Judul: Incidence and Severity of Corn Leaves Disease at Sukawening Village and Cibanteng Village in  Bogor Regency
Abstrak: Jagung merupakan komoditas pangan srategis di Indonesia. Salah satu penghambat budidaya jagung yaitu penyakit hawar daun jagung yang disebabkan Helminthosporium sp.. Hawar daun jagung menyebabkan kehilangan hasil hingga 50%. Penelitian ini bertujuan mendapatkan informasi mengenai kejadian serta keparahan penyakit hawar daun jagung di dua lokasi di Kabupaten Bogor. Metode yang digunakan dalam penelitian ini yaitu penentuan lokasi pengamatan, wawancara petani, pengamatan tanaman contoh, penghitungan kejadian dan keparahan penyakit, dan analisis data. Kejadian dan keparahan penyakit diamati langsung di lapangan pada 60 tanaman contoh yang dipilih secara zig zag. Wawancara dilakukan untuk mengetahui informasi teknik budi daya dan pengendalian penyakit hawar daun jagung oleh petani. Data kejadian dan keparahan penyakit dianalisis secara deskriptif. Berdasarkan hasil pengamatan, kejadian penyakit hawar daun jagung di Desa Sukawening dan Desa Cibanteng mencapai 100%. Tingkat keparahan penyakit di Desa Sukawening pada varietas Paragon sebesar 34,33%, tingkat keparahan penyakit pada varietas Exotic Pertiwi sebesar 28,33%, dan tingkat keparahan penyakit di Desa Cibanteng pada varietas Talenta sebesar 27,67%. Pengendalian penyakit dilakukan petani di lapangan dengan cara mencabut tanaman yang sakit, mengatur jarak tanam, dan mengaplikasikan fungisida. Kata kunci: Helminthosporium sp., pengendalian penyakit, penyakit tanaman, Corn is a strategic food commodity in Indonesia. One of the obstacles to maize cultivation is corn leaf blight caused by Helminthosporium sp. Corn leaf blight causes yield losses of up to 50%. This study aims to obtain information about the incidence and severity of corn leaf blight in Bogor Regency. The methods used in this study were determining the location of observations, interviewing farmers, observing sample plants, calculating the incidence and severity of the disease, and analyzing data. Disease incidence and severity were observed directly in the two locations on 60 plant samples selected in randomized zigzag design. Interviews were conducted to find out information on cultivation techniques and control of corn leaf blight by farmers. Disease incidence and severity data were analyzed descriptively. Based on the results of observations, the incidence of corn leaf blight at Sukawening Village and Cibanteng Village reached 100%. The severity of the disease at Sukawening Village on the Paragon variety was 34.33%, on the Exotic Pertiwi variety was 28.33%, and the disease severity at Cibanteng Village on Talenta variety was 27.67%. Disease management was carried out by farmers in the field by uprooting diseased plants, adjusting the spacing, and applying fungicides. Keywords: Helminthosporium sp., disease management, plant disease
Keyword: Helminthosporium sp., disease management, plant 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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