Judul: Identifikasi Organisme Pengganggu Tanaman Gandum (Triticum aestivum L.) di Kuningan dan Bogor, Provinsi Jawa Barat
Abstrak: The development of wheat crops in Indonesia has been struggling to fulfill domestic needs which increase over time. Information about plant pest organisms which attack introduced (SO9) and IPB bred strain (Kasifbey) wheat is one of the main constraints to maintain production capacity of the wheat crops. Therefore, this research needs to be performed. The aim of this research is to find out information about the plant pest organisms on the SO9 and Kasifbey wheat. Observations on the crops have been conducted at the two places cultivation: in Leuwimalang village, Cisarua Subdistrict, Bogor District (705 m above sea surface) and in Cilimus village, Cilimus Subdistrict, Kuningan District (418 m above sea surface) West Java Province. Symptoms of the plant pest organisms which appear on the crops were observed. Subsequently, the extent and intensity of the pest attacks on the crops were quantified. Finally, the samples of the diseased crops and insects were identified at the laboratory using determination key identification. The insects which found on the wheat crops are some species of the Lepidoptera caterpillars and several species of aphids (Hemiptera: Aphididae), species of Oxya sp. (Orthoptera: Acrididae), Nezara viridula (Hemiptera: Pentatomidae), Leptocorisa oratorius (Hemiptera: Alydidae), white grub larvae (Coleoptera: Scarabaeidae), and stem borer. Pathogens which are found on the wheat crops: Fusarium sp., Helminthosporium sp., Phoma sp., Curvularia sp., and Alternaria sp.. The dominant pest in each location are different. The Oxya sp. is a dominant pest in Kuningan and attacks 100% of the sample area of the SO9 and Kasifbey wheat crops. On the other hand, Mythymna unipuncta is a dominant pest in Cisarua with more than 50% attacked area. Diseases of the wheat crops at both location are mostly caused by the Helminthosporium sp. with 100% diseases incidence. The Kasifbey is more frequently attacked by insects and pathogens than the SO9.
Keyword: Helminthosporium sp., Mythymna unipuncta, Triticum aestivum, Oxya sp., Wheat

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: 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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