Judul: Incidence  of  entomopathogenic  fungi  on  spodoptera  exigua hubn.  (lepidoptera:  noctuidae)  in  tritrophic  interaction  on  green  onion
Abstrak: Penelitian dilakukan untuk mengetahui kejadian penyakit cendawan entomopatogen pada Spodoptera exigua (Lepidoptera: Noctuidae) dalam jaring tritrofik pada tanaman bawang daun. Populasi S. exigua dan infeksi cendawan entomopatogen pada S. exigua dilakukan dengan pengamatan langsung. Identifikasi cendawan terisolasi menginfeksi S. exigua dilakukan di laboratorium. Populasi S. exigua pada ketiga perlakuan, yaitu monokulktur bawang daun, monokultur bawang daun disemprot dengan ekstrak daun wortel, dan tumpang sari bawang daun dengan wortel tidak berbeda nyata. Kejadian penyakit yang disebabkan oleh Nomuraea sp. relatif rendah karena populasi S. exigua yang rendah. Kejadian penyakit Nomuraea sp. pada ketiga perlakuan, yaitu monokulktur bawang daun, monokultur bawang daun disemprot dengan ekstrak daun wortel, dan tumpang sari bawang daun dengan wortel tidak menunjukkan peberbedaan yang nyata, The study was conducted to determine the incidence of entomopathogenic fungus on Spodoptera exigua (Lepidoptera: Noctuidae) in net tritrophic on green onion. Population of S. exigua and fungal infection of S. exigua was recorded by direct observation. Identification of isolated fungus infecting S. exigua was carried out in the laboratory. Populations of S. exigua on three different treatments, green onion, green onion sprayed with carrot leaf extract and green onion intercropped with carrot, were not significantly different. Incidence of disease caused by Nomuraea sp. was relatively low due to the low population of S. exigua. Incidence of disease caused by Nomuraea sp. on three different treatments, green onion, green onion sprayed with carrot leaf extract and green onion intercropped with carrot, was not significantly different
Keyword: bawang daun, wortel, cendawan entomopatogen, Nomuraea sp, Spodoptera exigua

Judul: Kejadian Penyakit Entomovirus pada Spodoptera exigua Dalam Jaring Tritrofik pada Tanaman Bawang Daun.
Abstrak: This study was conducted to determine the impact of host plant on viral disease insidence in the beet armyworm (Spodoptera exigua). The method used was direct observation in the field by observing the population of S. exigua. Nucleopolyhedrovirus infected 3rd instar larvae S. exigua were collected in plastic cups, the collected larvae were observed for NPV and Ascovirus symptom. The population of S. exigua was not affected by composition of nutrients, neither the incidence of disease caused by both NPV and Ascovirus. The incidence of viral diseases were relatively low, because of the low population of S. exigua.
Keyword: Bogor Agricultural University (IPB), carrot., Spodoptera exigua, green onion

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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