Judul: Survei Penyakit Keriting (Cladosporium cladosporioides) pada Tanaman Pepaya di Bogor
Abstrak: Papaya is one fruit crops which are widely grown and consumed in Indonesia. Some pests and diseases in papaya are known to be limiting factor on the papaya production. Among o the diseases existing, the new disease namely leaf curl disease caused by Cladosporium cladosporioides has been reported since 2011 in Bogor. The objectives of this survey was to determine the status of this disease in the fields and same agricultural practices that may affect its development. The survey was conducted in two subdistricts Rancabungur and Sukaraja where papaya mostly cultivated. The results showed that leaf curl disease is widely spread in those two districts as indicated by the disease incidence, the disease incidence in Rancabungur and Sukaraja was 86.7% and 95.7% respectively. However, the disease severity is still moderate with average ranging from 24.2 to 27.6%. Generally the disease incidence in moderate type (Caliporan) and monoculture cropping system was lower than the large type (Bangkok) and multiple cropping system. Meanwhile, the disease severity did not show much differences due to the fruit type and cropping system. Other cultivated practices did not show much differences effect, both to the disease incidence and severity.
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Judul: Beberapa Panyakit Pada Tanaman Pepaya (Carica papaya L.) di Wilayah Kerja Balai Penyuluhan Pertanian (WKBPP) Rangkepanjaya D.T. II Bogor
Abstrak: Tujuan praktek lapang ini dimaksudkan untuk mengetahui penyakit-penyakit yang ada pada tanaman pepaya di daerah WKBPP Rangkepanjaya. Selain itu pula dilakukan penghitungan intensitas dan luas serangan patogen-patogen yang tergolong penting saat pelaksanaan praktek lapang. Selama pelaksanaan praktek lapang, pengamatan hanya dilakukan di beberapa desa saja. Pemilihan desa-desa sebagai desa contoh diharapkan sudah dapat mewakili seluruh desa di WKBPP Rangkepanjaya. Beberapa penyakit yang terdapat pada tanaman pepaya adalah penyakit embun tepung (patogen belum terdeterminasi), penyakit St. Croix decline disebabkan Corynespora cassiicola (Berk. & Curt.) Wei, penyakit hawar daun bakteri yang disebabkan Erwinia papayae (Rant.) Magrow, penyakit antraknosa yang disebabkan Colletotrichum gloeosporioides Penz. dan C. dematium (Pers ex Fr.) Grove, penyakit busuk buah disebabkan Fusarium sp., penyakit busuk buah, busuk batang dan busuk akar disebakan Phytophthora sp. Dari beberapa jenis patogen tersebut di atas hanya empat jenis saja yang terakhir tergolong penting, karena dapat menimbulkan kerugian yang cukup berarti bagi petani. Serangan Phytophthora sp. dijumpai di seluruh lokasi pengamatan contoh, dan paling banyak menimbulkan kerugian.
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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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