Judul: Biologi phthorimaea operculella zell. (lepidoptera:gelechiidae) dan kerentanan beberapa varietas kentang terhadapnya
Abstrak: Phthorimaea operculella atau ulat umbi kentang, merupakan hama penting pada kentang karena menyerang tanaman di lapang dan umbi di gudang. Penelitian ini dimaksudkan untuk mendapatkan informasi mengenai (i) biologi ulat umbi kentang pada umbi kentang, dan (ii) kerentanan beberapa varietas kentang terhadap ulat umbi kentang. Penelitian dilakukan di laboratorium Ilmu Hama Tumbuhan, Departemen Ilmu Hama dan Penyakit Tumbuhan, Fakultas Pertanian Institut Pertanian Bogor. Dalam penelitian biologi digunakan 30 butir umbi kentang varietas Rapan 106 untuk penentuan masa perkembangan, keperidian ngengat betina dan mortalitas telur, dan 200 butir umbi varietas Rapan 106 untuk penentuan ciri instar. Setiap umbi diinokulasi dengan larva ulat umbi kentang yang baru keluar dari telur kemudian dipelihara secara individual dalam kurungan plastik. Setiap hari dilakukan pengambilan contoh sebanyak 10 ekor larva untuk menentukan banyaknya instar, ukuran tubuh larva serta warna dari setiap instar larva.
Keyword: Potato variety;, Ngengat;, Kepompong;, Bogor Agricultural University;

Judul: Patogenisitas dan keefektifan nematoda entomopatogen Heterorhabditis sp. terhadap penggerek umbi kentang Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae).
Abstrak: Potato tuber moth, Phthorimaea operculella Zell. (Lepidoptera: Gelechiidae) is one of the important potato pest due to the potential loss can reach 100% if not well controlled. One of potential biological agents to control this pest is Entomopathogen Nematode Heterorhabditis. The effectiveness of Heterorhabditis has been studied to control several crop pests. Infective juveniles (IJ’s) of nematodes are able to find and penetrate the insects that live in the soil as well as in the plant tissues. The objective of this research is to study the pathogenicity of the Heterorhabditis sp. against P. operculella in the laboratory with direct and indirect (in the potato tuber) treatment. The experiments were conducted using completely randomized design with 6 treatments and 4 replications. The treatments were based on the density level of nematodes Heterorhabditis sp. (100, 200, 300, 400, and 500 IJ/ml) and the control. The result showed that P. operculella infected by Heterorhabditis sp. has symptoms by reducing the movement and feeding activity. The body of dead insects become soft and the color change to dark brown. For the direct treatment, Heterorhabditis sp. can kill P. operculella within 12 hours after application (HAA). At density level 100 IJ/ml, it can control P. operculella until 85% within 24 HAA. In contrast, the mortality rates of P. operculella in the indirect treatment (in the tubers) was 35% at doses of 1000 IJ/tubers.
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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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