Judul: Identifikasi dan patogenisitas cendawan penyebab mati pucuk pada bibit Sengon (Paraserianthes falcataria (L.) Nielsen) dan Cabai (Capsicum sp.)
Abstrak: Sengon (Paraserianthes falcataria (L.) Nielsen) merupakan tanaman kehutanan dan cabai (Capsicum sp.) adalah tanaman pertanian yang banyak digunakan dalam sistem agroforestri. Persemaian BPDAS (Balai Pengelolaan Daerah Aliran Sungai) Citarum-Ciliwung melaporkan >500 bibit sengon berumur 2 bulan terserang mati pucuk hingga menyebabkan kematian. Mati pucuk memiliki gejala berupa matinya bagian ujung tanaman hingga membuat tanaman inang mati. Penelitian dilakukan dengan tujuan mengisolasi dan mengidentifikasi penyakit penyebab mati pucuk pada bibit sengon dan mempelajari patogenisitas cendawan penyebab mati pucuk terhadap bibit sengon dan cabai. Patogenisitas adalah kapasitas atau kemampuan dari suatu patogen untuk menimbulkan suatu penyakit. Uji patogenisitas disusun dalam rancangan acak lengkap (RAL) faktorial. Perlakuan berupa tanpa dilukai dan diinokulasi, dilukai karborundum, inokulasi Rhizoctonia sp., serta inokulasi Rhizoctonia sp. dilukai karborundum. Hasil penelitian menunjukkan bahwa cendawan Rhizoctonia sp. sebagai penyebab primer penyakit mati pucuk pada bibit sengon dan cabai hingga menyebabkan kematian. Persentase kejadian penyakit mati pucuk terluas yaitu pada perlakuan inokulasi dilukai cabai (87.70%) dan sengon (87.30%). Persentase intensitas serangan mati pucuk terberat yaitu pada perlakuan inokulasi dilukai cabai (78.07%) dan sengon (67.04%).
Keyword: Chilli, dieback, pathogenicity, Rhizoctonia sp., sengon

Judul: Identification and Disease Severity of Dieback Disease on Sengon Seedlings in Persemaian Permanen Dramaga Bogor
Abstrak: Sengon merupakan salah satu komoditas tanaman kehutanan yang digemari masyarakat. Sehingga pengadaan semai sehat di persemaian sangat penting dilakukan dalam upaya mencapai keberhasilan tanam. Namun, sengon sangat rentan terhadap beberapa penyakit. Salah satu penyakitnya yaitu penyakit mati pucuk di persemaian. Penelitian ini bertujuan menghitung kejadian penyakit dan keparahan penyakit mati pucuk pada semai sengon di Persemaian Permanen Dramaga Bogorserta mengidentifikasi jenis patogen penyebab penyakit mati pucuk pada semai sengon. Metode pengambilan data dilakukan menggunakan metode sensus dan skoring. Selain itu, proses identifikasi dilakukan di bawah mikroskop cahaya dengan perbesaran 40x10. Analisis data dilakukan menggunakan analisis deskriptif. Persentase kejadian penyakit dan keparahan penyakit mati pucuk pada semai sengon berturut-turut sebesar 10,809% dan 73,764% yang mana keparahan penyakit dinyatakan berat. Berdasarkan hasil identifikasi, cendawan Rhizoctonia sp. diduga sebagai penyebab penyakit mati pucuk pada semai sengon., Sengon is one of the forestry plant commodities favored by the community. So that the provision of healthy seedlings in the nursery is significant to achieve successful planting. However, sengon is very susceptible to several diseases. One of the diseases is dieback in the nursery. This study aims to calculate the incidence and severity of shoot death in sengon seedlings in Persemaian Permanen Dramaga Bogor and identify the types of pathogens that cause dieback in sengon seedlings. Methods of data collection carried out using the census and scoring methods. In addition, the identification process carried out under a light microscope with a magnification of 40x10. Data analysis performed using descriptive analysis. The percentage of disease incidence and dieback severity in sengon seedlings were 10.809% and 73.764%, where the severity of the disease is declared as severe. Based on the identification results, the fungus Rhizoctonia sp. is suspect as the cause of dieback in sengon seedlings.
Keyword: dieback, disease severity, nursery, Rhizoctonia sp., sengon

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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