Judul: Kelimpahan, Biologi, dan Kemampuan Pemangsaan Oligota sp. (Coleoptera: Staphylinidae), Kumbang Predator Tungau pada Tanaman Ubikayu
Abstrak: Mites infestation is one of the main problem in many agricultural commodities. One of the best methods to control mites infestation is biological control using insect predators. The objective of this study is to know the abundance, biology, and predation ability of mites-predatory beetle, Oligota sp. on cassava. Surveys were conducted in cassava plantation around Bogor to know the abundance of Oligota sp. Oligota sp. collected from the field were reared in the laboratory to observe its biology. Experiment to know the predation ability of Oligota sp. was conducted using 3rd stage larvae, with 5, 10, 15, 20, and 25 adult mites as preys. Observations were carried out 3, 6 and 24 hours after treatment. The developmental time of male and female were 15.047 and 16.097 days, respectively. The longevity of male and female were 20.974 and 21.677 days respectively. Female laid 22.923 eggs in 14.154 days. The 3rd stage larva of Oligota sp. consumed 18 adult mites for 24 hours.
Keyword: Oligota sp., predation, biology, abundance

Judul: . The Strategy of Using a Predatory Mite, Neoseiulus  longispinosus Evans (Phytoseiidae), to Control Tetranychus kanzawai Kishida (Tetranychidae) on Cassava Plant
Abstrak: Tetranychus kanzawai Kishida (Acari: Tetranychidae) merupakan hama penting yang banyak menyebabkan kerugian pada beberapa jenis tanaman di Indonesia. Pengendalian tungau ini umumnya dilakukan secara kimiawi dengan akarisida. Penggunaan akarisida yang intensif dan tidak bijaksana dapat memicu munculnya dampak negatif. Metode alternatif yang lebih aman untuk mengendalikan hama ini perlu terus dikembangkan, salah satunya dengan memanfaatkan tungau predator sebagai agen pengendalian hayati. Salah satu musuh alami yang penting bagi T. kanzawai adalah tungau predator famili Phytoseiidae, di antaranya Neoseiulus dan Phytoseiulus. Neoseiulus longispinosus Evans (Acari: Phytoseiidae) merupakan tungau predator tipe II atau predator generalis yang memiliki preferensi terhadap tungau Tetranychidae. Penelitian ini bertujuan menentukan rasio dan waktu pelepasan N. longispinosus yang paling efektif dalam mengendalikan T. kanzawai pada tanaman ubi kayu. Percobaan menggunakan rancangan strip plot dengan tiga ulangan. Rasio pelepasan predator:mangsa adalah faktor A dengan empat taraf yaitu rasio pelepasan predator:mangsa 0 : 5, 1 : 5, 2 : 5, dan 3 : 5. Waktu pelepasan predator adalah faktor B dengan tiga taraf, yaitu satu, dua, dan tiga minggu T. kanzawai diinfestasi. (tiga minggu setelah tanam (MST), 4 MST, dan 5 MST). Infestasi T. kanzawai dilakukan pada tanaman ubi kayu kultivar Mentega saat tanaman berumur 2 MST. Pengamatan pengaruh pelepasan predator N. longispinosus terhadap intensitas serangan dan populasi T. kanzawai dilakukan saat tanaman berumur 6 MST. Pelepasan predator N. longispinosus dapat menekan populasi dan intensitas serangan T. kanzawai pada tanaman ubi kayu. Rasio predator:mangsa (N. longispinosus: T. kanzawai) yang optimum untuk menekan populasi T. kanzawai adalah rasio 2:5 dan 3:5. Penekanan populasi T. kanzawai tertinggi terjadi pada perlakuan pelepasan predator satu minggu setelah infestasi tungau hama. Pelepasan N. longispinosus hanya mampu menurunkan intensitas serangan T. kanzawai pada tanaman ubi kayu paling tinggi sebesar 8,55%., Tetranychus kanzawai Kishida is an important pest that causes a lot of damage to several types of crops in Indonesia. The control of this mite is generally carried out chemically using acaricide. The intensive use of acaricide triggers many negative impacts. Alternative ways for the control this pest are needed, and one of which is by using predatory mites as biological control agents. Some important natural enemies of T. kanzawai are phytoseiid mites, including Neoseiulus and Phytoseiulus. Neoseiulus longispinosus Evans (Acari: Phytoseiidae) is a type II predator or generalist predator which has preference for tetranychid mites. This study was aimed to determine the most effective release ratio and time of N. longispinosus in controlling T. kanzawai in cassava plants. The experiment was carried out using a strip plot design with three replications. The predator release ratio to prey as the factor A consisting of four levels, namely 0:5, 1:5, 2:5, and 3:5 of predator:prey ratio. Predator release time as factor B with three levels, namely one, two, and three weeks after T. kanzawai release (three weeks after planting (WAP), 4 WAP, and 5 WAP). Infestation of T. kanzawai was carried out on cassava plant cultivar Mentega when the plants were 2 WAP. Observations on the effect of N. longispinosus release on the attack intensity and population of T. kanzawai were carried out at 6 WAP. The results in
Keyword: biological control, predatory mite, predator to prey ratio, spider mite

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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