak daun (Curvularia sp.), hawar daun (Helminthsporium sp.), dan karat daun (Puccinia sp.). Bercak daun merupakan penyakit terpenting dengan insidensi 100% dan keparahan penyakit 67-73%. Insidensi penyakit hawar daun dan karat daun berkisar 63-73% dan 35-58%, dengan keparahan penyakit 43-48% dan 5-46%. Kondisi cuaca serta teknik budi daya yang dilakukan petani mungkin menjadi faktor pendukung tingginya tingkat insidensi dan keparahan penyakit yang terjadi di lokasi pengamatan., Corn (Zea mays L.) is one of the staple foods at several regions in Indonesia. Diseases can inhibit plant growth leading to reduced yields. This study aims to inventory, identify, and measure the incidence and severity of disease in maize in Cindaga Village, Kebasen District, Banyumas Regency, Central Java. The research was carried out in six stages, namely determining the research location, determining sample plants, identifying disease, observing the incidence and severity of disease, interviewing farmers, and analyzing data. Disease observations were carried out on three corn fields covering each area of 350 m2. A total of 40 sample plants per field were systematically observed. Interviews were conducted to obtain information on farmers' cultivation techniques. Based on the symptoms of the disease, three diseases of maize identified were leaf spot (Curvularia sp.), leaf blight (Helminthosporium sp.), and leaf rust (Puccinia sp.). Leaf spot was the most important disease with 100% disease incidence and 67-73% disease severity values. The disease incidence of leaf blight and leaf rust ranged from 63-73% and 35-58%, with disease severity 43-48% and 25-46%, respectively. Weather conditions and cultivation techniques practiced by farmers might become contributing factors to the high incidence and severity of the diseases.
Keyword: cultivation, Curvularia sp., Helminthosporium sp., Puccinia sp

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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