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: Pengelolaan penyakit hawar daun (Helminthosporium spp.) pada tanaman jagung (Zea mays) di Kabupaten Solok Selatan
Abstrak: Jagung merupakan komoditas penting di Kabupaten Solok Selatan. Hawar daun (Helminthosporium spp.) adalah salah satu penyakit penting yang menyerang tanaman jagung. Penelitian ini bertujuan menghitung insidensi dan keparahan penyakit, serta mengetahui tingkat pengetahuan, sikap, dan tindakan petani dalam pengelolaan penyakit hawar daun jagung di Kabupaten Solok Selatan. Pengamatan insidensi dan keparahan penyakit dilakukan di Kecamatan Sangir dan Kecamatan Pauh Duo, masing-masing kecamatan dipilih empat lahan. Pada setiap lahan diamati 60 tanaman contoh yang dipilih secara diagonal. Wawancara dilakukan untuk mengetahui teknik budi daya, pengetahuan, sikap dan tindakan petani tentang pengelolaan penyakit hawar daun jagung. Data insidensi dan keparahan penyakit ditabulasi menggunakan Microsoft Excel 2013 dan dianalisis secara deskriptif. Dua penyebab penyakit hawar daun jagung yang ditemukan adalah Helminthosporium turcicum dan H. maydis. Insidensi penyakit mencapai 100% dengan keparahan penyakit paling tinggi sebesar 43,33%. Dalam pengelolaan penyakit hawar daun jagung, tingkat pengetahuan dan tindakan petani responden tergolong masih kurang, sikap cukup baik., Corn is an important commodity in South Solok Regency. Leaf blight (Helminthosporium spp.) is one of the important diseases infecting corn plants. This study aims to calculate the development of the disease incidence and severity, as well as to determine the level of knowledge, attitudes, and actions of farmers in managing corn leaf blight in South Solok Regency. Observations of disease incidence and severity were carried out in Sangir and Pauh Duo sub-districts, each sub-district was selected four corn fields. In each field, 60 sample plants were observed which were selected diagonally. Farmer interviews were conducted to determine the cultivation techniques, knowledge, attitudes, and actions of farmers in managing the corn leaf blight. Data on the disease incidence and severity were tabulated using Microsoft Excel 2013 and analyzed descriptively. Base on disease symptom, two pathogens of corn leaf blight identified were Helminthosporium turcicum and H. maydis. The incidence of disease reached 100% with the highest disease severity of 43,33%. In the management of corn leaf blight, the level of knowledge and action respondent farmers are still lacking, while attitudes level is quite good.
Keyword: farmer behavior, plant disease, severity

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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