Judul: Pengaruh Cara Budidaya Bawang Daun Terhadap Serangan Ulat Grayak Spodoptera exigua dan Parasitoidnya
Abstrak: Pengendalian hama yang dinilai paling efektif adalah dengan memanfaatkan musuh alami. Dengan pola tanam tumpang sari dapat dilakukan untuk memanipulasi habitat yang sesuai bagi parasitoid. Tujuan penelitian ini adalah untuk mengetahui pengaruh dari pertanaman wortel yang menjadi tanaman tumpang sari bawang daun serta perlakuan ekstrak duan wortel pada pertanaman monokultur bawang daun terhadap tingkat serangan ulat grayak S. exigua yang menjadi hama penting bagi tanaman bawang daun dan kelimpahan parasitoid pada hama tersebut. Percobaan terdiri atas tiga perlakuan dan empat ulangan yang disusun dalam rancangan acak kelompok (RAK). Perlakuan tersebut yaitu 1) bawang daun yang ditanam monokultur (P1); 2) bawang daun yang disemprot ekstrak daun wortel (P2); dan 3) bawang daun yang ditanam tumpang sari dengan wortel (P3). Populasi ulat grayak diamati setiap minggu dengan cara melakukan pengamatan langsung. Tumpang sari wortel dengan bawang daun dan penerapan ekstrak daun wortel tidak berpengaruh nyata terhadap infestasi ulat grayak. Infestasi pada perlakuan bawang daun yang ditanam monokultur lebih tinggi dibandingkan dengan pada dua perlakuan yang lain. Parasitoid yang terdapat di lapangan adalah famili Braconidae dan famili Diapriidae
Keyword: S. exigua., bawang daun, parasitoid, tumpang sari, wortel

Judul: Pengaruh cara budidaya bawang daun terhadap serangan pengorok daun Liriomyza spp. dan parasitoidnya
Abstrak: Biological control by natural enemies such as parasitoids is considered as an effective pest control. Intercropping can be done to manipulate the habitat to make suitable for parasitoids. The aim of this research was to study the effect of intercropping of green onion with carrots and spraying of carrot leaf extract on the infestation of leaf miner, Liriomyza spp. (Diptera: Agromyzidae) on green onion and parasitization rate of parasitoids on the pest. The experiment consisted of three treatments and four replications arranged in randomized complete block design (RCBD). The treatments were 1) green onion grown in monoculture system, 2) green onion grown in monoculture system and sprayed with carrot leaf extract, and 3) green onion grown in intercropping system with carrot. Infestation of leaf miner, leaf miner population and parasitization were observed weekly by direct observation and using sticky trap. Two spesies of leafminer, i.e. Liriomyza huidobrensis and L. chinensis were found infesting green onion. Intercropping carrot with green onion and application of carrot leaf extract not affect the infestation of leafminer on green onion
Keyword: Bogor Agricultural University (IPB), parasitoids, Liriomyza spp., intercropping, green onion, carrots

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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