Judul: Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae): Serangan dan Parasitoidnya di Nagan Raya, Aceh
Abstrak: Spodoptera frugiperda merupakan hama invasif yang berasal dari daerah tropis Benua Amerika, Argentina, dan Afrika. Pada Maret 2019, hama ini dilaporkan telah menyerang pertanaman jagung di Kabupaten Pasaman, Sumatera Barat dan kini telah menyebar hampir di seluruh wilayah Indonesia. Pemanfaatan parasitoid merupakan cara yang tepat untuk mengatasi serangan S. frugiperda. Penelitian ini bertujuan menghitung tingkat kerusakan oleh S. frugiperda, mengiventarisasi parasitoidnya, dan menghitung tingkat parasitisasinya di pertanaman jagung di Kabupaten Nagan Raya, Aceh. Pengamatan dilakukan di dua desa yaitu Desa Sukaraja dan Alue Bilie. Pada setiap desa dipilih satu lahan dan pada setiap lahan dipilih 50 tanaman contoh yang dibagi menjadi lima plot. Plot terletak secara diagonal di keempat sisi lahan dan di tengah lahan. Pengamatan dilakukan sebanyak 12 dan 5 kali dengan interval waktu satu minggu. Tingkat kerusakan serangan S. frugiperda tertinggi di Sukaraja sebesar 37,6% tergolong kategori berat dan tingkat kerusakan di Desa Alue Bilie juga mencapai 37,6%. Parasitoid S. frugiperda yang ditemukan selama pengamatan termasuk Ordo Hymenoptera, yaitu Telenomus sp. (Scelionidae), Microplitis sp., dan Meteorus sp. (Braconidae). Telenomus sp. merupakan parasitoid yang dominan dengan tingkat parasitisasi di Desa Sukaraja 2,31% dan di Desa Alue Bilie 2,05%.
Keyword: damage level, invasive pest, mize, parasitization, Telenomus

Judul: Spodoptera frugiperda (J. E. Smith) (Lepidoptera:  Noctuidae): Attacks and Their Natural Enemies on Corn in Munte Village, Munte Sub district, Karo District, North S
Abstrak: Spodoptera frugiperda (Lepidoptera: Noctuidae) is a relatively new pest in Indonesia and an essential pest of the corn. Corn cultivation is dominant in Munte village. This study aimed to estimate the damage caused by S. frugiperda, inventory natural enemies, estimate parasitization level of parasitoids and population of predator and observe entomopathogen fungi in Munte Village, Karo District, North Sumatera. Observations were conducted on an area of ± 2500 m2 . Damage level were observed on five plots, each consist of 20 plants with an interval of one plant. Larvae and eggs were collected and reared in the laboratory, as well as suspected predatory insects. The level of damage from each observation for 8 weeks after planting (WAP) reached > 30% or was classified as heavy. Natural enemies found were parasitoids, predators, and entomopathogenic fungi groups. The parasitoids belong to Hymenoptera and Diptera, the proportion of population were 29.71% Telenomus sp. (Hym.: Scelionidae), 3.40% Trichogramma sp. (Hym.: Trichogrammatidae), 1.65% Microplitis sp. (Hym.: Braconidae), 0.41% Charops sp. (Hym.: Ichneumonidae), 1.23% Anomaloninae (Hym.: Ichneumonidae), 0.41% Megaselia sp. (Dipt.: Phoridae), and 0.41% of Tachinidae (Diptera). The other natural enemies found were predators Doru sp. (Der.: Forficulidae) and Oxyopes sp. (Ara.: Oxyopidae), entomopathogenic fungi was Metarhizium sp. Telenomus sp. wasthe most found in the field and had potentially reduced the eggs of S. frugiperda.
Keyword: damage level, parasitoid, parasitization level, predator

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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